THE RESEARCH AND ESIGN OF PEDIATRIC DENTAL HANDPIECES THAT 
OFER EDUCED APREHENSION FOR PEDIATRIC PATIENTS 
 AND ENHANCED ERGONOMICS FOR DENTISTS 
 
Except where reference is made to the work of others, the work described in this thesis is 
my own or was done in collaboration with my advisory commite. This thesis does not 
include proprietary or clasified information. 
 
 
 
 
_____________________________________ 
Alexander Garber Reynolds, Jr. 
 
 
 
Certificate of Approval: 
 
 
 
 
________________________    ________________________ 
Bret H. Smith       Tsai Lu Liu, Chair 
Profesor       Asistant Profesor 
Industrial Design      Industrial Design 
 
 
 
 
________________________    ________________________ 
T. Shea Tilman      Dr. Joe F. Pitman 
Asistant Profesor      Interim Dean 
Industrial Design      Graduate School 
 
 
THE RESEARCH AND ESIGN OF PEDIATRIC DENTAL HANDPIECES THAT 
OFER EDUCED APREHENSION FOR PEDIATRIC PATIENTS 
 AND ENHANCED ERGONOMICS FOR DENTISTS 
 
Alexander Garber Reynolds, Jr. 
 
A Thesis 
 
 
Submited to 
 
 
the Graduate Faculty of 
 
 
Auburn University 
 
 
in Partial Fulfilment of the 
 
 
Requirements of the 
 
 
Degre of Master of Industrial Design 
 
 
 
 
Auburn, Alabama 
May 10, 2008
ii 
THE RESEARCH AND ESIGN OF PEDIATRIC DENTAL HANDPIECES THAT 
OFER EDUCED APREHENSION FOR PEDIATRIC PATIENTS 
 AND ENHANCED ERGONOMICS FOR DENTISTS 
 
 
 
 
Alexander Garber Reynolds, Jr. 
 
Permision is granted to Auburn University to make copies of this thesis at its direction, 
upon the request of the individuals or institutions and at their expense. The author 
reserves al publication rights. 
 
 
 
 
 
 
________________________ 
Signature of Author 
 
 
 
 
________________________ 
Date of Graduation 
iv 
VITA 
 
In 1982 Alexander Garber Reynolds, Jr., also known as Alex Reynolds, was born 
in Birmingham, Alabama. This is where the author grew up, raised by his parents Al and 
Blair Reynolds. Upon graduating John Caroll Catholic High School in 2000, Alex 
moved to Colorado for college. During his time there, the writer met his future wife Kara 
Strawbridge. Five years later, Alex and Kara were maried on August 4 of 2006. 
Previously, in May of 2005, Alex graduated Colorado State University with a Bachelors 
of Science in Marketing. From there Alex moved to Auburn University to atain a BSEV 
in Environmental design (2006) and a masters in Industrial Design (2008). 
v 
ACKNOWLEDGMENTS 
 
Thank you to those who helped. Tsai Lu Liu was the chair of the commite, and 
the leadership that got this thesis from conception to completion. Thanks to Bret Smith 
and T. Shea Tilman for helping hone this thesis into the fine work that it has become. 
This thesis would never have been created, refined and finished without their help. 
This thesis would also be incomplete with out the personal help of a few dentists, 
Dr. Arthur Caroll, Dr. Laura Durham, Dr. Jan Elington, Dr. Bennie Evans, and Dr. 
Brian Roehl. They donated much of their time and knowledge to this project. 
Also, special thanks goes out to Dr. Evan?s daughter, and close friend of the 
author, Marise Evans, who suggested exploring projects in the dentistry field. Marise 
was very supportive as were the author?s other clasmates Mark Smith and Jacqueline 
Urda. The four put together proved to be a strong support group of friends and 
colleagues 
The input from al of the profesors and staf in the industrial design department 
has also helped shape the author and this project. Their help is imeasurable, as is the 
support of the author?s family. 
Kara?s undying patience and support, along with the continuous support from 
Alex?s parents, Al and Blair, his sister, Gordon, and the rest of his family, have al given 
the author the strength needed to complete this thesis. Thank you. 
vi 
THESIS ABSTRACT 
THE RESEARCH AND ESIGN OF PEDIATRIC DENTAL HANDPIECES THAT 
OFER EDUCED APREHENSION FOR PEDIATRIC PATIENTS 
 AND ENHANCED ERGONOMICS FOR DENTISTS 
 
Alexander Garber Reynolds, Jr. 
 
Masters of Industrial Design, May 10, 2008 
(BSEV, Auburn University, 2006) 
(BS, Colorado State University, 2005) 
 
116 Typed Pages 
 
 
Directed by Tsailu Liu 
 
10.7% of 5 to 11-year-olds are afraid of dental visits (Australian Dental Journal, 
2001). Interviews with five dentists revealed that reasons for this include separation from 
parents, dental workers? poor bedside manner and dental tools. While many of the fears 
are dificult to prevent, the fear of dental tools can be minimized through careful design 
of the dental handpieces (dental drils). Historicaly, most dental tools have been 
constructed using materials that tend to have a menacing appearance.  
The interviews of dentists revealed many elements of the dental dril that could 
use improvement. One dentist described the dril as having a knife-like appearance, and 
vii 
many of the dentists showed interest in a range of color options. Other complaints about 
the typical dental drils include slippery grips and the cord tugging on the back end of the 
dril, which throws of the balance of the tool. Al of these isues are addresed later 
through research and design.  
After acomplishing preliminary research and identifying problems, further 
research and design are executed to find ways to solve these problems. The further 
research and design includes reading related books and articles, conceptualizing, building 
mock up models and numerous ergonomic models, using those models for ergonomic 
testing and finaly administering surveys to collect opinions of a broad range of dentists 
and children. 
This research revealed new ays to use materials and technologies that are 
already used in dental equipment. With these materials and technologies it was possible 
to solve, or improve, the problem conditions mentioned earlier. A silicone rubber grip is 
used to add color while also improving the grip for dentists. Adding grooves to the grip 
channels water and saliva away from the gripping surface, which further improves grip 
for dentists. Implementing a downward bend in back end of the dril reduced the tug of 
the hose. A swivel ensures that the bend always points downward, no mater how the 
dentist holds the tool. 
This thesis details the redesigning of a dental dril to make the tool easier for the 
dentist to use and les intimidating to the pediatric patients. The approach used in this 
thesis is one that can be implemented for the redesign of any pediatric medical 
equipment.
vii 
Style manual or journal used:     APA Standard Guide, Fifth Edition 
Computer software used:      Microsoft Ofice: mac 2004, Student Teacher Edition 
Adobe Photoshop CS2 
Rhinocerous 4.0 
Maxwel Render 1.6 
ix 
TABLE OF CONTENTS 
 
LIST OF FIGURES....................................................xi 
 
LIST OF TABLES....................................................xii 
 
CHAPTER 1 
INTRODUCTION.....................................................1 
1.1 Problem Statement..................................................2 
1.2 Ned for Study.....................................................3 
1.3 Objectives of Study..................................................3 
1.4 Scopes and Limits...................................................4 
1.5 Literature Review...................................................4 
1.5.1 Dental Phobia...............................................4 
1.5.2 Oral Health In the U.S.A.......................................7 
1.5.3 Tooth Anatomy..............................................9 
1.5.4 The Cavity................................................10 
1.5.4.1 Treating Cavities....................................12 
1.5.5 The Dental Handpiece.......................................13 
1.5.5.1 New Types of Handpieces.............................15 
1.5.6 Ergonomics of Hand Tools....................................18 
1.5.6.1 The Wrist..........................................18 
1.5.6.2 Injuries Induced by Tools..............................19 
1.5.6.3 Principles of Hand Tool & Device Design.................20 
1.5.6.3.1 Maintain a Straight Wrist.......................21 
1.5.6.3.2 Avoid Tisue Compresion Stres................21 
1.5.6.3.3 Avoid Repetitive Finger Action..................22 
1.5.6.3.4 Design for Safe Operation......................23 
1.5.6.3.5 Remember Women & Left Handers...............24 
1.5.6.3.6 Vibration-Induced White Finger.................24 
1.5.6.4 Fundamentals of Handle Design.........................25 
1.5.6.5 Buttons, Switches, Etc................................27 
1.5.6.6 Handles & Grips.....................................29 
1.5.7 Silicone Rubber............................................31 
1.5.8 Fiber Optics & Swivels.......................................34 
1.5.9 Sound....................................................35 
1.5.9.1 Generation of Sound..................................36 
1.5.9.2 Soundproofing......................................37
1.5.10 Child Psychology..........................................40
1.5.10.1 Minimal Interference................................40 
x 
1.5.10.2 Questionnaires.....................................41 
1.5.11 Design Proces............................................44 
1.5.12 Concluding the Literature Review..............................48 
1.6 Definitions of Terms................................................49 
 
CHAPTER 2 
DEVELOPMENT PROCES............................................53 
2.1 Observations......................................................54 
2.1.1 User Interviews.............................................54 
2.1.2 Product Usage Observations...................................57 
2.2 Product Conceptualization............................................58 
2.3 Preliminary Ergonomic Models........................................62 
2.4 Secondary Ergonomic odels.........................................63 
2.5 Third Generation Ergonomic Model....................................66 
2.6 Questionnaires....................................................68 
2.6.1 Surveying Users............................................68 
2.6.1.1 Anticipated Outcome.................................68 
2.6.1.2 Statistical Findings...................................69 
2.6.2 Surveying Patients..........................................73 
2.6.2.1 Anticipated Outcome.................................80 
2.6.2.2 Statistical Findings...................................80 
2.7 Final Model.......................................................83 
 
CHAPTER 3 
CONCLUSION......................................................86 
3.1 Results from Studies of Proces........................................86 
3.2 Results from Studies of Design........................................87 
3.3 The Final Concept..................................................88 
3.4 Study Acomplishments.............................................92 
3.5 Areas for Further Study..............................................93 
 
BIBLIOGRAPHY.....................................................94 
Image References.....................................................98 
xi 
LIST OF FIGURES 
 
Figure 1. The anatomy of a tooth..........................................10 
Figure 2. Picture of a cavity.............................................11 
Figure 3. X-ray of a cavity..............................................11 
Figure 4. A dental handpiece (dental dril)..................................14 
Figure 5. Bur profile examples...........................................15 
Figure 6. Anatomy of the wrist...........................................19 
Figure 7. Conventional pliers vs. ergonomicaly designed pliers..................21 
Figure 8. Using a finger strip to spread the load..............................23 
Figure 9. Hand & handle interaction demonstration............................27 
Figure 10. Stephen Pheasant?s user-centered design...........................29 
Figure 11. Grip types..................................................31 
Figure 12. Low cost silicone grips.........................................33 
Figure 13. Fiber optic swivels for dental drils................................35 
Figure 14. The generation of sound waves..................................37 
Figure 15. The diferent dental ofices being visited...........................55 
Figure 16. Usage observations...........................................57 
Figure 17. Thumbnail sketches...........................................60
xii 
Figure 18. Refined preliminary sketches....................................61 
Figure 19. Clay ergonomic models........................................62 
Figure 20. Secondary ergonomic models....................................64 
Figure 21. Refining sketch..............................................66 
Figure 22. Third generation ergonomic model testing..........................67 
Figure 23. Average age of fearful patients...................................71 
Figure 24. Dental dril?s contribution to fear.................................71 
Figure 25. Friendlier drils could calm patients...............................72 
Figure 26. Aceptance of the silicone grip...................................73 
Figure 27. Survey administered to younger children...........................77 
Figure 28. Survey administered to older children.............................79 
Figure 29. Comfort at the dental ofice.....................................81 
Figure 30. Comfort around the dental dril..................................81 
Figure 31. Children prefer the new design...................................82 
Figure 32. Children prefer color..........................................82 
Figure 33. Model parts fresh off of the CNC machine..........................84 
Figure 34. Final model.................................................85 
Figure 35. Features....................................................89 
Figure 36. Color options................................................90 
Figure 37. Anodized color options........................................91 
Figure 38. Demonstration of swivel feature..................................92
xii 
LIST OF TABLES 
 
Table 1. Absence of teth among U.S. adults.................................8 
Table 2. Untreated dental cavities..........................................8 
 
 
 1 
CHAPTER 1 
INTRODUCTION 
 
A large percentage of adults are afraid of the dentist. The Australian Dental 
Journal administered a telephone survey that acquired 7,312 completed surveys from 
Australian residents, aged 5 and above. Acording to the article, ?The prevalence of high 
dental fear in the entire sample was 16.1 percent? (Armfield, Spencer and Stewart, 2006). 
The Journal of the American Dental Asociation published an article caled ?The 
Prevalence of Dental Fear and Avoidance: a Recent Survey Study.? This article summed 
up a survey which used a random dialing procedure to shed light on patients? fear of the 
dental office. Acording to the article ?results indicated that 11.7% of the respondents 
reported high dental fear, and another 17.5% reported moderate dental fear. 
Approximately 15.5% of the respondents surveyed have some degre of dental fear and 
are dental avoiders? (Gatchel, Ingersoll, Bowman, Robertson and Walker, 1983). 
This anxiety has been the subject of several articles. The Journal of the Canadian 
Dental Asociation published an article caled ?A Profesional Psychologist and Dental 
Phobic Speaks?? In this article, psychologist John Harvey writes about his experiences 
working with patients that have anxiety disorders. Dr. Harvey explains that these fears 
often start during childhood and worsen with age. ?An unpleasant day in a child?s life 
can grow into an afliction that can cripple an adult.? Many adult fears of the dental 
office begin as a bad childhood experience in the dental office. A survey of dentists that 
 2 
was administered as research for this thesis reveals that four out of nine dentists cite 
previous bad experiences at the dental ofice as the root of patients? fears. 
 
1.1 Problem Statement 
The fear of the dental ofice often starts with the dental handpiece that most 
people know as the dental dril. The dentists that were interviewed for this thesis point 
out this problem. Also, acording to a survey of 329 elementary school students which 
was administered as research for this thesis, 48 percent of children do not fel 
comfortable going to the dentist. When the dental dril appears, the number of children 
feling comfortable drops by 33 percent, and the number of children feling very 
uncomfortable quadruples. The dental handpiece may wel be the single most feared 
component of the dental office experience. 
Reducing the anxiety asociated with a visit to the dentist also improves the 
quality of the treatment. Acording to the survey of dentists administered for this thesis, 
five out of nine dentists say that patients who bring anxiety to the dentist office hinder 
treatment. These patients often suffer unnecesary additional anxiety. Many of these 
fears begin during childhood, as described by Dr. Harvey. Therefore, from a designer?s 
perspective, the best opportunity to reduce anxiety is to make dental visits more pleasant 
for pediatric patients and to make treatment easier for dentists through the improvement 
of dental equipment. The goal of the proces is to develop new dental equipment that 
both satisfies the dentists? needs and creates a more neutral experience for pediatric 
patients. This thesis wil focus on the redesign of the dental dril to make it easier for 
dentists to use and les intimidating to pediatric patients. 
 3 
1.2 Ned for Study 
When a patient has a cavity, dentists use a handpiece to remove the tooth decay 
(which is what a cavity consists of) and prepare the tooth for a filing. Acording to the 
Center for Disease Control and Prevention (CDC) ?More than half of children aged 5-9 
have had at least one cavity or filing? and ?78 percent of 17-year-olds have experienced 
tooth decay? (2007). That means that 78 percent of children require the use of a dental 
dril to remove tooth decay before they reach the adult age of 18.  
For those children with improper dental care, life is more chalenging. Acording 
to the CDC, ?the daily reality for children with untreated oral disease is often persistent 
pain, inability to eat comfortably or chew el, embarasment at discolored and 
damaged teth, and distraction from play and learning? (Center for Disease Control and 
Prevention, 2004). Tooth decay may even progres to the point that adult teth need to be 
removed. Acording to the CDC, ?By age 17, more than 7 percent of children have lost 
at least one permanent tooth to decay? (Center for Disease Control and Prevention, 
2004). These children?s teth could have been saved had the decay been treated sooner. 
If the handpiece did not have such an unpleasing presence, fears of the dental 
office would diminish. If children?s fears can be reduced, then many future adult 
apprehensions wil consequentialy be reduced. The result would likely be more adults 
visiting the dental ofice and receiving proper dental care.  
 
1.3 Objectives of Study 
 This study requires both field research and design conceptualization. The 
objectives for this study are as follows: 
 4 
? Develop a handpiece that has a more neutral presence, and can be used without 
scaring children. 
? Develop a handpiece that satisfies dentists? needs by being flexible enough and 
ergonomic enough to compete with existing drils, and sturdy enough to survive 
typical cleaning procedures. 
? Enhance the ergonomics of the dental handpiece. 
? Verify the efectivenes of the new design by collecting children?s and dentists? 
opinions regarding the new design verses existing handpieces. 
 
1.4 Scopes & Limits 
This research and design project results in the design of a new dental dril that has 
a more neutral presence in the eyes of children from kindergarten to 5
th
 grade. The new 
design also offers improved ergonomics for dentists.  
This thesis is limited to the construction and fabrication of an appearance model 
to embody the design. Because it is not a fully functional prototype, the user evaluations 
are limited to evaluating the appearance and ergonomics of the new design. 
 
1.5 Literature Review 
 
1.5.1 Dental Phobia 
As mentioned previously, fear of the dental office is a common problem among 
patients. The Australian Dental Journal administered a telephone survey that acquired 
7,312 completed surveys from Australian residents, aged 5 and above. ?The prevalence 
 5 
of high dental fear in the entire sample was 16.1 percent? (Armfield, Spencer and 
Stewart, 2006). This fear is common enough that there are many websites dedicated to 
dental phobia, ranging from forums for complaining about dentists to sites dedicated to 
helping people deal with their fears. These websites refer to this fear of dentists as 
?dental phobia.?  
Acording to the Royal College of Psychiatrists phobia is defined as follows: 
 
If felings [of fear] become too strong or go for too long, they can 
stop us from doing the things we want to and can make our lives 
miserable?  A phobia is a fear of particular situations or things that are 
not dangerous and which most people do not find troublesome?  A 
phobia wil lead a sufferer to avoid situations in which they know they 
wil be anxious, but this wil actualy make the phobia worse as time goes 
on?  Suferers usualy know that there is no real danger, they may fel 
sily about their fear but they are stil unable to control it. (Tims, 2001) 
 
The Journal of the Canadian Dental Asociation published one of these Web sites 
that discussed dental phobia. This site displayed an article writen by a psychologist, Dr. 
John Harvey. As a profesional who works with people suffering from debilitating 
psychological isues on a daily basis, Dr. Harvey has some viewpoints regarding phobias 
and bad childhood experiences. 
 6 
In his article, the doctor states, ?For many dental phobics, the anticipatory anxiety 
is the worst.? This is interesting because the worst part does not involve pain, but rather 
the anticipation of what is to come. 
As mentioned earlier, Dr. Harvey goes on to say that many adult fears come from 
childhood experiences. ?An unpleasant day in a child?s life can grow into an afliction 
that can cripple an adult.? Many of Dr. Harvey?s patients have aflictions which grew out 
of an unpleasant childhood experience. (2005) 
These fears become a problem when patients become so fearful that they begin to 
avoid going to the dentist. Also as mentioned earlier, the American Dental Asociation 
administered a survey using a random dialing procedure which shed light on patients? 
fear of the dental ofice. The survey is summed up in an article caled ?The Prevalence of 
Dental Fear and Avoidance: A Recent Survey Study? published in the Journal of the 
American Dental Asociation. Acording to this article ?results indicated that 11.7 
percent of the respondents reported high dental fear, and another 17.5 percent reported 
moderate dental fear. Results also disclosed that 36.5 percent of those surveyed had not 
been to the dentist in over a year.? The importance of this is that some of these people 
are crippled by this fear and avoid the dentist altogether. ?Approximately 15.5 percent of 
the respondents surveyed had some degre of dental fear and were dental avoiders? 
(Gatchel, Ingersoll, Bowman, Robertson and Walker, 1983). 
Upon further study, certain factors of the survey are found to be consistent across 
diferent demographics and geographic areas. This further study of the previous survey is 
summed up in an article caled ?Factor Analysis of the Dental Fear Survey with Cross-
 7 
Validation,? also published in the Journal of the American Dental Asociation. This 
article states: 
 
Factor analysis of the Dental Fear Survey disclosed?stable and 
reliable factors. The first factor related to paterns of dental avoidance and 
anticipatory anxiety?  Cross validation showed [dental avoidance and 
anticipatory anxiety]? to be consistent across four demographicaly and 
geographicaly diverse groups. (Kleinknecht, Thorndike, McGlynn, and 
Harkavy, 1984) 
 
1.5.2 Oral Health In the U.S.A. 
The Center for Disease Control and Prevention (CDC) wrote in an article caled 
?Summary Health Statistics for U.S. Adults: National Health Interview Survey? (2005) 
that tooth decay is the most common disease amongst children. It is ?five times as 
common as asthma and 7 times as common as hay fever.? 28 percent of two to five year 
olds have experienced tooth decay in their primary teth. More than 50 percent of 
children aged five to nine have had a cavity, while cavities afect 78 percent of 17 year 
olds. In fact, 7 percent of 17 year olds have lost a permanent tooth because of tooth 
decay. In 2005, 16,310 U.S. adults were mising al of their natural teth. Children with 
tooth decay that is not properly treated often suffer ?persistent pain, inability to eat 
comfortably or chew el, embarasment at discolored and damaged teth, and 
distraction from play and learning.? Such dental related ilneses acount for more then 
51 milion mised school hours every year. 
 8 
The CDC suggests that children receive one oral examination betwen the ages of 
one and two, and then receive oral examinations every 6 months after that. 
The tables provided by the CDC, tables 1 and 2, demonstrate how many U.S. 
adults have lost al of their permanent teth and what percentage of children have cavities 
that do not receive proper dental treatment. 
 
Age Range Absence of al natural teth (U.S. 2005) 
Total 16,310 
18-44 years old 1,993 
45-64 years old 5,033 
65-74 years old 3,917 
75 years & older 5,368 
 
Table 1. Absence of teth among U.S. adults 
 
 
 
Table 2. Untreated dental cavities 
 
 
To summarize, by the age of 9 more than half of the children in the U.S. have had 
tooth decay which required the help of a dental handpiece. This means that an improved 
handpiece could directly improve the dental office experience for over 50% of children. 
 Ages 2-5 Ages 6-17 
 1971-1974 1988-1994 1999-2002 1971-1974 1988-1994 1999-2002 
 Percent of persons with untreated dental cavities 
Total 25.0% 19.1% 19.3% 54.8% 23.6% 21.5% 
 9 
Another interesting fact is the rise in dental cavities that coincides with the rise of 
industrialized societies. Cavities have plagued mankind in industrialized cultures more 
and more over the last four centuries, not including a dip in the trend that correlates with 
the introduction of fluoride. Acording to Dr. Jery Gordon ?fossilized remains of men 
and women from the Iron Age discovered in Warwickshire, England showed a cavity rate 
of only 8%. When today?s Warwickshire inhabitants are compared, a remarkable high 
cavity rate of 48% was found.? This is most likely due to the high contents of procesed 
sugars in the modern diet (Gordon, 2000). 
 
1.5.3 Tooth Anatomy 
Before describing cavities and how dental drils are used it is important to 
understand the anatomy of the tooth. The outermost layer of the tooth, just above the 
gum line, is the enamel. This is the hardest and most mineralized part of the body. 
Cementum is what covers the roots of the tooth beneath the gum line. Dentin is located 
beneath enamel and cementum. It is made of the same substance as bone and includes 
nerve endings. Dental pulp is located beneath the dentin. Acording to Dr. Gordon, it ?is 
a vascular tisue, composed of capilaries, larger blood vesels, connective tisue, nerve 
fibers, and cels including odontoblasts, fibroblasts, macrophages, and lymphocytes.? 
During growth and development it is used to nourish the tooth, but as an adult tooth it is 
only used to indicate problems. It acomplishes this with the feling of pain (Gordon, 
2000). 
 
 10 
 
 
Figure 1. The anatomy of a tooth 
 
 
1.5.4 The Cavity 
In order to fully understand the handpiece and why it is used one must first 
understand cavities. Acording to Dr. Jery Gordon (2000), a cavity is a hole in the 
enamel of a tooth. These holes are created by plaque, which forms a ?film of bacteria? 
on teth. This bacterium creates acid as a byproduct of its metabolism. This acid is what 
eats holes in the enamel of teth. These holes, or cavities, are also known as caries. 
If the acid breaks al the way through the enamel it reaches the next layer of the 
tooth, the dentin. The dentin is much softer then the enamel. Since the dentin is softer, 
the acid eats through that layer much faster, straight to the core pulp, which is the 
innermost layer of the tooth. Once the acid reaches the pulp, it creates a tooth infection 
and the tooth wil require a root canal. 
 11 
When a bacterium that naturaly grows in the mouth mixes with carbohydrate-
containing foods, the bacteria fed on the carbohydrates and create acid as a byproduct. 
As the acid changes the pH balance of the mouth, the acid begins to disolve tooth 
enamel. The normal pH balance for a human mouth is 6.2 ? 7.0, which is a bit more 
acidic than water. Tooth decay happens at a balance of 5.2 - 5.5. This balance happens 
after every exposure to carbohydrate-containing foods (Gordon, 2000). 
 
 
Figure 2. Picture of a cavity 
 
 
Figure 3. X-ray of a cavity 
 
There are two types of cavity atacks (Gordon, 2000). 
1. Some cavities atack through pits and fisures, which are nothing more than the 
visible grooves in the top surface of the molars and premolars. Food is easily 
 12 
trapped in these areas and the enamel is thin. These cavities start as smal points 
and spread widely as they hit the dentin. 
2. The other type of cavity atacks are atacks to the smooth surfaces of teth. The 
fronts, backs and sides of teth are made up of these smooth surfaces. The 
enamel is much thicker there. These cavities start wide and tend to converge to a 
point as they go deeper.  
 
1.5.4.1 Treating Cavities 
The most common symptom of having a cavity is increased sensitivity to cold and/or 
swet foods and drinks. Typicaly, though, there are no symptoms because enamel has 
no nerves. Therefore, shalow cavities do not involve nerves and pain. (Gordon, 2000) 
Dentists have many ways of finding cavities (Gordon, 2000). 
1. Scraping teth with a hand held instrument caled the explorer or scaler is one 
way of finding cavities. If it catches it is likely the dentist has found a cavity. 
2. Visual examinations look for discoloration of teth. Discoloration is usualy 
brown or black. 
3. X-rays help to find cavities that cannot be sen or reached, like cavities betwen 
teth, under the gum or under a filing. 
4. If there is a suspicious area and al of the previous methods are inconclusive then 
a special disclosing solution is used to diagnose the tooth. 
 
Once a cavity is found it wil likely be treated. However, this depends on how deep 
the cavity has gone. Jery Gordon (2000) states, ?Early dental cavities that have not 
 13 
spread to the dentin or undergone cavitation should not be treated, as they can be healed 
or re-mineralized with fluoride.? More developed cavities require a more in depth 
treatment.  
When treating one of these more developed cavities there are two basic goals 
(Gordon, 2000): 
1. Remove the decayed material of the tooth using the dental handpiece, otherwise 
known as the dental dril. 
2. Use a fil material to rebuild the removed tooth material. This is usualy done 
with a filing, but in worse cases a crown is required to fil the mising tooth 
material. 
 
1.5.5 The Dental Handpiece 
Acording to the five dentists interviewed for this thesis, the dental dril is used to 
treat dental cavities by removing decayed tooth material and preparing the tooth for the 
insertion of a dental filing or crown. 
 
 
 14 
 
Figure 4. A dental handpiece (dental dril) 
 
The part of the handpiece that comes into contact with the tooth and does the 
cutting and driling is a hard metal aloy bit, which is caled the ?bur.? These burs are 
available in many diferent shapes for a variety of specific applications. Figure 5 
ilustrates just a few examples of the many diferent shapes of burs. Usualy these are 
constructed of stel with a tungsten carbide coating, or are made completely of tungsten 
carbide. Sometimes burs are also diamond coated (Sullivan-Schein, 2005). 
 
 15 
 
Figure 5. Bur profile examples 
 
1.5.5.1 New Types of Handpieces 
A number of alternative dental drils have been developed. These les traditional 
models do not use a bur like most handpieces. Each of these diferent handpieces has 
very promising features, but also have drawbacks which have kept them from becoming 
widely acepted. 
 16 
The plasma needle handpiece, rather than using a bur, uses a plasma tip and a 
flame to remove decay. Zeya Merali describes the dril as follows: 
 
Sticking a needle with a flaming plasma tip into your mouth may 
not at first strike you as much of an improvement on conventional 
dentistry. However, the plasma needle, which is cold and painles to the 
touch, could be just the panacea we have been waiting for. (2006) 
 
The advantage of the plasma needle is that it is a painles method of removing 
decay. The problem is that the flame on the tip, which is inserted into the patient?s 
mouth, can cause as much apprehension as a traditional dental dril. This open flame 
keeps it from being widely acepted as a handpiece that wil give patients a more pleasant 
experience in the dental chair. 
Another promising alternative to the traditional handpiece is the particle beam 
dril. James Schultz, author of the article ?New Type of Dental Dril Takes Fear Out of 
Filings,? claims, ?A new generation of ?particle beam? dental drils could take the 
fear - and pain - out of semi-annual checkups.? The article described the proces as 
follows: 
 
The dril, powered by compresed air just like conventional drils, 
uses ultra-fine abrasive powder to cleanse teth [and] to pinpoint cavities 
and other trouble spots. A narowly focused stream of miniscule 
aluminum oxide particles, each no more than a tenth the diameter of a 
 17 
single human hair, esentialy sandblasts away decay in preparation for 
repair. (1996) 
 
It is a proces that keeps the tooth cool and performs without any pain, sound or 
smels. 
Dr. James Baker, whose Chesapeake practice is one of a handful to offer the 
device, claims that patients love the new dril. Dr. Baker goes on to say, ?There?s no 
sound or smel of the dril.? Only 5 percent of Baker?s patients need anesthesia. 
The high cost is the most likely reason this dril has not yet been widely adopted. 
Acording to the above-mentioned article, a particle beam dril costs $9,500. Acording 
to a catalogue caled Everything Dental (Sullivan-Schein, 2005), traditional handpieces 
cost anywhere from $184.99 to $924.99. 
The last and most common alternative handpiece is the laser-based handpiece. 
There are many articles on this style dril, but the most informative of them is ?How 
Cavities and Filings Work? by Dr. Jery Gordon (2000). Acording to Dr. Gordon, 
lasers were approved for soft tisue (gum) dental work in the early 1990?s. ?In 1997, the 
Food and Drug Administration approved laser use in dental hard tisues (teth) for the 
treatment of cavities.? This is a promising treatment because it can be done in a virtualy 
painles manner versus the painful treatments with typical dental drils, which usualy 
require anesthetics. These lasers can be used to treat smal to medium-sized cavities in 
adults and children. The most common type of laser used for this is the erbium: yttrium-
aluminum-garnet (Er:YAG). 
 18 
There are reasons that laser dental treatments have not taken off and become 
widely popular. First, the tools are prohibitively expensive. Some companies that 
produce the laser tools lease them to dentists on a price per treatment basis. Secondly, 
the laser is not useful in approximately 90-95% of dental treatments. They cannot 
remove old, broken and worn-out filings and they have dificulty removing soft dental 
decay (present in deep cavities). Nor can these lasers prepare a tooth for crowns (caps), 
inlays, onlays, or porcelain veneers. They are also inefective for performing a root 
canal. 
Finaly some researchers stil worry that the laser may create excesive heat that 
can damage the dental pulp. Laser-based dental drils are not yet practical and may not 
be safe for the tooth (Gordon, 2000). 
 
1.5.6 Ergonomics of Hand Tools 
When designing a hand tool that wil be used repetitively on a daily basis, such as 
the dental handpiece, it is important to consider the ergonomics of that tool. By 
implementing good ergonomics in the tool?s design, one can ensure improved user 
comfort throughout daily work, thus decreasing the possibility of injury. 
 
1.5.6.1 The Wrist 
There are two key wrist movements that apply to this study: pronation and 
supination. Stephen Pheasant, author of Body Space: Anthropometry, Ergonomics and 
the Design of Work, describes these movements as such. Pronation is an inward rotation 
of the forearm. When the palm is turned down it is in the prone position. Supination is 
 19 
an outward rotation of the forearm. When the palm is turned upward it is in the supine 
position. It is important to note that these movements are not movements of the wrist. 
They are actualy movements created by rotation of the radius and ulna bones that run 
paralel with the radial and ulnar arteries in the forearm (1996). 
 
Figure 6. Anatomy of the wrist 
 
1.5.6.2 Injuries Induced by Tools 
A key consideration in developing hand tools is designing them to reduce both 
major and minor injuries. McCormick and Sanders, authors of Human Factors in 
 20 
Engineering and Design (1982, p.283), reference the findings of Ayoub, Purswel, and 
Hicks (1977) that state, ?Injuries resulting from hand tool use acounted for 5 to 10 
percent of al compensable injuries.? Interestingly, power tools caused only 21-29 
percent of those compensable injuries. 
McCormick and Sanders go on to say that most of the injuries cited in these 
reports are single incident traumatic injuries. These injuries usualy involve a knife, a 
wrench, or a hamer. Not mentioned in the reports are cumulative-efect traumas. This 
type of injury typicaly leads to ?reduced work output, poorer-quality work, increased 
absenteism, and single-incident traumatic injuries.? (p. 284) Thus, there is a need to 
design tools with improved ergonomics, with the intent to reduce both single incident 
traumas and cumulative-efect traumas. 
 
1.5.6.3 Principles of Hand Tool & Device Design 
McCormick and Sanders also discuss what they cal the ?Principles of Hand Tool 
and Device Design?. These principles include: 
?Maintain a Straight Wrist 
?Avoid Tisue Compresion Stres 
?Avoid Repetitive Finger Action 
?Design for Safe Operation 
?Remember Women and Left-Handers 
?Vibration-Induced White Finger? 
 
 
 21 
1.5.6.3.1 Maintain a Straight Wrist 
When the wrist is not kept straight during use of a hand tool, there are two general 
problems that arise. The first is that grip strength is compromised. McCormick and 
Sanders cite Terel and Purswel (1976) as reporting ?that grip strength is reduced if the 
wrist is bent in any direction.? This creates fatigue and increases likelihood that the tool 
wil be dropped, causing injury, or damage to the tool. 
The second problem is that ?radial deviation, particularly if combined with 
pronation and dorsiflexion, increases presure betwen the head of the radius and the 
capitulum of the humerus in the elbow? (McCormick & Sanders, 1982, p. 289). This is 
also what causes epicondylitis, which is more commonly known as tennis elbow. 
 
 
Figure 7. Conventional pliers vs. ergonomicaly designed pliers 
 
1.5.6.3.2 Avoid Tisue Compresion Stres 
Many tools place considerable presure on the palm of the hand. The ulnar and 
radial arteries pas through the palm, as do nerves. Thus, placing excesive presure on 
the palm is frowned upon and can be painful. Idealy, the tool should spread the presure 
over more area and focus presure on les sensitive areas like the ?tough tisue betwen 
the thumb and index finger.? Using the palm of the hand as a hamer is unaceptable. 
 22 
This can cause artery, nerve and tendon damage as wel as send shock waves up the arm 
to other parts of the body (McCormick & Sanders, 1982, p. 290-291). 
In addition, another consideration is the ever-popular finger grooves. ?Tichauer 
(1978) recommends not using deep finger grooves or receses in tool handles if repetitive 
high finger forces are required.? The higher points betwen the grooves become presure 
points for users with thicker fingers. Users with smaler hands tend to place two fingers 
into one groove, which creates discomfort by presing those fingers together. 
(McCormick & Sanders, 1982, p. 291) 
 
1.5.6.3.3 Avoid Repetitive Finger Action 
Repetitive finger actions can cause injuries, particularly when they involve the 
index finger. McCormick & Sanders describe this problem and its solutions as such: 
 
If the index finger is used excesively for operating triggers, a 
condition known as trigger finger develops. The aflicted person typicaly 
can flex but cannot extend the finger actively. It must be pasively 
straightened, and when it is, an audible click may be heard. 
 
If a repetitive finger action is unavoidable, it is best to use the thumb for those 
actions. Acording to McCormick & Sanders: 
 
Frequent use of the index finger should be avoided, and the thumb-
operated controls should be used. The thumb is the only finger that is 
 23 
flexed, abducted, and opposed by strong, short muscles located entirely 
within the palm of the hand. 
 
Avoid hyper extending the thumb. Finger strip controls are preferable over thumb 
controls because the load is spread across many fingers and the thumb is alowed to grip 
and guide. (1982, p. 291) 
 
 
Figure 8. Using a finger strip to spread the load 
 
1.5.6.3.4 Design for Safe Operation 
McCormick and Sanders recommend what should be considered when designing 
a hand tool in order to ensure safe operation. First, McCormick & Sanders say that 
?designing tools and devices for safe operation would include eliminating pinching 
hazards and sharp corners and edges.? This also reduces the chance of the operator 
quickly reacting to a pinch or sharp edge, reducing the chance the operator wil flinch and 
cause an indirect injury. The second point is that ?proper placement of the power switch 
for quick operation can also reduce acidents with power tools.? This creates more 
 24 
opportunity for operators to switch power tools of before someone gets hurt in the event 
of an emergency. The final point on this topic is that ?the designer must consider, in 
detail, how the tool wil be used by the operator, and also how it is likely to be misused 
by the user.? Most tools are misused at some time. It is important to make sure tools are 
as safe as possible, even when being misused. (1982, p. 292) 
 
1.5.6.3.5 Remember Women & Left-Handers 
McCormick and Sanders cite Barsley (1970) for saying that women make up 50 
percent of the population and, on average, have two-thirds the grip strength that men 
have. Left-handers make up about 8 to 10 percent of the population (McCormick & 
Sanders, 1982, p. 292-293). Tool design must acommodate both right and left-handed 
users, as wel as male and female users. Designing to acommodate these users wil give 
the tool a more universal design.  
 
1.5.6.3.6 Vibration-Induced White Finger 
Many powered hand tools create noticeable vibration. Constant use of vibrating 
hand tools over an extended period of time (months/years) can cause vibration-induced 
white finger (VWF), neuritis, decalcification and cysts of the radial and ulnar bones 
(McCormick & Sanders, 1982, p. 295). When designing tools that vibrate, eforts must 
be made to reduce handle vibration.  
 
 
 
 25 
1.5.6.4 Fundamentals of Handle Design 
Just as McCormick and Sanders offer what they cal the principles of hand tool and 
device design, Stephen Pheasent, author of Bodyspace; Anthropometry, Ergonomics and 
the Design of Work, offers what he cals the ?fundamentals of handle design.? Pheasent 
describes these fundamentals as follows: 
I. Force is exerted most efectively when hand and handle interact in 
compresion rather than shear. Hence, it is beter to exert a thrust 
perpendicular to the axis of a cylindrical handle than along the axis 
[Fb in Figure 9 rather than Fa]. If the later is necesary a knob on 
the end wil give extra purchase. 
I. Al sharp edges or other surface features, which cause presure hot 
spots when gripped, should be eliminated. These include: 
i. ?Finger shaping? (unles designed with anthropometric 
factors in mind) [should be eliminated.] 
i. The ends of tools such as pliers, which may dig into the 
palm (if the handle is short) [should be redesigned.] 
ii. The edges of flat or raised surfaces, e.g. for the application 
of labels, logos, etc. [should be removed from designs.] 
iv. Pinch points? betwen moving parts such as triggers, etc. 
[should also be avoided in any wel-designed tool.] 
II. Handles of circular cross-section (and appropriate diameter, e.g. 
30-50 m) wil be most comfortable to grip since there wil be no 
possibility of hot spots ? but they may not provide adequate 
 26 
purchase. Rectangular or polyhedral sections wil give greater 
purchase but wil be les comfortable. In general, wherever two 
planes met (within the area that engages the hand) the edges 
should be rounded; there are no exact figures but a minimum 
radius of curvature of about 25 m sems reasonable. 
IV. Surface quality should neither be so smooth as to be slippery nor 
be so rough as to be abrasive. The Frictional properties of the 
?hand/handle interface? are complex since the skin is both visco-
elasticaly deformable and lubricated. Heavily varnished wooden 
handles give a beter purchase than metal or plastic of similar 
smoothnes. The explanation is possibly in [metal or plastic?s] 
resilience (elastic compliance). Rubber is similar [to metal or 
plastic] but becomes ?tacky.? The subject is worthy of more 
extensive investigation. 
V. If part of the hand is to pas through an aperture (as in a suitcase or 
teacup) adequate clearance must be given. It is remarkable how 
often this perfectly obvious design principle is violated. The 
following spaces wil acommodate virtualy al users with a slight 
leway: 
i. For the palm, as far as the web of the thumb (as in the 
handle of a suitcase), alow a rectangle 115 m x 50 m. 
i. For a finger or thumb, a circle 35 m in diameter wil 
alow insertion, rotation and extraction. (1996, p. 86-87) 
 27 
 
 
Figure 9. Hand & handle interaction demonstration 
 
1.5.6.5 Butons, Switches, Etc. 
There are many diferent ways to control precision hand tools. Some tools are 
more complex than others in that they require butons, switches or other such devices to 
give the operator more control. When designing these complex tools, deciding which of 
these devices is used can be an important decision. The following is a listing of details 
about these devices and what distinguishes them, as described by Tiley and Henry 
Dreyfuss Asociates: 
 
Push Buttons 
Buttons should give the operator positive fedback to show 
activation of the control. This can be provided by incorporating a sensory 
or audible click when the motion is caried out. Push-on-push-off types 
are not as good, because they cancel out the expected movements for ?on.? 
 28 
 
Rocker & Toggle Switches 
Rocker switches cary important mesages on the front face in 
addition to the titles that must appear on the panel face. Rocker switches 
must be oriented the same way as the toggle switch: ?off? is always down 
or to the left. The simplest toggle switches are acurate if they follow this 
rule. If triple-position switches are used, their position may not be 
imediately apparent. 
 
Thumbwheels 
Thumbwheels, which are dificult to read, must also be ?of? when 
down or to the left. They are convenient and widely used on smal audio 
receivers and players. 
 
Triggers & Tool Grips 
Provide a full finger grip for the trigger of at least 1.1 in (27 m) 
in diameter for use with gloves. Other dimensions of the hand grip can 
vary depending on the force to be exerted as long as the minimums are 
preserved. (2002, p. 77) 
 
 
 
 
 29 
1.5.6.6 Handles & Grips 
Another aspect of hand tools is the most fundamental of parts, the handle. 
Stephen Pheasant describes a handle in a way that gives it new meaning through its 
function: 
 
The purpose of a handle is to facilitate the transmision of force 
from the musculoskeletal system of the user; to the tool or object he is 
using; in the performance of the task or purpose for which he is using it. 
As a general rule we can say that to optimize force transmision is to 
optimize handle design. (1996, p. 86) 
 
 
Figure 10. Stephen Pheasant?s user-centered design 
 
One cannot transmit force through a handle without gripping it. An important 
part of handle design is considering what type of grip should be used with the handle and 
acommodating the handle to that grip style. Pheasant talks about two diferent types of 
grips that are involved with handles: 
 
 30 
In a clasic and widely quoted paper on the subject (gripping 
actions vs. non-gripping actions), Napier (1956, p. 86) divided gripping 
into two main categories. 
I. Power Grips, in which the fingers (and sometimes the 
thumb) are used to clamp the object against the palm; 
I. Precision Grips, in which the object is manipulated 
betwen the tips (pads or sides) of the fingers and thumb. 
Note that both entail a closed kinetic chain. 
In the basic power grip?the thumb wraps around the back of the 
fingers to provide extra stability and gripping force. As the need for 
precision increases, however, the thumb moves along the shaft of the tool 
handle?providing extra control and the possibility of both power gripping 
and precision manipulation as the situation may demand (1996, p.86). 
 
 31 
 
Figure 11. Grip types 
1.5.7 Silicone Ruber 
Part of the problem with dental handpieces is hypothesized to be the cold, hard 
and metalic look. During our search for ways to give dental drils a softer, warmer and 
more comforting appearance, an interesting trend emerged. Many of today?s scalers use 
silicone rubber grips. Scalers are dental instruments characterized by their sharp tipped 
hook and used for removing tartar from teth.  These scalers go through the same daily 
use and cleaning proces as the dental drils. 
It is common to find scalers with silicone grips. Silicone is softer, more 
comfortable, and more ergonomic than a metal grip, plus it can withstand the extreme 
environment of an autoclave as wel as withstand cleaning chemicals. Even beter, 
silicone rubber is also resistive to les extreme, yet more typical, wear and tear. Another 
benefit is that silicone is inexpensive. Dental Catalog (155th ed.) offers products from a 
 32 
company caled Dentsply Profesional which caries many lines of scalers with silicone 
grips. For example, one line, caled Flexichange, sels silicone grips at the cost of $9.29 
(Dental Catalog, 2005). 
The same catalogue lists dental handpieces from $184.99 to $924.99. When 
silicone rubber grip is added, even the least expensive of handpieces would only se 
about a five percent increase in price. The average handpiece?s price would only increase 
approximately thre percent, which makes silicone rubber a realisticaly cost viable 
option. (2005) 
 
 33 
 
Figure 12. Low cost silicone grips 
 
 34 
1.5.8 Fiber Optics & Swivels 
During the research proces it became clear that designing a new, revolutionary 
dental handpiece should include some of the latest technology available. It would be 
helpful to include a fiber optics lighting feature to give dentists a wel-lit workspace. In 
addition, adding a swivel to the cable wil aid dentists by reducing the resistance from the 
dental dril?s hose. This often hinders dentist?s work, as was mentioned by almost every 
dentist interviewed. This raises the question: for air powered dental drils, is it possible 
to produce a swivel connection which acommodates fiber optic lighting and does not 
suffer significant loss of air presure and/or water presure? Acording to Dental 
Catalog (155th ed.), this can be achieved. The Sullivan Schein Catalog lists several fiber 
optic swivels which are already in production and available to dentists for the cost of 
$134.99 to $250.99 (2005). 
 
 35 
 
Figure 13. Fiber optic swivels for dental drils 
 
1.5.9 Sound 
After interviewing 5 dentists and their registered dental hygienists, it became clear 
that one of the most glaring problems with the experience surrounding the dental dril is 
the noise level. Each individual interviewed cited the noise of the dental dril as a 
problem, whether it scared patients or caused hearing loss for people involved with the 
sound on a daily basis. 
 36 
Acording to John Foreman, author of Sound Analysis and Noise Control, noise is 
?unwanted sound.? This unwanted sound can keep people from performing at maximum 
ability and eficiency. Foreman says it can increase nervous tension asociated with 
psychological efects. Noise is a form of air pollution (1990, p.1); therefore it is 
important to study sound and soundproofing to beter understand how to improve the 
experience surrounding the use of the dental handpiece. 
 
1.5.9.1 Generation of Sound 
Foreman also describes the generation of sound as follows: 
 
Sound requires a source, a medium for transmision, and a 
receiver. The source is simply an object, which is caused to vibrate by 
some external energy source. The medium is the substance which caries 
the sound energy from one place to another. (1990, p.1) 
 
As the source vibrates it is moving at a very high frequency. However, to beter 
understand what is occurring, consider a vibration as one movement at a time. Imagine 
the source as it moves to the right as part of a vibration. As it moves to the right, the 
source compreses molecules of the medium that are to the right of it. Eventualy that 
source moves back to the left and decompreses the molecules, creating a rarefaction 
(refer to figure 14). As the source continues to do this again and again, it creates a series 
of these compresions and rarefactions that travel through the medium away from the 
 37 
source. The ear and microphone receive these changes in presure, and translates the 
presure changes as sound. (Foreman, 1990, p.1) 
 
 
Figure 14. The generation of sound waves 
 
1.5.9.2 Soundproofing 
John Foreman explains thre diferent mechanisms for absorbing sound. These 
methods for soundproofing are viscous flow, internal friction and panel vibration. 
Foreman explains them as the following: 
 
 38 
Viscous Flow. An efective absorber consists of a series of 
interconnected pores and voids through which sound waves propagate. 
During propagation, the particle velocity asociated with the sound wave 
causes relative motion betwen the air molecules and the surrounding 
material. As a result, friction generates heat, which is disipated into the 
atmosphere as lost energy from the sound wave. 
Internal friction. Some absorptive materials have resilient fibrous or 
porous structures; disipation of energy occurs not only from the viscous 
flow losses, but also from the internal friction of the material itself. 
Panel vibration. Some increase in low-frequency absorption can 
often be obtained by mounting the absorption material at a suitable 
distance from the wals of a room. This is because the energy in the low-
frequency incident sound causes the material to vibrate like a panel, and in 
so doing some energy is removed from the incident sound wave. (For 
example, drapes should be hung away from a wal, not touching it, if it is 
desired to increase the low frequency absorption of the drape). 
The absorptive characteristics of an acoustical material are determined 
to a large extent by the pore or void size, interconnections betwen pores 
and voids, and material thicknes. (1990, p. 110) 
 
John Foreman continues by explaining sound absorbing materials and the thre 
diferent types: 
 
 39 
The types of porous materials in common use are fibrous materials 
(such as rock wool, mineral wool, and fiberglas), perforated loose-texture 
board, foam rubber (in particular, reticulated poly urethane foam-where 
there is a common air path betwen cels in the foam), fabrics, carpets, 
drapes, upholstery, etc. Commercial porous materials can be divided into 
thre categories: (1) prefabricated acoustical units, (2) acoustical plasters 
and sprayed-on material, and (3) acoustical (isolation) blankets. (1990, p. 
112) 
 
One method of sound absorption is NASA?s sound suppresion water system. The 
John F. Kennedy Space Center uses a sound suppresion water system to protect the 
orbiter and its payloads from damage created by acoustical energy and rocket exhaust 
reflected from the flame trench. This system uses a 300,000 galon elevated water tank, 
which fils in about 20 seconds just before ignition. As the space shuttle reaches an 
elevation of 300 fet above the platform acoustical levels reach their peak, and drift off 
until they are no longer a problem at an altitude of 1,000 fet. 
There are two primary components to this sound suppresion system, a water spray 
system, and a series of water baths. Together these water bariers block the path of the 
reflected presure wave from the rocket boosters, which decreases the intensity of the 
presure and sound (Morgan, JoAnn H., 2000). 
 
 
 
 40 
1.5.10 Child Psychology 
Since the focus of this thesis is creating a neutral appearance for the dental 
handpiece in the eyes of children, it is important to get children?s opinions on the subject. 
This can be a dificult task for a number of reasons. This section explores literature that 
discusses the topic of collecting children?s opinions, the dificulties involved, and what 
helpful hints are available. 
 
1.5.10.1 Minimal Interference 
One of the first things to keep in mind when conducting observations or surveys is 
to minimize interference. It is dificult to collect the opinions of others without 
influencing those opinions, but for the sake of research, that interference must be 
minimized. Pelegrini and Bjorklund describe the importance of this problem in some 
detail: 
 
The notion of minimal interference should be stresed to the extent 
that observers typicaly have an efect on those that are being observed 
albeit an unintentional influence. It is crucial that observers recognize the 
efects they have on those being observed and try to minimize them. In 
the final analyses, observers must also acount for these efects on the 
behavior of those being observed. (1998, p.73) 
 
 
 
 41 
1.5.10.2 Questionnaires 
Since observation is not as efective in collecting opinions from large quantities of 
children and dentists, questionnaires were used to acomplish this goal. Touliatos and 
Compton, authors of Approaches to Child Study, describe questionnaires in detail. 
Questionnaires usualy require litle explanation. The respondents are typicaly given as 
much time as they need to think about their answers without presure to respond. 
Questionnaires also have the advantage that there is typicaly les desire on the 
respondents? part than an interviewe to try to impres the investigator. Plus, the 
questionnaire is inexpensive and requires litle skil on the part of the administrator when 
compared to interviews. Also, it can be administered to a large group simultaneously 
while providing anonymity for the respondents. (1983, p. 188) 
Touliatos and Compton also describe the limitations of questionnaires in detail: 
 
Among the limitations of questionnaires are the diversity of 
meaning that may be atributed to a question by various respondents, the 
amount of education that may be required of a person in order to 
understand the questions and procedures, the dificulty of securing valid 
personal or confidential information, and the uncertainty of whether an 
adequate number of responses wil be received to represent the population. 
(1983, p. 188) 
 
 42 
These are chalenges that are taken into acount while writing the questionnaires 
and while analyzing the data collected from the questionnaires. Some of these problems 
are compounded when working with children.  
This is why Touliatos and Compton (1983, p. 188) claim that, ?Obviously, self-
administered questionnaires cannot be used with young children.? This is an interesting 
point because it is one that this thesis intends to disprove. Theoreticaly, if the 
questionnaire is graphicaly based and created with the explicit intent of being understood 
by a targeted age group of children, these dificulties can be overcome enough to collect 
relevant data. 
Michael P. Ricards also has some things to say about the dificulty of surveying 
children. Ricards breaks it down into thre main problems: 
 
? First, some children (especialy tenagers) may not take the 
questionnaire seriously.  
? Second, boys and girls often tend to regard the questionnaire as a 
?test? and they are more likely to choose the answer they fel is 
correct rather than the one that most closely coincides with their 
felings.  
? Third, the questionnaire by its very phraseology may be eliciting a 
specific response. (1973, p. 115) 
 
Michael P. Ricards (1973, p. 116) also warns that, ?researchers would stil have to 
be careful to use terms which have the same meaning for al children.? Ricards explains 
 43 
an example of research conducted which ?examined the child?s difering views of the 
good citizen.? They found that citizenship is used as synonym for conduct in elementary 
schools. ?Thus a wel-behaved pupil is termed a good citizen.? Therefore, instead of 
revealing what children felt made a good citizen, they found that children ?asociated 
citizenship with obeying the school?s rules and regulations.? 
Another thing to consider when asking questions of children is how far they are in the 
developmental proces. Older children tend to be more capable of answering more 
complicated questions because they are further developed and further educated. Ross 
Vasta, author of Strategies and Techniques of Child Study, describes this isue using 
mathematics as an example: 
 
As children develop they may employ strategies or proceses that 
either were simply not available earlier or were used inappropriately. For 
example, most 3- and 4-year-olds cannot answer questions like ?5 + 3 = ??, 
where as 7- and 8-year olds do so readily. The nature of developmental 
change here is that older children have acquired a set of rules for 
addition?that younger children simply do not have?  Older children 
might solve such problems more efectively than younger children, 
because they are able to hold and manipulate more information at one time 
than younger children?  The speed of specific proceses may increase 
with age in a way that enhances performance. (Vasta, 1982, p. 212-213) 
 
 
 44 
1.5.11 Design Proces 
The main point of this thesis is to outline a design proces, which can guide other 
designers in designing medical tools that ofer improvements over earlier tools. To 
develop such an outline, it is important to study the design proces. 
Mike Baxter, author of Product Design: Practical Methods for the Systematic 
Development of New Products, describes thre key concepts for a succesful design 
proces: 
 
1. Establish aims and scope for concept design 
Diferent design projects wil have very diferent objectives and 
constraints determining how radical or incremental the concepts need to 
be. These must be clearly established with guidance from the opportunity 
specification. 
 
2. Generate lots of concepts 
Concept design is usualy considered to be the creative heart of the design 
proces. As a result, creative idea generation techniques are used most 
often at this stage. Several techniques exist for the force-generation of 
new product concepts. These are likely to increase the number of ideas 
generated from a few to many tens or even hundreds of concepts. 
 
3. Select the best 
Concept selection techniques select the best concepts against criteria 
derived from the opportunity specification. Probably more importantly, 
 45 
they provide a framework for hybridizing and expanding the range of 
concepts generated initialy. Concept selection can, therefore, comprise a 
highly creative and invaluable conclusion to the concept design proces. 
(Baxter, 1995) 
 
These points are used in the design proces of this thesis in ways that are 
discussed later. 
Tim Brown, CEO and president of IDEO, one of the world?s leading product-
design firms, wrote an article caled ?Strategy by Design? for the magazine Fast 
Company. Brown has two specific tips that are very relevant to this research. The first is 
caled ?Hit the Strets?: 
 
Any real-world strategy starts with having fresh, original insights 
about your market and your customers. Those insights come only when 
you observe directly what?s happening in your market. As Jane Fulton 
Suri, who directs our human-factors group, notes in her book Thoughtles 
Acts? (Chronicle Books, 2005), ?Directly witnesing and experiencing 
aspects of behavior in the real world is a proven way of inspiring and 
informing [new] ideas. The insights that emerge from careful observation 
of people?s behavior? uncover al kinds of opportunities that were not 
previously evident.? 
 
Tim Brown also goes on to explain a strategy caled ?Build to Think?: 
 46 
 
Design thinking is inherently a prototyping proces. Once you 
spot a promising idea, you build it. The prototype is typicaly a drawing, 
model or film that describes a product, system or service. We build these 
models very quickly; they?re rough, ready, and not at al elegant, but they 
work. The goal isn?t to create a close approximation of the finished 
product or proces; the goal is to elicit fedback that helps us work 
through the problem we?re trying to solve. In a sense, we build to think? 
It?s a proces of enlightened trial and eror: Observe the world, identify 
paterns of behavior, generate ideas, get fedback, repeat the proces, and 
keep refining until you?re ready to bring the thing to market. (2007) 
 
As mentioned earlier, this thesis? design proces is also based on the design 
proces used by Apple, the company that designs Macintosh computers and iPods. Apple 
is known for continualy churning out innovative designs. Helen Walters (2008) says that 
many companies try to understand design in the way that Apple does, but fal short. 
Busines Wek highlighted her blog on their innovation web site. In this blog Walters 
details a presentation at South by Southwest (SXSW), by Michael Lopp, senior 
engineering manager at Apple. Walters quotes Michael Lopp?s answer to the question, 
?How the f*ck do you do that?? 
Lopp answered that question with elements of Apple?s design proces. There are 
two elements that are particularly relevant to this research. The first is caled ?10 to 3 to 
1?: 
 47 
 
Apple designers come up with 10 entirely diferent mock ups of 
any new feature. ?Not,? Lopp said, ?seven in order to make thre look 
good,? which sems to be fairly standard practice elsewhere. They?l take 
ten, and give themselves room to design without restriction. Later they 
whitle that number to thre, spend more months on those thre and then 
finaly end up with one strong decision. (Walters, 2008) 
 
The other element is caled the ?Pony Meting?. Walters says: 
 
This refers to a story Lopp told earlier in the sesion, which 
described the proces of a senior manager outlining what they wanted 
from any new application: ?I want WYSIWYG?I want it to support 
major browsers?I want it to reflect the spirit of the company.? Or, as 
Lopp put it: ?I want a pony!? He added: ?Who doesn?t? A pony is 
gorgeous!? The problem, he said, is that these people are describing what 
they think they want. And even if they?re misguided, they, as the ones 
signing the checks, realy cannot be ignored. 
The solution, he described, is to take the best ideas from the paired 
design metings and present those to leadership, who might just decide 
that some of those ideas are, in fact their longed-for ponies. In this way, 
the ponies morph into deliverables. (Walters, 2008) 
 
 48 
1.5.12 Concluding the Literature Review 
With the detailed information collected from these knowledgeable writers and 
researchers, one is beter equipped to redesign the dental handpiece with improved 
ergonomics for the dentists and a focus on eliminating fear that children asociate with 
this dental tool. One must understand considerations for the tool, the user, the recipient, 
and the ergonomics involved to create an improved design. This review details these 
considerations, except for the user, who wil be explored further with interviews that are 
discussed later in this thesis. 
The research that has already been discussed revealed what could and could not 
be done with this redesigned handpiece. For instance, in interviews with dentists that wil 
be discussed later, the sound of the dril is often cited as a significant factor that 
contributes to pediatric patients? fear of the dental office. The research of sound proofing 
and reduction discussed earlier revealed that reducing the sound of the dril would require 
an addition of weight and spatial volume, which would make the dril more dificult for 
dentists to work with. 
What the research revealed that could be acomplished with this redesign 
included these things. First of al, silicone grips can be used in order to improve thre 
problems. The silicone wil add color to the dril, making it more appealing and les 
intimidating to children. Silicone grips are also soft, which creates a more ergonomic 
grip. The silicone rubber also gives dentists a beter grip on the tool. The interviews 
mentioned later revealed that during use, the dental dril becomes covered in saliva and is 
very dificult to get a firm grip on. By using a silicone rubber grip with grooves to 
 49 
channel the saliva away from where dentists grip the tool, dentists can have the firm grip 
that they desire. 
 
1.6 Definition of Terms 
Capitulum is ?a rounded protuberance of an anatomical part as (a) the knob at the end of 
a bone or cartilage (b) the beak of a tick composed of the mouthparts and palpi? 
(Meriam-Webster?s Medical Dictionary, 2008). 
 
A cavity (also known as a cary) ?is a hole in the enamel (the outer very hard part of a 
tooth). These holes are created by plaque, which forms a ?film of bacteria? on teth. This 
bacterium creates acid as a byproduct of its metabolism. This acid is what eats holes in 
the enamel of teth? (Gordon, Jery, 2000). 
 
Cementum ?covers the roots of the tooth beneath the gum line? (Gordon, Jery, 2000). 
 
Dorsiflexion is ?flexion in a dorsal direction, especialy flexion of the foot in an upward 
direction? (Meriam-Webster?s Medical Dictionary, 2008). 
 
Dental Pulp is located beneath the dentin. It is ?a vascular tisue, composed of 
capilaries, larger blood vesels, connective tisue, nerve fibers, and cels including 
odontoblasts, fibroblasts, macrophages, and lymphocytes.? During growth and 
development it is used to nourish the tooth, but as an adult tooth it is only used to indicate 
problems. This is acomplished through pain (Gordon, Jery, 2000). 
 50 
 
Dentin is located beneath enamel and cementum. It is made of the same substance as 
bone and includes nerve endings (Gordon, Jery, 2000). 
 
Enamel is the outermost layer of the tooth just above the gum line. This is the hardest 
and most mineralized part of the body (Gordon, Jery, 2000). 
 
Epicondylitis is also known as Tennis Elbow. This is an injury caused by persistent 
rotation of the wrist during use of a hand tool (McCormick & Sanders, 1982). 
 
An explorer is a tool that dentist use by scraping along teth to find cavities (Gordon, 
Jery, 2000). 
 
The handpiece, also known as the dental dril, is ?a smal, high-speed dril used in 
dentistry to remove decayed tooth material prior to the insertion of a dental filing.? It is 
used to treat dental caries (cavities) (Wikipedia, 2007). 
 
The humerus is ?the longest bone of the upper arm or forelimb extending from the 
shoulder to the elbow, articulating above by a rounded head with the glenoid fossa, 
having below a broad articular surface divided by a ridge into a medial pulley-shaped 
portion and a lateral rounded eminence that articulates with the ulna and radius 
respectively, and providing various proceses and modified surfaces for the atachment of 
muscles? (Meriam-Webster?s Medical Dictionary, 2008). 
 51 
 
Internal friction occurs when ?some absorptive materials have resilient fibrous or 
porous structures, which create a disipation of energy, not only from the viscous flow 
losses, but also from the internal friction of the material itself? (Forman, 1990). 
 
Panel vibration is an ?increase in low-frequency absorption that is obtained by mounting 
the absorption material at a suitable distance from the wals of a room. This is because 
the energy in the low-frequency incident sound causes the material to vibrate like a panel. 
When that happens some energy is removed from the incident sound wave. (For 
example, drapes should be hung away from a wal, not touching it, if it is desired to 
increase the low frequency absorption of the drape)? (Forman, 1990). 
 
Pronation is an inward rotation of the forearm (turning the palm downwards) (Pheasant, 
1996). 
 
The radius: ?the bone on the thumb side of the human forearm, (or on the coresponding 
part of the forelimb of vertebrates, which are above fishes in the evolutionary scale) in 
humans is movably articulated with the ulna at both ends so as to permit partial rotation 
about that bone. The radius bears on its inner aspect, a prominence, somewhat distal to 
the head, for the insertion of the biceps tendon. The distal end of the radius has a 
broadened area for articulation with the proximal bones of the carpus, so that rotation of 
the radius involves the hand? (Meriam-Webster?s Medical Dictionary, 2008). 
 
 52 
Scaler is a ?dental instrument for removing tartar from teth? (Meriam-Webster?s 
Medical Dictionary, 2008). Its sharp tipped hook is the scaler?s defining characteristic. 
 
?Soundproofing is any means of reducing the intensity of sound with respect to a 
specified source and receptor? (Wikipedia, 2007). 
 
Supination is an outward rotation of the forearm (turning the palm upwards) (Pheasant, 
1996). 
 
Viscous Flow is a sound absorber which ?consists of a series of interconnected pores and 
voids through which sound waves propagate. During propagation, the particle velocity 
asociated with the sound wave causes relative motion betwen the air molecules and the 
surrounding material. As a result, friction generates heat, which is disipated into the 
atmosphere as lost energy from the sound wave? (Forman, 1990). 
 53 
CHAPTER 2 
DEVELOPMENT PROCES 
 
Every wel-designed product goes through a thorough design proces. Michael 
Lopp, senior engineering manager for Apple, describes how Apple produces one 
succesful design after another. What he describes as their factor for succes is Apple?s 
design proces. 
Though the proces used in this thesis is not identical, it is based on Apple?s 10 to 
3 to 1 design proces. Acording to Michael Lopp, Apple requires their designers to 
come up with 10 completely diferent concept mock-ups of each new feature or concept. 
From that 10, thre are selected to continue development. The designers spend a few 
months working on those thre, which are later narowed down to one concept which wil 
be further developed (2008). As mentioned before, the 10 to 3 to 1 proces is the basis 
for the proces writen about and exemplified in this thesis through the redesign of the 
dental dril. 
The design proces of this thesis is also based on Mike Baxter?s thre key 
concepts of design proces, which were discussed earlier: Establish aims and scope for 
concept design, Generate lots of concepts and Select the best (1995).
 
 
 
 54 
2.1 Observation 
Once a product has been chosen for redesign it is important that the designer 
become as familiar with the product and user as possible. In the article writen by Tim 
Brown, CEO and President of IDEO, he quotes IDEO?s director of human-factors group, 
Jane Fulton Suri. Suri said, ?Directly witnesing and experiencing aspects of behavior in 
the real world is a proven way of inspiring and informing [new] ideas. The insights that 
emerge from careful observation of people?s behavior?uncover al kinds of 
opportunities that were not previously evident.? This is typicaly best achieved by user 
interviews and product usage observation (2007).  
 
2.1.1 User Interviews 
To understand a product one must understanding the users, how the users perceive 
the product, what the users like about the product and what the users dislike about the 
product. It is also important to listen to what the users claim they want and distil that 
information down to the benefits that they realy want.  This is described in Michael 
Lopp?s speech that was mentioned earlier (2008). This senior engineering manager for 
Apple described metings with leadership figures above him in the company. These 
leadership figures would describe what they want from the designers. Michael summed 
up these great, yet unrealistic, ideas that they ask for as ?I want a pony!? ideas. Lopp 
mentions, ?Who doesn?t? A pony is gorgeous!? Helen Walters, who wrote the article 
about Lopp?s speech, describes Lopp as saying, ?The problem?is that these people are 
describing what they think they want.? Lopp?s solution is to take the ideas that the 
designers have, and the ideas that the upper management has, then fit these ideas together 
 55 
in a way that alows him to give upper management realistic deliverables. These 
deliverables may be very diferent than the ?pony? ideas, but they offer the same benefits. 
This way upper management may not get the exact ponies that they asked for, but they 
get the benefits they are looking for in a more realistic package that can be manufactured 
(Walters, 2008). Interviewing users should be approached in much the same way. Listen 
to what users claim they want, and then use that to figure out the benefits that they are 
realy looking for. The next task is to find realistic ways to deliver those benefits. 
This thesis began with interviews of four dentists ofices and one orthodontist?s 
office. 6 dentists were interviewed, Dr. Arthur Caroll, Dr. Laura Durham, Dr. Jan 
Elington, Dr. Bennie Evans, Dr. Chuck Lindsey and Dr. Brian Roehl, along with two 
registered dental hygienists Daye Blackmon and Fran Shaddix.  
 
 
Figure 15. The diferent dental ofices being visited 
 56 
 
The interviews provided a list of concerns involved with the dental dril. That list is 
as follows: 
? The sound is very intimidating 
? The dril?s appearance resembles a knife 
? The handle is too thin 
? Multiple color choices would ofer beter variety in the office 
? Neds beter grip 
o Slips under ideal conditions 
o Very slippery with use of gloves 
o Even worse when wet (dental drils are typicaly wet with 
saliva when in use) 
? Cleaned by high presure, high temperature steam 
? Acording to cleaning device manual (autoclave 
manual), handpieces must, for 12 minutes, withstand 134 
degres C steam that has been presurized to 216 kPa. 
? Cords can hinder work 
o Cords tangle 
o Curly Cords exhibit even more tangling problems 
o A cordles dental dril would be great 
o Long hand pieces weigh down the back end throwing off 
the balance of the tool 
? Smaler and lighter is always beter (les fatigue) 
 57 
 
Al of these things are considered during the design proces to guide this new 
handpiece in the right direction. 
 
2.1.2 Product Usage Observation 
User interviews are not enough. Often users do things that they are not conscious 
of. These unconscious acts are often revealed through field studies. 
In order to fully understand the handpiece and the entire proces that surrounds its 
use, dentists were observed using the drils to prepare teth for filings and crowns. 
During this time, pictures are taken as documentation for further study later. Thre dental 
offices mentioned earlier are visited and five patients are observed. 
 
 
Figure 16. Usage observations 
 58 
 
An in depth study of the pictures taken reveals the many diferent ways that 
dentists hold dental drils. This study reveals that dentists use not only the precision grip, 
but sometimes use a combination of both the precision grip and the power grip mentioned 
earlier. Dentists use the tip of their pointer finger and thumb for the precision grip, and 
sometimes use other fingers to brace or to apply force. This study also reveals that 
dentists tend to hold the dental dril in two diferent locations on the handle. They either 
hold it close to the head and in front of the bend in the handle, or further back, just behind 
the bend in the handle. Plus, when working on the upper teth, dentists tend to sit behind 
the patient?s head and use the dental dril upside down. Also, the dental dril is often 
rotated with the fingertips to get the perfect angle for the job. 
After analyzing the information collected from interviews and observations it is 
time to implement Mike Baxter?s first key concept, ?Establish aims and scope for concept 
design? (1995). The problems need to be clearly defined at this stage. Once that is done, 
it is important to decide which problems reveal realistic opportunities for innovation. 
Finaly, that information should be used to define the aims and scope for the new concept 
design.  
 
2.2 Product Conceptualization 
Once the aims and scopes are clearly defined it is time to implement Mike 
Baxter?s second key concept of design proces, ?Generate lots of concepts? (1995). The 
field data mentioned earlier is used to create numerous concepts.  
 59 
Mock up models are also an esential part of the design proces. As mentioned 
earlier, Tim Brown, CEO and President of IDEO, describes the importance of mock-ups 
in an article caled ?Strategy by Design? which was published by Fast Company: 
 
?The prototype is typicaly a drawing, model, or film that describes 
a product, system or service. We build these models very quickly; they?re 
rough, ready, and not at al elegant, but they work. The goal isn?t to create 
a close approximation of the finished product or proces; the goal is to 
elicit fedback that helps us work through the problem we?re trying to 
solve. In a sense, we build to think. [This is] a proces of enlightened 
trial and eror: Observe the world, identify paterns of behavior, generate 
ideas, get fedback, repeat the proces, and keep refining until you?re 
ready to bring the thing to market.? (2007) 
 
 At this stage sketching is useful because sketching has few limitations. The idea 
is that a designer can sketch whatever can be conceived in the mind. Some designers go 
straight to computer modeling, but this is a problem because the tools used for computer 
modeling are more restrictive than a writing utensil and paper. It is also slower than 
sketching. These two factors restrict the conceptualization proces. The designer needs 
sketches to quickly record and visualize ideas. The idea here is to create as many 
concepts as possible without restriction. Thumbnail sketches are used to provide a quick 
?snapshot? of form or detail ideas. 
 
 60 
 
Figure 17. Thumbnail sketches 
 
 Preliminary sketches are often drawn based on thumbnail sketches. They are 
typicaly larger and provide more detailed information. 
 
 
 61 
 
Figure 18. Refined preliminary sketches 
 
 
 62 
2.3 Preliminary Ergonomic Models 
Since the dental dril is a hand tool, it is important to study its ergonomics during 
the design proces. It is very important that the new model has ergonomics that are equal 
to, if not beter than, the ergonomics of existing handpieces. 
This is when Mike Baxter?s third key concept of design proces, ?Select the best? 
is used for the first time (1995). Initialy the top 8 sketches are chosen and built as rough 
clay models. These models are not intended to be finished appearance models. They are 
models used to determine which designs are generaly more ergonomic. The ergonomics 
that are examined include comfort and maneuverability. They are much like rough 3-D 
sketches. This is done to wed out some of the les practical ideas before user testing. 
 
 
Figure 19. Clay ergonomic models 
 
In the case of the existing dental dril there are thre pronounced ergonomic 
problems. These problems include grip control, visual fedback and balance. The grip is 
 63 
typicaly slippery because it is a smooth metal grip covered in back spray and saliva. 
Visual fedback is hindered by the large size of the dril?s head. The balance is thrown 
off by the hose which puts exces pull on the back end of the tool, creating more fatigue 
on the user?s hand and wrist during operation. 
After holding and simulating using the clay models it is determined that the two 
models with a large rear mas (shown in Figure 19) had very poor balance. The two 
models that wrap over the top of the hand proved to hinder maneuverability. They also 
were not universal enough to be used by both right handed and left handed people. The 
model in the bottom left corner of Figure 19 exhibited poor balance. 
The thre models circled in Figure 19 al exhibited reasonable balance and 
maneuverability. They also proved to be good universal solutions for both left handed 
and right handed users. With that in mind, Mike Baxter?s concept ?Select the best? 
(1995) is implemented once again, narowing the 8 concepts down to thre top concepts. 
 
2.4 Secondary Ergonomic Models 
After creating rough clay models it is time to create more refined ergonomic 
models to put into the hands of the users, in the case of this study, dentists. Clay is great 
for the preliminary ergonomic models, but a more solid material is necesary for the 
secondary models and user testing. Though the ability to change the models shape 
quickly and easily was great for the previous stage, it is important that the shape does not 
shift during the user testing of this stage. If the models inadvertently change shape in the 
users? hands during testing, it wil be dificult to atain acurate fedback from users. 
That is why this stage requires a model material that is more solid than clay. 
 64 
MDF (medium density fiberboard) is chosen as the secondary ergonomic model 
material. It is hard enough to hold the same shape through the user testing of 5 dentists, 
yet soft enough that the shape can be carved out with a dremel. It is also an inexpensive 
material that is easy to come by. The best material for the job wil change with the job 
and situation. 
 
 
Figure 20. Secondary ergonomic models 
 
It is now time for the first testing method, user testing. After the models are 
produced, they are taken to 5 dentists, Dr. Arthur Caroll, Dr. Laura Durham, Dr. Jan 
 65 
Elington, Dr. Bennie Evans and Dr. Brian Roehl. The doctors are asked to hold the 
models, play with them, simulate using them and then talk about their thoughts on the 
models. What do they like? What do they dislike? Is it comfortable? What can be 
improved? Which model is their favorite? Which model do they dislike the most? 
Two of the thre models are intended to be cordles (se Figure 20). Those two 
models have larger, heavier back ends to alow space and weight for extra components 
that are required to go cordles. The first thing learned about those two models is that the 
heavy weighted back end is too heavy and would interfere with work. They would also 
wear down dentists? wrist muscles more than present dental drils. They also suffered 
balance isues. The bent cordles model had poor rotational balance. The straight 
cordles model puts more leverage on the dentists? hands because the weight on the back 
end was so high.  
Moreover, it is discovered that there are already low speed cordles handpieces 
for sale and in use, though not widely used. This may be due to the heavy weight of the 
batery. Cordles high-speed handpieces have been tried too. As mentioned before, drils 
that operate at high-speeds require presurized water to cool the tooth while driling. 
This prevents nerve damage. As for cordles high-speed drils, there is no technology 
that can deliver presurized water from such a smal tool without the use of a cord. 
Dentists overwhelmingly prefered the corded concept (se Figure 20) because of 
the smal size, lightweight and slek shape. The main complaint is that the diameter of 
the handle is too smal, an easy adjustment for the next model. With this input, it is time 
to use Baxter?s third concept, ?Select the best,? (1995) one last time and narow down to 
the beter of the thre concepts, then move on to the next stage. 
 66 
2.5 Third Generation Ergonomic Model 
It is now time to build an exact ergonomic model of the corded concept. User 
suggestions should also be considered and analyzed in order to find adjustments that 
should be made to the concept.  This new model neds to go through user testing, just 
like its thre predecesors, for final suggestions from the users. 
Before building the model it is necesary to draw a few more sketches to refine 
the concept, which is a good demonstration of how some steps should be repeated 
throughout the proces as needed. 
 
 
Figure 21. Refining sketch 
 
The precise ergonomic model is drawn in Rhino (a 3-D computer aided designing 
software), then transfered to a computer-controled miling machine. The model was 
miled from HDPE plastic. The model is given the appropriate weight by adding metal 
pelets to the interior. 
 67 
Once the model is properly weighted and finished, it is time for user testing. The 
same dentist offices are visited again and the exact same user testing method is used 
again for the last ergonomic model. 
 
 
Figure 22. Third generation ergonomic model testing 
 
The user testing proves that the refinements are paying off. The dentists love the 
latest model with only two complaints. The first complaint is that the handle diameter is 
stil a bit too smal and the second complaint is that the weight balance is too far back. 
The handle thicknes is, again, easily adjusted. The balance is due to a model building 
restriction. Due to the smal form factor and lightweight building materials, it was not 
 68 
possible to properly balance the model, which leaves les acurate fedback, though the 
fedback is acurate enough for the purposes of this study. 
 
2.6 Questionnaires 
Though it is important to work closely with a few dentists in order to get detailed 
fedback, at some point it is important to get more general fedback from a larger number 
of dentists. This helps to make sure that the design is not just designed specificaly for a 
few dentists, but it is designed for a broad range of dentists. It is also important to survey 
a broad number of children for the same reasons. The target is 300 hundred responses for 
each group, the dentists and the children, to make sure that substantial fedback is 
collected. 
 
2.6.1 Surveying Users 
First the users are surveyed, which for this study, are the dentists. These surveys 
are a bit les chalenging than the children?s survey. Communication with adults who 
have profesional dental education is much easier. The survey can ask questions very 
directly and precisely. The only chalenges in surveying dentists is making sure that the 
language of the questions and answers is short, clear, to the point and unbiased. 
Surveying children has these same chalenges and many others that are discussed later. 
 
2.6.1.1 Anticipated Outcome 
Before administering the survey, certain results are anticipated. First, it is 
anticipated that a vast majority of dentists wil point to children as the patients that are 
 69 
most fearful of the dental office. As for asking, ?What was the most significant 
contributing factor to patients fear?? it is anticipated that about 30% of dentists wil 
indicate the dental dril, while the most common answer wil be bad experiences with a 
dentist. When asking dentists, ?Do fearful patients hinder work?? 90% or more are 
anticipated to agre. Fewer are expected to atribute a significant amount of this fear to 
the dental dril, though a majority of dentists are stil expected to agre with the dril 
being a significant factor. When asked if a dril with a friendlier appearance would help, 
the percentage of dentists expected to agre drops out of the majority, but is stil expected 
to be a significantly large percentage of agreing dentists. It is also anticipated that the 
majority of dentists wil select that 21-40% of their patients are afraid of the dental dril. 
As for the new design, it is expected that about 80% of dentists wil like the rubberized 
grip and about 20-30% to like the idea of a lighter, colorized plastic handle. 
 
2.6.1.2 Statistical Findings 
Before talking about how dentists responded to the survey, it is important to 
mention how many dentists responded to the survey. The target is to collect 300 dentist 
responses. Unfortunately, after much hard work, only 9 responses are collected. It is 
suggested that designers stil strive for 300 user responses. With that in mind, even 
though the target has not been reached, 9 responses are enough to give some indication of 
how dentists fel. Here are the results of how those dentists responded to the 
questionnaire.  
66% of dentists said that the patients most fearful of the dentist ofice are under 
the age of 10. This is certainly a majority, yet a bit smaler percentage than was 
 70 
expected. When dentists are asked what they think is the main contributing factor to 
patients? fear, the anticipated results are close. The responses to this question are broader 
than anticipated, though. The most common response is bad experiences with previous 
dentists, which is mentioned by thre of the nine dentists. Only one dentist mentions the 
dril, while two indicate the fear of pain. On the other hand, when they are directly asked 
if they fel the dental dril is a significant contributing factor to patients? fears, 77% of 
dentists agred that it is. This indicates that the dril may not be patients? main fear, but it 
is certainly a significant contributing factor to their fear. After fearful patients were 
watched during part of the observation stage, it is anticipated that the vast majority of 
dentists wil agre that fearful patients hinder their work. 55% of dentists fel this way, 
acording to the survey results. It was expected that there would be more agrement on 
this topic, but 55% is stil a substantial number of dentists. It is also surprising to se that 
the same number of dentists that fel the dental dril is a significant contributing factor, 
also fel that a dril with a friendlier appearance would help calm fearful patients. This 
included 7 out of 9 dentists. When asked what percent of their patients fear the 
handpiece, four of the dentists say les than 21% while 5 of the dentist claim over 20%. 
Two of those dentists even go as far as to say over 40% of their patients fear the dental 
dril. 
 
 71 
 
Figure 23. Average age of fearful patients 
 
 
Figure 24. Dental dril?s contribution to fear 
 72 
 
 
Figure 25. Friendlier drils could calm patients 
 
When asked about concepts involving the new design, a surprisingly high number 
of responses in favor of the new ideas are received. Not a single dentist is against a 
rubber grip, while only one dentist out of the nine is against using a plastic dental dril. 
Five of the dentists are in favor of the rubber grip and surprisingly; six dentists are in 
favor of trying a plastic dental dril if it means more color options and les weight. 
 
 73 
 
Figure 26. Aceptance of the silicone grip 
 
2.6.2 Surveying Patients 
The tool is ergonomicaly corect and has the approval of several users (dentists). 
Now it is time to se what the patients think about it and se what adjustments can be 
made in order to please them. This step is a bit more chalenging since the idea here is to 
work specificaly with pediatric patients, otherwise known as children. Soliciting adult 
opinions takes some skil, but soliciting information from children is even more 
chalenging for many reasons. John Touliatos and Norma H. Compton, authors of 
Approaches to Child Study, describe some of the dificulties of surveying adults: 
 
 74 
Among the limitations of questionnaires are the diversity of 
meaning that may be atributed to a question by various respondents, the 
amount of education that may be required of a person in order to 
understand the questions and procedures, the dificulty of securing valid 
personal or confidential information, and the uncertainty of whether an 
adequate number of responses wil be received to represent the population. 
(1983)  
 
The most prominent problem with gathering children?s opinions is that children?s 
reading, writing and comprehension skils are not as far developed as adults?. This makes 
communicating questions to them, as wel as figuring out the best way for children to 
communicate their answers, more chalenging. Ros Vasta (1982), the author of 
Strategies and Techniques of Child Study uses math as an example to explain this 
problem: 
 
As children develop they may employ strategies or proceses that 
either were simply not available earlier or were used inappropriately. For 
example, most 3 and 4 year-olds cannot answer questions like ?5 + 3 = ??, 
where as 7 and 8 year olds do so readily. The nature of developmental 
change here is that older children have acquired a set of rules for 
addition?that younger children simply do not have. (Vasta, 1982) 
 
 75 
Touliatos and Compton go as far as to say, ?Obviously, self-administered 
questionnaires cannot be used with young children.? Though this statement certainly 
holds some truth, this thesis sets forth to prove that it is not entirely true. It is certainly 
more dificult to collect useful data from self-administered questionnaires for children, 
but not impossible. With the use of graphics and the minimal use of text, helped along 
with reading questions out loud, children can be surveyed with such questionnaires, as is 
exemplified a bit further along in this thesis. 
Michael P. Ricards, author of The Making of the American Citizenry: An 
Introduction to Political Socialization, explains other dificulties in gathering children?s 
opinions. He describes dificulties that were encountered when trying to gather 
children?s opinions on politics. He wrote: 
 
First, some children (especialy tenagers) may not take the 
questionnaire seriously. Second, boys and girls often tend to regard the 
questionnaire as a ?test? and they are more likely to choose the answer 
they fel is correct rather than the one that most closely coincides with 
their felings. Third, the questionnaire by its very phraseology may be 
eliciting a specific response. (1973) 
 
Though the task is chalenging, it is important that children?s opinions are 
collected in order to design medical equipment that reduces apprehension in younger 
patients. This study does not involve surveying children one by one, though if a designer 
 76 
does have the time and resources for that, it is suggested. For those that do not, mas 
surveying can be efective. 
The problems of surveying children can be worked around by using more 
graphical pictures and les text. A picture is worth a milion words, and everyone knows 
how to read a picture, though a surveyor must be weary when using pictures. Pictures, 
much like words, can mean diferent things to diferent people. And as is the case with 
words on a survey, the only thing a survey writer can do about it is to make the pictures 
as simple, straightforward and clear as possible. Here is one of the surveys being used 
for this study, which exemplifies these principles. 
 
 77 
 
Figure 27. Survey administered to younger children 
 
 78 
Some text is stil used because it is impossible to make a survey that is purely 
graphical, while clearly stating the important points that this study needs to get across. It 
is more efective to make purely graphical answers than questions. In order to make the 
text easier for younger children, who could not read to understand, text is supplemented 
with related pictures and teachers read the questions to the children. The supplemental 
pictures help the children to follow along and beter understand what the teacher is 
reading to them. 
It is also important to note that questions number four and five on the first 
questionnaire are circle the answers, while they are fil in the blank for the second survey 
(shown in Figure 28.) Fil in the blank is a much more acurate way to acquire the 
information for this study, but with the understanding that there is no way for some of the 
younger children to fil in the blank with meaningful answers, younger children are given 
a simpler answering format. Therefore, fil in the blank questions are given to the older 
children who have no problem answering them, and simplified questions with circle the 
best answer are given to the younger children. Circle-shaped pictures are used to give a 
more intuitive indication that the answers are to be circled. 
 
 79 
 
Figure 28. Survey administered to older children 
 
 80 
After a great deal of time is spent developing and rewriting these surveys (much 
like any other design proces), plenty of copies are made and taken to Shades Cahaba 
Elementary School in Homewood, Alabama. There, 329 students are surveyed.  
 
2.6.2.1 Anticipated Outcome 
Before the surveys are administered, there are some anticipated outcomes, as 
follows. At least 90% of the students wil have sen the dentist, and about 30% wil not 
be comfortable at the dental ofice. It is anticipated that a majority wil dislike the dental 
dril, and that about 30% wil say the dental dril is what they like least at the dental 
office. As for the new design, it is anticipated that children wil be drawn to the new 
shape, softer textures and the introduction of color. 
 
2.6.2.2 Statistical Findings 
After the surveys are administered, collected, and tabulated, there are 329 
responses in total. 107 of those responses are kindergartners to 3
rd
 graders who took the 
survey without fil in the blank answers. 222 of the responses are 4
th
 and 5
th
 graders who 
took the survey with the fil in the blank answers. Out of those children, 97.6% have 
visited the dentist. The surveys also show that 48% of children are not comfortable at the 
dentist office. When the handpiece is introduced to the situation the percentage of 
children that fel comfortable drops by 33% and the number of children that fel 
uncomfortable quadruples.  
 
 81 
 
Figure 29. Comfort at the dental ofice 
 
 
Figure 30. Comfort around the dental dril 
 82 
 
The last part of the survey, which addreses the new design shows that the 
children prefer the new design to existing drils by 88.6%. The survey also reveals that 
61.9% of students are drawn in by the color, and 66% of students like the look of a 
lugged grip. 
 
Figure 31. Children prefer the new design 
 
 
Figure 32. Children prefer color 
 83 
 
There is no clear indication that the children are drawn to the shape or texture of 
the new dril, though there is also no indication that they dislike these atributes either. 
This may be due to the use of smal pictures that do not clearly communicate these 
diferences. 
 
2.7 Final Model 
Once thorough research has been done, and thorough development has been 
acomplished, it is time for the final model. This model should represent the final 
concept as realisticaly as possible. The model should look, fel and operate as much as 
possible like the concept tool would if it were in production. 
Building a working prototype is not in the scope of this project and therefore the 
final model for this study is a detailed appearance model. This is because it is unrealistic 
to build a working dental dril with the resources that are available, and because the final 
concept uses existing technology, there is litle need to prove that the concept would 
work. 
To build the final model a computer is used to ensure precision. There are final 
adjustments made to the last computer model, and then it is transfered to the computer 
controlled miling machine to be cut out of ren shape. Ren shape is used because it is a 
dense material that is more durable and has the ability to show fine detail. 
 
 84 
 
Figure 33. Model parts fresh off of the CNC machine 
 
After the CNC machine is done the parts are sanded and painted to simulate what 
the concept would look like if it were in production. The metal parts are painted to 
appear as metal, and the grip is painted to appear as a soft silicone rubber. A rubber tube 
is used on the back end to simulate the look and fel of having the dril connected to the 
compresor hose that dentists use to power such drils. The inside of the model is bored 
out to make room for weights. The weights are put into the model to simulate the weight 
and fel of a production model. For the final touch, a needle is used to simulate the 
appearance of the bur (dril bit) of the dental dril. With al of this work done, the model 
is a highly refined and a nearly exact representation of what a manufactured handpiece 
 85 
based on this new concept would look like and fel like. This model gives an acurate 
representation of many of the new concepts features that are explained in the next 
chapter. 
 
 
Figure 34. Final model 
 86 
CHAPTER 3 
CONCLUSION 
 
3.1 Results from Studies of Proces 
First of al, Apple?s 10 to 3 to 1 design proces gives a good foundation for 
building a design proces: build 10 mockup concepts, narow that to thre concepts, 
develop those further, then narow it down to the one best concept and develop that 
(Walters, 2008). It is not necesary that these numbers be followed exactly but they are a 
good guideline. A modified proces that might be described as a 100 to 8 to 3 to 1 
proces is used for this thesis. Apple?s proces is a very good one, but Lopp does not 
mention anything about the sketching that comes before mock up models, which is a very 
important element to the design proces. There are no constraints on what can be drawn 
on paper, so there are no constraints on the designer?s ability to imagine new concepts. 
As for the number 100, it is a general number that is meant to exemplify Mike Baxter?s 
key design proces concept ?Generate lots of concepts? and encourage designers to 
develop as many sketch concepts as possible before narowing them down to about 10 
concepts for mock up (1995). 
The research of this project also shows that user and patient fedback is 
invaluable as Tim Brown, CEO and president of IDEO, mentions when he cites their 
director of human factors group, Jane Julton Suri, as saying, ?The insights that emerge 
from careful observation of people?s behavior?uncover al kinds of opportunities that 
 87 
were not previously evident.? (Brown, 2007) It would have been impossible to come up 
with useful concepts without fedback from the five dentists that were interviewed and 
observed for this study. This project would not be able to satisfy the needs of dentists 
and improve the ergonomics without their fedback. The dentists are an important key to 
finding what areas of existing dental drils work wel and what areas need improvement. 
Patient fedback is also very useful in understanding what children like, but at the end of 
this study, it is clear that the children should have been interviewed earlier in the proces. 
About the time interviews with dentists began would have been about the time to start 
interviewing children. Their input is just as important as the dentists input for a design 
proces that is meant to increase ergonomics for dentists and reduce apprehension for 
young patients. Children should be interviewed early enough that their input, along with 
the doctors? input, could be used in the preliminary sketching and conception phase. 
 
3.2 Results from Studies of Design 
As for results pertaining to the new design, what is learned is that the dentists who 
were interviewed are drawn to the slek shape. On top of that, dentists are bothered by 
the tug of the hose atached to their handpieces. The tug interferes with their work and 
wears on their hand and wrist muscles. This is why the new design incorporates a bend 
to aleviate some of that tug. The swivel that rotates with the hose on the new dril 
ensures that the bend wil continue to bend down and operate, as it should, no mater 
what position the dentist uses the dril in. Studies revealed that this swivel could be made 
with existing technology for a reasonable price as wel. The Everything Dental catalogue 
offers swivels for dental handpieces that deliver the necesary presurized air and water, 
 88 
as wel as fiber optic lighting, for prices as low as $139.99. The same catalogue lists 
dental handpieces from$184.99 to $924.99. With the technology used in this design it 
could easily incorporate a fiber optic swivel and stil maintain a reasonably low priced 
handpiece. Studies also show that a silicone rubber grip could be added while holding 
this price point. Everything Dental lists silicone rubber scaler grips for $9.29 (Everything 
Dental, 2005). Theoreticaly, this new dental dril could be built and sold for a price 
below $250. At the price of $250, this new dril offers a silicone rubber grip that gives 
the tool a softer, more ergonomic handle for dentists, increases grip, and offers more 
color options in order to beter appeal to children. The dentists interviewed for this study 
complained that the grip of existing handpieces is one feature that could use 
improvement, and the survey of children revealed that children are clearly atracted to 
dental tools with color. 
 
3.3 The Final Concept 
 The final model and final concept incorporates a number of new features that 
solve problems that were cited by dentists during the initial interviews mentioned earlier. 
The intimidating appearance, which one dentist described as knife-like, is aleviated with 
a softer shape and form.  
 
 89 
 
Figure 35. Features 
 
The silicone grip gives dentists the thicker handle they desire as wel as a softer 
grip. This gives the new dental dril enhanced ergonomics. The silicone rubber grip also 
gives dentists the improved grip that they desire. The tacky grip of the rubber helps to 
improve the grip, as do the grooves in the rubber, which channel saliva and water away 
from the dentists? fingertips. The silicone rubber grip also alows color to be 
incorporated into the tool, which is a desired feature mentioned by dentists during the 
interviews. These colors are desired because they are more appealing to pediatric 
patients. The survey of children administered for this study showed that 63% of children 
prefered dental tools with color. To top it al of, silicone is a very durable rubber that is 
 90 
rated to withstand the extreme high temperatures that dental drils withstand every time 
they are cleaned. 
 
 
Figure 36. Color options 
 
Color can be added to more than just the rubber grip though. If the dril?s body is 
made of aluminum, which is a typical material for these tools, then the metal can be 
anodized to create more color choices as shown in Figure 37. 
 
 91 
 
Figure 37. Anodized color options 
 
 One other problem that this concept addreses is the tug of the hose on the back 
end of the dental dril. Dentists mentioned that this throws off the balance of the tool 
during use. The research mentioned earlier shows that creating a cordles dril is 
impractical, but there are other ways of aleviating this problem. This concept 
incorporates a downward bend on the back end of the dril where the hose ataches. This 
bend adjusts the angle of departure for the hose to be closer to the angle of the part of the 
hose that is fre hanging. With this improved angle the tug on the back of the dental dril 
is reduced. 
 Since the dental dril is held at many diferent angles during use, as demonstrated 
by the pictures of user observations (figure 16) shown earlier, it is important that this 
 92 
downward bend has some way to adjust itself. This adjustability should alow the bend to 
always bend downward, no mater how the dentist holds the dril. A swivel is 
incorporated into this design to do just that, as is demonstrated in Figure 38. 
 
 
Figure 38. Demonstration of swivel feature 
 
3.4 Study Acomplishments 
This study outlines a guideline for designing new medical equipment that wil be 
more ergonomic and more appealing for the doctors that use it, while also reducing the 
apprehension of the young patients that the tools are used for. This thesis streamlines the 
 93 
proces into a set of steps which are easy to understand and practice, and can be adapted 
to the redesign of any medical tool for doctors who work with pediatric patients. 
 
3.5 Areas for Further Study 
The scope of this study does not include developing a working prototype. One 
way to further this study would be to create a working prototype and create a comparison 
study that alows dentists to use the prototype and the leading existing dental drils. Such 
a study would reveal more details about the ergonomics and usability of the new design. 
Also, further study of how children fel about the final model, maybe with the use of 
larger pictures or by showing the model in physical form, may alow more fedback to be 
collected from young patients.  
Medical tools designed to reduce adult apprehension would also be another good 
subject to study. There may be a higher percentage of children that are afraid of any 
given medical tool, but children are not alone. Many adults also suffer fear of medical 
tools they come in contact with. 
With that said, the proceses and principles discussed in this thesis are a good 
guideline for the development of beter medical tools that wil be more ergonomic for 
dentists or doctors, and also les intimidating for children or adults. 
 94 
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Image Reference 
Figure 1. The anatomy of a tooth is an image from online source, retrieved March 11, 
2007, from http:/health.howstuffworks.com/cavity.htm 
 
 99 
Figure 2. Picture of a cavity is an image from online source, retrieved March 11, 2007, 
from http:/health.howstuffworks.com/cavity.htm 
 
Figure 3. X-ray of a cavity is an image from online source, retrieved March 11, 2007, 
from http:/health.howstuffworks.com/cavity.htm 
 
Figure 4. A dental handpiece (dental dril) has a file name of 
Dentalhandpiece0111-26-05.jpg. Image from online source, retrieved March 11, 
2007, from http:/en.wikipedia.org/wiki/Dental_handpiece 
 
Figure 5. Bur profile examples is a picture of page 109 from Dental Catalog (155th ed.) 
by Everything Dental. 
 
Figure 6. Anatomy of the wrist is a picture taken from page 285 of the book Human 
Factors in Engineering and Design Fifth Edition. Authored by McCormick, 
Ernest J., and Mark S. Sanders. 
 
Figure 7. Conventional pliers vs. ergonomicaly designed pliers is a picture taken from 
page 287 of the book Human Factors in Engineering and Design Fifth Edition. 
Authored by McCormick, Ernest J., and Mark S. Sanders. 
 
 100 
Figure 8. Using a finger strip to spread the load is a picture taken from page 291 of the 
book Human Factors in Engineering and Design Fifth Edition authored by 
McCormick, Ernest J., and Mark S. Sanders. 
 
Figure 9. Hand and handle interaction demonstration is a diagram from page 87 of 
Bodyspace; Anthropometry, Ergonomics and the Design of Work Second Edition 
authored by Pheasant, Stephen. 
 
Figure 10. Stephen Pheasant?s user-centered design is a diagram from page 6 of 
Bodyspace; Anthropometry, Ergonomics and the Design of Work Second Edition 
authored by Pheasant, Stephen. 
 
Figure 11. Grip types is a diagram from page 86 of Bodyspace; Anthropometry, 
Ergonomics and the Design of Work Second Edition authored by Pheasant, 
Stephen. 
 
Figure 12. Low cost silicone grips is a picture of page 473 from Dental Catalog (155th 
ed.) by Everything Dental. 
 
Figure 13. Fiber optic swivels for dental drils is a picture of page 319 from Dental 
Catalog (155th ed.) by Everything Dental. 
 
 101 
Figure 14. The generation of sound waves is a diagram from Sound Analysis and Noise 
Control by Foreman, John E. K. 
 
Figure 15. The diferent dental ofices being visited is a photo montage by Alex 
Reynolds. 
 
Figure 16. Usage observations is a photo montage by Alex Reynolds. 
 
Figure 17. Thumbnail sketches are sketches by Alex Reynolds. 
 
Figure 18. Refined preliminary sketches are sketches by Alex Reynolds. 
 
Figure 19. Clay ergonomic models is a montage by Alex Reynolds. 
 
Figure 20. Secondary ergonomic models is a photo taken by Alex Reynolds. 
 
Figure 21. Refining sketch is a sketch by Alex Reynolds. 
 
Figure 22. Third generation ergonomic model testing is a montage by Alex Reynolds. 
 
Figure 23. Average age of fearful patients is a graph created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 
 102 
Figure 24. Dental dril?s contribution to fear is a graph created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 
Figure 25. Friendlier drils could calm patients is a graph created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 
Figure 26. Aceptance of the silicone grip is a graph created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 
Figure 27. Survey administered to younger children is a survey created by Alex Reynolds 
to represent findings of a survey administered for the purposes of this thesis. 
 
Figure 28. Survey administered to older children is a survey created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 
Figure 29. Comfort at the dental ofice is a graph created by Alex Reynolds to represent 
findings of a survey administered for the purposes of this thesis. 
 
Figure 30. Comfort around the dental dril is a graph created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 
Figure 31. Children prefer the new design is a graph created by Alex Reynolds to 
represent findings of a survey administered for the purposes of this thesis. 
 103 
 
Figure 32. Children prefer color is a graph created by Alex Reynolds to represent 
findings of a survey administered for the purposes of this thesis. 
 
Figure 33. Model parts fresh off of the CNC machine is a photo by Alex Reynolds. 
 
Figure 34. Final model is a photo by Alex Reynolds. 
 
Figure 35. Features is a diagram by Alex Reynolds. 
 
Figure 36. Color options is a montage by Alex Reynolds. 
 
Figure 37. Anadized color options is a montage by Alex Reynolds. 
 
Figure 38. Demonstration of swivel feature is a montage by Alex Reynolds. 
 
Table 1. Absence of teth among U.S. adults is a table from Summary Health Statistics 
for U.S. Adults: National Health Interview Survey, 2005 By Center for Disease 
Control and Prevention. 
 
Table 2. Untreated dental cavities is a table from Summary Health Statistics for U.S. 
Adults: National Health Interview Survey, 2005 By Center for Disease Control 
and Prevention.