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LONG-TERM COMPARISON OF TREATMENT IMPACTS BETWEEN INVISALIGN AND
FIXED APPLIANCE THERAPY
AARON W. CARROLL
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
02007 Aaron W. Carroll
I thank the chair and members of my supervisory committee for their mentoring, the staff and
members at the UF Libraries for their keen research assistance, the participants in my surveys for
their honest and open participation. I thank Dr. Randol Womack for his assistance in enrolling
participants in my study.
TABLE OF CONTENTS
ACKNOWLEDGMENTS .............. ...............3.....
LIST OF TABLES ............ ..... .__ ...............5...
LI ST OF FIGURE S .............. ...............6.....
AB S TRAC T ......_ ................. ............_........7
1 INTRODUCTION .............. ...............8.....
2 MATERIAL AND METHODS ................ ...............10................
3 STATISTICAL ANALYSIS .............. ...............12....
4 RE SULT S .............. ...............13....
5 DISCUS SION ................. ...............16................
6 CONCLUSION ................. ...............18.................
A DAILY DIARY QUESTIONNAIRE ................. ...............19................
LIST OF REFERENCES ................. ...............21........... ....
BIOGRAPHICAL SKETCH .............. ...............23....
LIST OF TABLES
4-1 Group demographics data .............. ...............13__. .....
4-2 Group socioeconomic data and mean PAR scores. ............. ...............14.....
LIST OF FIGURES
4-1 Mean pain levels. ............. ...............14.....
4-2 Quality of life ........._..... ...............15._.._. .....
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
A LONG-TERM COMPARISON OF TREATMENT IMPACTS BETWEEN INVISALIGN
AND FIXED APPLIANCE THERAPY
Aaron W. Carroll
Chair: Timothy Wheeler
Major: Dental Sciences
A recent study found subj ects treated with Invisalign@ appliances reported significantly
less pain and negative impact on daily life during the first week of treatment than did subjects
treated with fixed orthodontic appliances. The aim of this study was to determine if these
differences persist throughout treatment. Eighteen of twenty-five subj ects, twelve to fifteen months
into treatment at the University of Florida College of Dentistry and at a private orthodontic
practice, completed one week surveys to measure the psychosocial and pain related impact of
orthodontic treatment with either Invisalign@ or fixed appliances. There were no significant
differences found between groups with respect to age, race, education, income or severity of initial
malocclusion. Also, no significant differences in pain levels or impact on daily life between the
two groups were reported. Based on a limited number of subj ects the results of this study suggest
that the higher pain levels and greater impact on daily life experienced during the first week of
treatment by patients treated with fixed appliances compared to those treated with Invisalign@ may
not persist throughout the duration of treatment.
Much of the orthodontic literature regarding orthodontic treatment with Invisalign@ is
limited to case reports, and descriptions of technique and mechanics. Few studies have compared
treatment with Invisalign@ to more traditional fixed appliances. Djeu reported Invisalign@
treatment to be less effective in occlusal and antero-posterior corrections in a retrospective study
based on a comparison of finished cases using the American Board of Orthodontics (ABO) scoring
methods. It was found that aligners were particularly effective in correcting rotations and marginal
ridge discrepancies, however. Plaque scores have been shown to be better in patients treated with
Invisalign@. 2 This was attributed to improved access for oral hygiene. Due to the weak evidence
in the literature and lack of randomized clinical trials, no strong conclusions can be made regarding
comparative treatment efficiency. 3
The orthodontic literature addressing the treatment experiences of orthodontic patients is
relatively limited. 4 Other than length of treatment, pain is the most frequent complaint during
orthodontic treatment. 5,6 This pain has been described as being more severe than the pain
experienced following dental extractions. The pain experience following initial appliance
placement or activation has been shown to follow a certain pattern, peaking at approximately 24
hours, then returning to baseline levels in five to six days. 5,7-12 A diurnal rhythm has also been
shown to exist, with pain levels decreasing during the day and then peaking each night, although
to a lower level then the previous night. Although different force levels are discernable by
patients for the first few days, increased force levelS10,13 have been shown not to affect pain
levels. Increased severity of malocclusion has been shown not to be a significant factor either. 14
Besides pain and discomfort, orthodontic appliances have additional impacts on the daily lives of
patients. Difficulties in eating, swallowing, speech and socializing have been reported with both
Eixed and removable appliances. 9,15-18 Patient anxiety, acceptance of and attitudes towards
treatment are the most significant factors contributing to these sequelae. 18,19
With the continuing growth in demand for more esthetic appliance systems such as
Invisalign@, it is important for orthodontists and patients to have sufficient information
regarding the impacts these new appliances will have on patients in order to support informed
decisions and realistic expectations of treatment. 20 Millerll reported that patients treated with
Invisalign@ experience less pain and discomfort and fewer psychosocial and functional impacts
than do patients treated with Eixed appliances. This study specifically examined the first week of
treatment, generally agreed upon in the literature to be the time period in which these impacts are
the greatest. Long-term studies however are lacking. Nedwed21 TepOrted patients adapt well to
Invisalign@ over the first three to six months. Functional and psychosocial aspects over this time
period diminished significantly although mild pain recurred with each new aligner in
approximately half of the patients, and severe discomfort in a few. Long-term adaptation has
been reported in fixed appliance treatment as well. Sergll" reported good adaptation to both fixed
and removable appliances. A greater number of long-term complaints were reported in patients
treated with removable appliances. The better adaptation to fixed appliances was not attributed to
the appliances themselves but rather to the patients' attitudes towards them.
The aim of this study was to determine whether or not the benefits of Invisalign@ treatment over
fixed appliance treatment with regards to pain, psychosocial and functional impacts persist
throughout the treatment period.
MATERIAL AND METHODS
A prospective, longitudinal cohort study was completed using daily diaries (Figure 2-1)
to measure the psychosocial and functional impacts of orthodontic appliances over a seven day
period, twelve to fifteen months into treatment with Invisalign@ or straightwire Eixed appliances.
Subj ects were recruited from the private practice of an orthodontist in Arizona and from the
University of Florida Orthodontic clinics. The Institutional Review Board of the University of
Florida approved the study, and participants provided written informed consent.
Subj ects for the study were selected by asking all patients meeting the inclusion criteria
over a one year period if they would like to participate at the beginning of their regularly
scheduled appointments. The inclusion criteria were (1) Upper and lower dental arches must be
treated; (2) The Eixed appliances group must be treated with wires and brackets only (no quad
helix, Rapid Palatal Expander (RPE), etc); (3) Must be 12 to 15 months into treatment; (4) Must
be 18 years of age or older; (5) Must be willing to sign and give written informed consent in
accordance with institutional and federal guidelines; (6) Must be in good general health; and (7)
Premolar and incisor extraction cases were acceptable.
Twenty-Hyve adult subj ects agreed to participate in the study and complete the one week
daily diary. The diary measured impacts such as teeth soreness, soft tissue irritation, eating
problems and speech impairment. Baseline data was taken the day of the appointment just prior
to appliance adjustment or new aligner delivery. Informed consent was obtained and
demographic and socioeconomic data were collected at the appointment as well. Subj ects were
asked to begin the diary on the day after their appointment and fill it out each day at the same
time and then return it in the envelope provided. Subj ects were mailed a movie rental gift card
once their diary was received. Nineteen subjects returned completed diaries, seven male and
twelve female. Eight subj ects were being treated with Invisalign@, ten were being treated with
fixed appliances, and one subj ect was being treated with Invisalign@ in one arch and fixed
appliances in the other. This patient was excluded from the analyses.
The diary questionnaire form (Appendix A) was adapted from the well-validated Geriatric
Oral Health Assessment Index, 22 which was developed to measure the psychosocial impacts of
oral conditions. The daily diary questionnaire form consisted of 13 questions with ordinal
responses on a Likert scale, and one pain-related question using a visual analog scale (VAS). The
responses from the first 13 questions were summed to give a total 'impact score' for each subject.
The pain responses from the visual analog scale were used to give a more exact measure of pain
experienced during these seven days of therapy. The design of this study is similar to one
previously reportedly which examined these factors and variables during the first week of
treatment. Some but not all of the subj ects in the present study were participants in the prior study.
Because of the anonymity of the study design, direct long-term comparisons for these subj ects
were not possible.
The response variable measured was the impact of therapy as assessed with the daily diary.
Factors of interest were: treatment type (Invisalign@ or Fixed Appliances), time (days one through
seven after fixed appliance adjustment or new aligner delivery), and initial malocclusion as
accessed with the Peer Assessment Rating (PAR) index23 by the same calibrated investigator
(A.W.C.). Subj ects were not randomly assigned to treatment groups and the examiner could not be
blinded as to the treatment group because PAR scores were assessed on electronic casts. Casts for
patients in the Invisalign@ treatment group were ClinCheck files whereas the casts from the fixed
appliance group were OrthoCAD files.
The data was input and analyzed to determine relevancy and significance. Data from the
subject treated with both fixed appliances and Invisalign@ was omitted from the analyses. For
the purposes of group characteristic comparisons, non-Caucasian subj ect data was combined and
subjects with at least some college education were analyzed together. Initial power analysis
indicated an optimum sample size of one-hundred subj ects, fifty per treatment group. Due to the
relatively small sample size attained, variables were analyzed and groups compared by Fisher
exact and Wilcoxon rank sum tests.
Preliminary analysis (Tables 4-1, 4-2) showed that the Invisalign@ and fixed appliance
treatment groups were balanced with regard to age (Wilcoxon rank sum p=0.90), sex (Fisher exact
p=0.37), ethnicity (FE p=0.66) and level of education (FE p=0.64). Subjects treated with
Invisalign@ did report higher incomes than those treated with fixed appliances, however these
differences did not reach statistical significance (WRS p=0. 13). PAR scoring of pretreatment casts
revealed no significant group differences in severity of initial malocclusion (WRS p=0.20).
No significant group differences were present in baseline pain as measured on a visual
analog scale (VAS) or quality of life as measured by diary questionnaire Geriatric Oral Health
Assessment Index impact scores. During the week after new aligner delivery or appliance
adjustment, mean pain levels in both groups increased, peaking on day 1 or day 2 (Figure 4-1).
Pain levels in both groups returned to baseline levels by day 6 or day 7. No statistically significant
differences in pain levels were reported between treatment groups on any particular day during the
seven day period. Two subjects (20%) in the fixed appliances group and one subject (13%) in the
Invisalign@ group reported using an analgesic at some point during this week. Impact scores
quantifying the functional and psychosocial impacts of orthodontic appliances in both groups
dropped slightly on day 1, the day following the subj ects' appointments (Figure 4-2). Impact scores
quickly returned to baseline levels by day 3. There were no statistically significant group
differences in mean impacts scores found on any day of the survey.
Table 4-1. Group demographics data as reported on the Demographics Questionnaire
Age Sex Race
Mean SE Male Female Caucasian Hispamic Asian
Invi salign@ 30.225 3.442 2 6 1 5 1 1
Braces 30.920 3.620 5 5 2 5 2 1
P value p=0.90 p=0.37 p=0.66 (Caucasian vs. non-Caucasian)
Table 4-2. Group socioeconomic data and mean PAR scores
Education Income* Initial Malocclusion
Treatment High Some College
Mean SD PAR score SD
Group school College Graduate
Invi salign@ 0 5 3 3.75 1.753 20.00 7.792
Braces 1 3 6 2.50 1.958 24.90 9.550
P value p=0.64 (H. S. vs. College) p=0.13 p=0.20
*Income groups: 2=$10,000-24,999; 3=$25,000-49,999; 4=$50,000-74,999
o" o;" o~"
Figure 4-1. Mean pain levels. Mean (+ standard error) pain intensity scores for week following
appliance adjustment / new aligner delivery appointment, twelve to fifteen months
into treatment. Data was taken from question 2 on subj ect daily diary questionnaires
-* Invisalign -=- Fixed Appliances
Quality of life. Group means (+ standard error) measured by impact scores for the
week following appliance adjustment / new aligner delivery appointment. Scores
indicate the group means from the summed component totals of question 1 on the
daily diary questionnaires (Appendix A).
People seeking orthodontic treatment need to know and often inquire about what to expect
during treatment. Orthodontists need information at their disposal in order to help patients make
informed decisions when deciding to undergo treatment and when choosing between various
treatment options. Few studies have examined the functional and psychosocial impacts new
orthodontic appliances such as Invisalign@ have on patients. In a similar study"l conducted during
the first week of treatment, subjects in the Invisalign@ group reported a significantly lower
negative impact on daily life from day one through day seven with all p-values I 0.0001.
Nedwed21 TepOrted patients adapt well to Invisalign@ over the duration of treatment. Although
Invisalign@ appliances were not studied, Sergll" reported good adaptation to both fixed and
This study investigated whether or not the differences in negative impacts on patients'
daily lives found in a prior study persist in the long-term, throughout the duration of treatment. In
order to attain the desired sample size of one-hundred subj ects, the study design included the
recruitment of twenty subj ects, ten in each treatment group, from each of five locations around
the United States. Due to lack of interest by patients in three of the four private orthodontic
practices, subj ects were enrolled in this study from only the two locations. Only six patients
agreed to participate in the study from the remaining private practice. As a result of missed
appointments and discontinuation for or modification with fixed appliances of the limited
number of Invisalign@ cases at the university extending at least twelve months, only thirty of these
patients were asked to participate in the study. Despite little interest by patients in the study,
nineteen patients from the University agreed to participate. Twelve of these nineteen subj ects, and
five of the six subj ects from the private practice returned completed surveys.
When comparing impact scores after one year of treatment, impact scores in both
treatment groups dropped slightly the day after their braces were adjusted or new aligners were
delivered. Impact scores returned to baseline levels in a few days just as were the patterns during
the first week of treatment as previously reported. 11 However, in this study the Invisalign@ group
did not report significantly less negative impact than did the fixed appliance group, indicating that
long-term adaptation to appliances has eliminated any significant differences in quality of life
between the two treatment modalities.
The most frequently reported complaint and apprehension of orthodontic treatment
reported in the literature is pain and discomfort. 5,6 Subj ects in both treatment groups in this study
experienced the typical pattern of pain and discomfort over the seven day study period as has been
reported elsewhere pattern. 5,7-12 However, the subjects being treated with fixed appliances did not
experience significantly greater pain than did those treated with Invisalign@ as was found during
the initial week of treatment previously reported. 11 The results of this study suggest that, as was
found with other types of removable appliances," patients adapt to fixed appliances to the extent
that the benefits oflInvisalign@ over fixed appliances with regards to pain and discomfort do not
persist throughout the duration of treatment.
Based on a limited number of subj ects (N=18), the results of this study suggest that while
patients treated with Invisalign@ experience lower pain levels, psychosocial and functional impacts
initially, these benefits may be limited to the beginning of treatment and do not persist throughout
the duration of treatment. Further studies are necessary to confirm these results. Orthodontists can
utilize the results of this and prior studies to inform patients contemplating a decision between
Invisalign@ and braces. Patients can be told that while their apprehensions towards braces of
higher pain levels, greater psychosocial and functional impacts are well founded, the long-term
benefits oflInvisalign@ in these respects are not long-term as they will in all likelihood adapt well
to the appliances. Patients can also expect mild transient increases in pain and other negative
impacts with both appliances following each adjustment or new aligner.
DAILY DIARY QUESTIONNAIRE
SUBJECT ID #
Instructions: Please complete the following survey about how your teeth or orthodontic
appliances (braces or aligners) have affected your life since your last visit. Answer only what
you feel and have experienced, not what you think is the right answer. There are no right or
wrong answers to these questions.
1. Please circle one response for each of the following questions.
In the past 24 hours, how often: Always Often Some- Seldom Never
a. did you limit the kinds or amounts of food
you eat because of problems with your 1 2 3 4 5
mouth, teeth, or orthodontic appliances?
b. did you have trouble biting or chewing any
kinds of food, such as firm meat or apples? 1 2 3 4 5
c. were you able to swallow comfortably? 1 2 3 4 5
d. did your teeth or orthodontic appliances
prevent you from speaking the way you 1 2 3 4 5
e. were you able to eat without feeling 1 2 3 4 5
f. did you limit contact with people because of
the condition of your teeth or orthodontic 1 2 3 4 5
g. were you pleased or happy with the looks of 1 2 3 4 5
your teeth or orthodontic appliances?
h. did you use medication to relieve pain or
discomfort from around your mouth? 1 2 3 4 5
i. were you worried or concerned about the
problems with your teeth or orthodontic 1 2 3 4 5
j. did you feel nervous or self-conscious
because of problems with your teeth or 1 2 3 4 5
k. did you feel uncomfortable eating in front of
people because of problems with your teeth 1 2 3 4 5
or orthodontic appliances?
1. were your teeth sensitive to hot, cold or
1 2 3 4 5
m. did your orthodontic appliances cause
1 2 3 4 5
discomfort to your cheeks, lips, or tongue
Daily Diary Questionnaire. Answers from question 1 are summed to give the impact score.
2. Please mark an "X" on the line below to indicate how severe your discomfort has been
within the last 24 hours:
No pain Severe Pain
3. Please indicate what time of the day you are filling out this survey: AM/PM
4. A) Have you taken any medications today? Y / N (please circle)
B) If so, please write in which medications you took today:
5. Are you having any other problems or concerns about your teeth or orthodontic appliances
since your last orthodontic visit? If so, please describe.
LIST OF REFERENCES
1. Dj eu G. Shelton C. Maganzini A. Outcome Assessment of Invisalign and traditional
orthodontic treatment compared with American Board of Orthodontics objective
grading system. American Journal of Orthodontics & Dentofacial Orthopedics
2. Miethke RR. Vogt S. A Comparison of the Periodontal Health of Patients during
Treatment with the Invisalign@ System and with Fixed Orthodontic Appliances.
Journal of Orofacial Orthopedics 2005;66:219-229.
3. Lagravere MO. Flores-Mir C. The treatment effects of Invisalign orthodontic
aligners, A systematic review. Journal of the American Dental Association
4. Stewart FN, Kerr JW, Taylor P. Appliance wear: the patient' s point of view.
European Journal of Orthodontics 1997; 19:3 77-3 82.
5. Ngan P, Kess B, Wilson S. Perception of discomfort by patients undergoing
orthodontic treatment. American Journal of Orthodontics & Dentofacial Orthopedics
6. Lew KK. Attitudes and perceptions of adults toward orthodontic treatment in an
Asian community. Community Dentistry and Oral Epidemiology 1993;21:31-35.
7. Jones M, Chan C. The pain and discomfort experienced during orthodontic
treatment: a randomized controlled clinical trial of two initial aligning arch wires.
American Journal of Orthodontics & Dentofacial Orthopedics 1992; 102:3 73 -381.
8. Wilson S, Ngan P, Kess B. Time Course of discomfort in young patients undergoing
orthodontic treatment. Pediatric Dentistry 1989;11(2):107-110.
9. Scheurer P, Firestone A, Burgin W. Perception of pain as a result of orthodontic
treatment with fixed appliances. European Journal of Orthodontics 1996; 18:349-3 57.
10. Soltis J, Nakfoor P, Bowman D. Changes in ability of patients to differentiate
intensity of forces applied to maxillary central incisors during orthodontic treatment.
Journal of Dental Research 1971;50:590-596.
11. Miller K, McGorray S, Womack R, Quintero J, Perelmuter M, Gibson J, Dolan T,
Wheeler T. A comparison of treatment impacts between Invisalign aligner and fixed
appliance therapy during the first week of treatment. American Journal of
Orthodontics and Dentofacial Orthopedics 2007 131(3);302:el-9.
12. Sergl HG, Zentner A. A comparative assessment of acceptance of different types of
functional appliances. European Journal of Orthodontics 1998;20:517-524.
13. Erdinc AME, Dincer B. Perception of pain during orthodontic treatment with fixed
appliances. European Joumnal of Orthodontics 2004.26:79-85.
14. Jones ML, Richmond S. Initial tooth movement: force application and pain- a
relationship? American Journal of Orthodontics & Dentofacial Orthopedics
15. Lewis HG, Brown WA. The attitude of patients to the wearing of a removable
orthodontic appliance. Brit Dent J 1973;134:87-90.
16. Sergl HG, Klages U, Zenter A. Pain and discomfort during orthodontic treatment:
Causative factors and effects on compliance. American Joumnal of Orthodontics and
Dentofacial Orthopedics 1998;114:684-690.
17. Sergl HG, Klages U, Zentner A. Functional and social discomfort during orthodontic
treatment-effects on compliance and prediction of patient' s adaption by personality
variables. European Journal of Orthodontics 2000;22:307-315.
18. Doll GM, Zentner A, Klages U, Sergl HG. Relationship between Patient Discomfort,
Appliance Acceptance and Compliance in Orthodontic Therapy. Journal of Orofacial
19. Firestone A, Scheurer P, Burgin. Patient' s anticipation of pain and pain-related side
effects, and their perception of pain as a result of orthodontic treatment with fixed
appliances. European Journal of Orthodontics 1999;21:387-396.
20. Wong B. Invisalign@ A to Z. American Journal of Orthodontics and Dentofacial
21. Nedwed V. Miethke RR. Motivation, Acceptance and Problems of Invisalign
Patients. Journal of Orofacial Orthopedics 2005;66: 162-173.
22. Atchison K, Dolan TA. Development of the geriatric oral health assessment index.
Journal of Dental Education 1990;54:680-7.
23. Richmond S, Shaw WC. The development of the PAR index (peer assessment rating):
reliability and validity. European Joumnal of Orthodontics 1992; 14: 125-13 9.
Aaron William Carroll was born on November 10, 1974 in Tallahassee, Florida. With a
younger sister, he grew up in a rural area outside of Tallahassee, Florida, graduating from James
S. Rickards High School in 1992. He earned his B.S. from the Florida State University (FSU) in
1997. During college and after graduation, Aaron was employed as an Information Technology
Specialist by the Florida Supreme Court until 2000. Aaron entered dental school at the
University of Florida College of Dentistry in 2000 and graduated magna cum laude in 2004, after
which he began his residency in orthodontics at the University of Florida.
Upon completion of his residency and master' s program, Aaron will enter private practice
in Sarasota, Florida. Aaron was recently married to Tiffany, and they are expecting their first
child in September.