LONGITUDINAL GROWTH EVALUATION OF TREATED AND UNTREATED
ANGLE CLASS II, DIVISION 2 MALOCCLUSIONS
Daniel A. Lovell, 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
2011
ABSTRACT
Objective: The aim of this study was to compare the
longitudinal skeletal changes in Class II, Division 2
subjects treated by non-extraction therapy with untreated
Class II, Division 2 and normal controls that are matched
by gender and age.
Thus, the goal is to determine how
growth is expressed when the mandible is “unlocked” in
Class II, Division 2 skeletal patterns.
Materials and Methods: Serial cephalograms of 29
Caucasian Class II, Division 2 subjects who were treated by
non-extraction orthodontic therapy were analyzed at three
timepoints: T1-start (mean age: 12 years, 11 months),
T2-debond (mean age: 15 years, 2 months) and T3-retention
(mean age: 16 years, 6 months). The treated group was
compared to an untreated Class II, Division 2 and Class I
normal sample that were matched for age and gender across
the three time points. Fifteen landmarks were identified
and angular and ratio measurements analyzed (10 skeletal
and 3 dental) in both vertical and horizontal vectors.
Results: Dental and skeletal means were evaluated across
three time points using analysis of variance (ANOVA).
There were significant dental and horizontal skeletal
changes, but no significant vertical changes observed with
treatment between the groups.
Two measurements confirmed
1
that the mandible was more anteriorly positioned in
relation to the cranial base in the treated sample.
Thus,
the mandible grew forward slightly more in the treated
sample than the controls.
Conclusions: 1. In the treated Class II, Division 2
group there was a significant proclination of the maxillary
and mandibular incisors.
2. When compared across the three
time points there were no significant vertical changes
between the treated and untreated samples.
3. In the
horizontal dimension, there was a statistically significant
increase in the anterior position of the mandible in
relation to the cranial base for the treated Class II,
Division 2 group when compared to untreated controls.
4.
There is a positive effect of orthodontic treatment in
Class II, Division 2 subjects, resulting in a slightly more
anteriorly positioned mandible.
2
LONGITUDINAL GROWTH EVALUATION OF TREATED AND UNTREATED
ANGLE CLASS II, DIVISION 2 MALOCCLUSIONS
Daniel A. Lovell, 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
2011
COMMITTEE IN CHARGE OF CANDIDACY:
Professor Eustaquio Araujo,
Chairperson and Advisor
Professor Rolf G. Behrents
Adjunct Professor Peter H. Buschang
i
DEDICATION
I dedicate this project to my always supportive and
loving family.
To my wife, Megan, for her endless love and
encouragement for without her the completion of this
educational journey would not have been achievable.
To my son Hudson and daughter Hadley, who have brought
so much joy and unconditional love to my life.
To my parents, John and Sheila, whose love, support
and guidance have shaped me into the person I am today.
ii
ACKNOWLEDGEMENTS
Thank you to Dr. Araujo for guiding me through this
process.
Your constant encouragement, motivation, and
patience have made this all possible.
Thank you to Dr. Behrents for his knowledge and
guidance throughout this educational process.
Thank you to Dr. Buschang for his assistance in the
project design, statistics and for providing the untreated
sample.
Thank you to Dr. Lisa Alvetro and staff for allowing
the use of the treated records and for aiding in the
records collection process.
iii
TABLE OF CONTENTS
List of Tables. . . . . . . . . . . . . . . . . . . . . ..v
List of Figures. . . . . . . . . . . . . . . . . . . . . vi
CHAPTER 1: INTRODUCTION
Description of the Problem. . . . . . . . . . . . . .1
CHAPTER 2: REVIEW OF THE LITERATURE
Normal Occlusion. . . . . . . . . . . . . . . . . . .3
Definition. . . . . . . . . . . . . . . . . . . 3
Prevalence. . . . . . . . . . . . . . . . . . . 4
Class II, Division 2 Malocclusion. . . . . . . . . . 4
Definition. . . . . . . . . . . . . . . . . . . 4
Etiology. . . . . . . . . . . . . . . . . . . . 6
Prevalence. . . . . . . . . . . . . . . . . . . 8
Characterization. . . . . . . . . . . . . . . . 9
Untreated developmental characteristics. . . . 15
Treatment . . . . . . . . . . . . . . . . . . .17
References. . . . . . . . . . . . . . . . . . . . . 23
CHAPTER 3: JOURNAL ARTICLE
Abstract. . . . . . . . . . . . . . . . . . . . . . 28
Introduction. . . . . . . . . . . . . . . . . . . . 30
Materials and Methods. . . . . . . . . . . . . . . .32
Sample. . . . . . . . . . . . . . . . . . . . 32
Methodology. . . . . . . . . . . . . . . . . . 34
Statistical Analyses. . . . . . . . . . . . . .37
Results. . . . . . . . . . . . . . . . . . . . . . .38
Discussion. . . . . . . . . . . . . . . . . . . . . 47
Conclusions. . . . . . . . . . . . . . . . . . . . .51
Literature Cited. . . . . . . . . . . . . . . . . . 52
Vita Auctoris. . . . . . . . . . . . . . . . . . . . . . 55
iv
LIST OF TABLES
Table 2.1:
Comparative Cephalometric Studies
Describing Class II, Division 2
Characteristics. . . . . . . . . . . . . . 14
Table 2.2:
Cephalometric Studies Evaluating Treatment
and Growth in Class II, Division 2
Malocclusions. . . . . . . . . . . . . . . 22
Table 3.1:
Age and Gender Distribution
of Study Sample. . . . . . . . . . . . . . 33
Table 3.2:
Landmark Definitions and Abbreviations. . .34
Table 3.3
Cephalometric comparisons between
the three groups at T1. . . . . . . . . . .38
Table 3.4:
Dental Comparisons and Statistically
Significant changes over time within each
group. . . . . . . . . . . . . . . . . . . 40
Table 3.5:
Horizontal and Vertical Skeletal
Comparisons and Statistically Significant
over time within each group. . . . . . . .42
Table 3.6:
Dental Comparisons between the three
groups for T1, T2, and T3. . . .. . . . . .43
Table 3.7:
Horizontal and Vertical Comparisons
between the three groups
for T1, T2, and T3. . . . . . . . . . . . .46
v
LIST OF FIGURES
Figure 2.1:
Dental Appearance of Class II, Division 2. .5
Figure 3.1:
Anatomical Landmarks. . . . . . . . . . . .35
Figure 3.2:
Cephalometric Measurements. . . . . . . . .36
vi
CHAPTER 1: INTRODUCTION
Description of the Problem
Class II, Division 2 malocclusions are one of the
least prevalent malocclusions represented in populations
today.
There is limited knowledge about this malocclusion
that typically presents difficult vertical and anteroposterior abnormalities which require the aid of growth or
surgery to correct.
It is a common belief in the orthodontic literature
that “unlocking” the mandible in Class II, Division 2
malocclusions allows growth of the mandible to be expressed
in a more anterior direction, which will aid in the
correction of the disto-occlusion.
Currently, this claim
is unsupported in the orthodontic literature.
In assessing growth, longitudinal research designs are
the gold standard. Many cephalometric studies have been
conducted characterizing the malocclusion, but few have
longitudinally evaluated the effects of orthodontic
treatment and growth of the mandible in the treated Class
II, Division 2 with matched untreated controls.
The aim of this study is to compare the longitudinal
dental and skeletal changes in Class II, Division 2
subjects treated by non-extraction therapy with untreated
Class II, Division 2 and normal controls that are matched
1
by gender and age.
Thus, the goal is to determine how
growth is expressed when the mandible is “unlocked” in
Class II, Division 2 skeletal patterns.
2
CHAPTER 2: REVIEW OF THE LITERATURE
Normal occlusion
Definition
Normal occlusion was first described by E.H. Angle in
the early 1900’s.
It was proposed that the upper first
molars were the key to occlusion and that the upper and
lower molars should have a relationship in which the
mesiobuccal cusp of the upper molars occluded with the
buccal groove of the lower molar.1
In addition, the teeth
needed to exhibit a relationship in which they were aligned
in a smooth curving line of occlusion.1,2
Andrews later expanded on Angle’s original definition
of normal occlusion by including 6 keys that defined normal
occlusion.
He evaluated 120 non-orthodontically treated
normals and defined the following six keys that contributed
to the definition of normal occlusion: molar relationship,
crown angulation, crown inclination, no rotations, tight
contacts, and a flat occlusal plane.3
These keys outline
the foundation of ideal orthodontic treatment that result
in a desirable normal occlusion for years.
3
Prevalence
The Division of Health Examination Statistics
conducted a survey that collected data about the health of
the United States population ages 12-17.
It was reported
that approximately 54% of the subjects had neutroclusion,
in which the anteroposterior relationship of the upper with
the lower back teeth were characteristic of normal
occlusion.4
In a more recent study, the National Center for
Health Statistics conducted the third National Health and
Nutrition Examination Survey (also known as the NHANES III)
which included an evaluation of oral health in the United
States from 1988 to 1994. Profitt et al used the
information from this national survey to estimate the
prevalence of malocclusion in the United States.
They
found that at most, 30% of the population has Angle’s
normal occlusion.5
Class II, Division 2 Malocclusion
Definition
Angle first defined the Class II, Division 2
malocclusion in 1907 in the Treatment of Malocclusion of
the Teeth as the following: “the malocclusion characterized
specifically by distal occlusion of the teeth in both
lateral halves of the lower dentition, indicated by the
4
mesio-distal relations of the first permanent molars, but
with retrusion instead of protrusion of the upper
incisors.”1
Angle proceeds to describe that the
distocclusion and recession of the lower jaw and chin
results in a facial deformity that is caused by the distal
position of the mandible and lack of vertical growth below
the nose.
In addition, the upper incisors tipping down and
inward and the lingual tipping of the lower incisors is the
result of the molars not erupting to the normal vertical
height.1
Figure 2.1: Dental appearance of class II, division 2
5
Etiology
Although the evidence in the literature is
inconclusive as to the origin of Class II, Division 2
malocclusions, there are many theories discussed as to why
this malocclusion forms.
Angle first stated that since
there are no complications of the nasal passages, the mouth
can be kept closed and the lips perform their functions,
resulting in retrusion of the upper incisors during
eruption until they come into contact with the retruded
lower incisors, which ultimately equates to crowding in the
upper arch in the canine area.1
The Eastern Component Group of the Angle Society
thought that the mandible was in normal position like that
seen in normal occlusions.
This group also believed that a
failure in metabolic or developmental processes resulted in
less than normal vertical growth in the posterior teeth.
This combined with hypertrophied sucking muscles due to
habits produced posterior pressure on the anterior part of
the mandible which produced less forward growth of the
mandible which resulted in a distal locking of the
mandibular molar teeth.6
The authors proceed to list 12 etiologic factors
possibly associated with the development of Class II,
Division 2 malocclusion:
6
1) Dysfunctional activity of the lip muscles
2) Excess contraction of the mentalis
3) Dysfunctional swallowing patterns
4) Early loss of primary molars
5) Tense lip musculature
6) Hypertrophy of the cheek muscles
7) High strung temperament
8) Malnutrition in infancy
9) Hypertrophied mentalis muscles
10) Posterior pull of hyoid muscles
11) Posture habit
12) Delayed anterior growth of the mandible.6
Hedges believed that the Class II, Division 2
malocclusion was not a specific stereotyped clinical
syndrome, but rather that it could arise from a combination
of eruptive disharmony and muscular pressure placed on the
teeth resulting in a malocclusion that was a result of
compensatory variation.7
Strang made clinical observations that it is possible
that the maxillary buccal segments shift forward resulting
in axial inclination of the lateral incisors that overlap
the central incisors.
He also believed that heredity was a
key factor, but that faulty growth resulted in decreased
vertical growth below the nose and a distal positioning of
the mandible.8
Like Strang, Graber stated that there is in fact a
hereditary pattern to Class II, Division 2 malocclusion and
that there is usually normal activity of the lip and cheek
muscles.
In addition, he states that there is a tendency
7
for the tongue to increase the curve of Spee by interfering
with the eruption of the posterior teeth by filling the
interocclusal spaces.
It has also been noted that this
type of malocclusion exhibited tooth guidance problems that
could result in temporomandibular joint problems.9
Another indication of a heredity factor was described
by Peck et al.10 who found that the mesiodistal tooth
diameter in Class II, Division 2 malocclusion were
significantly smaller when compared to a normal control
sample, which is indicative of the existence of a
significant genetic influence in the development and
formation of Class II, Division 2 malocclusions.
Prevalence
Class II, Division 2 malocclusions represent a small
number of the total malocclusions in a population,
regardless of racial group. The occurrence of this
malocclusion has been reported to represent 3-4% of the
population.6
Other populations have also been investigated.
In a study on the incidence and manifestations of
malocclusion in Australian Caucasians, Taylor concluded
that Class II, Division 2 malocclusions represented 5% of
their population.11
Other studies conducted on the
8
Caucasian population have reported the prevalence of Class
II, Division 2 malocclusion to be between 2.3%-3.4%.12-14
Different ethnic groups have also been studied.
In African
American individuals the prevalence of Class II, Division 2
malocclusion was reported to be 1.6%, while 1.7% was found
for the Arab population and the Chinese
approximately 1%.15-17
Characterization
Although Angle’s definition and classification has
stood the test of time, many have tried to further explain
the characteristics of the specific malocclusion using
facial pattern observations as well as skeletal and dental
cephalometric analyses. Sassouni18 noted that when
discussing the characteristics of any malocclusion, it is
important to point out both positional deviations, and
dimensional deviations from normal, which make a
malocclusion unique.
In describing that facial pattern of Class II,
Division 2 subjects, Ricketts observed: “This malocclusion
is frequently present in brachyfacial patterns with
resulting strong musculature.
The lower facial height and
mandibular arc are below normal range, therefore the teeth
9
are deep in the basal bone.”19 Some authors believe this
hypodivergent pattern is due to a decreased lower facial
third19-22, while others believe that this is not a verified
characteristic of the malocclusion and that the vertical
facial height is similar to Class I malocclusions.23-25
It
has also been shown that the chin is prominent in Class II,
Division 2 malocclusions and even resembles the chin
position of Class I malocclusions.21,22
The aforementioned facial observations are a result of
the underlying skeletal structures of the face and jaws.
Pradhan (1979) conducted a cephalometric study on Class II,
Division 2 malocclusions and concluded that it was a
specific entity resulting in a skeletal deformity that
modified normal muscle length, which resulted in a
skeletal-dental anomaly.26
In the vertical dimension, it has been shown that the
ramus height in Class II, Division 2 malocclusions is
normal27 and the gonial angle is more acute resulting in a
more horizontal mandibular plane.23,24,27,28
However,
Hitchcock29 would argue that the mandibular plane is not
flatter in Class II, Division 2 malocclusions when compared
to Class I normal skeletal types.
There is much discussion in the literature surrounding
the anteroposterior skeletal positioning of the mandible in
10
Class II, Division 2 malocclusions.
Swann tried to further
classify Class II, division 2 malocclusions into three
groups.
Type 1 represented a normal path of closure from a
resting position to maximum intercuspation with the
permanent first molars in a Class II relationship.
Type 2
indicated a bimaxillary Class II, Division 2 in which the
mandible had a normal path of closure and the molars were
in normal mesio-distal relationship.
The third type
exhibited a functional Class II, Division 2 that was
representative of type 1, except that mandibular closure
was in a distal relationship.30
He concluded that nearly
33% of Class II, Division 2 subjects represent this type 3
group that has a functional posterior mandibular
displacement.30
Ingervall performed a study looking at the
relationship between the retruded contact position,
intercuspation, and rest position in Class II, Division 2
subjects to determine if the mandible exhibited a “distally
locked” position.
He showed that there is no significant
evidence to Swann’s claim that the mandible is locked in a
distal position due to the angulation of the maxillary
central incisors.23 In the positional dimension, the
mandible has been shown to be distally positioned when
compared to normal,20,21,23,29 however other studies have shown
the mandible to be in correct position.22,31
11
With regards to the size of the mandible, multiple
studies have shown the size to be smaller than normal.25,27
Hellman32 reported that the mandible was narrower and longer
and was in a more normal anteroposterior position when
compared to Class II, division 1 malocclusion.
This
finding was supported by other studies that concluded that
Class II, Division 2 subjects resemble Class I
malocclusions more than Class II, Division 1
malocclusions.31,33
On the level of the occlusion there are pathognomonic
characteristics of Class II, Division 2 malocclusions.
Heide described the Class II, Division 2 malocclusion as
having an overbite in which the incisal edges of the lower
incisors are in contact with the palatal soft tissue of the
maxilla.
In addition, this malocclusion displays an
inverted upper occlusal plane, two different occlusal
planes in the lower arch, and a large freeway space.34 Deep
overbite and a larger overjet have been observed in these
malocclusions when compared to normal occlusions.21,23,24,29
Although it has been reported that there is considerable
variation in the upright position of the lower incisors in
Class II, Division 2 subjects,33,7 the upright position of
the maxillary and mandibular incisors resulting in an
increased inter-incisal angle remains a classic
12
characteristic of this malocclusion.21,23-25,29
Finally,
several studies agree that the alveolar process and
dentition are in a subnormal position when compared to
normal occlusions.19,22,32
The following cephalometric
findings are reported in Table 2.1.
13
Table 2.1: Comparative cephalometric studies describing Class II, Div. 2
characteristics
Author (Date)
Baldridge(1941)
Renfroe(1948)
Wallis(1963)
Godiawala &
Joshi(1974)
Sample (N)
Cl I (50)
Cl II/1 (32)
Cl II/2 (21)
Cl I (43)
Cl II/1 (36)
Cl II/2 (16)
Cl I (47)
Cl II/1 (105)
Cl II/2 (81)
Cl I (30)
Cl II/2 (25)
14
Hitchcock(1976)
Cl I
Cl II/1 (57)
Cl II/2 (42)
Maj &
Lucchese(1982)
Cl I (28)
Cl II/2 (60)
Karlsen(1994)
Cl I (25)
Cl II/2 (22)
Brezniak(2002)
Cl I (34)
Cl II/1 (54)
Cl II/2 (50)
Class II/2 Findings
Mandible in correct anteroposterior position
Mandible may be longer
No lack of mandibular development
Posteriorly positioned dental arches
Chin as anterior as Cl I
Square type mandibular border (horizontal)
Smaller mandibular body length (like Cl II/1)
Normal ramus height (like Cl I)
Acute gonial angle and mandibular plane
Mandibular length slightly smaller
Vertical height of face same as Cl I
Retroclined upper central incisors only distinct feature
Position of maxilla is the same as Cl I
Mandibular plane is not flatter than Cl I
Mandible more distally positioned compared to Cl I
Have a unique skeletal pattern
Smaller gonial angle
Hyperdevelopment of component parts of the mandible
B point more retruded
Retroclined symphysis
Larger incisal height and smaller molar height
Lower anterior facial height
Maxilla is orthognathic
Mandible short with retrognathic parameters
Chin is relatively prominent
Facial pattern is hypodivergent
Upper incisors are retroclined and the overbite is deep
Untreated Developmental Characteristics
In a longitudinal radiographic implant study, Bjork
showed that the mandible becomes more prognathic in
relation to the maxilla as individuals age, and that the
mandible rotates forward in the face in relation to the
cranial base, thus exhibiting a counterclockwise rotation.35
Given the information on mandibular growth, FischerBrandies et al.36 conducted a cephalometric study, in which
adult Class II, Division 2 subjects were compared to normal
controls. The results showed that after the completion of
mandibular growth there was no significant difference in
skeletal structure between the groups with the exception of
B point.
Lisson and Pyka found that there were significant
differences between Division 1 and Division 2 Class II
malocclusions in an untreated sample.
Specifically, they
found that the angle between the anterior cranial base and
mandibular plane, the maxillary plane to mandibular plane,
and the gonial angle were all smaller in the untreated
Division 2 sample.37
In a similar study, Isik et al.38
compared untreated subjects in an effort to determine
dental and skeletal differences between the two divisions
of Class II malocclusions by looking at arch width and
cephalometrics.
They concluded that the Division 2
15
subjects had more concave profiles exhibiting a prominent
chin and lower vertical proportions.
In addition, the
authors concluded that Class II, Division 2 subjects were
found to be similar to Class I skeletal subject with no
mandibular retrognathia, and thus, when treated,
dentoalveolar mechanics can be used in correcting the
malocclusion.38
In 2009, Al-Khateeb conducted a study that evaluated
551 cephalometric radiographs in Class II, Division 1 and 2
untreated subjects.
The results of the study showed that
the maxilla was prognathic in both divisions, and the
mandible was retruded in the Division 1 group, and
orthognathic in the Division 2 group.
In the vertical
dimension, the Division 1 group displayed an increase in
lower anterior facial height, and the Division 2 group
exhibited a decrease in lower anterior facial height.
The
Division 2 group had both an increased interincisal angle
and a normal inclination of the lower incisors when
compared with the Division 1 group.
The author states
“that Class II, Division 2 differs in almost all of the
cephalometric features from Class II, Division 1 in the
anteroposterior and vertical dimensions and should thus be
considered as a separate entity.”39
16
Treatment of Class II, Division 2 Malocclusions
In orthodontic treatment there are many different
methods to consider when correcting a malocclusion.
Throughout the orthodontic literature, practitioners and
researchers alike present methods considered to be
beneficial in successfully correcting a malocclusion.
Therefore, it is important to distinguish the clinical
observations and theories from the scientific evidence and
distinguish those theories that are supported by the
scientific evidence.
Given the characteristics and etiology of Class II,
Division 2 malocclusions, the Eastern Component Group of
the Angle Society recommended the following for successful
treatment of these cases:
1) Distalizing the maxillary dentition using anchorage
in the lower arch.
2) Increasing the growth in the mandibular canine and
premolar areas and align the lower incisors
3) Tipping the maxillary teeth labially and intrude
4) Utilizing a bite plate to elevate the posterior
teeth.6
Taylor was one of the first to discuss the idea of
“releasing” the distally held mandible in Class II,
Division 2 malocclusions and claimed that the mandible was
locked in a posterior position by the maxillary central
incisors.
He recommended “early treatment of this
17
malocclusion at the time of eruption of the upper central
incisors, even before the laterals have erupted, once it is
determined that a Class 2, Division 2 is in the making.”40
Steps in treating the malocclusion were presented in the
following order:
1)Expand the upper arch
2)Add cervical traction with molar anchorage
3)Move upper incisors labially
4)Move upper laterals lingually.40
Arvystas agrees that growth is paramount in both the
vertical and anteroposterior correction of Class II,
Division 2 malocclusions.
He explains that in non-growing
individuals, surgical correction of this malocclusion often
needed to produce an ideal result.41
Levy said, “Clinicians often refer to correction of
the incisor position in the Class II, Division 2 case as
unlocking the occlusion or a “free-ing” of the mandible.
This resultant freedom may be due to any one or a
combination of three factors.
They are: positional changes
of the condyle; rotational changes of the mandible; and
actual growth of the maxillary and mandibular processes.”42
In this study the author discovered that the mandible grew
more than normal when compared to the cranial base, which
was thought to be a result of the deep bite inhibiting the
growth of the mandible.
18
Three possible treatment modalities for Class II,
Division 2 malocclusions were presented by Ricketts et al.
These include: distalizing the upper arch, advancing the
lower arch, or a combination of the both.
The authors
believed that it was important to “unlock” the deep bite by
advancing the upper incisors, which would resemble a Class
II, Division 1 malocclusion that could be treated with a
concentration on a dental change instead of a skeletal
change.19
The records of 60 Class II, Division 2 malocclusions
using cephalometric radiographs that were taken prior to
the start of treatment and at least one year after the end
of retention were compared by Mills.43
This study showed
that successful reduction of the deep bite was associated
with the decrease in inter-incisal angle and lowering of
the mandibular lip-line.
In addition growth was an
integral part in correcting the deep bite as well as
favorable mandibular rotation.43
A cephalometric study conducted by Cleall and Begole
looked at 115 subjects with pre-treatment, post-treatment,
retention, and at least 2 years following the removal of
the retainers. The results showed that there was a
prevalence of mandibular movement pattern irregularities.
They recommended extraction of maxillary first premolars,
19
finishing in a Class II molar relationship in non-growing
patients exhibiting minimal to no distal shift.33
However,
in growing patients with a distal shift, it was best to
treat non-extraction relying on the aid of mandibular
growth in the correction of the Class II.33
In another study comparing the effects of orthodontic
treatment on growth and position of the mandible by
different treatment modalities, Erickson and Hunter showed
that the mandible grew significantly more in the anterior
direction when compared to untreated controls.
Although
the type of treatment did not make a significant
difference, treatment alone enhanced the growth of the
mandible in the cases studied.44
This finding was in
agreement with a study done two year previous.45
Finally,
in just over half of the treated subjects, 12% grew more
horizontally and 41% grew more vertically.44
The idea that the curve of Spee and crowding should be
relieved by expansion of the premolar and canine region and
labial movement of the lower incisors was introduced by
Selwyn-Barnett.
If the lower incisor is not advanced it
will be extremely difficult to get the proper torque of the
upper incisor due to the limits of the palatal bone.46
20
Contrary to previous research, Demisch et al.47 showed
in a cephalometric study that the mandible is not
posteriorly displaced in Class II, Division 2
malocclusions, which confirmed previous evidence recorded
in the literature.23
Binda et al.48 also conducted a cephalometric study in
which 4 time points were compared to longitudinally
evaluate growth and treatment in Class II, Division 2
subjects.
It was shown that vertical and sagittal
components of the face increased due to growth and therapy,
and that anterior growth rotation of the mandible masked
some of the vertical facial development that was
accomplished during treatment.
In a similar study comparing treatment of Class I and
both divisions of Class II malocclusion exhibiting at least
a 70% deep bite, it was noted that there was no significant
difference in the treatment type used to correct the deep
bite.49
It was also shown that in Class II, Division II
cases, treatment resulted in an increased total facial
height, anterior facial height, maxillary and mandibular
incisor proclination, and a decrease in inter-incisal angle
and overbite.50,49
The findings of these studies are
summarized in Table 2.2.
21
Table 2.2: Cephalometric Studies Evaluating Treatment and
Growth in Class II, Division 2 Malocclusions.
Author(Date)
Mills (1971)
Cleall&Begole
(1982)
Erickson &
Hunter (1985)
Demisch
(1992)
Sample (N)
Cl I (47)
Cl II/2 (60pre-tx,1yr
post-tx)
Cl II/2 (115pre-tx,posttx,retention,
2yrs postretention)
Cl II/2 (34
pre and post
treatment)
Cl II/2
untreated
(15)
Cl II/2 (22
pre and post
treatment)
Binda (1994)
Cl II/2 (81pre-tx,posttx, 2 & 5 yrs
post-tx)
Devereese
(2007)
Cl II/2 (61pre-tx,posttx, 3.5 yrs
retention)
Findings
Reduced inter-incisal angle
Growth important in overbite reduction
Favorable rotation mandible maybe a factor
in over-bite reduction
SNA reduced, SNB increased
Upper and Lower incisors proclined
Reduced inter-incisal angle
Forward rotation of the mandible
Cl II/2 resemble Cl I more than Cl II/1
Treatment enhanced forward growth of the
mandible (1.5mm/yr)
In approximately half of the treated group
growth in the mandible changed 12%
horizontally and 41% vertically.
No significant changes in mandibular
length among treated group
Mandible is not displaced in Class II,
Division 2 malocclusions.
Sagittal and vertical facial dimensions
increased by growth and therapy
Inter-incisal angle and over-bite
decreased with treatment
In retention, upper and lower incisors
relapsed, overbite and inter-incisal angle
increased and the chin was more prominent
15.2 degree change in upper incisor
angulation with treatment
Upper incisor relapsed 2.2 degrees 3.5
years after treatment
Given the aforementioned literature, this study is
needed to address the inadequacies and limited number of
longitudinal growth studies comparing the Class II,
Division 2 subjects with untreated controls.
The results
of this study will provide a better understanding of how
the mandible grows in this particular skeletal pattern.
22
References
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8. Strang R. Class II, Division malocclusion. Angle Orthod.
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9. Graber T. The "three M's": muscles, malformation, and
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10. Peck S, Peck L, Kataja M. Class II Division 2
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11. Taylor T. A study of the incidence and manifestations
of malocclusion and irregularity of the teeth. D J
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12. Massler M, Frankel JM. Prevalence of malocclusion in
children aged 14 to 18 years. Am J Orthod. 1951;37(10):751768.
23
13. Ast D, Carlos J, Cons N. The prevalence and
characteristics of malocclusion among senior high school
students in upstate New York. Am J Orthod. 1965;51:437-455.
14. Mills L. Epidemiologic studies of occlusion, IV. The
prevalence of malocclusion in a population of 1455 school
children. J Dent res. 1966;45:332-336.
15. Altemus L. Frequency of the incidence of malocclusion
in American Negro children. Angle Orthod. 1959;29:189-200.
16. Steigman S, Kawar M, Zilberman Y. Prevalence and
severity of malocclusion in Israeli Arab urban children 13
to 15 years of age. Am J Orthod. 1983;84(4):337-343.
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19. Ricketts R, Bench R, Gugino C, Hilgers J, Schulhof R.
Bioprogressive Therapy. In: Bioprogressive therapy.
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20. Karlsen AT. Craniofacial characteristics in children
with Angle Class II Div. 2 malocclusion combined with
extreme deep bite. Angle Orthod. 1994;64(2):123-130.
21. Brezniak N, Arad A, Heller M, et al. Pathognomonic
cephalometric characteristics of Angle Class II Division 2
malocclusion. Angle Orthod. 2002;72(3):251-257.
22. Renfroe EW. A study of the facial patterns associated
with Class I, Class II, Division 1, and Class II, Division
2 malocclusion. Angle Orthod. 1948;18:12-15.
23. Ingervall B. Relation between retruded contact,
intercuspal, and rest positions of mandible in children
with angle Class II, Division 2 malocclusion. Odontol Revy.
1968;19(3):293-310.
24. Ingervall B, Lennartsson B. Cranial morphology and
dental arch dimensions in children with Angle Class II,
Div. 2 malocclusion. Odontol Revy. 1973;24(2):149-160.
24
25. Godiawala RN, Joshi MR. A cephalometric comparison
between Class II, Division 2 malocclusion and normal
occlusion. Angle Orthod. 1974;44(3):262-267.
26. Pradhan KL, Chopra KK, Pradhan R. A cephalometric study
of Class II Division 2 malocclusion. J Indian Dent Assoc.
1979;51(6):167-171.
27. Wallis S. Integration of certain variants of the facial
skeleton in Cl II, Division 2 malocclusion. Angle Orthod.
1963;33:60-67.
28. Maj G, Lucchese FP. The mandible in Class II, Division
2. Angle Orthod. 1982;52(4):288-292.
29. Hitchcock HP. The cephalometric distinction of class
II, division 2 malocclusion. Am J Orthod. 1976;69(4):447454.
30. Swann G. The diagnosis and interpretation of Class II,
Division 2. Am J Orthod. 1954;40:325-340.
31. Baldridge J. A study of the relation of the maxillary
first permanent molars to the face in Class I and Class II
malocclusion (Angle). Angle Orthod. 1941;11:100-109.
32. Hellman M. Studies of the etiology of Angle's Class II
malocclusion manifestations. Int. J. Orthod. 1922;8:129150.
33. Cleall JF, BeGole EA. Diagnosis and treatment of Class
II Division 2 malocclusion. Angle Orthod. 1982;52(1):38-60.
34. Heide M. Class II, Division 2, a challenge. Angle
Orthod. 1957;27:159-161.
35. Bjork A. Variations in the growth pattern of the human
mandible: longitudinal radiographic study by the implant
method. J Dent Res. 1963;42(1)Pt 2:400-411.
36. Fischer-Brandies H, Fischer-Brandies E, König A. A
cephalometric comparison between Angle Class II, Division 2
malocclusion and normal occlusion in adults. Br J Orthod.
1985;12(3):158-162.
25
37. Lisson JA, Pyka C. Determining skeletal parameters in
angle Classes II, Division 1 and II, Division 2. J Orofac
Orthop. 2005;66(6):445-454.
38. Isik F, Nalbantgil D, Sayinsu K, Arun T. A comparative
study of cephalometric and arch width characteristics of
Class II Division 1 and Division 2 malocclusions. Eur J
Orthod. 2006;28(2):179-183.
39. Al-Khateeb EAA, Al-Khateeb SN. Anteroposterior and
vertical components of Class II Division 1 and Division 2
malocclusion. Angle Orthod. 2009;79(5):859-866.
40. Taylor A. Release mechanisms in the treatment of Class
II, Division 2 malocclusions. Aust. Dent. J. 1966;11:27-37.
41. Arvystas MG. Treatment of severe mandibular retrusion
in Class II, Division 2 malocclusion. Am J Orthod.
1979;76(2):149-164.
42. Levy P. Growth of the mandible after correction of the
Class II, Division 2 malocclusion, Proceed Found Ortho
Research., Dept. of Orthodontics, UCLA School of Dentistry,
1979.
43. Mills JR. The problem of overbite in Class II, Division
2 malocclusion. Br J Orthod. 1973;1(1):34-48.
44. Erickson L, Hunter W. Class II, Division 2 treatment
and mandibular growth. Angle Orthod. 1985;55:215-224.
45. Edwards JG. Orthopedic effects with "conventional"
fixed orthodontic appliances: a preliminary report. Am J
Orthod. 1983;84(4):275-291.
46. Selwyn-Barnett BJ. Rationale of treatment for Class II
Division 2 malocclusion. Br J Orthod. 1991;18(3):173-181.
47. Demisch A, Ingervall B, Thüer U. Mandibular
displacement in Angle Class II, Division 2 malocclusion. Am
J Orthod Dentofacial Orthop. 1992;102(6):509-518.
48. Binda SK, Kuijpers-Jagtman AM, Maertens JK, van 't Hof
MA. A long-term cephalometric evaluation of treated Class
II Division 2 malocclusions. Eur J Orthod. 1994;16(4):301308.
26
49. Parker CD, Nanda RS, Currier GF. Skeletal and dental
changes associated with the treatment of deep bite
malocclusion. Am J Orthod Dentofacial Orthop.
1995;107(4):382-393.
50. Devreese H, De Pauw G, Van Maele G, Kuijpers-Jagtman
AM, Dermaut L. Stability of upper incisor inclination
changes in Class II Division 2 patients. Eur J Orthod.
2007;29(3):314-320.
27
CHAPTER 3: JOURNAL ARTICLE
Abstract
Objective: The aim of this study was to compare the
longitudinal skeletal changes in Class II, Division 2
subjects treated by non-extraction therapy with untreated
Class II, Division 2 and normal controls that are matched
by gender and age.
Thus, the goal is to determine how
growth is expressed when the mandible is “unlocked” in
Class II, Division 2 skeletal patterns.
Materials and Methods: Serial cephalograms of 29
Caucasian Class II, Division 2 subjects who were treated by
non-extraction orthodontic therapy were analyzed at three
timepoints: T1-start (mean age: 12 years, 11 months),
T2-debond (mean age: 15 years, 2 months) and T3-retention
(mean age: 16 years, 6 months). The treated group was
compared to an untreated Class II, Division 2 and Class I
normal samples that were matched for age and gender across
the three time points. Fifteen landmarks were identified
and angular and ratio measurements analyzed (10 skeletal
and 3 dental) in both vertical and horizontal vectors.
Results: Dental and skeletal means were evaluated
across three time points using analysis of variance.
There
were significant dental and horizontal skeletal changes,
but no significant vertical changes observed with treatment
28
between the groups.
Two measurements confirmed that the
mandible was more anteriorly positioned in relation to the
cranial base in the treated sample.
Thus, the mandible
grew forward slightly more in the treated sample than the
controls.
Conclusions: 1. In the treated Class II, Division 2
group there was a significant proclination of the maxillary
and mandibular incisors.
2. When compared across the three
time points there were no significant vertical changes
between the treated and untreated samples.
3. In the
horizontal dimension, there was a statistically significant
increase in the anterior position of the mandible in
relation to the cranial base for the treated Class II,
Division 2 group when compared to untreated controls.
4.
There is a positive effect of orthodontic treatment in
Class II, Division 2 subjects, resulting in a slightly more
anteriorly positioned mandible.
29
Introduction
E.H. Angle first described Class II, Division 2
malocclusion in 1907.1
Since then, there have been many
studies describing the characterization of this specific
malocclusion and yet there is still no conclusive evidence
as to the cause of the malocclusion.2-9
In addition, these malocclusions are one of the least
prevalent types represented in populations today as the
prevalence is reported to be between 1.6% and 5% depending
on the racial demographic.10-17
Due to this low prevalence,
there is limited knowledge about this malocclusion that
typically presents difficult vertical and antero-posterior
abnormalities which require the aid of growth to
orthodontically correct.
Although there is little evidence, it is a common
belief in the orthodontic literature that “unlocking” the
mandible in Class II, Division 2 malocclusions allows
growth of the mandible to be expressed in a more anterior
direction, which will aid in the correction of the distoocclusion.18-22
Currently, there is only one study published
which evaluates mandibular growth of treated and untreated
Class II, division 2 subjects using linear cephalometric
measures that treatment enhanced the forward growth of the
mandible.18
30
In assessing growth, longitudinal research designs are
the gold standard. Given that this type of malocclusion has
a strong tendency to relapse, much of the focus of the
effects of treatment that include longitudinal data have
been to assess relapse.23-26
Many cephalometric studies have
been conducted characterizing the malocclusion, but to
date, none have longitudinally evaluated the effects of
orthodontic treatment and growth of the mandible in the
treated Class II, Division 2 with matched untreated
controls.
The aim of this study is to compare the longitudinal
horizontal and vertical skeletal and dental changes in
Class II, Division 2 subjects treated by non-extraction
therapy with untreated Class II, Division 2 and normal
controls that are matched by age.
Thus, the goal is to
determine how growth is expressed when the mandible is
“unlocked” in Class II, Division 2 skeletal patterns and if
treatment results in a more anteriorly positioned mandible.
31
Materials and Methods
Sample
The experimental data for the following study
consisted of serial cephalograms from orthodontically
treated patients who met the following inclusion criteria:
(1) All cases had a previous diagnosis of Class II,
Division 2 malocclusion. This diagnosis consisted of at
least an end-to-end molar relationship, Class II canine
relationship, and at least a 70% deep bite. (2) All
subjects had comprehensive non-extraction orthodontic
treatment consisting of one or a combination of the
following: headgear, Class II elastics, and a Forsus
appliance.
(3) None of the cases exhibited congenital
anomalies, or congenitally missing teeth. (4) Pretreatment,
posttreatment and retention cephalograms of diagnostic
value were available for each subject.
The subjects were
selected using photographs, study models and cephalograms.
The records of the orthodontically treated patients were
obtained from both the archives at Saint Louis University
Center for Advanced Dental Education, Orthodontic
Department and one single private orthodontic practice.
The treated Class II, Division 2 sample consisted of 29
subjects with lateral head films at the following three
timepoints: before initiating fixed orthodontic therapy
32
(T1), at the time treatment is completed (debond) and the
fixed appliances are removed (T2), and during retention
(T3).
The treated sample was matched in age with the control
sample that was taken from the Human Growth and Research
Center, University of Montreal.
The two control groups
consisted of 20 subjects with Class I normal occlusion and
20 subjects with Class II, Division 2 malocclusion, based
on Angle’s original definitions.
Both control groups had
no previous orthodontic treatment.
The age and gender
distribution for the three time points for the treated
Class II, division 2; untreated normal and untreated Class
II, division 2 samples are summarized below.
Table 3.1: Age and Gender Distribution of Study Sample
Group
Treated
Class II,
Div.2
Untreated
Class II,
Div. 2
Control
Untreated
Class I
Control
Females:Males
T1 (initial)
Mean Age ± SD
(Range)
T2 (debond)
Mean Age ± SD
(Range)
T3(retention)
Mean Age ± SD
(Range)
17:12
12.9 ± 1.1
(11y1m-15y3m)
15.2 ± 1.2
(12y9m-17y9m)
16.5 ± 1.3
(14y8m-19y4m)
12.7 ± .49
14.6 ± .75
(13y-16y)
16.0 ± 1.1
(12y-13y)
12.6 ± .50
14.6 ±.83
16.2 ± .89
9:11
9:11
(12y-13y)
33
(13y-16y)
(14y-18y)
(15y-17y)
Methodology
Landmarks were defined based on the control groups
because the untreated control sample data had previously
been recorded.
Definitions of the anatomical landmarks are
presented below (Table 3.2).
Table 3.2: Landmark Definitions and Abbreviations
Landmark
A Point
Abbrev
A
Anterior Nasal
Spine
ANS
Articulare
Ar
B Point
B
Gnathion
Gn
The point midway between the anterior and
inferior points on the border of the chin
Gonion
Go
Lower Incisor
root apex
Lower Incisor
edge tip
L1-A
The point on the curvature of the mandible
located by bisecting the angle formed by the
lines tangent to the posterior ramus and the
inferior border of the mandible
The tip of the root apex of the mandibular
central incisor
The tip of the incisal edge of the mandibular
central incisor
Menton
Me
The most inferior point of the mandibular
symphysis
Nasion
N
The most anterior point of the frontonasal
suture
Posterior
Nasal Spine
PNS
The most posterior point on the bony hard
palate
Pogonion
Sella
Upper Incisor
root apex
Pog
S
U1-A
The most anterior point on the chin
The center of the pituitary fossa
The tip of the root apex of the maxillary
central incisor
Upper Incisor
edge tip
U1-E
The tip of the incisal edge of the maxillary
central incisor
L1-E
Definition
The most posterior point in the concavity
between ANS and the maxillary alveolar process
The anterior tip of the nasal spine
The intersection of the posterior border of the
ramus and the inferior border of the posterior
cranial base
The most posterior point in the concavity
between the chin and the mandibular process
34
Acetate paper was fixed to each cephalogram and 15
hard tissue landmarks were identified by the principle
investigator and are presented in Figure 3.1.
Figure 3.1: Anatomical landmarks
35
Following landmark identification, the cephalograms were
digitized with a Numonics Accugrid Digitizer and analyzed
with Dentofacial Planner software.
The Dentofacial Planner
7.0 software was used to turn each landmark into x-y
coordinates. After digitizing the cephalometric landmarks,
all the cephalometric measurements were analyzed by the
software.
Figure 3.2: Cephalometric measurements
36
Only angular and proportional measurements were used
in the evaluation of the sample to avoid magnification
errors produced by the different cephalometric x-ray
machines. Twelve angular and one ratio measurement were
used to analyze the skeletal and dental effects of growth
and treatment in the horizontal and vertical dimensions.
These included the following: SNA, SNB, ANB, Y-axis angle,
SN-GoGn, SN-palatal plane, gonial angle, palatal-plane to
mandibular plane angle, posterior to anterior facial height
ratio, interincisal angle, Upper incisor to SN angle, lower
incisor to mandibular plane angle.
Statistical Analyses
The data was statistically analyzed using Statistical
Package for Social Sciences.
Descriptive statistics were
used to calculate the mean and ranges for each group being
compared across each of the three time points.
Analysis of
variance (ANOVA) was employed to compare the three time
points between the three groups.
Lastly, a Bonferroni post
hoc test was used to address with the inaccuracies of
multiple comparisons.
37
Results
Although the sample was chosen based on Angle
classification, ANOVA was run with Bonferroni Post Hoc
tests on the sample at T1 to clarify that the sample was
had cephalometric differences prior to initiating any
treatment.
These results show that the sample chosen was
indeed significantly different than the Class I normal
controls.
The data is summarized below in Table 3.3.
Table 3.3: Cephalometric Comparisons Between the Three
Groups at T1. (p<.05)
Cl II/2
Treated
Cephalometric
Measurement
U1-SN
IMPA
U1/L1
SNA
SNB
ANB
Y-Axis
SN-Pg
Go Angle
SN-GoGn
SN-PP
PP-MP
P:A Ratio
Cl II/2
Untreated
CL I Normal
Group Differences
Mean
±SD
Mean
±SD
Mean
±SD
1vs2
2vs3
1vs3
95.3
94.2
142.3
81.6
77.4
4.23
65.2
78.7
122.5
28.2
7.6
20.6
.66
8.5
7.7
11.6
3.0
3.1
1.66
3.1
3.2
5.3
3.9
3.4
3.5
.04
96.8
92.4
140.8
82.7
78.9
3.8
65.9
80.0
113.7
30.4
7.5
22.9
.67
5.7
6.4
8.5
2.4
2.4
1.9
2.6
2.4
6.0
3.9
1.7
3.7
.03
101.5
95.5
130.1
81.7
78.5
3.3
66.6
79.1
116.2
32.9
7.1
25.8
0.64
4.4
7.4
8.1
3.6
2.3
2.4
2.8
2.4
8.3
4.8
2.7
4.9
0.04
NS
NS
NS
NS
NS
NS
NS
NS
<.001
NS
NS
NS
NS
NS
NS
.003
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
.007
NS
<.001
NS
NS
NS
NS
NS
.004
.001
NS
<.001
NS
38
The means for each of the thirteen measurements across
three time points were calculated for each of the three
groups.
Changes between the measurements were also
calculated to determine significant changes within each of
the groups.
The Class II, Division 2 treated group was
then compared with the Class II, Division 2 untreated and
Class I normal control groups using the analysis of
variance, with a significance level predetermined at p<.05
to determine significant dental and skeletal changes over
time.
When comparing the time points within each group,
there were no dentally significant changes in either of the
Class II, Division 2 untreated or Class I normal control
samples.
However, in the treated Class II, Division 2
sample, there were significant changes in U1-SN, IMPA, and
U1-L1 (Table 3.4)
39
Table 3.4: Dental Comparisons and Statistically Significant
Changes Over Time Within Each Group.
T1
Cl II/2
Mean
±SD
Treated
95.3
8.5
U1-SN
94.2
7.7
IMPA
142.3
11.6
Ul-L1
Cl II/2
Untreated
96.8
5.7
U1-SN
92.4
6.4
IMPA
140.8 8.5
U1-L1
Cl I
Normal
101.5 4.4
U1-SN
95.5
7.4
IMPA
130.1 8.1
U1-L1
* denotes p<0.05
T2
T3
T1-T2
T2-T3
T1-T3
Mean
±SD
Mean
±SD
107.3
102.4
122.2
6.6
7.6
10.3
106.4
100.9
125.9
6.9
8.0
10.4
*
*
*
NS
*
*
*
*
*
96.3
92.3
142.5
5.3
7.0
8.3
96.3
92.4
142.9
5.4
7.9
8.8
NS
NS
NS
NS
NS
NS
NS
NS
NS
101.1
95.0
131.1
4.5
7.8
8.3
100.7
94.9
132.4
4.8
9.1
10.7
NS
NS
NS
NS
NS
NS
NS
NS
NS
40
In comparing both the horizontal and vertical
measurements, both untreated control groups had no
significant changes in the horizontal measurements, but
displayed significant changes between T2-T3 and T1-T3 in
vertical changes.
The measurements SN-Pg,P:A ratio
increased for both groups and SN-GoGn and PP-MP decreased
for both control groups.
When comparing the horizontal and vertical changes
over time for the Class II, Division 2 treated group, there
were significant changes in both horizontal and vertical
measurements.
decreased.
The SNA decreased, SNB increased, and ANB
In addition the SN-Pg and PA ratio increased,
while the SN-GoGn, Gonial Angle and PP-MP measurements
decreased (Table 3.5).
41
Table 3.5: Horizontal and Vertical Skeletal Comparisons and
Statistically Significant Changes Over Time Within Each
Group.
T1
CL II/2
Mean
Treated
SNA
81.6
SNB
77.4
ANB
4.2
Y-Axis
65.2
78.7
SN-Pg
Go Angle 122.5
SN-GoGn
28.1
SN-PP
7.6
PP-MP
20.6
P:A ratio
.66
CL II/2
Untreated
SNA
82.7
SNB
78.9
ANB
3.8
65.9
Y-Axis
80.0
SN-Pg
Go Angle 113.7
SN-GoGn
30.4
SN-PP
7.5
PP-MP
22.9
P:A ratio
.67
CL I
Normal
SNA
81.7
SNB
78.5
ANB
3.3
66.6
Y-Axis
79.1
SN-Pg
Go Angle 116.2
SN-GoGn
32.9
SN-PP
7.1
25.8
PP-MP
.64
P:A Ratio
* denotes p<0.05
T2
T3
T1-T2
T2-T3
T1-T3
±SD
Mean
±SD
Mean
±SD
3.0
3.1
1.7
3.1
3.2
5.3
3.9
3.4
3.5
.04
80.4
78.0
2.4
65.4
79.6
122.0
28.2
8.0
25.4
.67
3.1
3.4
1.9
3.4
3.4
5.6
4.5
3.7
5.1
.04
80.9
78.5
2.4
65.0
80.2
121.3
27.0
7.6
19.3
.68
3.7
4.1
2.0
3.7
4.0
5.1
4.8
4.0
4.7
.04
*
*
*
NS
*
NS
NS
NS
NS
*
NS
NS
NS
NS
*
NS
*
NS
NS
*
*
*
*
NS
*
*
*
NS
*
*
2.4
2.4
1.9
2.6
2.4
6.0
3.9
1.7
3.7
.03
82.7
78.9
3.8
66.1
80.4
114.0
29.7
7.3
22.4
.67
2.6
2.6
2.4
2.9
2.8
7.7
4.8
1.8
4.5
.05
82.5
78.9
3.6
66.2
80.7
113.8
29.2
7.6
21.7
.68
2.6
2.4
2.4
2.9
2.6
6.9
4.5
1.9
4.0
.04
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
*
NS
NS
NS
*
NS
NS
NS
NS
NS
*
NS
*
NS
*
*
3.6
2.3
2.4
2.8
2.4
8.3
4.8
2.7
4.9
.04
81.5
78.5
3.1
67.3
79.1
117.8
33.0
7.6
25.4
.65
3.3
2.2
2.1
3.0
2.3
9.0
5.1
2.6
5.1
.04
81.8
78.8
2.9
67.1
79.7
116.9
32.0
7.4
24.6
.65
3.7
2.3
2.4
2.8
2.3
8.9
5.0
2.5
5.1
.04
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
*
NS
*
NS
*
*
NS
NS
NS
NS
*
NS
*
NS
*
*
42
When the three groups were compared across the three
age-matched time points, there were no significant
differences between any of the three groups when comparing
T2-T3.
However, when comparing the changes between T1-T2
and T1-T3, there were significant differences between the
Class II, Division 2 treated group and both Class II,
Division 2 untreated and Class I normal control groups for
all three dental measurements (Table 3.6).
Table 3.6: Dental Comparisons Between the Three Groups for
T1, T2, T3.
T1-T2
U1-SN
IMPA
U1/L1
CL II/2
Treated
Mean
±SD
Δ
12.0
9.0
8.2
7.6
-20.2
14.0
CL II/2
Untreated
Mean
±SD
Δ
-0.56
2.1
-0.1
2.8
1.7
4.0
CL I
Normal
Mean
±SD
Δ
-0.8
3.7
-0.6
3.6
1.6
3.8
-0.9
-1.5
3.7
3.7
3.2
5.4
0.04
0.07
0.40
2.5
3.2
5.0
0.03
0.01
0.5
11.1
6.6
7.9
6.6
11.7
-0.5
-0.04
2.1
3.7
5.1
6.9
-0.7
-0.6
2.2
Group
Differences
1vs2
2vs3
1vs3
<.001
<.001
<.001
NS
NS
NS
<.001
<.001
<.001
3.0
2.6
3.0
NS
NS
NS
NS
NS
NS
NS
NS
NS
2.7
4.3
5.6
<.001
<.001
<.001
NS
NS
NS
<.001
<.001
<.001
T2-T3
U1-SN
IMPA
U1/L1
T1-T3
U1-SN
IMPA
U1/L1
p<.05
-16.5
43
There were no significant horizontal or vertical
changes between the untreated Class II, Division 2 and
Class I normal controls.
There were significant changes
between the Class 2, Division 2 treated groups and both
control groups for SNA and ANB between T1 and T2.
There
was also a significant difference between the Class II,
Division 2 treated group and the Class I normal control
between T1 and T2 for the SN-Pg measurement.
There were no
significant changes between the groups for T2-T3.
Lastly,
for the T1-T3 changes, there were significant differences
between the Class II, Division 2 treated group and both
controls for the ANB and SN-Pg measurements.
There was
also a significant difference between the Class II,
Division 2 treated group and the Class II, Division 2
untreated group for SNB (Table 3.4)
The results showed that there were significant dental
changes (U1-SN, IMPA, U1/L1) for the treated group and
significant differences between T1 and T3 when compared to
the untreated control groups.
In addition, the Class II,
Division 2 treated sample showed significant changes in the
horizontal and vertical skeletal measurements, while the
untreated control groups showed a significant change in the
vertical skeletal components.
When the three groups were
compared to each other, there were significant dental
44
changes between the treated group and both untreated
controls.
Lastly when comparing the horizontal and
vertical skeletal components of the three groups, there
were more significant horizontal changes than vertical
changes between the treated group and untreated controls
(Table 3.7).
45
Table 3.7: Horizontal and Vertical Comparisons Between the
Three Groups for T1, T2, and T3.
T1-T2
SNA
SNB
ANB
Y-Axis
SN-Pg
Go Angle
SN-GoGn
SN-PP
PP-MP
P:A ratio
T2-T3
SNA
SNB
ANB
Y-Axis
SN-Pg
Go Angle
SN-GoGn
SN-PP
PP-MP
P:A ratio
T1-T3
SNA
SNB
ANB
Y-Axis
SN-Pg
Go Angle
SN-GoGn
SN-PP
PP-MP
P:A ratio
CL II/2
Treated
Mean
±SD
Δ
-1.2
1.6
.66
1.4
-1.9
1.2
.28
1.2
.93
1.2
-.50
2.5
.007
1.5
.37
1.5
-.37
2.3
.007
.02
CL II/2
Untreated
Mean
±SD
Δ
-.02
.88
-.01
1.2
-.004
.85
.21
1.1
.39
1.2
.32
3.8
-.74
2.1
-.25
.90
-.49
2.0
.01
.02
CL I
Normal
Mean
±SD
Δ
-.19
.88
.02
.79
-.21
.83
.71
.75
.09
.82
1.6
3.0
.08
1.8
.52
1.1
-.44
1.5
.002
.02
.47
.44
.003
-.51
.57
-.72
-1.2
-.33
-.94
.01
1.4
1.4
.83
1.3
1.4
2.3
1.5
1.6
1.4
.01
-.20
-.01
-.19
.06
.24
-.23
-.43
.28
-.72
.01
.54
.50
.50
.51
.52
2.1
1.2
.90
1.2
.01
.22
.33
-.11
-.17
.55
-.94
-1.0
-.15
-.84
.01
-.73
1.1
-1.8
-.23
1.5
-1.2
-1.2
.04
-1.3
.02
1.6
1.6
1.1
1.5
1.4
2.7
1.8
2.1
2.8
.02
-.22
-.02
-.19
.27
.63
.09
-1.2
.03
-1.2
.02
.97
1.1
.90
1.1
1.1
3.1
2.0
1.2
1.8
.02
.02
.35
-.32
.54
.64
.71
-.91
.37
-1.3
.01
46
Group Differences
1vs2
2vs3
1vs3
0.04
NS
<0.001
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
0.02
NS
<0.001
NS
0.038
NS
NS
NS
NS
NS
1.1
.56
.95
.67
.73
2.1
1.2
.79
1.3
.01
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
.91
.83
.90
.74
.88
2.3
1.2
1.0
1.2
.01
NS
0.01
<0.001
NS
0.042
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
NS
<0.001
NS
0.046
NS
NS
NS
NS
NS
Discussion
In this retrospective study, longitudinal
cephalometric data was compared by evaluating both the
dental and skeletal changes that occur through orthodontic
treatment in the vertical and horizontal dimensions.
In
addition, through comparing these findings with untreated
Class II, Division 2 and Class I normal occlusions, both
growth and treatment effects could be compared to determine
any dental or skeletal changes that result from orthodontic
treatment and ultimately determining if there is more
anterior growth of the mandible in treated Class II,
Division 2 subjects.
There were no significant changes within the untreated
control groups for any of the dental measurements, which
can be expected because there was no orthodontic therapy
conducted on these samples.
For the orthodontically
treated Class II, Division 2 group, there were significant
changes for all the dental measurements.
U1-SN increased
11 degrees from T1-T3, the IMPA increased 8 degrees from
T1-T2 and the inter-incisal angle decreased by 20 degrees,
all of which were confirmed treatment changes in the
literature.23-26
From T2—T3, there was significant relapse
in the IMPA, which decreased 1.5 degrees, and inter-incisal
angle which increased 3.7 degrees for the group.
47
These
findings were also confirmed by other studies that had
longitudinal data that was compared post treatment.23,25
Like the dental changes seen within the groups, there
were no significant horizontal skeletal changes in the
untreated control sample.
However, the Class II, Division
2 treated sample exhibited a decrease in SNA (0.7 degrees),
and increase in SNB (1.1 degrees) resulting in a decrease
in ANB (1.8 degrees)for T1-T3.
These findings are
consistent with the studies looking at the effects of
treatment on Class II, Division 2 subjects.
Comparing the skeletal changes within the groups,
there were four measurements (SN-Pg, P:A ratio, SN-GoGn,
and PP-MP) that were significant, which confirmed vertical
growth changes in all three groups.
This change is
indicative of an anterior rotational pattern of growth, as
it was significant in all three groups.26-28
The only other
measurement that was significant in the vertical dimension
was a slight decrease in the gonial angle from T1-T3 in the
treated Class II, Division 2 group.
When the treated Class II, Division 2 group was
compared with both untreated Class II, Division 2 and Class
I normal control groups there were significant differences
between the treated group and untreated groups, but no
differences between the untreated control groups.
48
The
dental comparisons only showed significant changes between
T1 and T3.
The upper and lower incisors flared anteriorly
with treatment which resulted in a decrease in the interincisal angle.
This result is consistent with the
literature on orthodontic treatment of this specific
malocclusion.23-26,18
In the horizontal dimension the significant
differences between the treated group and untreated groups
were evident from T1-T2 and from T1-T3, but not between T2
and T3.
The maxillary position in relation to the cranial
base moved posteriorly.
This is most likely due to the
remodeling of A point that occurs when the upper incisors
are flared, which is evident from the dental measurements
previously discussed.
Interestingly, SNB showed no
significant changes from T1 to T2, but significant anterior
movement from T1 to T3, indicating a more anterior position
of the mandible in relation to the cranial base.
Both of
these horizontal skeletal changes can be confirmed in the
ANB measurement as it decreased significantly more for the
treated group.
This horizontal change was probably due to
the longer growth period between T1 and T3, when compared
to the T1-T2 period.
The change in SN-Pg confirms the
findings that the mandible was in a more anterior position
at the time of retention and this change was due to growth,
49
because the change was not significant between the pretreatment and post-treatment records.18
This retrospective study evaluated growth of treated
Class II, Division 2 subjects and compared them to matched
controls.
The sample cephalograms were taken on several
machines, so magnification could not be properly assessed.
Therefore, no linear measurements were performed on the
sample, which would have aided in defining the amount of
change between the samples.
group was 12.9 years old.
The mean age for the treated
Since the majority of the
treated sample were females, most of these subjects would
have completed the majority of their skeletal growth prior
to the start of the study.
Given that there is little work done on Class II,
Division 2, more prospective studies with defined treatment
modalities and larger sample sizes are indicated to
identify the effects of treatment on growth.
50
Conclusions
The results of this study demonstrate that:
1.
In the treated Class II, Division 2 group there was a
significant proclination of the maxillary and
mandibular incisors.
2.
When compared across the three time points there
were no significant vertical changes between the
treated and untreated samples.
3.
There were no significant differences between any of
the groups compared between the post-treatment and
retention records.
4.
In the horizontal dimension, there was a slight
increase in the anterior position of the mandible in
relation
to the cranial base for the treated Class
II, Division 2 group when compared to untreated
controls.
5.
There is a positive effect of orthodontic treatment in
Class II, Division 2 subjects, resulting in a slightly
more anteriorly positioned mandible.
51
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54
VITA AUCTORIS
Daniel A. Lovell was born on February 25th, 1982 in
Pekin, Illinois to John E. Lovell, M.D. and Sheila D.
Lovell.
He is the middle of three boys.
He was raised in Tremont, Illinois and graduated from
Peoria Christian High School in 2000.
Dr. Lovell received
his Bachelors of Arts degree with a major in Biology and a
minor in Business from Greenville College in 2004,
graduating magna cum laude.
After earning his
undergraduate degree, he began his dental training at
Southern Illinois University School of Dental Medicine
where he received his D.M.D. (Doctor of Dental Medicine) in
2008.
Immediately following, Dr. Lovell started his
orthodontic residency at St. Louis University in June 2008.
Dr. Lovell expects to receive a Masters of Science in
Dentistry degree from Saint Louis University in January
2011.
He plans on practicing orthodontics in central
Illinois.
55