Download A STUDY OF TREATMENT DURATION USING THE DISCREPANCY INDEX

A STUDY OF TREATMENT DURATION USING
THE DISCREPANCY INDEX
Bradley G. Simister, D.D.S.
An Abstract Presented to the Faculty of the Graduate
School of Saint Louis University in Partial
Fulfillment of Requirements for
The Degree of Master of
Science in Dentistry
2007
ABSTRACT
A constant question in any orthodontic office is “When
do I get my braces off?”
A better understanding of those
factors that influence treatment duration would be a great
benefit for both the patient and the doctor.
The purpose
of this retrospective study was to look at the influence of
pretreatment malocclusion on treatment duration.
The
severity of malocclusion was defined by the American Board
of Orthodontics’ Discrepancy Index. Data were gathered from
one orthodontic office on 98 patients treated with
comprehensive orthodontics.
The patient sample was
collected so as to eliminate, to the greatest degree
possible, the variability of patient cooperation.
The DI
measurements were used to collect pretreatment information
and relate it to treatment duration.
time was 22.1 months.
The average treatment
Six of the fourteen pretreatment
variables were found to be significant in contributing to
treatment variability: Class II malocclusion, buccal
posterior crossbite, palatal impingement, total DI score,
ANB angle, and overjet.
Quality of the finished cases was
not evaluated.
1
A STUDY OF TREATMENT DURATION USING
THE DISCREPANCY INDEX
Bradley G. Simister, D.D.S.
A Thesis Presented to the Faculty of the Graduate School
of Saint Louis University in Partial
Fulfillment of Requirements for
The Degree of Master of
Science in Dentistry
2007
COMMITTEE IN CHARGE OF CANDIDCACY
Clinical Professor Sheldon Rosenstein
Chairperson and Advisor
Assistant Professor Maria Atique
Assistant Professor Heidi Isreal
i
ACKNOWLEDGEMENTS
I would like to thank all the members of my committee
for their time and effort.
encouragement.
I appreciate their guidance and
I would also like to thank the orthodontist
who so graciously made his office available to me.
A
special thanks to his staff for their kindness and
generosity in helping me with the data collection.
you all.
ii
Thank
DEDICATION
I would like to dedicate this work to my wife and
children.
This was the culmination of eight years in
school together.
Sondra thank you for your endless
patience and love.
I love you all.
iii
TABLE OF CONTENTS
List of Tables...........................................v
List of Figures..........................................vi
CHAPTER 1: INTRODUCTION..................................1
CHAPTER 2: REVIEW OF THE LITERATURE......................3
Socioeconomic Factors..........................3
Age......................................3
Gender...................................4
Socioeconomic status.....................5
Treatment Method...............................5
Extraction vs. Non extraction............5
One Phase vs. Two Phase..................6
Detail and Finish........................7
Patient Cooperation............................8
Oral Hygiene.............................8
Broken Appointments/Appliances...........8
Elastics/Headgear Compliance.............9
Malocclusion Characteristics..................10
Dental..................................10
Skeletal Discrepancies..................11
Discrepancy Index.............................11
History.................................11
References....................................19
CHAPTER 3: JOURNAL ARTICLE..............................22
Abstract......................................22
Introduction..................................23
Materials and Methods.........................25
Results.......................................28
Discussion....................................31
Conclusions...................................32
Literature Cited..............................34
Appendix
..............................................36
Vita Auctoris...........................................41
iv
LIST OF TABLES
Table I: Mean Values of Study Sample with Similarities
and Differences for Malocclusion
Classification (N=98)..........................36
Table II: Correlation of Continuous Variables of Class I
and Class II Patients with Treatment
Time (N=98)...................................36
Table III: Correlation of Categorical Variables of
Class I and Class II Patients with
Treatment Time (N=98)........................37
Table IV: Total Treatment Time and Other Discriminating
Variables Found in an Analysis of Variance for
Occlusal Classification Defined by
3 Groups (Class I, Mild Class II, Class II)...37
Table V: Tukey HSD Post Hoc Test Differences Found
Between Class II and Other Classifications
Of Variables in the Analysis of Variance
(Class I, Mild Class II, Class II).............38
v
LIST OF FIGURES
Figure 1: Overjet Measurement...........................12
Figure 2: Overbite Measurement..........................13
Figure 3: Anterior Openbite Measurement.................13
Figure 4: Lateral Openbite Measurement..................14
Figure 5: Crowding......................................14
Figure 6: Occlusion.....................................15
Figure 7: Lingual Posterior Crossbite...................15
Figure 8: Buccal Posterior Crossbite....................16
Figure 9: Cephalometric Measurements....................17
Figure 10A: Receiver Operator Curve of Class II
Malocclusion and Treatment Time.............39
Figure 11A: Receiver Operator Curve for the Dichotomized
DI (>15) and Treatment Time.................40
vi
CHAPTER 1: INTRODUCTION
A constant question in any orthodontic office is “When
do I get my braces off?”
A better understanding of those
factors that influence treatment duration would therefore
be of great benefit for both patient and doctor.
Patients
are anxious to be finished with the braces and observe the
outcome of their investment.
Treatment time in braces can
have an impact on family, missed school, work, and
finances. The orthodontist in turn would have a more
efficient office; patients are more likely to be happy when
appliances are removed in a timely manner.
Numerous studies have looked at factors involved in
treatment duration in an attempt to explain variability.
Some factors have been consistently documented while others
have had mixed results.
The use of an occlusal index is one way to study and
quantify a malocclusion and subsequently there have been a
number of different indices developed.
The American Board
of Orthodontics has in recent years developed an index for
the purpose of evaluating case selection to be presented to
the board for certification, the Discrepancy Index (DI).
The goal of this index was not to assess treatment need but
treatment complexity.
1
The purpose of this retrospective study was to look at
the influence of the pretreatment malocclusion, as defined
by the American Board of Orthodontics’ (ABO) Discrepancy
Index (DI), on treatment duration.
2
CHAPTER 2: REVIEW OF THE LITERATURE
Factors that influence the duration of orthodontic
treatment can be divided into four broad categories:
socioeconomic characteristics, treatment method, patient
cooperation, and malocclusion characteristics.1 Many studies
have looked at these various categories and their impact on
the duration of treatment.
Socioeconomic Factors
Socioeconomic factors that influence treatment
duration include age, gender, and socioeconomic status.2-4
Age
The age of a patient has been cited as a factor in
treatment time. Weiss and Eiser noted that age is a
significant factor, but it was due to the fact that
children under the age of 12 are much more likely to
cooperate.5 Poor cooperation has been consistently shown to
be of great significance in increasing treatment
duration.1,6-10 Adolescents with significant growth remaining
can contribute to reduction of treatment time, and this is
particularly true for the Class II patient where growth can
significantly modify the treatment outcome.11
3
Others have
reported that age did not play a key role in treatment
duration.6,7,10,12
Gianelly has stated that the stage of
dental development is more significant that the
chronological age of the patient.
Factors such as presence
of primary teeth, eruption of second molars, and eruption
of the entire permanent dentition, all impact and effect
treatment time to a greater extent than chronological age.13
Gender
Gender of the patient may also play a role in
treatment duration.
Boys have been shown to be in
treatment longer than girls.1,3,14,15
Starnbach and Kaplan3
have reported that this phenomenon may be attributed to
males lack of cooperation rather than some physiological
difference.
Since the teenage female matures earlier than
the male, this too has been postulated as a cause for lack
of cooperation in the male population.
Although many
studies have shown male treatment to last longer than
females, Beckwith and colleagues did not find differences.6
They were able to show that lack of cooperation contributed
to increase in treatment duration but that it did not
coincide with gender.
4
Socioeconomic Status
Socioeconomic status has not been thoroughly
investigated and at present its relationship to treatment
duration is unknown.2-4
Treatment Method
Orthodontic treatment itself is fraught with
variability, due to differences in treatment philosophy,
diagnosis (i.e. extraction vs. non extraction), and
appliances utilization.
Extraction vs. Non extraction
Vig et al.16 studied 5 different orthodontic offices
and showed that within each office extraction treatment did
take longer.
Vig and colleagues also reported that when
the offices were pooled together, treatment time was not
significantly different between extraction and non
extraction.
He concluded treatment time variation was a
variable between practitioners, and others have found
similar results.6,17
Conversely, many have reported that
extraction treatment did take longer than non extraction
treatment.1,4,7,8
Skidmore et al.1 looked at consecutively
treated cases by one orthodontist and found extractions
prolonged treatment by 2.6 months, and delaying extractions
5
also increased treatment duration, adding an additional 5.3
months.
These results are in agreement with Shia18 who
stated that delaying extractions increases treatment time
significantly more than extracting at the beginning of
treatment.
Fink and Smith7 in a multiple office study,
reported that two premolar extractions increased treatment
length by 4 months and four premolar extractions by 5.1
months.
Alger19 found extraction cases took 4.6 months
longer than non extraction cases.
Thus, there is
considerable evidence that extraction therapy correlates to
longer active treatment time.
One Phase vs. Two Phase Treatment
There have been numerous reports about the differences
between one and two phase treatment.8,13,20,21
Typical two
phase treatment generally employs a functional appliance
for the first phase of treatment, followed by a period of
retention; the second phase generally requires full
appliances. It has been well established that two phases of
treatment take longer than a single phase.4,6,8,16,17,21
Beckwith et al.6 found that two phase treatment lasted, on
average, 8 months longer than a single phase. Vig et al.16
found an even larger disparity of 13.5 months.
Popowich17
reported that a single phase of treatment that included
6
headgear was much more efficient (i.e. treatment time) than
Herbst therapy, followed by a second phase of full
appliances.
Although there seems to be considerable
evidence that one phase treatment may be more favorable
when related to treatment duration, two phase treatment
continues to be a popular approach in the correction
malocclusions.
Detail and Finish
The duration of treatment can certainly be affected by
the amount of detail and finish at the end of treatment.
The time and effort spent detail and finish of a case
varies from one practitioner to another.
Fink and Smith7
support the idea that there is a large variation in the
amount of detail needed to finish a case.
They felt that a
large amount of variation found within their data could be
explained by the differences in detail, because the
Salzmann Index used in the study was not sensitive enough
to objectively grade differences in finishing.
The only
index reported to have the ability grade the fine details
of finish is the ABO objective grading system.22
Variation
in the amount and quality of finish at the end of a case
can have an impact on the overall duration of treatment.
7
Patient Cooperation
Patient cooperation has been shown to be a
contributing factor to lengthening treatment time.1,6-8,10
Much of what is accomplished in treatment of a case
requires the help of the patient.
Poor oral hygiene,
missed appointments, broken appliances, and poor elastic
wear have all been shown to increase treatment duration.
Oral Hygiene
Poor oral hygiene is a problem every practitioner
faces, for fixed appliances in the mouth are more difficult
to clean.
Not only does poor oral hygiene contribute to an
increased incidence of caries and periodontal health, but
poor hygiene has been linked to longer treatment time.
A
likely explanation for this phenomenon would be that
patients who exhibit poor hygiene are less likely to be
compliant in other areas of treatment.23,24
Recent studies
have confirmed a link between longer treatment times and
poor oral hygiene.1,6,8,14,23,24
Broken Appointments/Appliances
Broken appointments can be a major issue of concern in
the orthodontic office.
Robb et al.10 showed that a
8
significant amount of variability in treatment duration can
be attributed to broken appointments.
As the number of
missed appointments increases, so in turn, will naturally
prolong treatment time.1,6-8
Along with missed appointments,
broken and damaged appliances also contribute to prolonged
treatment time.1,6,8,10,18
O’Brien et al.8 have reported that
the numbers of appliance repair was a major cause for
treatment overruns.
Shia18 noted that many times broken
appliances not only take time to repair, but often create
trauma and possible need for healing time for the patient.
further extending treatment.
Elastics/Headgear Compliance
Elastics and headgear are often used to supplement
full fixed appliances.
They can be effective means to move
teeth, but require the cooperation of the patient.
Beckwith et al.6 noted that the use of headgear was
associated with longer treatment.
This may be due to lack
of cooperation, or it may represent the underlying
malocclusion for which the headgear was prescribed.
Skidmore et al.1 also correlated poor elastic wear to longer
treatment time; thus, patient compliance is an important
issue for all clinicians.
It is difficult to know who will
be compliant in all these aspects of treatment.
9
Malocclusion Characteristics
Characteristics of malocclusion can be considered
dental, skeletal, or a combination of the two combined.
Dental
Dental occlusal classification has been shown to have
significant influence upon treatment duration.
Reports
show that the Angle Class II malocclusion patient takes
longer to than treat than the Class I malocclusion.1,4,15,17
Harrington.15 used a Deflection Index to measure the molar
deflection from ideal Angle Class I.
He used millimetric
measurements to quantify how far the molar occlusion
deviated from a class I relationship and concluded that the
further the molar relationship is from Class I, the greater
the increase in treatment time.15
Skidmore and associates reported maxillary crowding of
at least 3mm to be a significant factor in increasing
treatment duration.1
Conversely, others have not found a
relationship between the amount of crowding and treatment
duration.6,7
10
Skeletal Discrepancies
Fink and Smith7 found that a larger ANB was associated
with increase in treatment duration and amount of molar
deflection. Unexpectedly, a higher mandibular plane angle
contributed to decrease in the length of treatment time.
They suggested that this could possibly reflect a
correction of a deepened overbite rather than a true linear
trend of mandibular plane angle change.
Skidmore et al.1
recently noted that despite the various studies about
treatment duration, few have looked at the anatomic
differences in pretreatment malocclusion.
Discrepancy Index
The Discrepancy Index (DI) is the ABO’s current
approach to summarizing the clinical features of a
patient’s
pretreatment condition with a quantifiable,
objective list of target disorders that represent common
problems associated with orthodontic diagnosis.25
History of Discrepancy Index
The DI was developed over a number of years from 19982003.
A panel of eight ABO directors and six former
directors worked together in a series of meetings and
studies that involved cases presented to the ABO for phase
11
III examination.
With the information gathered from these
field tests, modifications were made to the index.25
The
final outcome was a number of target disorders that were
chosen for use as measurements in the DI.
The categories
measured are as follows:
Overjet- The distance between the lingual incisal edge of
the most forwardly positioned maxillary incisor to the
labial incisal edge of the most forwardly positioned
mandibular incisor. (Fig.1)
Fig 1. Overjet Measurement*
Overbite- The amount the maxillary incisor overlaps
vertically with the lower incisor. (Fig. 2)
*All figures modified from Cangialosi TJ. et al. Am J
Orthod Dentofacial Orthop 2004;125:270-278.
12
Fig 2. Overbite Measurement
Anterior Openbite- If the maxillary and mandibular incisors
are edge to edge or open. (Fig. 3)
Fig 3. Anterior Openbite Measurement
13
Lateral Openbite- Any maxillary tooth from first premolar
to third molar in an open bite relationship (Fig. 4)
Fig 4. Lateral Openbite Measurement
Crowding- The most crowded dental arch is scored (Fig.5)
Fig 5. Crowding
Occlusion- The Angle occlusal relationship is used to score
the buccal occlusion.
When the mesial buccal cusp of the
maxillary first molar is found anywhere in between the two
buccal cusps of the mandibular first molar it is classified
14
as class I.
If there is a cusp to cusp relationship it is
classified as end on.
If the mesial buccal cusp of the
maxillary first molar is beyond cusp to cusp, anterior or
posterior, the case is classified full step class II or
class III respectively. (Fig. 6)
Fig 6. Occlusion
Lingual Posterior Crossbite- Every maxillary posterior
tooth in lingual crossbite is measured. (Fig. 7)
Fig 7. Lingual Posterior Crossbite
15
Buccal Posterior Crossbite- All maxillary teeth from first
premolar to third molar in complete buccal crossbite are
noted. (Fig. 8)
Fig 8. Buccal Posterior Crossbite
There is also a category labeled “other.”
This section of
the DI is used to score any other clinical entity that may
contribute to case complexity.
Additional points may be
added for ectopic eruption, missing or supernumerary teeth,
transposition, anomalies of tooth size and shape, CR-CO
discrepancies, skeletal asymmetry, excess curve of Wilson.25
These are relatively common findings in orthodontics but
were not accounted for in the previous categories.
16
Cephalometric measurements used are the ANB angle, IMPA,
and SN-GoGn. (Fig. 9)
Fig 9. Cephalometric Measurements
The DI was not designed to assess treatment need.
The
primary purpose of the DI was an objective way to measure
the complexity of the treatment.25
Currently it is used for
case selection for phase III of ABO board certification.
Board candidates present a total of 6 cases, 3 must have a
DI score of at least 20 and 3 must have a DI score of at
17
least 10.
The candidate can measure the cases before
submission with the board verifying the scores.
The ability to more accurately predict treatment
duration would be a valuable asset to orthodontists.
This
area of orthodontic research is still relatively young.
Many studies have looked at the multiple variables such as
socioeconomic characteristics, treatment method, patient
cooperation, and malocclusion characteristics. The purpose
of this study is to look at the influence of pretreatment
malocclusion on treatment duration.
The pretreatment
malocclusion will be defined by the Discrepancy Index.
18
References
1. Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors
influencing treatment time in orthodontic patients. Am J
Orthod Dentofacial Orthop 2006;129:230-238.
2. Egolf RJ, BeGole EA, Upshaw HS. Factors associated with
orthodontic patient compliance with intraoral elastic and
headgear wear. Am J Orthod Dentofacial Orthop 1990;97:336348.
3. Starnbach HK, Kaplan A. Profile of an excellent
orthodontic patient. Angle Orthod 1975;45:141-145.
4. Turbill EA, Richmond S, Wright JL. The time-factor in
orthodontics: what influences the duration of treatments in
National Health Service practices? Community Dent Oral
Epidemiol 2001;29:62-72.
5. Weiss J, Eiser HM. Psychological timing of orthodontic
treatment. Am J Orthod 1977;72:198-204.
6. Beckwith FR, Ackerman RJ, Jr., Cobb CM, Tira DE. An
evaluation of factors affecting duration of orthodontic
treatment. Am J Orthod Dentofacial Orthop 1999;115:439-447.
7. Fink DF, Smith RJ. The duration of orthodontic
treatment. Am J Orthod Dentofacial Orthop 1992;102:45-51.
8. O'Brien KD, Robbins R, Vig KW, Vig PS, Shnorhokian H,
Weyant R. The effectiveness of Class II, division 1
treatment. Am J Orthod Dentofacial Orthop 1995;107:329-334.
9. Popowich K, Nebbe B, Heo G, Glover KE, Major PW.
Predictors for Class II treatment duration. Am J Orthod
Dentofacial Orthop 2005;127:293-300.
10. Robb SI, Sadowsky C, Schneider BJ, BeGole EA.
Effectiveness and duration of orthodontic treatment in
adults and adolescents. Am J Orthod Dentofacial Orthop
1998;114:383-386.
11. Proffitt WR Contemporary Orthodontics Second Edition.
St Louis MO, Mosby, 2000.
19
12. Harris EF, Dyer GS, Vaden JL. Age effects on
orthodontic treatment: skeletodental assessments from the
Johnston analysis. Am J Orthod Dentofacial Orthop
1991;100:531-536.
13. Gianelly AA. One-phase versus two-phase treatment. Am J
Orthod Dentofacial Orthop 1995;108:556-559.
14. Kreit LH, Burstone C, Delman L. Patient cooperation in
orthodontic treatment. J Am Coll Dent 1968;35:327-332.
15. Harrington CF. Deflection index and duration of
treatment. master's thesis, University of Saint Louis,
Saint Louis MO, 2004 (unpublished)
16. Vig PS, Weintraub JA, Brown C, Kowalski CJ. The
duration of orthodontic treatment with and without
extractions: a pilot study of five selected practices. Am J
Orthod Dentofacial Orthop 1990;97:45-51.
17. Popowich K. Comparison of Class I and Class II
Treatment Duration Among Three Different Orthodontic
Practices. Seminars of Orthodontics 2006;12:52-59.
18. Shia GJ. Treatment overruns. J Clin Orthod 1986;20:602604.
19. Alger DW. Appointment frequency versus treatment time.
Am J Orthod Dentofacial Orthop 1988;94:436-439.
20. O'Brien K, Wright J, Conboy F, Sanjie Y, Mandall N,
Chadwick S et al. Effectiveness of early orthodontic
treatment with the Twin-block appliance: a multicenter,
randomized, controlled trial. Part 1: Dental and skeletal
effects. Am J Orthod Dentofacial Orthop 2003;124:234-243;
quiz 339.
21. Tulloch JF, Proffit WR, Phillips C. Outcomes in a 2phase randomized clinical trial of early Class II
treatment. Am J Orthod Dentofacial Orthop 2004;125:657-667.
22. Casko JS, Vaden JL, Kokich VG, Damone J, James RD,
Cangialosi TJ et al. Objective grading system for dental
casts and panoramic radiographs. American Board of
Orthodontics. Am J Orthod Dentofacial Orthop 1998;114:589599.
20
23. El-Mangoury NH. Orthodontic cooperation. Am J Orthod
1981;80:604-622.
24. Nanda RS, Kierl MJ. Prediction of cooperation in
orthodontic treatment. Am J Orthod Dentofacial Orthop
1992;102:15-21.
25. Cangialosi TJ, Riolo ML, Owens SE, Jr., Dykhouse VJ,
Moffitt AH, Grubb JE et al. The ABO discrepancy index: a
measure of case complexity. Am J Orthod Dentofacial Orthop
2004;125:270-278.
21
CHAPTER 3: JOURNAL ARTICLE
Abstract
A constant question in any orthodontic office is “When do I
get my braces off?”
A better understanding of those
factors that influence treatment duration would be a great
benefit for both the patient and the doctor.
The purpose
of this retrospective study was to look at the influence of
pretreatment malocclusion on treatment duration.
The
severity of malocclusion was defined by the American Board
of Orthodontics’ Discrepancy Index. Data were gathered from
one orthodontic office on 98 patients treated with
comprehensive orthodontics.
The patient sample was
collected so as to eliminate, to the greatest degree
possible, the variability of patient cooperation.
The DI
measurements were used to collect pretreatment information
and relate it to treatment duration.
time was 22.1 months.
The average treatment
Six of the fourteen pretreatment
variables were found to be significant in contributing to
treatment variability: Class II malocclusion, buccal
posterior crossbite, palatal impingement, total DI score,
ANB angle, and overjet.
Quality of the finished cases was
not evaluated.
22
Introduction
A constant question in any orthodontic office is “When
do I get my braces off?”
A better understanding of those
factors that influence treatment duration would be a great
benefit for both the patient and the doctor.
Patients are
anxious to be finished with the braces and see the outcome
of their investment in orthodontics.
Treatment length can
have an impact on family life, missed school or work,
finances.
Orthodontists would benefit in that greater
accuracy in predicting treatment duration, could enhance
office management.
This would help balance scheduling,
inventory and allow an office to run at full capacity.
Patients are more likely to be happy when appliances are
removed at the time indicated at the original diagnosis.
There have been a number of studies that have looked
at the factors involved in treatment duration.1-3
Skidmore
et al. classified these factors into four broad categories:
Sociodemographic characteristics, malocclusion
characteristics, treatment method, and patient cooperation.3
This study will focus on the pretreatment malocclusion.
Pretreatment malocclusion characteristics studied
previously include ANB, mandibular plane angle, crowding,
overjet, occlusion, and overall index score.1-9
23
It has been
a consistent finding that Class II treatment takes longer
than Class I.3,4,6,9,10
Fink and Smith found that higher ANB
and Salzmann score correlated to longer treatment time.2
Skidmore noted that crowding greater than 3mm in the
maxillary arch increased treatment duration.3 Robb and
others have found a correlation with overjet.7,10
O’Brien et
al. reported the Peer Assessment Rating (PAR) score was an
indicator of longer treatment time while Popowich was
unable to substantiate this.5,6
The use of an occlusal index is one way to study and
quantify a malocclusion, and there have been a number of
different indices developed for a variety of reasons.
Some
study treatment need, while others look at pre and post
treatment outcomes.11-14
Additionally there have been
studies that have attempted to correlate indices such as
the PAR, Salzmann, and Deflection Index to treatment
duration.4,12,15,16 The American Board of Orthodontics has in
recent years developed an index for the purpose of
evaluating case selection to be presented to the board for
certification, it is the Discrepancy Index (DI).17
The goal
of the DI was not to assess treatment need but treatment
complexity.
The purpose of this retrospective study was to
look at the influence of the pretreatment malocclusion on
treatment duration.
The severity of malocclusion will be
24
defined by the American Board of Orthodontics Discrepancy
Index.
Materials and Methods
The sample of the present study was obtained from the
files of one orthodontic office.
Pretreatment lateral
cephalometric radiographs, pretreatment plaster models,
treatment plans, and progress notes were examined for 98
patients that fit the selection criteria.
The selection
criteria included both inclusion criteria and exclusion
criteria.
Inclusion Criteria:
- Finishing elastics worn no more than 3 months.
- Correction of Class II with Herbst appliance
for 8-10 months prior to bonded appliances.
- Patient started and completed treatment in the
same office.
Exclusion Criteria:
- Extraction of permanent teeth.
- The use of Class II intermaxillary elastics.
- Headgear use.
- Negative chart entries due to lack of
cooperation or poor oral hygiene.
25
- More than one chart entry signifying broken
appliances, including brackets.
- More than on chart entry signifying more than
one missed appointment.
The orthodontist was located in the Midwest and is
board certified in the specialty of orthodontics.
All
measurements on both the study models and the lateral
cephalometric radiographs were completed by one examiner.
The study models were measured with a ruler and
digital caliper according to instructions by Cangialosi et
al.17 as follows:
•
Overjet-the distance between the lingual incisal
edge of the most forwardly positioned maxillary
incisor to the labial incisal edge of the most
forwardly positioned mandibular incisor.
•
Overbite-The amount the maxillary incisor
overlaps vertically with the lower incisor.
•
Anterior Openbite- If the maxillary and
mandibular incisors are edge to edge or open.
•
Lateral Openbite- Any maxillary tooth from first
premolar to third molar in an open bite
relationship.
26
•
Crowding- Only the most crowded dental arch is
scored.
•
Occlusion- The Angle occlusal relationship is
used to score the buccal occlusion.
When the
mesial buccal cusp of the maxillary first molar
is found anywhere in between the two buccal cusps
of the mandibular first molar it is classified as
Class I.
If there is a cusp to cusp relationship
it is classified as end on.
If the mesial buccal
cusp of the maxillary first molar is beyond cusp
to cusp the case is classified full step Class II
or Class III.
•
Lingual Posterior Crossbite- Every maxillary
posterior tooth in lingual crossbite is measured.
•
Buccal Posterior Crossbite- Every maxillary tooth
from first premolar to third molar in complete
buccal crossbite is measured.
The cephalometric
radiographs were measured using acetate paper and
lead pencil.
The measures obtained included ANB,
SN-GoGn, and IMPA.
Descriptive statistics were used to characterize the
data set. Both parametric and non-parametric statistics
explored the relationships among key variables. Bivariate
correlation methods were used to describe the relationship
27
between continuous and categorical variables when
appropriate. Chi square statistic was used to compare
nominal variables.
A one way ANOVA was used to describe the relationships
between the various types of occlusions used as the
dependent variable and the independent variables of DI
score, overjet, palatal impingement, overbite, crowding,
ANB, IMPA, SN-GoGn in the predictive model.
The alpha
level was established at the conventional level (p<.05).
Post Hoc Tukey Honestly Significant Differences (HSD) was
used to discriminate between occlusal classifications on
significant variables.
Receiver Operator Curves (ROC) were used to look at
predictive nature of Class II malocclusion.
In the first
curve Class II was dichotomized as Class II vs. other
classifications.
A ROC curve was then performed on the
dichotomized classifications and treatment time as a
continuous variable.
dichotomized at 15.
In the second curve total DI was
Fifteen points was chosen in an
attempt to find a reasonable number which would represent
the midpoint from what the ABO defines as a more complex
case (20 points) and a more basic case (10 points). An ROC
curve was then performed on the dichotomized DI score with
28
treatment time used as the continuous variable. The data
was analyzed using SPSS14.
Results
Table I shows the mean values for all patients as well
as Class I and Class II separately.
The average treatment
time for patients in the study was 22.1 months with a total
average DI score of 12.6 points.
Class I patients average
treatment time was 19.9 months with an average DI score of
9.9 points.
Class II patients showed higher treatment time
and DI score at 25.6 months and 16.9 points respectively.
The average age for patients in the study at the start of
treatment was 14.8 years.
Chi square analysis showed no
difference between age and gender.
Tables II and III show the correlation relationship of
all variables with treatment time using either a Pearson’ r
or a Spearman’ rho as the data type indicates.
DI score
(r=.52), Class II malocclusion (rho=.43), ANB (r=.42),
overjet (r=.28), palatal impingement (rho=.43), and
posterior buccal crossbite (rho=.28) were found to be
significant (p<.05).
Of these variables, DI score, Class
II malocclusion, palatal impingement, and ANB showed a
29
moderate relationship with treatment time. No other
variables studied correlated with length of treatment.
The
DI score showed the highest correlation to treatment time
(r=.52, p<.00).
The Class II patients were further divided into mild
Class II and Class II. Table IV shows an Analysis of
Variance (ANOVA) which compares occlusal classification
types with all variables studied.
Significant ANOVA
results show there are differences among occlusal
classifications.
Table V shows the Post Hoc Tukey HSD
test results indicate which occlusal classifications are
different with these variables.
The Class II differed
significantly from the mild Class II and Class I patients.
While the average treatment time for the study was
22.1 months, a significant difference was found between
Class I and Class II patients.
Predictive curves using ROC
were used to model the comparison.
Variables that account
for greater than 50% of the variance are considered to be
predictive. The higher the percentage the variable accounts
for on the graph or conversely, that the variable accounts
for area under the curve, the more predictive the variable.
The percentage of prediction of these variables can be
accounted for by the amount of variance under the curve
that the variable is able to predict.
30
Figure 10A is the
ROC showing treatment time and Class II malocclusion with
the area under the curve at 0.757.
Figure 11A is the ROC
showing treatment time and the dichotomized DI score at 15
points.
The area under the curve for DI score was 0.849.
These results indicate that Class II occlusion as well as
total DI score can be predictive of treatment time.
Discussion
The purpose of this study was to look at pretreatment
malocclusion and its’ effect on treatment duration.
The
study was designed to eliminate as much as possible the
influence patient cooperation would have on treatment
duration.
It was found that Class II molar malocclusion,
increased overjet, total DI score, ANB, buccal posterior
crossbite, and palatal impingement all predict longer
treatment times.
The average treatment time in this study was 22.1
months.
The Class I patients averaged 19.9 months and
Class II 25.6 months.
Other Class II studies that included
2-phase treatment were 28.61 and 31.2.8
When 2-phase
treatment was excluded, treatment times of 2218, 23.12, and
23.53 have been reported.
Most Class II patients in this
study were treated with fixed Herbst appliances, a method
31
of Class II correction that does not require patient
cooperation.
Many prior studies have noted that males take longer
to treat than females.3,4,19,20
Starnbach and Kaplan
attributed this phenomenon to the males lack of
cooperation.20
The present study attempted to eliminate the
variable of patient compliance, this may be one of the
reasons there was no difference in treatment time between
males and females. Previous studies have reported that age
was not a factor in treatment time, and this would appear
to be confirmed in the present study.1,2,10
This study represents the first time the DI has been
correlated to treatment time.
Fink and Smith used the
Salzmann Index and found a correlation.2,21
the PAR with mixed results.4-6
Others have used
The present study also found
that the DI did correlate with treatment time.
The ROC
(Figure 11A) showed that a DI score of at least 15 points
would predict treatment time longer than 22.1 months 84.9%
of the time.
The curve for Class II (Figure 10A) would
predict the same thing at 75.7%.
Overall, this was of some
value when used to help predict length of treatment time.
The index is relatively easy to measure and only requires
models and a cephalometric radiograph. Thus, the DI may be
used as an aid when one wishes to predict treatment
32
duration. The finished cases were not evaluated for
quality.
Conclusions
Based on the findings of this study which included 98
patients from one orthodontic office the following
conclusions may be drawn:
1. Pretreatment malocclusion characteristics which
significantly contributed to treatment time were DI score,
class II occlusion, ANB, overjet, palatal impingement, and
posterior buccal crossbite.
2. Patients with Class II malocclusion treatment time
averaged almost 6 months longer than Class I.
3. Age and sex did not influence treatment duration.
4. The DI score and Class II malocclusion showed similar
predictive value.
33
Literature Cited
1. Beckwith FR, Ackerman RJ, Jr., Cobb CM, Tira DE. An
evaluation of factors affecting duration of orthodontic
treatment. Am J Orthod Dentofacial Orthop 1999;115:439-447.
2. Fink DF, Smith RJ. The duration of orthodontic
treatment. Am J Orthod Dentofacial Orthop 1992;102:45-51.
3. Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors
influencing treatment time in orthodontic patients. Am J
Orthod Dentofacial Orthop 2006;129:230-238.
4. Harrington CF. Deflection index and duration of
treatment. master's thesis, University of Saint Louis,
Saint Louis MO, 2004
5. O'Brien KD, Robbins R, Vig KW, Vig PS, Shnorhokian H,
Weyant R. The effectiveness of Class II, division 1
treatment. Am J Orthod Dentofacial Orthop 1995;107:329-334.
6. Popowich K. Comparison of Class I and Class II Treatment
Duration Among Three Different Orthodontic Practices.
Seminars of Orthodontics 2006;12:52-59.
7. Popowich K, Nebbe B, Heo G, Glover KE, Major PW.
Predictors for Class II treatment duration. Am J Orthod
Dentofacial Orthop 2005;127:293-300.
8. Vig PS, Weintraub JA, Brown C, Kowalski CJ. The duration
of orthodontic treatment with and without extractions: a
pilot study of five selected practices. Am J Orthod
Dentofacial Orthop 1990;97:45-51.
9. Vig KW, Weyant R, Vayda D, O'Brien K, Bennett E.
Orthodontic process and outcome: efficacy studies-strategies for developing process and outcome measures: a
new era in orthodontics. Clin Orthod Res 1998;1:147-155.
10. Robb SI, Sadowsky C, Schneider BJ, BeGole EA.
Effectiveness and duration of orthodontic treatment in
adults and adolescents. Am J Orthod Dentofacial Orthop
1998;114:383-386.
34
11. Richmond S, Shaw WC, Roberts CT, Andrews M. The PAR
Index (Peer Assessment Rating): methods to determine
outcome of orthodontic treatment in terms of improvement
and standards. Eur J Orthod 1992;14:180-187.
12. Salzmann JA. Handicapping malocclusion assessment to
establish treatment priority. Am J Orthod 1968;54:749-765.
13. O'Brien KD, Shaw WC, Roberts CT. The use of occlusal
indices in assessing the provision of orthodontic treatment
by the hospital orthodontic service of England and Wales.
Br J Orthod 1993;20:25-35.
14. Shaw WC, Richmond S, O'Brien KD. The use of occlusal
indices: a European perspective. Am J Orthod Dentofacial
Orthop 1995;107:1-10.
15. Richmond S, Shaw WC, O'Brien KD, Buchanan IB, Jones R,
Stephens CD et al. The development of the PAR Index (Peer
Assessment Rating): reliability and validity. Eur J Orthod
1992;14:125-139.
16. Salzmann JA. Editorial: Seriously handicapping
orthodontic conditions. Am J Orthod 1976;70:329-330.
17. Cangialosi TJ, Riolo ML, Owens SE, Jr., Dykhouse VJ,
Moffitt AH, Grubb JE et al. The ABO discrepancy index: a
measure of case complexity. Am J Orthod Dentofacial Orthop
2004;125:270-278.
18. Alger DW. Appointment frequency versus treatment time.
Am J Orthod Dentofacial Orthop 1988;94:436-439.
19. Kreit LH, Burstone C, Delman L. Patient cooperation in
orthodontic treatment. J Am Coll Dent 1968;35:327-332.
20. Starnbach HK, Kaplan A. Profile of an excellent
orthodontic patient. Angle Orthod 1975;45:141-145.
21. Salzmann JA. Definition and criteria of handicapping
malocclusion: a progress report. Am J Orthod 1966;52:209212.
35
APPENDIX
Table I Mean Values of Study Sample with Similarities and Differences for
Malocclusion Classification (N=98)
Variable
Class I
Class II
Total
________________________________________________________________________
Age
Treatment Time
DI score
ANB
IMPA
SN-GoGn
Overjet
Overbite
Crowding
14.9
19.9
9.9
3.0
92.6
33.7
2.7
2.8
3.3
14.8
25.6
16.9
4.0
94.2
31.4
4.3
4.2
3.8
14.8
22.1
12.6
3.4
93.2
32.9
3.4
3.3
3.4
Table II Correlation of Continuous Variables of Class I and Class II Patients with
Treatment Time (N=98)
Variable
Pearson correlation
“r” Value
p value
Age
Total DI score
ANB
IMPA
SN-GoGn
Overjet
Overbite
Crowding
-.08
.52**
.42**
.02
.07
.28*
.17
.15
NS
.000
.000
NS
NS
.005
NS
NS
36
Table III Correlation of Categorical Variables of Class I and Class II Patients with
Treatment Time (N=98)
Variable
Spearman’s rho
p value
________________________________________________________________________
Palatal Impingement
Anterior Crossbite
Anterior Openbite
Edge to Edge Openbite
Lateral Openbite
Lingual Posterior Crossbite
Buccal Posterior Crossbite
Crowding location
Class II occlusion
.43**
.01
.01
-.05
.09
.15
.28*
.13
.43**
.000
NS
NS
NS
NS
NS
.005
NS
.000
Table IVa Total Treatment Time and Other Discriminating Variables Found in an
Analysis of Variance for Occlusal Classification Defined by 3 Groups (Class I, Mild
Class II*, and Class II)
Independent Variable
Sum of
Squares
mean square
F,df
p<.05
Treatment Time
Between Groups 756.5
Within Groups 2700.4
378.2
13.3, 2
.000
Total DI
Between Groups 1164.2
Within Groups 4160.2
582.1
12.9, 2
.000
Overjet
Between Groups 69.5
Within Groups 252.7
34.8
13.1, 2
.000
Overbite
Between Groups 46.0
Within Groups 171.8
23.0
12.7, 2
.000
Palatal Impingement
Between Groups 4.2
Within Groups 10.5
2.1
18.7, 2
.000
ANB
Between Groups 29.9
Within Groups 406.7
15.0
3.5, 2
.034
*Mild Class II- half step Class II
37
Table V Tukey HSD Post Hoc Test Differences Found Between Class II and Other
Classifications of Variables in the Analysis of Variance (Class I, Mild Class II*, Class II)
Dependant Variable
Class II
Class I or Mild Class II
Treatment Time
Class II
Class I, mild Class II
Total DI
Class II
Class I, mild Class II
Overjet
Class II
Class I, mild Class II
Overbite
Class II
Class I, mild Class II
Palatal Impingement
Class II
Class I, mild Class II
ANB
Class II
Class I
*Mild Class II- half step Class II
38
1.0
Sensitivity
0.8
0.6
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1 - Specificity
Diagonal segments are produced by ties.
Figure 10A: Receiver Operator Curve of Class II Malocclusion and
Treatment Time
39
1.0
Sensitivity
0.8
0.6
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
1 - Specificity
Diagonal segments are produced by ties.
Figure 11A: Receiver Operator Curve for the Dichotomized DI Score (>15) and
Treatment Time
40
VITA AUCTORIS
Bradley G. Simister was born in Las Vegas, NV on
October 10, 1975.
his family.
Brad was the fourth of five children in
He graduated from Bonanza High School in 1994.
Following a year of college in Salt Lake City, he served a
two year mission in Madrid, Spain for The Church of Jesus
Christ of Latter-Day Saints. In 1997 he matriculated at
Brigham Young University graduating with a B.A. of Science
in 2000.
He then attended Creighton Dental School
graduating with a D.D.S. in 2004.
After dental school Brad
was accepted into the Orthodontic Program in Saint Louis
University and plans to graduate in December 2006.
He will
be in private practice St. George, UT. Brad married Sondra
Jacobsen August 8, 1998.
They are the parents of four
children.
41