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 A CEPHALOMETRIC STUDY OF ADULT MILD CLASS II NONEXTRACTION
TREATMENT WITH THE INVISALIGN SYSTEM
Brian M. Klein, D.M.D.
An Abstract Presented to the Graduate Faculty of
Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2013
Abstract
Objective: The aim of this retrospective study was to
examine the skeletal and dental effects of nonextraction
Class II treatment in the adult dentition with the
Invisalign system and interach elastics.
Materials and
Methods: Twenty-eight adult patients (18 females, 10 males,
mean age at start of treatment: 35.5 years) who have
undergone Class II nonextraction treatment with only
Invisalign aligners and interarch elastics were identified
from two private practitioners.
Pre-treatment and post-
treatment lateral cephalograms were hand-traced and
digitized.
Eight angular and seven linear measurements
were taken from each cephalogram.
Descriptive statistics,
paired t-tests, and intra-class correlations were computed
to analyze the data and determine whether there were
significant changes during treatment.
Results:
Statistically significant (p<.05) differences were found in
overall treatment change for SN-MP and U1-SN.
Statistically significant (p<.01) differences were found in
overall treatment change for SNB, ANB, IMPA, overjet,
overbite, molar relationship, upper molar linear distance
from the Y-axis, and lower molar linear distance from the
Y-axis.
The upper molars moved distally in every subject
1 and the lower molars moved mesially resulting in a molar
correction along the functional occlusal plane.
The ANB
angle, SN-MP, U1-SN, IMPA, overjet and overbite all
decreased throughout the course of treatment.
Conclusions:
The Invisalign system is a viable option for nonextraction
mild Class II treatment in adults.
Class II treatment with
the Invisalign system is capable of providing reliable
upper molar distalization and improvement in molar
relationship while maintaining an element of control in the
vertical dimension.
Assuming compliance by the patient and
an understanding of how the Invisalign software relates to
clinical tooth movements, the practitioner can expect some
dentoalveolar Class II correction in the adult dentition.
2 A CEPHALOMETRIC STUDY OF ADULT MILD CLASS II NONEXTRACTION
TREATMENT WITH THE INVISALIGN SYSTEM
Brian M. Klein, D.M.D.
A Thesis Presented to the Graduate Faculty of Saint
Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2013
COMMITTEE IN CHARGE OF CANDIDANCY:
Professor Eustaquio A. Araujo,
Chairperson and Advisor
Professor Rolf G. Behrents
Associate Clinical Professor Donald R. Oliver
i
DEDICATION
This work is dedicated to my wife, Jane.
I thank her
greatly for her constant love over the last five years and
the promise of many, many more.
Where most spouses would
be good just to give encouragement, she shows genuine
interest.
My orthodontic accomplishments are made all the
more enjoyable because they are shared through her
understanding of the specialty.
I am lucky to have such a
devoted wife and I love her very much.
To my parents, Christopher and Dianne, whose example
is my barometer for life.
Their love, sacrifice, and
support have allowed me more opportunities than I deserve.
I love and respect them to the highest degree.
And to the faculty of Saint Louis University, who have
taught me invaluable life and professional lessons.
The
selflessness of their approach to my education will bear
benefit for the rest of my life and it is much appreciated.
ii
ACKNOWLEDGEMENTS
I would like to thank Dr. Araujo for accepting the
position as chair of my thesis committee.
I very much
appreciate his knowledge, time, and perpetual passion.
We
should all be challenged to do more for and receive more
enjoyment from orthodontics, as Dr. Araujo has set the
standard in both respects.
Thank you Dr. Behrents for the remarkable opportunity
to learn under his leadership at such a prestigious
orthodontic program.
His ability to extract every last
drop of potential from his residents makes us better as
people, as a program, and as a specialty.
Thank you Dr. Oliver for his knowledge, enthusiasm,
and incredible attention to detail.
All are appreciated
and of great benefit in both research and clinical
endeavors.
Thank you Dr. Sam Daher, Dr. Farhad Moshiri, Dr.
Mazyar Moshiri, Dr. William Kottemann, and their respective
orthodontic staffs for providing the records used in this
study and a prior pilot study.
Despite demanding schedules
and busy practices all were thorough and kind in their
assistance.
iii
Thank you Dr. Heidi Israel for her time and expertise
in statistical analysis.
Thank you Align Technology, Inc. for their interest
and support in this study.
In particular, Dr. Rene
Sterental, Shawn Pemberton, and John Missey for their
efforts in database navigation and facilitating contacts.
iv
TABLE OF CONTENTS
List of Tables ........................................... vi
List of Figures ......................................... vii
CHAPTER 1:
INTRODUCTION .................................. 1
CHAPTER 2: REVIEW OF THE LITERATURE
Class II Malocclusion ..................................... 5
Definition .............................................. 5
Prevalence .............................................. 6
Etiology ................................................ 7
Nonextraction Treatment with Interarch Elastics ........ 10
Adult Class II Orthodontics .............................. 15
Statistics ............................................. 15
Correction ............................................. 16
Extraction Treatment ................................... 18
Functional Appliance Treatment ......................... 23
Invisalign ............................................... 26
History of Clear Removable Appliances .................. 26
Introduction of Invisalign ............................. 28
Invisalign as an Alternative Orthodontic Treatment ..... 30
Invisalign in Nonextraction Adult Class II Treatment .. 36
Statement of Thesis ...................................... 37
References ............................................... 38
CHAPTER 3: JOURNAL ARTICLE
Abstract .................................................
Introduction .............................................
Materials and Methods ....................................
Sample .................................................
Data Collection ........................................
X-Y Axis Coordinate System .............................
Statistical Methods ....................................
Results ..................................................
Cephalometric Comparison ...............................
X-Y Axis Coordinate System .............................
Discussion ...............................................
Skeletal A-P Changes ...................................
Skeletal Vertical Changes ..............................
Maxillary Dental Changes ...............................
Mandibular Dental Changes .............................
Dental Relationship Changes ..............................
Conclusions ..............................................
References ...............................................
Appendix .................................................
46
47
50
50
52
55
58
58
58
62
64
64
65
66
67
68
69
70
73
Vita Auctoris ............................................ 85
v
LIST OF TABLES
Table 2.1 – Adult orthodontics practice trends ........... 16
Table 3.1 – Sample age, gender, and treatment duration ... 51
Table 3.2 – Cephalometric definitions .................... 54
Table 3.3 – Descriptive statistics of T1 and T2 .......... 60
Table 3.4 – Descriptive statistics of treatment changes .. 61
Table A.1 – Sample ages and treatment duration ........... 73
Table A.2 – Sample Angle classification statistics ...... 74
Table A.3 – Anatomical landmark definitions .............. 75
Table A.4 – Intra-class correlation values ............... 79
Table A.5 – Mean X-Y axis coordinates .................... 80
vi
LIST OF FIGURES
Figure 2.1
– Angle Class I and Class II malocclusions ... 6
Figure 2.2
– Example of an Invisalign aligner .......... 29
Figure 3.1
– Anatomical landmarks ...................... 53
Figure 3.2
– Horizontal X-Y axis measurements .......... 56
Figure 3.3
– Vertical X-Y axis measurements ............ 57
Figure 3.4
– Graphic overlay of treatment changes ...... 63
Figure A.1
– Cephalometric planar measurements ......... 76
Figure A.2
– Cephalometric angular measurements ........ 77
Figure A.3
– Fucntional occlusal plane measurements .... 78
Figure A.4
– Graphic overlay of T1 measurements ........ 81
Figure A.5
– Graphic overlay of T2 measurements ........ 82
Figure A.6
– Class II division I graphic overlay ....... 83
Figure A.7
– Class II division II graphic overlay ...... 84
vii
Chapter I: Introduction
“Orthodontic therapy is essentially a game of strategy
against Nature. In this game, Nature is neither
malevolent nor capricious. She plays by rules that can
at least be described and against which optimal
strategies can be formulated.”1
- Lysle Johnston, Jr.
In orthodontics Class II malocclusion presents as a
complexity in both origin and correction.
Both have been
studied extensively and yet, both remain a continuing
challenge for each generation of practitioners.
of Class II malocclusion is multifactorial.
The origin
The
malocclusion is defined as a distal relation of the lower
dentition to the upper, but the underlying causes are not
simplistic.
Genetics, growth, environmental effects,
occlusal development, dental positions, and skeletal
positions are all to be considered when evaluating a Class
II patient.
An appropriate diagnosis and understanding of
the malocclusion is vital to responsible treatment.
The correction of Class II malocclusion is
multifactorial as well.
A Class I molar and canine
relationship is considered a successful treatment outcome,
but there are numerous ways to arrive at this goal in
treating Class II malocclusions.
1
Interarch elastics,
extractions, distalizers, headgear, fixed functional
appliances, removable functional appliances, and surgical
interventions are some of the commonly used approaches to
treat Class II malocclusion.
Proper Class II correction
also requires knowledge of potentially adverse effects
inherent in the aforementioned correction methods.
Upper
incisor retroclination, lower incisor proclination, lower
molar extrusion, and tipping of the occlusal plane can be
unwanted results of certain Class II treatments.
Class II diagnosis and correction are heavily
dependent on whether and how much growth can be expected
from the patient.
The anticipated amount of differential
growth by the mandible as compared to the maxilla can
influence the orthodontic treatment planning process.
Typically, adolescents are expected to contribute varying
amounts of favorable skeletal growth, while adults are
relegated to mostly dental compensations.
The
pervasiveness of Class II malocclusion, growing interest in
orthodontics by the adult population, and demand for
esthetic treatment in all age groups has created a niche
for techniques capable of satisfying those prerequisites.
Invisalign clear, removable aligners as a mode of
orthodontic treatment have gained increasing attention
2
since their first U.S. commercial sales to orthodontists in
1999.
Although limited in publication through refereed
journals, studies have shown Invisalign to be a reasonable
strategy for correction of minor malocclusions.
Initially
branded as an esthetic alternative to traditional braces
for low complexity cases, patient demand and advances in
technologies have led some orthodontists to broaden their
use of Invisalign.
Theoretical effects of the aligners
such as a biteplate effect, incisor angulation control, and
vertical control appeal to some practitioners.
To date, no
appropriate studies have been published on any of the
aforementioned assertions with regard to Invisalign when
used as a mode of Class II treatment.
The purpose of this study is to evaluate the skeletal
and dental effects of Class II nonextraction treatment in
adults using the Invisalign system of treatment and
interarch elastics.
Pre-treatment and post-treatment
cephalometric analysis will allow a description of the
changes in molar relationship, overjet and overbite
correction, incisor angulation, vertical dimension, and
changes of the occlusal plane.
Of particular importance
will be how this method of Class II treatment contrasts
3
with conventional fixed appliance treatment using interarch
elastics in adolescents and adults.
4
Chapter II: Review of Literature
Class II Malocclusion
Definition
In the 1890s, Edward H. Angle developed a
classification system for occlusal relationships in the
natural dentition.2
The basis of the normal occlusion and
subsequent malocclusions was the position of the upper
first molar.
In normal occlusion the mesiobuccal cusp of
the upper first molar occludes with the buccal groove of
the lower first molar.
Normal occlusion and Class I
malocclusion share the same molar relationship, but Class I
malocclusion also presents with rotated or malposed teeth.
Class II malocclusion, as described by Angle, is the distal
relation of the lower dentition to that of the upper
(Figure 2.1).
This malocclusion is evident specifically by
the buccal grove of the lower first molar presenting distal
by at least one-half cusp to the mesiobuccal cusp of the
upper first molar.2
A common goal of orthodontic treatment
is to return the patient to normal occlusion whenever
possible.
5
22
CHAPTER 1
The Decision-Making Process in Orthodontics
Normal occlusion
Class II malocclusion
Class I malocclusio
Class III malocclusi
FIGURE 1-10 Angle suggested that in ideal occlusion the mesiobuccal cusps of the maxil
rest in the buccal grooves of the mandibular first molars. He called the permanent first mo
Figure 2.1. Angle
Class
I and Class
IImolar
malocclusion.
Modified
from that two variations of
sion and
designated
this ideal
relationship Class
I. He observed
th
exist,
and
he
designated
these
Class
II
and
Class
III.
Subsequently,
Graber, Orthodontics: Current Techniques and Principles 5 ed. the relationship of the can
of the description of Class I, II, and III probably as a result of Simon’s influential but erroneou
textbook.3
lary canines were the keys to occlusion. Nonetheless, the maxillary canines should ideally
between the mandibular canines and first premolars.
Prevalence
into orthodontic therapy has made it necessary for
this system is defined as a s
orthodontists to add arch-perimeter analysis as an addiin a set have some commo
tional
step
in
classification.
There are two major co
In the 1970s an effort was made by the United States
A final, but not inconsequential, difficulty with Angle’s
scheme: (1) dentofacial ap
classification
procedure
is
that
it
does
not
indicate
the
tionships of the teeth and j
Public Health Service (USPHS) to better gauge the nationcomplexity and severity of the problem.
five or fewer major chara
It
is
for
these
reasons
that
we
advocate
systematically
wide health status. A massive survey was performedcondition
by the is needed to ful
enhancing the Angle classification by describing the five
are several other factors th
major
characteristics
of
malocclusion.
arriving
at these five desc
Division of Health Examination Statistics to examine
youths
listed as follows:
Ackerman-Proffit
agesSystematic
12 to 17. Description:
Among the data
collected was information
1. Dentofacial appearance
• Facial symmetry/ver
regarding
malocclusion.
It
was
estimated
that
32%
of
• the
To overcome the difficulties just discussed, we recomAnterior tooth displ
• Orientation of the
mend using a classification scheme in which five or 4
7,500
youth
sample had
Classinterrelationships
II malocclusion.
fewer
characteristics
anda their
are
NHP (natural head
63,64
•
assessed.
A complex of interrelated variables, as
Profile consideration
encountered in many orthodontic conditions, may be
2. Spatial relationships of
• Arch alignment and
represented most conveniently through the use of sets.
• Anteroposterior cha
Venn proposed this representation in 1880, and his idea
6
• Transverse character
has become prominent in symbolic logic for computer
• Vertical characteristi
use. The set theory deals with collections or groups of
• Orientation of the o
entities and it represents the relationships between these
groups by graphic patterns. A Venn diagram offers a
visual demonstration of interaction or overlap among
The five or fewer descrip
Classification (the Orthogonal Analysis)
A broadened national health survey was performed in
1989-1994 known as the National Health and Nutrition
Estimates Survey III (NHANES III).
The NHANES III used a
sample of 14,000 participants to provide health information
for children, youths, and adults.5
This information served
as a tool that oral health professionals could reference
for various data sets organized by age and ethnic groups.
Class II malocclusion, described by the NHANES III as more
than 4 mm of overjet, appeared in 11% of the sample and
made up 20% of all malocclusions making it the most common
skeletal discrepancy.
Class II malocclusion was featured
in 10.1% of Caucasians, 11.8% of African Americans, and
6.5% of Hispanics.5
Etiology
Given that Class II malocclusion is the most common
jaw discrepancy in the United States, an effort has been
made by the orthodontic community to understand its
origins.
An assortment of skeletal and dental
predispositions comprise the underlying causes and
appearance of Class II malocclusion.
Moyers performed a
multivariate cluster analysis using cephalometric data of
610 patients to determine the facial types associated with
7
Class II malocclusion.
By analyzing phenotype
characteristics, he was able to define six subgroups based
on horizontal components and five subgroups based on
vertical components.6
The horizontal subgroups were defined
as either; maxillary dental protrusive, midface protrusive,
maxillary and mandibular retrognathic with dental
protrusion, maxillary and mandibular retrognathic with only
maxillary protrusion, maxillary prognathic with maxillary
dental protrusion, or mandibular retrognathic.
Vertical
subgroups were based on comparisons to the Michigan Growth
Study norms utilizing the position of the cranial base,
palatal plane, occlusal plane, and mandibular plane.
Moyers concluded that not all vertical types are found in
each horizontal type, but there is a strong relationship
between horizontal and vertical features.
The study
suggests there are 15 Class II subtypes that can be defined
by pairing the horizontal and vertical subgroups.
McNamara looked at lateral cephalometric radiographs
of 277 children ages 8 to 10 with Class II malocclusion.7
He found mandibular skeletal retrusion to be the most
common single characteristic of Class II malocclusion with
the maxilla usually in a neutral skeletal position.
In
evaluating the dentition he found less maxillary incisor
8
proclination than previous studies and generally neutral
lower incisor angulation.
McNamara also found that nearly
half of the sample featured an excessive vertical
component, which was determined by mandibular plane angle
and lower face height.
In all, the study recognized 77 of
the 243 possible combinations of Class II malocclusions
from the skeletal, dental, and vertical components.
The
combination of neutral maxillary position, retrusive
mandibular skeletal, and excessive vertical dimension was
the most common, representing only 10% of the overall
sample.
In a longitudinal study, Buschang and Martins looked
at childhood and adolescent growth changes in the
anteroposterior and vertical dimensions.8
Lateral
cephalometric radiographs of 49 females and 50 males with
roughly equivalent Class I and Class II malocclusions were
analyzed for childhood and adolescent growth changes
respectively.
Childhood growth was described as 6 to 10
years for females and 8 to 12 years for males.
Adolescent
growth was described as 9 to 13 years for females and 11 to
15 years for males.
The distance between ANS and pogonion
was used to determine the skeletal vertical relationship
and distance between pogonion and gonion was used to
9
determine the skeletal anteroposterior relationship.
It
was found that anteroposterior discrepancies had greater
potential to improve during childhood than adolescence.
They attributed worsening of the anteroposterior
relationship in adolescence primarily to deficiency of
horizontal mandibular growth.
Vertical growth changes were
found to be significantly greater in adolescence than
childhood.
The study concluded that neither
anteroposterior or vertical relationships were stable
during growth.6
Nonextraction Class II Treatment with Interarch Elastics
There are a number of methods available to
orthodontists for correction of nonextraction Class II
malocclusions, but the most common is use of interarch
elastics.
Widespread and long-term use of this method has
allowed for thorough study of the clinical effects.
In
1955, Tovstein published a study on the effects of Class II
correction with elastics on the occlusal plane.9
He looked
at 81 nonextraction Class II patients at time points before
treatment, at the end of treatment, and at least 2 years
into retention.
The results showed that Class II elastics
increased the SN-occlusal plane angle and decreased the ANB
10
angle.
Subjects displaying the most growth during the
course of treatment showed a lesser increase in the
occlusal plane angle and more improvement in ANB angulation
than subjects with the least growth.
The study showed that
tipping of the occlusal plane occurs with Class II elastic
use, but severity is related to growth of the patient.
Hanes later investigated skeletal profile changes of
38 Class II patients treated with interarch elastics.10
His
results showed that Class II elastics moved A-point and Bpoint distally 2.5 mm and 0.9 mm respectively.
Despite
mesial force exerted on the mandibular dentition by the
elastics, a net posterior movement of B-point was due to
the mean 0.8 degrees clockwise mandibular rotation.
Hanes
determined that skeletal Class II correction is mostly from
distally moving A-point and Class II elastics do not
enhance chin projection due to clockwise mandibular
rotation.
Gianelly et al. did a cephalometric comparison of
Class II treatment with elastics utilizing different
bracket systems.11
43 cases were treated with either light
wire (Begg) or edgewise appliances and evaluated for linear
and angular changes.
There were no statistically
significant differences between the techniques.
11
Both
appliances showed a decrease in SNA angle, an increase in
SNB angle, and an increase in mandibular plane angle.
The
SNA angle was reduced slightly more and mandibular plane
increased slightly less in the edgewise group.
The SNB
angle increased slightly more in the Begg group.
Meistrell et al. performed a study on 42 nonextraction
Class II cases treated with the Begg appliance and Class II
elastics.12
They found a mean decrease in the ANB angle of
1.3 degrees and mandibular incisor proclination of 3.67
degrees.
The occlusal plane rotated counterclockwise 0.3
degrees.
Both maxillary and mandibular molars moved
mesially at 0.2 mm and 1.2 mm respectively.
Also, both
maxillary and mandibular molars showed extrusive movement
at 2.1 mm and 2.6 mm respectively.
Ellen et al. looked at horizontal and vertical
cephalometric changes in 56 nonextraction Class II patients
treated with edgewise appliances and elastics.13
Their
results showed a mean 4.0 mm mesial and 4.1 mm extrusive
movement of the mandibular first molars.
The maxillary
incisors extruded 3.7 mm and retroclined 1.4 degrees, while
the mandibular incisors proclined 1.4 degrees.
The
occlusal plane displayed a clockwise rotation of 0.8
12
degrees. SNA and ANB angles decreased significantly with
only minimal decrease in the SNB angle.
Nelson et al. performed a two-part study on
nonextraction Class II correction with interarch elastics.
The first study was prospective and looked at 18 Class II
patients treated with the Begg technique.14
The results
showed a 3.7 mm distal movement of the maxillary incisors
and a 1.0 mm mesial movement of the mandibular incisors.
Maxillary molar movement was insignificant, while there was
2.0 mm mesial movement of the mandibular molars.
mandibular plane angle increased 1.0 degree.
The
Mean overjet
reduction was 5.8 mm and mean molar correction was 3.0 mm.
The second study utilized a different sample involving 18
nonextraction Class II patients treated with Begg
appliances and elastics.15
The authors found a 5.1 mm
distal movement of the maxillary incisors and 1.4 mm mesial
movement of the mandibular incisors.
The maxillary and
mandibular molars both moved mesially with 1.3 mm and 1.6
mm of movement respectively.
The mean mandibular plane
angle increased 1.3 degrees.
Mean overjet reduction was
6.7 mm and mean molar correction was 3.1 mm.
Combrink et al. looked at dentoskeletal changes in 35
Class II patients treated nonextraction with Class II
13
elastics.16
Results from the study showed a mean decrease
in the SNA and ANB angles with 1.6 degrees and 1.7 degrees
respectively.
The inter-incisal angle decreased 21.8
degrees and overjet correction was measured at 3.8 mm.
An
evaluation of the soft tissue profile showed slightly more
lower lip advancement than compared to the upper, which
improved the profile and lip relationship.
Jones et al. compared nonextraction Class II patients
treated with either the Forsus appliance or elastics.17
Thirty-four growing patients were treated with each Class
II correction method and evaluated for post-treatment
changes.
Both groups showed mesial movement of the
maxilla, mandible, and dentition.
The group treated with
elastics featured 3.8 degrees of mandibular incisor
proclination, 3.2 mm of mandibular molar extrusion, and
clockwise occlusal plane rotation of 1.0 degree.
Overjet
correction was measured as 2.8 mm and molar correction was
2.4 mm.
The authors concluded that both Forsus and
interarch elastics were capable of efficiently correcting
Class II malocclusion.
Janson et al. recently performed a systematic review
of the orthodontic literature relating to Class II
treatment with elastics.18
Eleven articles satisfied the
14
inclusion criteria from a search of multiple databases on
the topic.
The authors concluded that Class II elastics
are an effective method for treatment of Class II
malocclusion and correction is mostly dentoalveolar in
nature.
Component dentoalveolar effects of Class II
elastics were retraction and extrusion of the maxillary
incisors, proclination of the mandibular incisors, and
mesial and extrusive movements of the mandibular first
molars.
Adult Class II Orthodontics
Statistics
The ability to effectively treat the varying
malocclusions of the adult patient is a necessary tool in
modern orthodontics.
The 2011 Journal of Clinical
Orthodontics (JCO) practice study on trends throughout the
specialty revealed that adult patients comprise 20% of all
case starts and command a consistently higher treatment fee
than adolescent cases (Table 2.2).19
Multiple studies, both
American and international, have found the incidence of
adult malocclusion to be as high as 70%.5,20-23
Data from the
NHANES III indicated that of the adult population, defined
15
as people ages 18 to 50, 57% presented with inadequate
overjet and 50% with inadequate overbite.5
A 2012
retrospective study by Cedro et al. of nonsurgical adult
patients identified the mean age of adult patients as 31.2
years of age.
The patients were predominantly female at
76.2% of the sample with Class II division I malocclusion
being the most commonly presenting malocclusion.24
Practice Activity (Medians)
1981
1989
1997
2003
2009
2011
150
150
180
212
220
200
15.4%
22.3%
19.1%
18.8%
20.0%
20.0%
300
350
400
500
495
450
15.2%
20.0%
15.4%
16.7%
18.0%
17.8%
Child Fee
$1,900
$2,800
$3,600
$4,390
$5,150
$5,200
Adult Fee
$2,100
$3,000
$3,900
$4,800
$5,500
$5,550
Case Starts
Adult Case Starts
Active Treatment Cases
Adult Active Cases
Table 2.1. Adult orthodontics practice trends. Modified from 2011 JCO
Orthodontic Practice Study, Part 1: Trends.19
Correction
Knowledge of the contributing factors to Class II
malocclusion helps in determining the appropriate
treatment.
Identifying the component or components of the
malocclusion can dictate the most effective method of
correcting the jaw discrepancy.
Differential skeletal
growth of the craniofacial structures is evident in how
16
mandibular growth outpaces that of the maxilla during
development.
Since we understand Class II malocclusion as
a distal positioning of the mandible in relation to the
maxilla, a common misconception is that natural growth
could be self-correcting in adolescent patients.
However,
Proffit describes differential growth as only capable of
providing 3-4 mm towards Class II correction.25
Orthodontists faced with treating Class II malocclusion of
adult patients lose the advantage of differential jaw
growth, regardless of the increment.
Furthermore, multiple
growth studies on untreated Class II samples show that
growth in the vertical dimension actually creates more
convexity, exacerbating the Class II facial pattern.26-28
Without the benefit of horizontal growth and the
potential hindrance of continued vertical growth there are
fewer options in treating adult Class II malocclusions.
Methods for addressing this condition are primarily
isolated to orthodontic camouflage and orthognathic
surgery.
Orthodontic camouflage is an attempt at
correction of the overjet via extraction of upper first
premolars while leaving the posterior in Class II occlusion
or extraction of upper and lower premolars.
17
This approach
relies almost entirely on dental movement and does little
to address the underlying skeletal discrepancy.
Fixed functional appliances are a common approach for
Class II correction in the growing patient, but some
practitioners see a niche for them in adult patients as
well.
This technique is aimed at producing remodeling of
the temporomandibular joint for some skeletal improvement,
but mostly dental reaction to the force system.29,30
Orthognathic surgery for Class II correction features
proper alignment of the intra-arch dentition with
orthodontics followed by a mandibular advancement
osteotomy.
This is a combined technique that addresses
both the dental and skeletal aspect of the malocclusion.
As this study is investigating nonsurgical Class II
correction, it is only appropriate to review literature
concerning adults treated with orthodontic camouflage or
fixed functional appliances.
Extraction Treatment
In 1991, Harris et al. looked at the dental and
skeletal effects of Class II treatment in adolescents and
adults with Tweed edgewise mechanics.31
18
The sample
consisted of 30 adolescent girls with a mean age of 12.5
years and 26 adult females with a mean age of 27.6 years.
The entire sample displayed a Class II division I
malocclusion and were treated with extraction of four
premolars.
Cephalometric analysis showed a 1.2 mm distal
tipping of the maxillary molars in the adult sample with a
2.5 mm mesial translation of the maxillary molars, due to
growth in the adolescent sample.
Relative to the maxilla,
the adult mandibular molars moved forward less than half
that of the adolescents by 2.8 mm and 6.1 mm respectively.
The maxillary incisal edge of both samples was retracted
significantly in both samples.
The adolescent mean
functional occlusal plane rotated by counterclockwise 0.96
degrees and rotated clockwise 4.44 degrees in the adult
sample.
This steepening of the occlusal plane in the adult
reduced maxillary and mandibular molar movements relative
to the plane.
In 1992, Proffit et al. compared the outcomes of
orthodontic versus surgical intervention in adult Class II
malocclusions.32
Thirty-three patients treated
orthodontically with extractions were evaluated. A point
moved distally 0.9 mm, B point moved distally 0.8 mm, the
ANB angle decreased 0.4 degrees, and the mandibular plane
19
angle increased 0.3 degrees.
Overjet was reduced by 2.9 mm
and overbite was reduced by 1.1 mm.
The authors matched
the post-treatment measurements with an acceptable range
and an ideal value to determine the percentage goal
achieved.
While both orthodontic and surgical treatments
scored most values in the acceptable range, the surgical
method of treatment score significantly better in achieving
an ideal value.
In 1993, Cassidy et al. analyzed Class II treatment in
adults deemed “borderline” between orthodontic and surgical
correction.33
The orthodontic sample consisted of 27 adults
treated with either nonextraction or a variety of
extraction protocols.
Cephalometric analysis showed a 2.7
mm reduction in overjet, 0.3 mm increase in overbite and
0.1 mm improvement in molar relationship.
SNA reduced 0.4
degrees, SNB reduced 0.5 degrees, and ANB increased 0.1
degrees.
SN-GoGn increased 0.5 degrees and the SN-
functional occlusal plane increased 2.4 degrees.
After
thorough analysis of both samples, the authors determined
that orthodontic treatment for adult Class II “borderline”
patients would be the better choice.
In 1995, Vaden et al. compared Class II correction in
adolescent and adult patients.34
20
The adolescent sample
consisted of 22 patients who were 15.1 years at posttreatment and the adult sample consisted of 23 patients who
were 31.9 years at post-treatment.
All patients were
female, had four premolars extracted, and were treated with
Tweed edgewise mechanics.
In the adolescent sample, SNA
moved distally 1.75 degrees and SNB moved distally 0.10
degrees.
The maxillary incisor retracted 5.91 mm and the
mandibular incisor protracted 1.49 mm.
The maxillary
molars moved mesially 2.47 mm and extruded 1.89 mm, while
the mandibular molars moved mesially 3.87 mm and extruded
3.11 mm.
Change in the mandibular plane angle was
negligible, the functional occlusal plane to Frankfort
horizontal reduced 0.46 degrees, and the IMPA reduced 0.59
degrees.
In the adult sample, SNA moved distal 1.22 degrees and
SNB moved distally 0.48 degrees.
The maxillary incisor
retracted 7.47 mm and the mandibular incisor protracted
0.51 mm.
The maxillary molars moved distally 0.08 mm and
intruded 0.98 mm, while the mandibular molars moved
mesially 2.49 mm and extruded 2.43 mm.
The mandibular
plane angle increased 0.57 degrees, the functional occlusal
plane to Frankfort horizontal increased 4.42 degrees and
the IMPA reduced by 0.47 degrees.
21
The authors concluded
that there are major differences between Class II treatment
of both age groups, but a lack of growth doesn’t exclude
the adult patient from correction of the malocclusion.
In 2009, Liu et al. evaluated the skeletal and dental
effects of nonextraction Class II treatment in postpeak
growth stage patients with Multiloop Edgewise (MEAW)
mechanics and Class II elastics.35
Cephalometric analysis
was performed on 16 patients, 11 females and 7 males, with
a mean age of 15.9.
A point moved mesially 0.7 mm and B
point moved mesially 1.6 mm.
The maxillary incisors
retracted 1.7 mm the mandibular incisors protracted 1.9 mm.
The maxillary molars moved mesially 0.5 mm and extruded 0.4
mm, while the mandibular molars moved mesially 1.4 mm and
extruded 1.2 mm.
SN-PP and SN-GoGn angles reduced 0.8
degrees and 0.4 degrees respectively.
Given the postpeak
growth status of the sample, the authors credited skeletal
change with 30% of the incisal changes and 54% of molar
changes.
22
Functional Appliance Treatment
In 1999, Ruf and Pancherz performed a prospective
study on dental and skeletal changes in adult Class II
treatment with the Herbst fixed functional appliance.36
Fourteen young adults with a mean pre-treatment age of 16.5
years were evaluated immediately before and after Herbst
wear.
Dental component evaluation showed a 3.6 mm
retraction of the maxillary incisors and 3.8 mm
proclination of the mandibular incisors.
The maxillary
molars were measured at 2.7 mm of distal movement and the
mandibular molars 3.8 mm of mesial movement.
Further
analysis of the data claimed a 22% skeletal correction
concerning the overjet and 78% dental.
Molar correction
was portrayed as 25% skeletal and 75% dental.
Ruf and Pancherz later presented a study comparing
surgical adult Class II correction with Herbst Class II
treatment.37
Twenty-three patients who received a
mandibular sagittal split osteotomy and 23 patients treated
with the Herbst appliance were evaluated for pre-treatment
and post-treatment skeletal and dental changes.
For the
Herbst group, results showed a mean decrease in overjet of
6.7 mm with the maxillary incisors retruding 3.2 mm and
mandibular incisors proclining 2.7 mm.
23
The maxillary
molars moved distally 1.8 mm and mandibular molars moved
mesially 1.4 mm.
The Herbst group showed more overjet
correction, more maxillary incisor retroclination, more
mandibular incisor proclination, less molar correction, an
increased facial height, and less profile correction when
compared to the surgical group.
The dental components of
overjet and molar correction for the Herbst group were
found to be 87% and 78% respectively.
Kinzinger et al. performed a cohort study measuring
the effects of adult Class II treatment with orthodontic
camouflage, dentofacial orthopedics, and orthognathic
surgery.38
Sixty young adults, 20 for each treatment
method, were evaluated for linear and angular changes in
pre-treatment and post-treatment cephalograms.
The
orthopedic group, which was represented by Herbst appliance
treatment, had a mean pre-treatment age of 18.7 years.
This group showed no significant changes skeletal changes
for either the maxilla or mandible.
The maxillary incisors
were retracted 2.35 mm and retroclined 3.9 degrees, while
the mandibular incisors moved mesially 2.46 mm and were
proclined 7.27 degrees.
The total overjet correction was
largest in the functional appliance group with 4.9 mm and
the overbite decreased by 0.7 mm.
24
The maxillary molars
moved distally 1.88 mm and the mandibular molars moved
mesially 0.77 mm.
The SN-MP decreased 0.38 degrees and SN-
PP decreased 0.66 degrees.
In the extraction group there were no statistically
significant movements of the maxilla or mandible.
The
maxillary incisors retracted 4.96 mm and retroclined 6.36
degrees, while the mandibular incisors retracted 4.07 mm
and retroclined 4.16 degrees.
Total overjet correction was
0.97 mm and the overbite increased 0.56 degrees.
The
maxillary molars moved mesially 0.45 mm and the mandibular
molars moved mesially 1.51 mm.
The SN-MP increased 1.25
degrees and SN-PP increased 0.49 degrees.
Despite some
bony chin projection and reduction in the soft tissue
profile convexity for the functional appliance group, only
the orthognathic surgery group produced significant
treatment-related changes.
A 2012 prospective clinical study by Upadhyay et al.
compared Class II correction in young adult females treated
with either temporary anchorage device assisted (TAD) upper
first premolar extractions or fixed functional appliances.39
Eighteen female patients with a mean age of 16.5 years
underwent nonextraction Class II treatment with the Forsus
appliance.
This group showed a reduction in the ANB angle
25
of 1.5 degree through a decrease in SNA angle of 0.6 degree
and increase in SNB angle of 1.0 degree.
The maxillary
incisors retroclined 7.3 degrees and the mandibular
incisors proclined 10.7 degrees.
The SN-MP angle decreased
0.3 degree, while the SN-occlusal plane angle increased 0.7
degree.
The authors noted that both the extraction and
functional appliance groups both provided adequate dental
compensation to correct the Class II malocclusion, but did
not affect the skeletal discrepancy.
The authors also
noted that fewer side effects were noted in the functional
appliance group resulting in less time required for
finishing and an overall shorter treatment time.
Invisalign
History of Clear Removable Appliances
Kesling is credited with the introduction of removable
aligners through use of positioning trays in 1945.
These
one-piece pliable rubber mouth guards, or “tooth
positioners,” were made from idealized lab set-ups and used
as a finishing technique to close residual spaces after
debanding.40
Kesling’s technique was promising in that it
could serve in both minor correction and retention.
26
However, material limitations of the era and extensive lab
preparation prevented a broadened use of the appliances.
Ponitz and later McNamara et al. employed the same general
lab arrangements previously described by Kesling, but
utilized thermoformed plastic for the aligner material.41,42
In 1993, Sheridan et al. introduced thermoplastic
copolyester trays primarily as a mode of retention, but
also minor tooth movement.
Advantages attributed to the
aligners were durability, ease of cleaning, ease of
fabrication, low cost of fabrication, and esthetics.43
The
idea was to perform interproximal reduction and apply
sequential retainers that could result in minimal range
tooth movements.
Eventually, thermoforming pliers were
added to the armamentarium to facilitate control of aligner
movements at chairside.44
Again, lab preparation often
outweighed the benefits of minor tooth movements as new
impressions and model set-ups were required at each
appointment.
In 1997, Rinchuse and Rinchuse presented a
set of case reports showing minor malocclusion correction
with Essix trays in conjuction with bonded attachments,
finger springs, or palatal expanders.45
Vacuum-formed Essix
retainers, originally coined Sheridan’s Simple System of
27
Stabilizing the Social Six, remain a staple of orthodontic
retention.46
Introduction of Invisalign
Founded in 1997 by Stanford University business
students Kelsey Wirth and Zia Chishti, Align Technology
Inc. (Align Technology, Santa Clara, Calif) became the
first company to mass-produce aligners for the treatment of
malocclusion with the introduction of Invisalign.3
Invisalign aligners are generated by computer-aided
design/computer-aided manufacturing (CAD/CAM) technology
from either polyvinylsiloxane or digital impressions.
Impressions are scanned or imported into the Align system
to create a detailed digital study model.
From this model,
Align technicians generate a virtual correction of the
malocclusion through the ClinCheck software.
The clinician
can then use the software to manipulate the process or
outcome by describing revisions to Align.
When the
clinician has given final approval the lab will use a
movement algorithm to generate sequenced stages of
orthodontic correction.
An acrylic model of each stage is
produced by stereolithography, which is a method of making
solid objects by printing successive thin layers of
28
photocurable material on top of one another.47
Finally,
0.75 mm trays are made for each model and designated for
shipping.
Each Invisalign aligner (Figure 2.3) is
predetermined for 0.25 mm to 0.33 mm of tooth movement and
is to be replaced in sequence every two weeks.48,49
Align
received FDA approval in 1998, began its first commercial
sales of Invisalign to U.S. orthodontists in 1999, and
spread to European markets in 2001.
Currently, the
Invisalign system is offered in 45 countries and has been
used to treat more than 1.5 million patients.50
Figure 2.2. Example of an Invisalign aligner.50
29
Invisalign as an Alternative Orthodontic Treatment
Practitioners are charged with determining whether
patients seeking a superior esthetic alternative to braces
can be properly treated in that fashion.
As the popularity
of Invisalign has increased, so has the scope of cases
deemed treatable with the removable aligner system.
The
first university study concerning Invisalign was performed
by Boyd et al. in 2000.
The results suggested that
Invisalign treatment was acceptable for nonextraction adult
dentition cases with mild to moderate crowding, mild to
moderate spacing, nonskeletal constricted arches, and
relapse.51
Since then a myriad of case report studies have
featured Invisalign in correction of malocclusions far
beyond the initial complexity parameters such as: extensive
restorative, open bite, deep bite, Class II, Class III,
extraction, and surgical cases.52-64
Aside from select case reports, editorials, and
material studies, relatively few clinical studies have been
published by peer-reviewed journals on Invisalign
biomechanical efficiency or overall treatment outcomes.
In
2005, Lagravere and Flores-Mir conducted a systematic
review on the treatment effects of Invisalign aligners.65
multiple database search for “Invisalign” retrieved 22
30
A
articles and only 2 of those articles met their inclusion
criteria of a human clinical trial concerning treatment
effects.
Furthermore, the authors determined the 2
remaining articles yielded only a low level of evidence due
to inadequate evaluation of the treatment effects and
various methodological problems.
Still, genuine efforts have been made to better
understand and critique the Invisalign system.
A three-
part study out of the University of Washington looked at
activation time and material stiffness of Invisalign
aligners.
The first study by Bollen et al. looked
specifically at the ability of Invisalign to effectively
finish prescribed orthodontic treatments.66
Fifty-one
patients, based on their pre-treatment peer assessment
rating (PAR) and need for extractions, were assigned to
different Invisalign treatment specifications.
The
treatment variations were using either hard or soft plastic
for the aligners and either 1-week or 2-week activation
time per aligner.
Patients were evaluated after completion
of the initial series of aligners.
The authors found no
significant difference in the completion rate for hard
versus soft plastic appliances.
It was found that changing
the aligners every 2 weeks resulted in a higher completion
31
rate than changing every week (37% vs 21%).
Patients with
PAR scores less than 15 and no extractions showed the
highest completion rate, while those with 2 or more
premolars extracted showed the lowest completion rate (46%
vs 0%).
The study suggests that minimal complexity,
nonextraction cases using a 2-week activation protocol are
more likely to treat to completion.
The second study in the series by Clements et al.
looked at Invisalign correction evaluated by individual
dental components of the PAR.67
The same 51 patients from
the first study were stratified by PAR score and need for
extractions.
The patients were again grouped into soft or
hard plastic appliances and 1-week or 2-week activation
treatment regimens.
The authors found the 2-week
activation protocol to have a greater percentage reduction
on the PAR score and more extraction space closure.
Invisalign was successful at correcting anterior alignment,
moderately successful at correcting midline and overjet,
and least successful at correcting buccal occlusion.
Incisor extraction sites showed a significantly greater
percentage of space closure than premolar extraction sites.
The third study in the series by Baldwin et al. looked
at space closure and adjacent tooth movements in premolar
32
extraction cases treated with Invisalign.68
Twenty-four
Invisalign patients featuring at least one premolar
extraction site were evaluated at pre-treatment, end of
aligner sequence, and end of fixed appliances.
Results of
the study showed that teeth adjacent to the premolar
extraction sites displayed significant tipping at the end
of aligner treatment.
Subsequent measurements made after
placement of fixed appliances showed significant uprighting
of the same teeth.
The authors concluded that Invisalign
premolar extraction space closure could result in
significant, but correctable dental tipping.
Also of note
in the study was the mean treatment time of 40 months due
to waiting for the aligner sequence to finish and then
utilizing fixed appliance mechanics.
Kravitz et al. performed a prospective clinical study
to compare planned virtual tooth movements with the
clinical results using Invisalign software and aligners.69
Four hundred one anterior teeth were measured from 37
Invisalign patients, 198 maxillary and 203 mandibular.
Virtual models of predicted tooth position were
superimposed over virtual models created from the posttreatment impressions and analyzed with Invisalign’s
superimposition software.
Expansion, constriction,
33
intrusion, extrusion, mesiodistal tip, and labiolingual tip
movements were evaluated.
The authors found that the
average accuracy of Invisalign tooth movement was 41% with
lingual constriction being the most accurate and extrusion
the least accurate.
Extrusion of maxillary incisors was
the single least accurate movement studied with 18.3%
accuracy.
The study showed lingual crown movements was
more accurate than labial movements and there was no
statistical difference in accuracy for like movements
between the maxillary and mandibular dentition.
Djeu et al. performed a retrospective comparative
cohort study looking at treatment results of 48 Invisalign
cases and 48 conventional fixed appliance cases.70
The
American Board of Orthodontics (ABO) discrepancy index was
used to control for initial severity of malocclusion and
the objective grading system (OGS) was used to evaluate
final records.
The authors found that the Invisalign group
lost 13 points more on average than the fixed appliance
group and had a 27% lower passing rate.
Invisalign scores
were lower than fixed appliances in the categories of
buccolingual inclination, occlusal contacts, occlusal
relationships, and overjet.
Findings showed that
Invisalign cases finished 4 months quicker on average than
34
the fixed appliance cases.
Vincent did a similar study
scoring 65 pre-treatment and post-treatmentt Invisalign
cases with the ABO OGS.71
He found significant improvements
in alignment, buccolingual inclination, and interproximal
spaces.
Conversely, his results showed that Invisalign
treatment had a negative impact on posterior occlusal
contacts.
Kuncio et al. used the ABO OGS to evaluate retention
outcomes in Invisalign and conventional fixed appliance
treatment.72
Eleven cases were recovered from Djeu’s
previous Invisalign sample and matched with 11
nonextraction tip-edge fixed appliance cases for treatment
length and retention length.
The authors found significant
changes in total alignment and mandibular anterior
alignment of both groups.
The Invisalign group displayed
significantly more total misalignment and maxillary
anterior alignment than the fixed group.
Although the
Invisalign group actually showed a better OGS score at
debond, the overall score and alignment score worsened in
retention.
The fixed group improved in overall OGS score
in retention, while only getting worse in the alignment
category.
35
Invisalign in Nonextraction Adult Class II Treatment
In 2012, Daher presented a study at the Invisalign
Summit of consecutively finished Invisalign adult Class II
cases and evaluated the skeletal and dental effects.73
The
patients were treated with his customized sequential
distalization method of Class II Invisalign treatment.74
The method is based on distal movement of the maxillary
second molars by pitting them against the anchorage of the
12 anterior teeth.
Class II elastics are then used to
reinforce anchorage and sequentially move the buccal
segments into a Class I relationship.
The study sample consisted of 14 consecutively treated
Class II patients with a mean age of 32 years and average
treatment time of 19.3 months.
Eleven patients were end-on
Class II and three were full-step molar relationship.
Six
patients were Class II division 1 and eight were Class II
division 2.
Every patient showed distal movement of the
maxillary molars with the mean being 1.1 mm and change in
molar relation toward Class I had a mean of 1.3 mm.
The
lower incisors moved mesially, while holding a consistent
IMPA.
36
Statement of Thesis
The purpose of this study is to describe the skeletal
and dental effects of nonextraction Class II treatment in
adult dentition with the Invisalign system.
These effects
will be compared to nonextraction Class II treatment with
elastics and conventional fixed appliances in adolescents
and nonsurgical Class II treatments in adults.
To date, the orthodontic literature does not feature
any university studies on Class II treatment with
Invisalign or any thorough cephalometric evaluations of the
skeletal and dental effects of Invisalign treatment.
It is
the responsibility of our profession as a whole to
investigate new appliances and techniques.
Given the high
demand for esthetic orthodontic treatment and the incidence
of Class II malocclusion, data from this study will help
practitioners make a more informed decision when
considering suitable treatments for their patients.
37
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52. Fischer K. Invisalign treatment of dental Class II
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44
72. Kuncio D, Maganzini A, Shelton C, Freeman K. Invisalign
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73. Daher S, editor Invisalign treatment for Class II
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2013].
45
CHAPTER 3: JOURNAL ARTICLE
Abstract
Objective: The aim of this retrospective study was to
examine the skeletal and dental effects of nonextraction
Class II treatment in the adult dentition with the
Invisalign system and interach elastics.
Materials and
Methods: Twenty-eight adult patients (18 females, 10 males,
mean age at start of treatment: 35.5 years) who have
undergone Class II nonextraction treatment with only
Invisalign aligners and interarch elastics were identified
from two private practitioners.
Pre-treatment and post-
treatment lateral cephalograms were hand-traced and
digitized.
Eight angular and seven linear measurements
were taken from each cephalogram.
Descriptive statistics,
paired t-tests, and intra-class correlations were computed
to analyze the data and determine whether there were
significant changes during treatment.
Results:
Statistically significant (p<.05) differences were found in
overall treatment change for SN-MP and U1-SN.
Statistically significant (p<.01) differences were found in
overall treatment change for SNB, ANB, IMPA, overjet,
overbite, molar relationship, upper molar linear distance
from the Y-axis, and lower molar linear distance from the
Y-axis.
The upper molars moved distally in every subject
46
and the lower molars moved mesially resulting in a molar
correction along the functional occlusal plane.
The ANB
angle, SN-MP, U1-SN, IMPA, overjet and overbite all
decreased throughout the course of treatment.
Conclusions:
The Invisalign system is a viable option for nonextraction
mild Class II treatment in adults.
Class II treatment with
the Invisalign system is capable of providing reliable
upper molar distalization and improvement in molar
relationship while maintaining an element of control in the
vertical dimension.
Assuming compliance by the patient and
an understanding of how the Invisalign software relates to
clinical tooth movements, the practitioner can expect some
dentoalveolar Class II correction in the adult dentition.
Introduction
In orthodontics Class II malocclusion presents as a
complexity in both origin and correction.
Both have been
studied extensively and yet, both remain a continuing
challenge for each generation of practitioners.
of Class II malocclusion is multifactorial.
The origin
The
malocclusion is defined as a distal relation of the lower
dentition to the upper, but the underlying causes are not
simplistic.
Genetics, growth, environmental effects,
occlusal development, dental positions, and skeletal
47
positions are all to be considered when evaluating a Class
II patient.
An appropriate diagnosis and understanding of
the malocclusion is vital to responsible treatment.
The correction of Class II malocclusion is
multifactorial as well.
A Class I molar and canine
relationship is considered a successful treatment outcome,
but there are numerous ways to arrive at this goal in
treating Class II malocclusions.
Interarch elastics,
extractions, distalizers, headgear, fixed functional
appliances, removable functional appliances, and surgical
interventions are some of the commonly used approaches to
treat Class II malocclusion.
Proper Class II correction
also requires knowledge of potentially adverse effects
inherent in the aforementioned correction methods.
Upper
incisor retroclination, lower incisor proclination, lower
molar extrusion, and tipping of the occlusal plane can be
unwanted results of certain Class II treatments.
Class II diagnosis and correction are heavily
dependent on whether and how much growth can be expected
from the patient.
The anticipated amount of differential
growth by the mandible as compared to the maxilla can
influence the orthodontic treatment planning process.
Typically, adolescents are expected to contribute varying
48
amounts of favorable skeletal growth, while adults are
relegated to mostly dental compensations.
The
pervasiveness of Class II malocclusion, growing interest in
orthodontics by the adult population, and demand for
esthetic treatment in all age groups has created a niche
for techniques capable of satisfying those prerequisites.
Invisalign clear, removable aligners as a mode of
orthodontic treatment have gained increasing attention
since their first U.S. commercial sales to orthodontists in
1999.
Although limited in publication through refereed
journals, studies have shown Invisalign to be a reasonable
strategy for correction of minor malocclusions.
Initially
branded as an esthetic alternative to traditional braces
for low complexity cases, patient demand and advances in
technologies have led some orthodontists to broaden their
use of Invisalign.
Theoretical effects of the aligners
such as a biteplate effect, incisor angulation control, and
vertical control appeal to some practitioners.
To date, no
appropriate studies have been published on any of the
aforementioned assertions with regard to Invisalign when
used as a mode of Class II treatment.
The purpose of this study is to evaluate the skeletal
and dental effects of Class II nonextraction treatment in
49
adults using the Invisalign system of treatment and
interarch elastics.
Pre-treatment and post-treatment
cephalometric analysis will allow a description of the
changes in molar relationship, overjet and overbite
correction, incisor angulation, vertical dimension, and
changes of the occlusal plane.
Of particular importance
will be how this method of Class II treatment contrasts
with conventional fixed appliance treatment using interarch
elastics in adolescents and adults.
Materials and Methods
Sample
The data in this retrospective clinical study were
obtained by analyzing pre- (T1) and post-treatment (T2)
lateral cephalograms of adult Class II Invisalign patients
selected from the offices of two private practice
orthodontists.
The sample consisted of 28 adult Class II
patients (18 females, 10 males) with a mean age at start of
treatment of 35.5 years (Table 3.1, Tables A.1 and A.2).
breakdown of the sample into divisions of Class II
malocclusion reveals 19 Class II division 1 patients (14
females, five males, mean age at start of treatment: 37.7
years) and 9 Class II division 2 patients (four females,
50
A
five males, mean age at start of treatment: 31.0 years).
Twenty-one sets of records were from practice A and seven
sets of records were from practice B.
Patients were
selected without consideration of post-treatment results.
The criteria for patient selection were:
•
Pre-treatment occlusion of at least half-step
unilateral or bilateral Class II molar malocclusion
•
At least 16 years of age at pre-treatment records
•
No congenitally missing teeth (excluding third molars)
•
Treatment completed without extraction of any
permanent teeth (excluding third molars)
•
Treatment completed without orthognathic surgery
•
Patients treated solely with Invisalign and elastics
throughout the course of treatment
•
Diagnostic pre- and post-treatment lateral
cephalograms
Table 3.1. Sample age, gender, and treatment duration.
Patients
Female:Male
Mean Age
at T1
Mean Tx
Time
28
18:10
35y6m
(16y5m – 62y5m)
25m
(18m – 35m)
51
The present study was designed to analyze the posttreatment skeletal and dental changes of adult
nonextraction Class II treatment with Invisalign.
The goal
of each treatment was to improve the overjet, overbite, and
molar relationship by distal movement of the maxillary
molars.
Practice A utilized a sequential distalization
method based on distal movement of the maxillary second
molars by pitting them against the anchorage of the 12
anterior teeth.1,2
Class II elastics were then used to
reinforce anchorage and sequentially move the buccal
segments into a Class I relationship.
Practice B mainly
utilized Class II elastics to reinforce anchorage in molar
rotation.
Obtaining a sample from two practitioners was an
attempt to limit variation in treatment technique.
The
decision to use practitioners with at least a “premium
provider” standing with Invisalign assumed experience with
the product.
Data Collection
Pre-treatment (T1) and post-treatment (T2) lateral
cephalograms were collected for each patient.
Each
cephalogram was hand-traced by a single investigator.
Eighteen hard-tissue and two reference landmarks were
52
identified on each cephalogram (Figure 3.1, Table A.3).
The landmarks were then digitized with a Numonics Accugrid
Digitizer (Numonics digitizing board, Model A30Bl.H,
Numonics Corporation, Montgomeryville, PA) and analyzed
using a customized cephalometric analysis (Table 3.2,
Figure A.1-A.3) with Dentofacial Planner software
(Dentofacial Planner version 5.23, Toronto, Canada).
19
1
18
20
2
17
3
4
16
13
15
14
6
5
12
7
8
9
11
10
Figure 3.1. Anatomical landmarks: Nasion (1); Anterior nasal spine (2);
A point (3); Upper incisor apex (4); Upper incisor tip (5); Lower
incisor tip (6); Lower incisor apex (7); B point (8); Pogonion (9);
Gnathion (10); Menton (11); Inferior Gonion (12); Lower 1st molar distal
contact (13); Lower 1st molar mesiobuccal cusp (14); Lower 1st premolar
cusp (15); Upper 1st molar distal contact (16); Posterior nasal spine
(17); Sella (18); Reference point 1 (19); Reference point 2 (20).
53
Table 3.2. Cephalometric measurements.
Measurement
Definition
SNA
Angle formed by SN and NA
SNB
Angle formed by SN and NB
ANB
Angle formed by NA and NB
SN-MP
Angle formed by SN and the mandibular plane (inferior gonion
to menton)
SN-PP
Angle formed by SN and the palatal plane (ANS to PNS)
SN-FOP
Angle formed by SN and the functional occlusal plane (plane
drawn through the occlusal contacts of the molars and
premolars)
U1-SN
Angle formed by the longitudinal axis of the upper central
incisor and SN
IMPA
Angle formed by the longitudinal axis of the lower central
incisor and mandibular plane
Overjet
Horizontal distance from the upper central incisor tip to the
lower central incisor tip along the functional occlusal plane
Overbite
Vertical distance from the upper central incisor tip to the
lower central incisor tip perpendicular to the functional
occlusal plane
Molar relation
Horizontal distance from the distal contact of the upper 1st
molar to the distal contact of the lower 1st molar along the
functional occlusal plane
Hor U6
Horizontal distance from the distal contact point of the
upper 1st molar to the Y-axis
Ver U6
Vertical distance from the distal contact point of the upper
1st molar to the X-axis
Hor L6
Horizontal distance from the distal contact point of the
lower 1st molar to the Y-axis
Ver L6
Vertical distance from the distal contact point of the lower
1st molar to the X-axis
54
X-Y Axis Coordinate System
In order to provide graphic representation of
treatment changes, a Cartesian coordinate system (X-Y axis)
was constructed.
Sixteen linear distances were measured
from each coordinate system axis.
X-axis measurements are
horizontal distances from the vertical plane represented by
a perpendicular line to the sella-nasion minus 7 degrees
plane (Figure 3.2).
Y-axis measurements are vertical
distances from the horizontal plane represented by the
sella-nasion minus 7 degrees plane (Figure 3.3).
The
corresponding points were then plotted in a scatter graph
to show pre-treatment and post-treatment relationships.
55
SN – 7 perpendicular
(Y axis)
1
SN – 7
(X axis)
2
17
3
4
16
15
14
13
6
5
12
7
8
9
11
10
Figure 3.2. Horizontal X-Y axis measurements: Nasion to Y-axis (1); ANS
to Y-axis (2); A point to Y-axis (3); U1 apex to Y-axis (4); U1 tip to
Y-axis (5); L1 tip to Y-axis (6); L1 apex to Y-axis (7); B point to Yaxis (8); Pogonion to Y-axis (9); Gnathion to Y-axis (10); Menton to Yaxis (11); Inferior gonion to Y-axis (12); Distal of L6 to Y-axis (13);
Mesiobuccal cusp of L6 to Y-axis (14); L4 tip to Y-axis (15); Distal of
U6 to Y-axis (16); PNS to Y-axis (17).
56
SN – 7 perpendicular
(Y axis)
1
SN – 7
(X axis)
2
17
3
4
16
13
14
15
6
5
12
7
8
9
11
10
Figure 3.3. Vertical X-Y axis measurements: Nasion to X-axis (1); ANS
to X-axis (2); A point to X-axis (3); U1 apex to X-axis (4); U1 tip to
X-axis (5); L1 tip to X-axis (6); L1 apex to X-axis (7); B point to Xaxis (8); Pogonion to X-axis (9); Gnathion to X-axis (10); Menton to Xaxis (11); Inferior gonion to X-axis (12); Distal of L6 to X-axis (13);
Mesiobuccal cusp of L6 to X-axis (14); L4 tip to X-axis (15); Distal of
U6 to X-axis (16); PNS to X-axis (17).
57
Statistical Methods
Data was collected and organized into spreadsheet
format using Microsoft Office Excel 2007.
Statistical
analysis was performed using SPSS statistical analysis
software (PASW Statistics Version 18.0, SPSS Inc., Chicago,
IL).
Paired t-tests were used to evaluate differences in
pre- and post-treatment measurements.
Means and standard
deviations were used to describe central tendencies and
dispersion.
To test intra-examiner reliability, 6 sets of pre- and
post-treatment radiographs were randomly selected for retracing and re-measuring.
Cronbach’s Alpha test for
reliability showed that intra-class correlation was 0.961
(Appendix A.4).
This value is above the generally accepted
0.800 value indicating a high reliability of measurements.
Results
Cephalometric Comparison
Descriptive statistics of 15 variables were calculated
for pre-treatment (T1), post-treatment (T2), and overall
treatment changes (Table 4.1, Table 4.2).
Ten of the 15
measured variables showed a statistical significance in
overall treatment change.
Statistically significant
58
(p<.05) differences were found in overall treatment change
for SN-MP and U1-SN.
Statistically significant (p<.01)
differences were found in overall treatment change for SNB,
ANB, IMPA, overjet, overbite, molar relationship, upper
molar linear distance from the Y-axis, and lower molar
linear distance from the Y-axis measurements.
A “p-value”
of less than .05 indicates a 95% confidence in the data and
a “p-value” of less than .01 indicates a 99% confidence in
the data.
The other differences between groups were not
statistically significant.
Anteroposterior skeletal treatment changes were
represented by insignificant change of the SNA, the SNB
moving anteriorly 0.8 degrees, and the ANB decreasing
1.1 degrees.
Vertical skeletal treatment changes were
represented by a 0.7 degree decrease in SN-MP and
insignificant change in SN-PP and SN-FOP angles.
Maxillary dental changes showed the U1-SN angle
decreased 2.7 degrees.
The upper molars moved distally
1.4 mm and intruded 0.3 mm.
Mandibular dental changes
showed the IMPA decreased 1.1 degrees.
The lower molars
moved mesially 0.6 mm and intruded 0.3 mm.
Dental
relationship changes showed a decrease in overjet of
1.2 mm, decrease in overbite of 1.2 mm, and a Class I molar
movement of 1.8 mm along the functional occlusal plane.
59
Table 3.3. Descriptive statistics of T1 and T2.
Pre-treatment (T1)
Measurement
Post-treatment (T2)
Mean
S.D.
Mean
S.D.
SNA (o)
83.9
4.4
83.5
4.5
SNB (o)
78.6
3.7
79.4
3.5
5.3
2.2
4.2
2.6
27.3
6.7
26.6
6.6
SN-PP ( )
4.9
4.4
4.6
4.5
o
11.0
4.5
10.4
4.8
102.3
9.3
99.6
5.2
Hor U6 (mm)
37.3
5.2
35.9
5.2
Ver U6 (mm)
60.4
4.2
60.1
4.3
IMPA (o)
98.5
5.5
97.4
5.1
Hor L6 (mm)
35.8
5.6
36.4
5.8
Ver L6 (mm)
63.9
4.1
63.6
3.8
Overjet (mm)
4.8
2.1
3.6
1.2
Overbite (mm)
4.3
2.1
3.1
1.3
-1.4
0.9
0.4
0.7
A-P
o
ANB ( )
Vertical
SN-MP (o)
o
SN-FOP ( )
Maxillary dental
U1-SN (o)
Mandibular dental
Dental Relation
Molars (mm)
60
Table 3.4. Descriptive statistics of treatment changes. Positive
values represent mesially-directed or extrusive movements. Negative
values represent distally-directed or intrusive movements.
T1-T2 Difference
Measurement
Mean
S.D.
Significance
SNA (o)
-0.4
1.2
0.107
A-P
o
SNB ( )
0.7**
0.9
<0.001
ANB (o)
-1.1**
1.0
<0.001
SN-MP (o)
-0.7*
1.5
0.041
SN-PP (o)
-0.3
1.5
0.252
o
-0.6
1.9
0.086
U1-SN (o)
-2.7*
6.3
0.034
Hor U6 (mm)
-1.4**
0.8
<0.001
Ver U6 (mm)
-0.3
0.8
0.179
-1.1**
1.9
0.006
0.6**
0.7
<0.001
-0.3
0.6
0.139
Overjet (mm)
-1.2**
1.8
0.005
Overbite (mm)
-1.2**
1.7
0.001
1.8**
0.8
<0.001
Vertical
SN-FOP ( )
Maxillary dental
Mandibular dental
IMPA (o)
Hor L6 (mm)
Ver L6 (mm)
Dental Relation
Molars (mm)
* denotes changes are significant at p<.05
** denotes changes are significant at p<.01
61
X-Y Axis Coordinate System
Inferential statistics were not run for all of the X-Y
axis variables due to a deficient variable-to-sample ratio.
In order for variables to have statistical significance the
variable-to-sample ratio should ideally be 1:10.
However,
graphic representations of the X-Y axis findings are used
in the discussion to help describe treatment changes
(Figure 5.1, Figures A.4-A.7).
62
Figure 3.4. Graphic overlay of treatment changes. Dashed black lines
represent the pre-treatment graphic (T1) and solid red lines represent
the post-treatment graphic (T2).
63
Discussion
This study was designed to evaluate the skeletal and
dental effects of adult Class II nonextraction treatment
using the Invisalign system of treatment with interarch
elastics.
To date, no study on this topic has been
published in the refereed orthodontic literature.
Skeletal A-P Changes
Significant treatment changes were found for the SNB
angle and the ANB angle.
The SNB angle increased and the
ANB angle decreased indicating improvement in the
maxillomandbiular relationship.
The observed reduction in
SNA angle was not statistically significant.
This
indicates that skeletal improvement toward Class I was
primarily due to the mandible moving mesially.
These results generally agree with the literature for
Class II treatment in adult patients.3-6
Without
significant maxillary skeletal growth, A point tends to
move distally or remain unchanged.
The Class II correction
force vector attempts to move the mandible and mandibular
dentition mesially.
These A-P skeletal changes can result
in a decreased ANB angle.3,6-8
The graphic representation of a T1 and T2 overlay show
the aforementioned changes.
The T2 A point is positioned
64
distally to that of T1 and B point is positioned mesially.
A slight projection of the T2 pognonion is also evident.
Skeletal Vertical Changes
The SN-MP angle showed a statistically significant
decrease.
A generally unwanted side effect of Class II
treatment is the tendency for an increased vertical
dimension due to elastic wear.
As this study features non-
growing patients treated without extractions or headgear,
the decrease in vertical dimension is of interest.
A
possible explanation of this could be the constant presence
of aligner material between the opposing dental arches.
These results contrast with the majority of the Class II
literature as most of the studies reviewed showed an
increase in SN-MP.4,5,9-13
Only three of the studies reviewed
showed a decrease in SN-MP.6,13,14
The observed reduction of SN-PP angle and SN-FOP were
not statistically significant.
The Class II literature
shows a general increase in SN-OP.4-7,10,12,15
The most
significant increases in SN-OP were noted in adult
extraction studies.4,5,12
The graphic overlay depicts a slight decrease along
the palatal plane and mandibular plane for T2 compared to
T1.
65
Maxillary Dental Changes
Statistically significant changes were found for the
U1-SN angle and the linear distance of the upper molars to
the Y-axis.
The U1-SN angle decreased contributing to a
reduction in overjet.
These results agree with the studies
that measured U1-SN change.6,10,13
The upper molars showed movement distally for every
patient in the study contributing to an improvement in
molar relationship.
The vertical measurement from the
upper molar to the X-axis was not statistically
significant.
These results agree with the reviewed
functional appliance adult Class II studies in that the
upper molars moved distally throughout the course of
treatment.13,16,17
Presumably due to maxillary growth, none
of the adolescent Class II studies showed distalization of
the upper molars and only one adult conventional fixed
appliance study showed appreciable upper molar movement
distally.3
The graphic overlay shows a mean T2 decrease in
overjet and overbite through uprighting and intrusion of
the upper incisors.
The uprighting appears to be more
movement distally of the incisal tip than the apex.
66
The
graphic overlay also shows distalization of the upper
molars with no notable extrusion.
Mandibular Dental Changes
Statistically significant changes were found for the
IMPA and the linear distance of the lower molars to the Yaxis.
The IMPA decreased slightly despite Class II elastic
wear.
This may be explained by interproximal reduction of
the lower anterior dentition, which is often prescribed by
the Invisalign treatment software to alleviate crowding and
protrusion.
Other contributing factors could be dispersion
of the Class II elastics force across the entire mandibular
dentition, complete faciolingual coverage of the dentition,
and dental expansion built into the treatment plan.
This
finding is in contrast to nonextraction Class II
conventional fixed appliance studies in the literature as
all that measured showed an increase in IMPA.12,13,17,18
The
functional appliance studies that measured IMPA showed
seven to 10 times the amount of increase that was found in
the current study.6,13
The lower molars showed movement mesially contributing
to the molar relationship improvement.
This finding agreed
with the literature in direction of movement, but the
current study featured less distance than the other
67
studies.5,10-14,16-20
The lower molars showed a statistically
insignificant intrusion.
Every previous Class II study
reviewed that measured for a vertical dental component of
the lower molars found extrusion.5,10,14,15,18,19
The T1 versus T2 graphic shows a slight retroclination
of the lower incisors.
The incisal tip features a movement
distally as the apex appears unchanged.
The T2 lower
molars show movement mesially with no visible extrusion
from their T1 position.
Dental Relationship Changes
Overjet, overbite, and molar relationship showed
statistically significant changes.
Overjet and overbite
both decreased over the course of treatment.
These
findings are in agreement with the Class II literature,
although the current study showed less overjet reduction by
comparison.3,4,8,11,13,15-17,20
The upper molars moved distally and the lower molars
moved mesially resulting in an improved molar relationship
in every patient.
This finding agrees with the Class II
literature that measures for molar correction.4,11,15-17,20
The
upper molars moved a distance nearly triple that of the
lower molars indicating that molar correction was primarily
due to distalization of the upper molars.
68
Despite statistical significance, treatment changes
were relatively small and some did not exceed the
cephalometric measurement error values presented by
Baumrind and Frantz.21
Future studies in this area may see
different results given recent advances in materials and
software available to the clinician.
Conclusions
1)
The Invisalign system in conjunction with interarch
elastics is a viable option for mild Class II
nonextraction treatment in the adult dentition.
2)
Class II treatment with the Invisalign system is
capable of providing reliable upper molar
distalization and improvement in molar relationship
while maintaining an element of control in the
vertical dimension.
69
References
1. Daher S, editor Invisalign treatment for Class II
correction. 2012 Invisalign Summit; 2012; Las Vegas,
NV.
2. Align Technology, Inc. Dr. Sam Daher's techniques for
Class II correction with Invisalign and elastics:
Align Technology, Inc.; 2011 [cited 2013 July 1,
2013].
3. Proffit WR, Phillips C, Douvartzidis N. A comparison of
outcomes of orthodontic and surgical-orthodontic
treatment of Class II malocclusion in adults. Am J
Orthod Dentofacial Orthop. 1992;101:556-565.
4. Cassidy DW, Jr., Herbosa EG, Rotskoff KS, Johnston LE,
Jr. A comparison of surgery and orthodontics in
"borderline" adults with Class II, division 1
malocclusions. Am J Orthod Dentofacial Orthop.
1993;104:455-470.
5. Vaden JL, Harris EF, Behrents RG. Adult versus
adolescent Class II correction: a comparison. Am J
Orthod Dentofacial Orthop. 1995;107:651-661.
6. Upadhyay M, Yadav S, Nagaraj K, Uribe F, Nanda R. Miniimplants vs fixed functional appliances for treatment
of young adult Class II female patients: a prospective
clinical trial. Angle Orthod. 2012;82:294-303.
7. Tovstein B. Behavior of the occlusal plane and related
structures in treatment of Class II malocclusions.
Angle Orthod. 1955;25:189-198.
8. Combrink FJ, Harris AM, Steyn CL, Hudson AP.
Dentoskeletal and soft-tissue changes in growing Class
II malocclusion patients during nonextraction
orthodontic treatment. J South African Dent Assoc.
2006;61:344-350.
9. Gianelly AA, Arena SA, Bernstein L. A comparison of
Class II treatment changes noted with the light wire,
edgewise, and Frankel appliances. Am J Orthod.
1984;86:269-276.
70
10. Ellen EK, Schneider BJ, Sellke T. A comparative study
of anchorage in bioprogressive versus standard
edgewise treatment in Class II correction with
intermaxillary elastic force. Am J Orthod Dentofacial
Orthop. 1998;114:430-436.
11. Nelson B, Hansen K, Hagg U. Class II correction in
patients treated with Class II elastics and with fixed
functional appliances: a comparative study. Am J
Orthod Dentofacial Orthop. 2000;118:142-149.
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. Kinzinger G, Frye L, Diedrich P. Class II treatment in
adults: comparing camouflage orthodontics, dentofacial
orthopedics and orthognathic surgery--a cephalometric
study to evaluate various therapeutic effects. J
Orofac Orthop. 2009;70:63-91.
14. Liu J, Zou L, Zhao ZH, Welburn N, Yang P, Tang T, et
al. Successful treatment of postpeak stage patients
with class II division 1 malocclusion using nonextraction and multiloop edgewise archwire therapy: a
report on 16 cases. Int J Oral Sci. 2009;1:207-216.
15. Jones G, Buschang PH, Kim KB, Oliver DR. Class II nonextraction patients treated with the Forsus Fatigue
Resistant Device versus intermaxillary elastics. Angle
Orthod. 2008;78:332-338.
16. Ruf S, Pancherz H. Dentoskeletal effects and facial
profile changes in young adults treated with the
Herbst appliance. Angle Orthod. 1999;69:239-246.
17. Ruf S, Pancherz H. Orthognathic surgery and dentofacial
orthopedics in adult Class II Division 1 treatment:
mandibular sagittal split osteotomy versus Herbst
appliance. Am J Orthod Dentofacial Orthop.
2004;126:140-152.
18. Meistrell ME, Jr., Cangialosi TJ, Lopez JE, CabralAngeles A. A cephalometric appraisal of nonextraction
Begg treatment of Class II malocclusions. Am J Orthod
Dentofacial Orthop. 1986;90:286-295.
71
19. Janson G, Sathler R, Fernandes TM, Branco NC, Freitas
MR. Correction of Class II malocclusion with Class II
elastics: a systematic review. Am J Orthod Dentofacial
Orthop. 2013;143:383-392.
20. Nelson B, Hansen K, Hagg U. Overjet reduction and molar
correction in fixed appliance treatment of Class II,
division 1, malocclusions: sagittal and vertical
components. Am J Orthod Dentofacial Orthop.
1999;115:13-23.
21. Baumrind S, Frantz R. The reliability of head film
measurements. 2. Conventional angular and linear
measures. Am J Orthod. 1971;60:505-517.
.
72
Table A.1. Sample ages and treatment duration.
Pt #
Age at T1
T1 Ceph
T2 Ceph
1
26y 1m
11/24/09
12/15/11
25
2
53y 1m
3/18/10
7/31/12
20
3
16y 5m
4/6/10
5/8/12
25
4
23y 0m
9/2/10
5/24/12
20
5
39y 2m
10/7/08
10/7/10
24
6
34y 9m
2/19/09
5/2/11
27
7
52y 2m
6/7/10
3/5/12
21
8
47y 11m
3/9/10
4/11/12
25
9
16y 8m
7/20/10
5/8/12
22
10
29y 10m
1/5/10
6/7/12
29
11
36y 3m
1/25/10
11/17/11
22
12
35y 3m
1/26/11
7/12/12
18
13
24y 6m
11/16/09
8/25/11
21
14
18y 2m
10/21/09
6/5/12
32
15
54y 0m
9/29/09
4/6/11
19
16
45y 7m
1/11/11
11/27/12
22
17
17y 10m
8/11/08
5/10/10
21
18
26y 9m
7/17/08
8/24/10
25
19
18y 0m
6/10/10
3/14/12
21
20
24y 2m
12/7/09
8/1/12
33
21
31y 6m
11/4/09
9/20/11
22
22
46y 11m
11/15/10
1/21/13
26
23
34y 0m
11/8/10
8/7/13
33
24
62y 5m
4/13/10
10/10/12
30
25
39y 3m
5/28/09
9/3/11
28
26
36y 11m
12/8/10
7/30/13
32
27
51y 3m
11/13/08
10/11/11
35
28
52y 11m
11/22/11
7/18/13
20
73
Tx Time (mo)
Table A.2. Sample Angle classification statistics.
Patients
Classification
Females:Males
Mean Age
Range
19
Class II div 1
14:5
37y9m
16y5m – 62y5m
9
Class II div 2
4:5
31y0m
16y8m – 52y0m
28
All
18:10
35y6m
16y5m – 62y5m
74
Table A.3. Anatomical landmark definitions.
Landmark
Definiton
Nasion
The most anterior point of the frontonasal
suture
Anterior Nasal Spine
The most anterior tip of the nasal spine
A point
The most posterior point in the concavity
between the maxillary alveolar process and the
anterior nasal spine
Upper incisor apex
The root apex of the upper central incisor
Upper incisor tip
The incisal tip of the upper central incisor
Lower incisor tip
The incisal tip of the lower central incisor
Lower incisor apex
The root apex of the lower central incisor
B point
The posterior point in the concavity between the
mandibular alveolar process and the mandibular
symphysis
Pogonion
The most anterior point of the mandibular
symphysis
Gnathion
The point midway between the anterior and
inferior points of the mandibular symphysis
Menton
The most inferior point of the mandibular
symphysis
Inferior Gonion
The most inferior point of the mandibular gonial
angle
Lower 1st molar distal
contact
The distal contact point of the lower 1st molar
Lower 1st molar
mesiobuccal cusp
The mesiobuccal cusp tip of the lower 1st molar
Lower 1st premolar
cusp
The cusp tip of the lower 1st premolar
Upper 1st molar distal
contact
The distal contact point of the upper 1st molar
Posterior Nasal Spine
The most posterior point of the bony hard palate
Sella
The center of the pituitary fossa
Reference point 1
Point representing 15 mm on the cephalometric
ruler
Reference point 2
Point representing 0 mm on the cephalometric
ruler
75
Sella-Nasion
1
2
3
Palatal Plane
(ANS-PNS)
Functional Occlusal
Plane
(Occlusal L6-Tip L4)
Mandibular Plane
(Go-Me)
Figure A.1. Cephalometric plane measurements: Sella-Nasion to palatal
plane angle (1); Sella-Nasion to functional occlusal plane angle (2);
Sella-Nasion to mandibular plane angle (3). 76
3
4
1
2
5
Figure A.2. Cephalometric angular measurements: SNA (1); SNB (2); ANB
(3); U1-SN (4); IMPA (5).
77
3
1,2
Figure A.3. Functional occlusal plane measurements: overjet (1);
overbite (2), molar relationship (3).
78
Table A.4. Intra-class correlation values. Measurements at the initial
time point (T1) were matched against a calibration measurement (call)
at the initial time point.
Intra-class
Correlation
Range
Mean
SNAT1-SNAcal
0.998
0.907-0.999
0.961
SNBT1-SNBcal
0.996
ANBT1-ANBcal
0.941
SN-MPT1-SN-MPcal
0.985
SN-PPT1-SN-PPcal
0.943
SN-FOPT1-SN-PPcal
0.944
U1-SNT1-U1-SNcal
0.999
IMPAT1-IMPAcal
0.933
OJT1-OJcal
0.918
OBT1-OBcal
0.994
MolarsT1-Molarscal
0.934
HorU6T1-HorU6cal
0.994
VerU6T1-VerU6cal
0.907
HorL6T1-HorL6cal
0.996
VerL6T1-VerL6cal
0.931
Measurement
79
Table A.5. Mean X-Y axis coordinates.
Measurement
Pre-treatment (T1)
Horizontal
Vertical
Post-treatment (T2)
Horizontal
Vertical
S-N
69.5
8.5
69.6
8.5
S-U6
37.3
-60.4
35.9
-60.1
S-L6
35.8
-63.9
36.4
-63.6
S-U1 tip
73.7
-67.2
71.8
-66.1
S-U1 apex
66.4
-45.1
65.2
-44.1
S-L4 tip
52.4
-63.5
52.5
-63.6
S-L1 tip
69.1
-62.3
68.9
-62.3
S-Pg
64.7
-97.0
65.0
-96.4
S-PNS
22.8
-41.0
22.6
-41.0
S-ANS
73.9
-39.7
73.7
-39.5
S-A point
70.6
-44.9
69.9
-44.7
S-L1 apex
59.2
-80.5
59.2
-80.6
S-B point
62.9
-81.1
63.3
-81.0
S-Gn
62.1
-100.8
62.4
-100.3
S-Go
4.7
-83.1
4.7
-83.0
S-Me
55.6
-101.2
55.9
-100.8
80
Pre+Treatment"
20.000&
0.000&
0.000&
10.000&
20.000&
30.000&
40.000&
50.000&
60.000&
70.000&
80.000&
Nasion&
U6&
U1&4p&
!20.000&
U1&apex&
L6&
L4&4p&
!40.000&
Y"Axis"
L1&4p&
Pogonion&
PNS&
!60.000&
ANS&
A&point&
L1&apex&
B&point&
!80.000&
Gnathion&
Gonion&
Menton&
!100.000&
!120.000&
X"Axis"
Figure A.4. Graphic overlay of T1 measurements.
81
Post+treatment"
20.000&
0.000&
0.000&
10.000&
20.000&
30.000&
40.000&
50.000&
60.000&
70.000&
80.000&
Nasion&
U6&
U1&4p&
!20.000&
U1&apex&
L6&
L4&4p&
!40.000&
Y"Axis"
L1&4p&
Pogonion&
PNS&
!60.000&
ANS&
A&point&
L1&apex&
B&point&
!80.000&
Gnathion&
Gonion&
Menton&
!100.000&
!120.000&
X"Axis"
Figure A.5. Graphic overlay of T2 measurements.
82
Figure A.6. Class II division 1 graphic overlay. Dashed lines
represent the pre-treatment graphic (T1) and solid lines represent the
post-treatment graphic (T2).
83
Figure A.7. Class II division 2 graphic overlay. Dashed lines
represent the pre-treatment graphic (T1) and solid lines represent the
post-treatment graphic (T2).
84
Vita Auctoris
Brian Michael Klein was born on September 24, 1982 in
Alton, Illinois.
In 1985 he and his family moved to Mount
Vernon, Illinois where he was raised and attended school.
In 2006 he graduated from Indiana University in
Bloomington, Indiana with a B.S. in Nutrition Science and a
minor in Biology.
In 2011 he received his D.M.D. with
honors from Southern Illinois University School of Dental
Medicine in Alton, Illinois.
In December 2011 he married
the beautiful Jane Alexandra Walde in St. Louis, Missouri.
Following graduation from dental school in 2011, he began
his studies at Saint Louis University in pursuit of a
Master’s degree from the Orthodontics program.
Upon
graduation he and Jane will return to Mount Vernon where
they’ll anxiously await the birth of their first child in
February 2014.
Brian will proudly join his father,
Christopher, as a partner in Klein Orthodontics.
85