Download COMPARISON OF SKELETAL AND DENTOALVEOLAR EFFECTS OF THE

COMPARISON OF SKELETAL AND DENTOALVEOLAR EFFECTS OF THE
FORSUS AND MARA IN TREATMENT
OF CLASS II MALOCCLUSIONS
Shereen Azizollahi, D.D.S.
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 (Research)
2012
Abstract
Purpose: The objective of this study was to compare the skeletal and dental effects of the
Forsus and the MARA, which are two types of compliance-free interarch appliances.
Materials and Methods: This study was a retrospective clinical investigation that
included 25 MARA patients (13 females, 12 males) with a mean start age of 12.7 ± 0.8
years and 25 Forsus patients (13 females, 12 males) with a mean start age of 12.1 ± 1.3
years. The MARA and Forsus were matched according to age, gender, and cervical
maturation stage at the start age. Pre-treatment (T1), appliance removal (T2), and posttreatment (T3) cephalograms were hand traced; and compared with the pitchfork analysis.
The dental and skeletal effects of each fixed inter-arch appliance were analyzed using
independent t-tests to compare the differences between each treated sample.
Results: The MARA and Forsus both demonstrated a general trend of forward skeletal
movement of the maxilla and mandible, with greater movement in the mandible.
However, the MARA group showed a significantly greater amount of forward movement
of the maxilla and mandible than the Forsus group. Greater proclination of the lower
incisors was observed in the Forsus group during T1-T2. The overall median treatment
duration of the Forsus was shorter than the MARA.
Conclusions: The Forsus and the MARA are both effective compliance-free interarch
appliances for Class II correction. In comparison to the MARA, the Forsus has a greater
restraint on the maxilla. However, the MARA produces significantly greater forward
displacement of the mandible than the Forsus. The Forsus may produce greater lower
incisor proclination than the MARA in the correction of overjet.
1
COMPARISON OF SKELETAL AND DENTOALVEOLAR EFFECTS OF THE
FORSUS AND MARA IN TREATMENT
OF CLASS II MALOCCLUSIONS
Shereen Azizollahi, D.D.S.
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 (Research)
2012
COMMITTEE IN CHARGE OF CANDIDACY:
Professor Eustaquio A. Araujo,
Chairperson and Advisor
Adjunct Professor Peter H. Buschang
Associate Clinical Professor Donald R. Oliver
i
Dedication
To my husband Jonathan, for believing in me and encouraging me in the pursuit
of my career. You have brought laughter and love into my life.
To my brother Elliot, for being supportive and always someone I can rely on.
To my parents Arsalan and Nasrin, for their unconditional love and support. I
would not be where I am today without them. They came to this country with no family
and money, but the will to create a more beautiful life for my brother and I.
A special thanks to my mom, who has been my role model. She graduated dental
school from Tehran University in Iran and moved to the United States with the
determination to attain her dental license in America. With her perseverance, she has
motivated me to pursue my dreams.
ii
Acknowledgements
I would like to acknowledge the following individuals, without their support this
research project would not be possible:
Dr. Eustaquio Araujo, my mentor and chairperson, he has been there whenever I
needed guidance throughout this process. I feel honored to have him as my instructor
with his vast knowledge in orthodontics and life.
Dr. Donald Oliver, who is an invaluable part of this school and his dedication to
the students and patients, is beyond measure. He supported me throughout this research
process and was always someone I could depend on for help.
Dr. Peter Buschang, I am thankful for his help with my study design and his
enthusiasm in my research.
Dr. Rolf Behrents, my program director, for giving me the opportunity to be a part
of this orthodontic program. I am forever grateful for this experience.
Dr. Valmy Pangrazio-Kulbersh, who not only provided me with the MARA
sample, but was gracious enough to help me with the research design and so much more
beyond her call of duty.
Dr. Lisa Alvetro and her staff, for providing me with the Forsus sample and
answering any questions I had promptly.
Dr. Alex Tsourakis, my fellow colleague, for his help with any questions I had
regarding the pitchfork analysis.
Dr. Hiroshi Ueno, my fellow colleague, for his help with my statistics.
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TABLE OF CONTENTS
LIST OF TABLES .........................................................................................................vi
LIST OF FIGURES .......................................................................................................vii
CHAPTER 1: INTRODUCTION ................................................................................... 1
CHAPTER 2: REVIEW OF LITERATURE
Class II Problem Defined ............................................................................... 3
Prevalence of Class II malocclusion ............................................................... 3
Etiology of Class II malocclusions ................................................................. 4
History of Class II correction.......................................................................... 6
One Phase versus Two Phase Treatment ......................................................... 8
Role of Compliance in Treatment ................................................................... 9
Compliance Free Interarch Appliances ......................................................... 11
Herbst....................................................................................................... 11
Mandibular Anterior Repositioning Appliance (MARA) .......................... 14
Mandibular Protraction Appliance (MPA) ................................................ 16
Jasper Jumper ........................................................................................... 17
Forsus....................................................................................................... 19
Summary and Statement of Thesis ................................................................ 22
References.................................................................................................... 23
CHAPTER 3: JOURNAL ARTICLE
Abstract........................................................................................................ 26
Introduction.................................................................................................. 28
Methods and Materials ................................................................................. 30
Sample ..................................................................................................... 30
Data Collection......................................................................................... 32
Statistical Methods ................................................................................... 34
Results ......................................................................................................... 34
Forsus and MARA Treatment Effects (T1-T2).......................................... 34
Forsus and MARA Post-Treatment Effects (T2-T3).................................. 37
Forsus and MARA Overall Treatment Effects (T1-T3) ............................. 40
Discussion .................................................................................................... 43
Maxillary Skeletal Effects ........................................................................ 44
Mandibular Skeletal Effects ...................................................................... 45
Maxillary Dental Effects........................................................................... 46
Mandibular Dental Effects ........................................................................ 46
Overall Effects ......................................................................................... 47
Conclusions .................................................................................................. 48
References.................................................................................................... 49
iv
Appendix ....................................................................................................................... 51
Vita Auctoris ................................................................................................................. 52
v
LIST OF TABLES
Table 3.1:
Median Treatment Duration and Inter-quartile Range (months) ................. 31
Table 3.2:
Age, gender and cervical vertebral maturation stage-matched
Forsus and MARA samples ....................................................................... 32
Table 3.3:
T1-T2 Pitchfork comparison of Forsus and MARA ................................... 37
Table 3.4:
T2-T3 Pitchfork comparison of Forsus and MARA ................................... 40
Table 3.5:
T1-T3 Pitchfork comparison of Forsus and MARA ................................... 43
Table 3.6:
Comparison of the Forsus appliance effects reported in the literature......... 44
Table 3.7:
Comparison of the MARA appliance effects reported in the literature ....... 44
Table A.1: Description of pitchfork analysis variables ................................................. 51
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LIST OF FIGURES
Figure 3.1:
Pitchfork analysis diagram ....................................................................... 33
Figure 3.2:
Pitchfork treatment changes from T1-T2 in Forsus Sample ...................... 35
Figure 3.3:
Pitchfork treatment changes from T1-T2 in MARA Sample ..................... 36
Figure 3.4:
Pitchfork treatment changes from T2-T3 in Forsus Sample ...................... 38
Figure 3.5:
Pitchfork treatment changes from T2-T3 in MARA Sample ..................... 39
Figure 3.6:
Pitchfork treatment changes from T1-T3 in Forsus Sample ...................... 41
Figure 3.7:
Pitchfork treatment changes from T1-T3 in MARA Sample ..................... 42
vii
CHAPTER 1: INTRODUCTION
Class II malocclusions are frequently encountered in orthodontics.
Approximately 15% of the population has a Class II malocclusion according to the
NHANES III study from 1988 to 1991.1 There are many different dental and skeletal
combinations that can create a Class II malocclusion. However, mandibular retrusion is
one of the most common characteristics.2
There are various techniques to correct Class II malocclusions including
headgear, elastics, removable and fixed appliances, extractions and even surgery. But,
often the limiting factor in achieving the ideal treatment result in orthodontics is
compliance. By removing the burden of compliance from the patient, the practitioner is
able to achieve more predictable results with reasonable treatment durations.3 Thus,
many clinicians use compliance-free interarch appliances in order to correct Class II
malocclusions. There are many different compliance-free appliances including the:
Herbst, Mandibular Anterior Repositioning Appliance (MARA), Mandibular Protraction
Appliance, Jasper Jumper and Forsus. All of these appliances can improve Class II
malocclusions, but each one has advantages and disadvantages. An advantage of some of
these appliances is the ability to use them in conjunction with comprehensive fixed
therapy. However, some side effects from these fixed interarch appliances may be lower
incisor proclination4-10 and upper molar tipping.10 Examples of appliances that can be
used simultaneously with fixed treatment are the Forsus and MARA.
1
The MARA is a fixed functional appliance made in the laboratory that was
introduced by Eckhart and Toll and launched by Ormco to the orthodontic community.11
The MARA is fixed with maxillary and mandibular stainless steel crowns on the first
molars, which produce an interference that is designed to position the mandible forward.
There have been numerous studies on the skeletal and dental effects of the MARA9,12-14
and its comparison to other fixed functional appliances.13
The Forsus Fatigue Resistant Device is a fixed Class II appliance that was
developed by Vogt.15 It is prefabricated intermaxillary push spring that is composed of a
push rod that inserts into a telescoping cylinder.16 The push rod, which the mesial end of
the appliance, is attached to the mandibular archwire distal to the canine or first premolar
bracket. The telescoping cyclinder is the distal end of the appliance and is inserted into
the maxillary molar headgear tube.16 Previous investigations have evaluated the effects
of the Forsus7,8,15 and compared it to intermaxillary elastics7 and untreated controls.8
While the skeletal and dental effects of the MARA and Forsus have been
previously studied, 8-10,13-16 these two appliances have not been compared to one another.
The objective of this study is to compare the skeletal and dental effects of the MARA and
Forsus at three timepoints. Moreover, this investigation will assess the possible side
effects of the appliances, including lower incisor proclination and molar tipping. The
treatment duration will also be recorded for each appliance due to the relationship
between treatment time and cooperation.17
2
CHAPTER 2: REVIEW OF THE LITERATURE
The Class II Problem Defined
In the 1890s Angle provided the first formal definition of normal occlusion in the
natural dentition.11 Angle’s definition was based on the upper first molar, which was the
“key to occlusion.”11 The mesiobuccal cusp of the upper first molar should occlude in
the buccal groove of the lower first molar on a smooth curving line of occlusion. Angle
also described three classes of malocclusion, one of which was the Class II. This was
illustrated as the lower molar distally positioned relative to the upper molar. After World
War II, cephalometric radiography became more commonly used in orthodontic
treatment planning.11 With this new method of diagnosis, it was more apparent that the
jaw relationship as well as the dental relationship contributed to the Class II
malocclusion.2,11
Prevalence of Class II Malocclusions
The Class II malocclusion is a common skeletal problem seen in orthodontics.
From 1966 to 1970 the Division of Health Examination Statistics performed a National
Health Survey, which collected data about the health of the U.S. population between the
ages of 12 to 17.18 The survey studied the occlusion of these adolescents from a sample
of approximately 7,500. One part of the survey observed buccal segment relationships
among these adolescents. They described the Class II malocclusion as “distoclusion,”
characterized by the “lower molars occluding with the upper molars behind the normal
position.”18 They found that 32% of the adolescents had Class II malocclusions
(unilateral and bilateral). Caucasians had a significantly larger percentage of Class II
3
malocclusion with 33.6% as opposed to 18.0% in the African American population. In
this survey, the amount of overjet was also evaluated and it was found that about 15% of
the population had a severe overjet that was considered greater than 5 mm.18
In the third National Health and Nutrition Examination Survey (NHANES III)
conducted from 1988 to 1991, the prevalence of malocclusion and orthodontic treatment
need in the United States was studied from a sample of 7,000 people.1 Class II
malocclusions were considered when there was 5 mm or more overjet. Similar to the
National Health Survey from 1966 to 1970, Class II malocclusions were observed in
approximately 15% of the population.1,18 Slightly increased overjet of 3-4 mm was seen
in about 40% of the population, which was about the same as the ideal overjet of 1-2 mm.
Moreover, with an increase in age, the prevalence of excessive overjet declined probably
due to late mandibular growth. In fact, over 20% of children from age eight to eleven
years are considered to have a Class II malocclusion. This number plummets to 13% in
adulthood. Class II malocclusions are more common in Caucasians than African
Americans.1,18 However, severe Class II malocclusions that are seen in about 4% of the
population are more common in African Americans and Mexican-Americans. This study
portrays that the Class II skeletal problem is the most frequent jaw discrepancy found in
the United States.1
Etiology of Class II Malocclusions
With the large number of Class II malocclusions, there has been a great deal of
focus on its nature throughout orthodontic literature. In 1981, McNamara dissected the
components of the Class II malocclusion in his study of 277 children eight to ten years of
4
age.2 Specifically, he looked at the frequency of each component including the:
maxillary skeletal position, maxillary dental position, mandibular dental position,
mandibular skeletal position, and vertical in the Class II patient. The component that was
the most common characteristic in his study was mandibular skeletal retrusion. He
discussed that only a small percentage of subjects in his study portrayed maxillary
skeletal protrusion. In fact, his study showed that the maxilla was usually in a neutral
position. If the maxilla was not in the neutral position then it was more likely to be in a
retruded than protruded position. Interestingly, maxillary skeletal retrusion was often
seen with excessive vertical development. Even though there was a large range of
vertical development in his sample, excessive vertical development was a frequent
finding that, according to the author, may be attributed to an altered respiratory function.
As far as dental relationships, he explained that the lower incisors were normally well
positioned and the amount of maxillary dental protrusion was less frequently displayed
than what was previously reported in other studies. Overall, his results illustrated that the
nature of the Class II malocclusion is not a result of a single component, but a variety of
different dental and skeletal combinations.2
In a longitudinal study by Buschang and Martins, the differences of
anteroposterior (AP) and vertical changes were assessed between childhood and
adolescence.19 The sample consisted of 49 females and 50 males that had approximately
equivalent amounts of Class I and Class II subjects. These individuals were followed
during childhood and adolescence between 6 to 15 years of age and lateral cephalograms
were taken annually. Childhood skeletal changes were evaluated in females between 6 to
10 years of age and in males 8 to 12 year of age. Adolescent skeletal changes were
5
observed in females between 9 to 13 years of age and in males 11 to 15 years of age. The
results showed that AP changes were largely due to the differential growth of the
mandible rather than the maxilla. Furthermore, there was a greater tendency for AP
discrepancies to decrease or improve during childhood as opposed to adolescents. Also,
this study demonstrated that AP discrepancies had a greater likelihood of increasing
during adolescence. Those subjects whose AP relationship improved portrayed a
different pattern of developmental growth in comparison to those whose AP relationship
worsened. Buschang and Martins explain that this increase in AP discrepancy that is
more apparent during adolescence is usually due to a deficiency in mandibular growth.
As far as vertical changes, there were greater changes in vertical during adolescence than
childhood. Moreover, Buschang and Martins observed a relationship between AP and
vertical changes. In about 29% of the females and 34% of the males, this study found
that there were greater than average changes in the vertical and AP relationships. In the
subjects that the AP relationships decreased, 34% to 37% were likely to have less than
average increases in vertical changes. Furthermore, those with the greatest increases in
AP relationships tended to have the greatest increases in vertical relationships.
History of Class II Correction
As mentioned in the study by Buschang and Martins the growth of the mandible is
developmental in nature and occurs during childhood as well as adolescence.19 In Class
II individuals whose AP discrepencies worsened during growth, there was less anterior
movement of pogonion19. Thus, it is doubtful that skeletal growth will provide more than
3-4 mm to help correct a Class II malocclusion.11
6
Throughout the history of orthodontics there have been many ways to correct a
Class II malocclusion. Some methods focus on orthopedic change while others affect
dental changes alone. Beginning in the late 1800s Americans used extraoral forces to the
maxilla. The idea behind this was to prevent the growth of maxilla and subsequently
allow differential growth of the mandible.11 Headgear treatment could also be used for
dental change alone by distalizing molars or maintaining their position. Although,
headgear use was successful it was overcome by a new wave of thought by Angle and his
followers.11 Angle, who did not believe in extraction, thought that Class II elastics would
be a simplified way to correct Class II malocclusions by growing the mandible forward.11
Today, we know that effects of elastics are solely dental. At that time Angle’s beliefs
were disputed by Case, who believed that extractions were sometimes necessary when
long term stability and esthetics were questionable in non-extraction patients with
protrusion, crowding, or skeletal discrepancies.11 Case’s concerns with non-extraction
were echoed in the 1930s with Charles Tweed, who frequently found relapse in his nonextraction treatments.11 After presenting his retreated four bicuspid extraction patients at
an orthodontic meeting, he reintroduced extraction treatment into the orthodontic
community.11
Another method of Class II treatment, which came about toward the end of the
nineteenth century by Kingsley and Case was the “bite jumping appliance.”20 The device
by Kingsley was tooth-borne and used upper anterior guide planes to push the mandible
forward upon closure.20 Later Robin developed the monobloc for infants with
underdeveloped mandibles, which was a tissue-borne device.20 This concept of jumping
the bite was described by Wolff and Roux to create “functional stress” or “shaking of the
7
bone” on the internal bony structure that would help shape and stimulate bone growth.20
Today, there are many different types of removable as well as fixed functional appliances
that are used to distalize the maxillary dentition and bring the mandibular dentition
forward.
More recently, fixed intra-arch appliances have been used to distalize the
maxillary dentition. Furthermore, fixed inter-arch appliances utilizing upper and lower
dentition simultaneously help correct Class II malocclusions.
When the jaw discrepancy is so severe that it is out of the realm of orthodontics,
then orthognathic surgery can also be an option to treat Class II patients. This can be
done in a one or two jaw surgery depending on the soft tissue profile of the individual.
With each of the treatment options mentioned above, one is capable of treating a
Class II patient. However, the severity of the Class II problem has an effect on the
treatment rendered. Moreover, with each appliance or technique used there are
advantages and disadvantages.
One Phase versus Two Phase Treatment
Once cephalometric radiography became a regular part of treatment planning in
orthodontics it became apparent that the Class II correction with “functional” appliances
as well as intermaxillary elastics was more dentoalveolar than skeletal. However, in the
1980s functional appliances came back into play with questions of whether or not they
really stimulate mandibular growth. In 1995, a study by Livieratos and Johnston
compared one-stage (edgewise) treatment versus two-stage (functional/edgewise)
nonextraction treatment.21 According to Liveratos and Johnston both groups achieved
8
molar and overjet correction largely from skeletal changes yet the two groups were
virtually “indistinguishable.” The functional active phase had a greater increase in the
rate of growth, which declined during the fixed phase. Therefore, the overall amount of
growth was not significantly different between the two samples. The functional
appliance basically placed a “mortgage” on the growth of the mandible.21 Moreover, the
two-phase treatment took an average of a year and a half longer than the one-phase
treatment.21,22 This was later supported in a randomized clinical trial at University of
North Carolina in which preadolescent children with overjet greater than 7 mm were
randomly assigned to observation, headgear, or functional appliance treatment for 15
months and then later treated with fixed appliances.22 The results showed that there were
little skeletal differences between the groups at the end of treatment.22 Furthermore,
more patients in the functional group required extractions during the second phase of
treatment.22 There may be an “acceleration” of growth seen in the early treatment but
overall no significant “net gain.”22 Therefore, early treatment with headgear or functional
appliances may not be as efficient as one-phase treatment, but this does not mean that it is
never indicated.11 For instance, children with self-esteem issues due to their dental
appearance and those more likely to have incisal trauma due to protruded incisors can
benefit from early treatment.23 Also, in cases where patients are non-compliant, a fixed
functional appliance could be an option.
Role of Compliance
Compliance can play a crucial role in a successful orthodontic treatment. In fact,
there have been many studies on compliance in the literature. In the treatment of Class II
malocclusions patient cooperation may consist of wearing headgear, intermaxillary
9
elastics, or removable functional appliances. Brandão evaluated compliance objectively
using a timing device.24 Patients were asked to wear their headgear for 14 hours a day for
a given number of days. These headgears had recorders that patients were not told about.
However, they were told to track their wear times during this time. After a period of time
patients were told that their headgear use would be monitored electronically. The
conclusions showed that patients tend to “over report their headgear wear times.” The
patients tend to only wear their headgear 56.7% of the actual time asked by the providers.
There was an increase to 62.7% when patients were aware a recording device was being
used. Interestingly, boys were more compliant than girls in this study. However, once
they learned there was an electronic recording device, the girls had improved
compliance.24 In another study, subjective versus objective methods of monitoring
compliance with headgear use were evaluated by comparing questionnaires with a
headgear timing device.17 The results showed there were “significant differences among
the estimates of orthodontists, patients, parents and headgear timer scores.” It appeared
that subjective measures may result in overestimation of compliance.17 However,
subjective measures are usually the only source available to assess compliance.25 This
makes it very difficult to determine whether or not a patient is compliant or noncompliant.
In general, younger patients are more compliant than older patients.17,24,26
Furthermore, patients in treatment less than 8 months wore their headgear longer and
more often than patients treated more than 8 months.17
Being able to predict patient compliance can intercept problems during treatment,
so that treatment can be changed to decrease the need for cooperation. Therefore, having
“identifying characteristics” of this problem can be helpful. However, predicting
10
cooperation is multi-factorial and it is extremely complex.27 Thus, there is a dilemma
when working with poor cooperators because not only are the treatment results unreliable
and unpredictable, but the treatment time is also longer.3,28 Patient’s whose treatment is
not done in a timely manner maybe less likely to refer patients to their orthodontist.28
Furthermore, Skidmore says that Class II malocclusions usually have longer treatment
times.29 Thus, Class II correctors that reduce compliance could be advantageous because
they can reduce the reliability on the patient so that more predictable results can be
attained.3
Compliance-Free Interarch Appliances
Compliance-Free Appliances are attached to the maxilla and the mandible and are
used when a limited amount of compliance is required. In Class II correction, they are
used to posture the mandible forward; in effect bringing the lower dentition forward and
the upper dentition back. Some of these appliances include the: Herbst, MARA, MPA,
Jasper Jumper, and Forsus.
Herbst
The Herbst appliance was developed by Herbst in 1905 and presented at the 1909
International Dental Congress in Berlin.20,30 However, the appliance did not gain
popularity until 1979 when Pancherz revived this Class II treatment therapy in the
orthodontic community.30 In his study, Pancherz describes the “continuous bite jumping”
effect of this fixed functional appliance and its advantage in patient cooperation, which
appealed to many clinicians.30
11
The design of the Herbst is a bilateral telescoping mechanism that protracts the
mandible in a forward position.20,30 The components of this telescoping mechanism
consist of a tube and plunger that fit together and are attached to the maxillary molar and
mandibular premolar bands with screws. At this point of attachment the tube and plunger
are able to rotate freely like an “artificial joint between the maxilla and mandible.”30 A
lower lingual holding arch is standard and often a TPA or palatal expander is used in
conjunction with this appliance.
In Pancherz 1979 study, 10 Class II subjects were treated with the Herbst for a 6
month period and another 10 Class II subjects were observed for a 6 month period.30
According to Pancherz, the mandibular length increased 3.2 mm in the treated subjects
and 1.0 mm in the control. There was also a decrease in ANB,that consisted of a
decrease in SNA by 0.7° and an increase in SNB by 1.2°. Pancherz suggested that these
results indicated a restraint in the maxilla and stimulation of growth in the mandible. He
also mentioned an increase in the vertical dimension with an increase in lower facial
height. Overall, there was a 3.8 mm decrease in overjet and 2.5 mm decrease in overbite.
In a later study, Pancherz included 22 Class II subjects and 20 controls, which showed
that the Class II was corrected with skeletal and dental changes. The overall treatment
effect had a 6.7 mm molar correction that was mostly a result of increase in mandibular
length of 2.2 mm, 1.0 mm forward movement of mandibular molars and 2.8 mm
distalization of maxillary molars. The overjet correction was also greatly due to the
increase in mandibular length mentioned above and the forward movement of mandibular
incisors of 1.8 mm. There was a minimal amount of restriction of growth from the
maxilla, with 0.4 mm. Fifteen years later, Pancherz looked at the long term effects of the
12
Herbst appliance in a prospective study.31 He found that although there was an increase
in mandibular growth during treatment most of this effect was not retained long term.
Moreover, there can be a “headgear effect” on the maxilla, but this is transient without
appropriate retention.
This finding was supported in the study by Lai and McNamara in 1998.6
However, in this study the Herbst appliance was an acrylic splint type, which is said to
have more control over lower incisor proclination. Forty Class II subjects were treated
with the Herbst for 12 months and were matched to 40 subjects from a Class II untreated
sample from The University of Michigan Elementary and Secondary School Growth
Study. Lateral cephalograms were taken before treatment, after Herbst removal, and after
phase-II edgewise treatment. Long term effects showed that during Herbst treatment the
rate of mandibular growth increased, but this declined during the second phase. Thus at
the end there was small increase in mandibular length (1 mm) compared to controls. In
the maxilla there was a significant decrease in SNA that was seen in both phases. The
main dental effects at the end of phase II in the Herbst were forward movement of the
mandibular dentition with proclination of lower incisors. Also, the maxillary molars and
lower incisors were restrained from eruption while the mandibular molars were free to
erupt. In general, the skeletal effects in the Herbst phase improved 55% of the molar
correction while in the second part of treatment improved 80% of the molar correction.
The advantages of the Herbst appliance are the ability to treat a patient’s Class II
malocclusion without major patient compliance, the wealth of documentation,
accessibility and the ability to make modifications to its design. There are some pitfalls
to this treatment, which include: the patients’ likelihood of “burn out” because of long
13
treatment, cost of laboratory fabrication, breakage, use of specially made crowns, and its
rigidity that makes lateral mandibular movements difficult.20
Mandibular Anterior Repositioning Appliance
The Mandibular Anterior Repositioning Appliance (MARA) is a fixed functional
appliance often used as a non-compliant appliance for Class II patients. In 1998 it was
launched by Ormco after being developed by Eckhart and Toll.11 The MARA is
comprised of maxillary and mandibular first molar stainless steel crowns that produce an
interference with one another in order to push the mandible forward. This interference is
accomplished through a vertical bar that is attached to the upper first molar crown also
known as the “elbow” and a horizontal bar attached to lower first molar extending out
buccally, which is also known as the “arm.” Thus, when the “elbow” meets the “arm”
the patient is forced into a Class I malocclusion. If subsequent activations are necessary,
then shims can be added. It is standard to have a lower lingual holding arch, but TPA’s
and expansion screws can also be added.20
In a study by Pangrazio-Kulbersh, 30 Class II patients were treated with the
MARA.9 There were 12 boys with an average age of 11.2 years and 18 girls with an
average age of 11.3 years in the treated group. There were also 21 Class II untreated
subjects for the control from the Michigan Growth Study. Two cephalograms were
taken, one pretreatment that was 2 weeks before treatment, and a post-treatment
cephalogram 6 weeks after removal of the MARA. The average treatment time was 10.7
months. Pangrazio-Kulbersh’s results showed that the MARA produces 5.8 mm of Class
II molar correction; 47% of which was skeletal and 53% that was dental. However, the
14
orthopedic effects were solely in the mandible. There was no “headgear effect”, which is
often seen with the Herbst appliance. According to Pangrazio-Kulbersh, there was an
increase in mandibular length, the chin point moved forward and ANB decreased in the
MARA group. Also, there was an increase in anterior and posterior face height.
However, there were no significant vertical dental movements in the mandibular teeth.
The dental movements observed were mainly due to distalization of the maxillary molar.
There was also forward mandibular molar and incisor movement and mild proclination of
the mandibular incisor.9 A study by Gönner showed that there was less lower incisor
movement with the MARA than with other fixed Class II appliances such as the
Cantilever Bite Jumper, Clip-on Twin Block, Jasper Jumper, or Forsus.12
Later in a study by Siara-Olds et al., the long-term dentoskeletal effects of the
Bionator, Herbst, Twin Block and MARA were examined.13 There were 80 treated
subjects with 20 Class II subjects within each treatment group. The control consisted of
21 matched Class II untreated subjects from the Michigan Growth Study. Lateral
cephalograms were taken at three timepoints: initial, completion of functional therapy,
and completion of fixed therapy. This study found no significant difference in “longterm dento-skeletal” movements between the control and treated samples.13 When
compared to other functional appliances, the MARA after the Herbst had a significant
impact on the restraint of the maxilla, which is in contrast to Pangrazio-Kulbersch’s
previous findings.
In a more recent study by Ghislanzoni et al., the treatment and post-treament
orthopedic and dental outcomes of the MARA were evaluated.14 There were 23 patients
treated with the MARA appliance. Cephalograms were taken pretreatment, post-MARA,
15
and at least 1 year after post-MARA. The control sample was comprised of 17 untreated
Class II subjects from the University of Michigan and Denver Child Growth Studies.
Fixed appliances were often used concurrently with the MARA or after a few months of
active treatment. Lower molars were also stabilized with a lower lingual holding arch.
During the active part of treatment, the lower incisor came forward and there was an
increase in mandibular length. However, long term there was some relapse in the incisor
proclination. Moreover, there were significant orthopedic effects seen in the mandible as
well as the maxilla long term. The mandible had 2.0 mm increase in length Co-Gn and
there was restriction of the maxilla, with SNA decreasing 1.2°.14
There are many advantages of the MARA when compared to the Herbst including
its ability to be used with full fixed appliances, it is more esthetic, it has fewer problems
with breakage and disengagement, and it can be activated unilaterally. The disadvantages
of the MARA include the need for stainless steel crowns which can cause an increase in
anterior face height and molar mobility.
Mandibular Protraction Appliance
The Mandibular Protraction Appliance (MPA) was presented by Coelho in
1995.32 This appliance is similar to other fixed functional appliances because of its bite
jumping ability with the advantage of being fabricated at the chair. It has been modified
since Coelho introduced it with 4 different versions. The most recent model uses a tube
and piston similar to a Herbst. The tube attaches through the distal of the headgear tube
on the maxillary molar and the piston engages the lower archwire through a helix on the
wire distal to the mandibular canine.5
16
A study comparing the MPA with the Herbst was performed by Alves and
Oliveira in 2008, which looked at the skeletal, dental and soft tissue effects of each
appliance.5 There were 43 Class II subjects in total with 15 subjects in the MPA sample,
12 subjects in the Herbst sample and 16 subjects in the control sample. The MPA group
was treated an average of 8.3 months at an average age of 13 years and 2 months, the
Herbst group was treated an average of 8.7 months at an average age of 12 years and 4
months and the control group was observed for 10 months starting at an average age of
10 years and 4 months. Lateral cephalograms were taken before placement of each
appliance and at removal. The control group had two lateral cephalograms taken; one
initial and 10 months later while being followed. The study concluded that there were
statistically significant increases in mandibular length in both treated groups in
comparison to the control, although the MPA group portrayed more growth than the
Herbst. Moreover, both groups showed proclination of mandibular incisors and retrusion
of the upper lip compared to the controls.5
Thus this appliance can be a low-cost alternative to a traditional laboratory
fabricated fixed functional appliance. However, it has had a tendency toward breakage
and archwire distortion in the past.20
Jasper Jumper
The Jasper Jumper is an intermaxillary flexible force module that can be used in
conjunction with existing fixed appliances.33 It is essentially made up of heavy coil
springs in compression that are encased in an opaque plastic covering and postures the
lower jaw forward. There are two ways to attach the Jasper Jumper: on the main arch
wire or on an auxillary arch wire called an “outrigger.” In both methods the distal end of
17
the force module is attached to the upper arch by a ball pin that threads through the distal
end of the headgear tube on the upper first molar. When placed on the main arch wire,
the mesial end is attached to the lower arch wire distal to the mandibular canines. The
removal of the lower premolars is recommended to allow the force module to move more
freely. When using an outrigger, the premolar brackets can remain on and the force
module’s mesial end is attached to the auxillary. This is basically a sectional wire
attached to the distal end of the mandibular canine through the auxillary tube of the lower
first molar.33
There have been many cephalometric based studies on the Jasper Jumper. In
1994 Cope et al. looked at 31 Class II subjects treated with the Jasper Jumper and
compared them to 31 untreated Class II controls from the Human Growth Research
Center at Montreal.10 The treatment time for the Jasper Jumper was 0.4 years and with a
mean age of 12.9 years. Most of the Class II correction seen was dentoalveolar, with a
slight maxillary skeletal restraint and no significant increase in mandibular length. In the
maxilla, the molars had significant distal tipping and intrusion and the incisors were
retroclined with extrusion. In the mandible, the molars moved forward with bodily
movement as well tipping and were extruded. The mandibular incisors had a significant
amount of proclination and intrusion.10 In 1999 Covell’s study supported Cope’s
previous findings, which showed the significant amount of dental effects compared to
skeletal effects created by the Jasper Jumper.4 In contrast, Weiland and Banteleon found
a considerable amount of mandibular orthopedic effect in their study.34 They looked at
17 Class II subjects treated with the Jasper Jumper for 6 months with an average age of
11 years and 4 months at start and compared them to the Bolton standards of dentofacial
18
developmental growth. Lateral cephalograms were taken before insertion of the
appliance and after its removal. Similar to Cope and Covell, Weiland and Banteleon
found a limited skeletal effect on the maxilla and overall more dental than skeletal
effects.5,10,34 However, they found a significant increase in mandibular length of 1.7 mm,
an increase in SNB of 1.2°, and a forward movement of pogonion by 2.1 mm.34
Similarly, Stucki and Ingervall found markedly increased mandibular prognathism and
only a slight retrusion of the maxilla.35
In general, the various studies have shown that the Jasper Jumper has mainly
dentoalveolar effects, which were shown in Cope’s initial study.4,10,34,35 Although, the
Jasper Jumper can be used as an effective method to correct Class II malocclusions it
does have its drawbacks. It has a tendency towards breakage as shown in the study by
Stucki and Ingervall who reported a 9% incidence of breakage.35 A couple other
disadvantages are the large inventory needed and a lack of force when the mouth is
slightly open.20 However, it can easily be adapted to a full banded case and limits the
amount of chair time with its easy use.20
Forsus
The Forsus Fatigue Resistant Device was developed by Vogt as a fixed Class II
appliance.15 Vogt explains that the Forsus is an intermaxillary push spring that is
comprised of a push rod which inserts into a telescoping cylinder.16 This push rod is
attached onto the mandibular archwire either distal to the canine or first premolar
brackets and will complement a comprehensive fixed appliance.16 The distal end of the
telescoping tube attaches through the maxillary headgear tube with either an L-pin from
19
the distal or the EZ-module from the mesial in more recent models.16 The push rods
come in four different sizes and when fully compressed produce about 200g of force.
Usually, the force level is not this high and is comparable to heavy Class II elastics. It
transfers its force on the maxillary molars by distalizing and intruding, while using the
lower arch as anchorage.16
One study evaluated Forsus treatment over a 4 month period based on 13 Class II
subjects with an average age of 14.2 years.15 Lateral cephalograms were taken before
Forsus spring insertion and after removal. Also, a questionnaire was administered to the
adolescents, which quantified how content the subjects were with the Forsus. The
radiographs showed that about 66% of the anterior-posterior correction was due to
dentoalveolar effects. The molar correction was improved by three-fourths a cusp width
by distal movement of the maxillary molars and mesial movement of the mandibular
molars. Furthermore, there was correction of the overjet by retrusion of the upper
incisors by 5.3° and proclination of the lower incisors by 9.6°. A vertical force was also
expressed with intrusion of the lower incisors and maxillary molars creating a clockwise
rotation of the occlusal plane of 4.2°. Overall, the upper and lower arches were expanded
during treatment with a greater effect in the upper arch. The questionnaire, which was
taken two months after treatment start showed that nearly half of the patients had
difficulty brushing their teeth. However, the major complaint was the restriction from
yawning. In general, more than two-thirds of the adolescents preferred the Forsus to their
previous compliant dependent Class II therapy.15
As mentioned above, Vogt suggests that the Forsus is a non-compliant treatment
alternative to Class II elastics.16 In a study by Jones in 2008, 34 Class II subjects with
20
Class II elastic treatment with an average age of 12.6 years were compared to 34 Class II
subjects with Forsus therapy with an average age of 12.2 years.7 Pretreatment and
Posttreatment cephalograms were taken and analyzed using the pitchfork analysis and a
vertical cephalometric analysis. Except for the amount of forward movement of the
lower molars and total molar correction, there were no significant differences among the
two groups. In the Forsus group, there was 1.1 mm greater forward movement of the
lower molars and 0.8 mm greater molar correction compared to the intermaxillary elastics
group. Both groups showed upper and lower molar extrusion and lower incisor
proclination. Moreover, both the Forsus and elastics groups portrayed skeletal and
dentoalveolar forward movement in the maxilla and the mandible, with more movement
in the latter.7
In a more recent study by Franchi et al., the efficacy of the Forsus was tested
against a control group.8 The Forsus sample consisted of 32 Cl II subjects with a mean of
12.7 years and the control was comprised of 27 matched untreated Class II subjects from
the University of Michigan Growth Study and the Denver Child Growth Study with a
mean age of 12.8 years. Lateral cephalograms of the treated patients were taken before
treatment and at the end of comprehensive treatment. The average comprehensive
treatment time was 2.4 years. This study evaluated both the dental and skeletal
components of the Class II correction. Contrary to Jones study, Franchi suggests the
maxilla was orthopedically restrained in the Forsus group, which was the major part of
Class II correction skeletally. The SNA decreased 2.1° and Pt A to Nasion perp was
restricted 1.2 mm in comparison to the controls, while mandibular length increased (CoGn) 1.8 mm. Similar to the previous studies, the lower incisors significantly proclined
21
and intruded and the mandibular molars came forward and extruded.7,15 Also, there was a
significant correction in overjet and molar relationship.7,15
The Forsus has shown through previous studies to have dental as well as
orthopedic effect. It is also adaptable to a fully fixed appliance and is pre-fabricated so it
is easily accessible when needed. Similar to its predecessors it does have problems with
breakage.36 However, it is the least likely to break in comparison to other intermaxillary
compression springs.20 The Forsus does disengage when the mouth is opened beyond 60
mm, which may pose a problem and it is also costly.20
Summary and Statement of Thesis
There have been various studies on fixed functional appliances. Some of these
appliances, such as the Forsus and MARA, can be used in conjunction with complete
fixed appliances, which poses an advantage. The MARA is a laboratory made appliance
while the Forsus is pre-fabricated. The MARA and Forsus have both been shown to have
skeletal and dental effects for Class II correction8,9,9,13,13,14, 15 To date, there has not been
a direct comparison between these two appliances. The purpose of this study is to
evaluate the skeletal and dental differences between these devices using lateral
cephalograms at three timepoints: initial, after appliance removal and final. In the past
studies of the Forsus, only two timepoints have been observed. Differences in treatment
time between these appliances will also be recorded since this can be an important factor
in patient cooperation.
22
References
1.
Proffit WR, Fields HW Jr, Moray LJ. Prevalence of malocclusion and orthodontic
treatment need in the United States: estimates from the NHANES III survey. Int J
Adult Orthodon Orthognath Surg. 1998;13:97–106.
2.
McNamara JA Jr. Components of Class II malocclusion in children 8-10 years of
age. Angle Orthod. 1981;51:177–202.
3.
McSherry PF, Bradley H. Class II correction-reducing patient compliance: a review
of the available techniques. J Orthod. 2000;27:219–25.
4.
Covell DA Jr, Trammell DW, Boero RP, West R. A cephalometric study of Class II
Division 1 malocclusions treated with the Jasper Jumper appliance. Angle Orthod.
1999;69:311–20.
5.
Alves PFR, Oliveira AG. A comparison of the skeletal, dental, and soft tissue
effects caused by Herbst and mandibular protraction appliances in the treatment of
mandibular Class II malocclusions. World J Orthod. 2008;9:e1–19.
6.
Lai M, McNamara JA Jr. An evaluation of two-phase treatment with the Herbst
appliance and preadjusted edgewise therapy. Semin Orthod. 1998;4:46–58.
7.
Jones G, Buschang PH, Kim KB, Oliver DR. Class II non-extraction patients treated
with the Forsus Fatigue Resistant Device versus intermaxillary elastics. Angle
Orthod. 2008;78:332–8.
8.
Franchi L, Alvetro L, Giuntini V, Masucci C, Defraia E, Baccetti T. Effectiveness
of comprehensive fixed appliance treatment used with the Forsus Fatigue Resistant
Device in Class II patients. Angle Orthod. 2011;81:678–83.
9.
Pangrazio-Kulbersh V, Berger JL, Chermak DS, Kaczynski R, Simon ES, Haerian
A. Treatment effects of the mandibular anterior repositioning appliance on patients
with Class II malocclusion. Am J Orthod Dentofacial Orthop. 2003;123:286–95.
10. Cope JB, Buschang PH, Cope DD, Parker J, Blackwood HO 3rd. Quantitative
evaluation of craniofacial changes with Jasper Jumper therapy. Angle Orthod.
1994;64:113–22.
11. Proffit WR, Fields HW, Sarver DM. Contemporary Orthodontics. 4th ed. St. Louis:
Mosby; 2007.
12. Gönner U, Ozkan V, Jahn E, Toll DE. Effect of the MARA appliance on the
position of the lower anteriors in children, adolescents and adults with Class II
malocclusion. J Orofac Orthop. 2007;68:397–412.
23
13. Siara-Olds NJ, Pangrazio-Kulbersh V, Berger J, Bayirli B. Long-term dentoskeletal
changes with the Bionator, Herbst, Twin Block, and MARA functional appliances.
Angle Orthod. 2010;80:18–29.
14. Ghislanzoni LTH, Toll DE, Defraia E, Baccetti T, Franchi L. Treatment and
posttreatment outcomes induced by the Mandibular Advancement Repositioning
Appliance; a controlled clinical study. Angle Orthod. 2011;81:684–91.
15. Heinig N, Göz G. Clinical application and effects of the Forsus spring. A study of a
new Herbst hybrid. J Orofac Orthop. 2001;62:436–50.
16. Vogt W. The Forsus Fatigue Resistant Device. J Clin Orthod. 2006;40:368–77; quiz
358.
17. Bos A, Kleverlaan CJ, Hoogstraten J, Prahl-Andersen B, Kuitert R. Comparing
subjective and objective measures of headgear compliance. Am J Orthod
Dentofacial Orthop. 2007;132:801–5.
18. Kelly JE, Harvey CR. An assessment of the occlusion of the teeth of youths 12-17
years. Vital Health Stat 11. 1977;1–65.
19. Buschang PH, Martins J. Childhood and adolescent changes of skeletal
relationships. Angle Orthod. 1998;68:199–206; discussion 207–8.
20. Graber T, Vanarsdall R, Vig K. Orthodontics: Current Principles and Techniques.
4th ed. St. Louis: Mosby; 2005.
21. Livieratos FA, Johnston LE Jr. A comparison of one-stage and two-stage
nonextraction alternatives in matched Class II samples. Am J Orthod Dentofacial
Orthop. 1995;108: 118–31.
22. Tulloch JF, Phillips C, Proffit WR. Benefit of early Class II treatment: progress
report of a two-phase randomized clinical trial. Am J Orthod Dentofacial Orthop.
1998;113:62–72, quiz 73–4.
23. O’Brien K. Is early treatment for Class II malocclusion effective? Results from a
randomized controlled trial. Am J Orthod Dentofacial Orthop. 2006;129:S64–5.
24. Brandão M, Pinho HS, Urias D. Clinical and quantitative assessment of headgear
compliance: a pilot study. Am J Orthod Dentofacial Orthop. 2006;129:239–44.
25. Sahm G, Bartsch A, Witt E. Reliability of patient reports on compliance. Eur J
Orthod. 1990;12:438–46.
26. Egolf RJ, BeGole EA, Upshaw HS. Factors associated with orthodontic patient
compliance with intraoral elastic and headgear wear. Am J Orthod Dentofacial
Orthop. 1990;97:336–48.
24
27. Nanda RS, Kierl MJ. Prediction of cooperation in orthodontic treatment. Am J
Orthod Dentofacial Orthop. 1992;102:15–21.
28. Beckwith FR, Ackerman RJ Jr, Cobb CM, Tira DE. An evaluation of factors
affecting duration of orthodontic treatment. Am J Orthod Dentofacial Orthop.
1999;115:439–47.
29. Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors influencing treatment
time in orthodontic patients. Am J Orthod Dentofacial Orthop. 2006;129:230–8.
30. Pancherz H. Treatment of class II malocclusions by jumping the bite with the Herbst
appliance. A cephalometric investigation. Am J Orthod. 1979;76:423–42.
31. Pancherz H. The effects, limitations, and long-term dentofacial adaptations to
treatment with the Herbst appliance. Semin Orthod. 1997;3:232–43.
32. Coelho Filho CM. Mandibular protraction appliance IV. J Clin Orthod. 2001;35:18–
24.
33. Jasper JJ, McNamara JA Jr. The correction of interarch malocclusions using a fixed
force module. Am J Orthod Dentofacial Orthop. 1995;108:641–50.
34. Weiland FJ, Bantleon HP. Treatment of Class II malocclusions with the Jasper
Jumper appliance--a preliminary report. Am J Orthod Dentofacial Orthop.
1995;108:341–50.
35. Stucki N, Ingervall B. The use of the Jasper Jumper for the correction of Class II
malocclusion in the young permanent dentition. Eur J Orthod. 1998;20:271–81.
36. Ross AP, Gaffey BJ, Quick AN. Breakages using a unilateral fixed functional
appliance: a case report using The Forsus Fatigue Resistant Device. J Orthod.
2007;34:2–5.
25
CHAPTER 3: JOURNAL ARTICLE
Abstract
Purpose: The objective of this study was to compare the skeletal and dental effects of the
Forsus and the MARA, which are two types of compliance-free interarch appliances.
Materials and Methods: This study was a retrospective clinical investigation that
included 25 MARA patients (13 females, 12 males) with a mean start age of 12.7 ± 0.8
years and 25 Forsus patients (13 females, 12 males) with a mean start age of 12.1 ± 1.3
years. The MARA and Forsus were matched according to age, gender, and cervical
maturation stage at the start age. Pre-treatment (T1), appliance removal (T2), and posttreatment (T3) cephalograms were hand traced; and compared with the pitchfork analysis.
The dental and skeletal effects of each fixed inter-arch appliance were analyzed using
independent t-tests to compare the differences between each treated sample.
Results: The MARA and Forsus both demonstrated a general trend of forward skeletal
movement of the maxilla and mandible, with greater movement in the mandible.
However, the MARA group showed a significantly greater amount of forward movement
of the maxilla and mandible than the Forsus group. Greater proclination of the lower
incisors was observed in the Forsus group during T1-T2. The overall median treatment
duration of the Forsus was shorter than the MARA.
Conclusions: The Forsus and the MARA are both effective compliance-free interarch
appliances for Class II correction. In comparison to the MARA, the Forsus has a greater
26
restraint on the maxilla. However, the MARA produces significantly greater forward
displacement of the mandible than the Forsus. The Forsus may produce greater lower
incisor proclination than the MARA in the correction of overjet.
27
Introduction
Individuals with Class II malocclusions comprise a considerable part of the
population. In the National Health Survey from 1966 to 1970, Class II malocclusions
(unilateral and bilateral) defined as “distoclusion” were found in 32% the population.1
Later in the NHANES III study from 1988 to 1991 Class II malocclusions, which were
categorized as people with an overjet of 5 mm or greater, consisted of 15% of the
population.2 The nature of the Class II malocclusion is due to a number of different
dental and skeletal combinations, although one of the most common characteristics is
mandibular skeletal retrusion.3
The correction of Class II malocclusions has been performed using headgears,
elastics, removable and fixed appliances, extractions and even surgery. However,
compliance has been a constant problem in orthodontic treatment. Using Class II
appliances that reduce the need for compliance can be advantageous, since less
responsibility is placed on the patient and more predictable results can be achieved.4 This
has often lead practitioners to use fixed interarch appliances, which are compliance-free.
The most commonly used fixed appliances include the Herbst, Mandibular Anterior
Repositioning Appliance (MARA), Mandibular Protraction Appliance, Jasper Jumper,
and Forsus.
Each of these appliances can be effective in achieving Class I occlusion,
but may have advantages and disadvantages. Some of these appliances can be used
simultaneously with complete fixed treatment, which can be advantageous. Generally,
the undesirable effects in these appliances include lower incisor proclination5-11 and
upper molar distal tipping.10 In the case of both the MARA and Forsus, the appliances
can be used in conjunction with complete fixed therapy.
28
The MARA is a laboratory made fixed functional appliance that was introduced
by Ormco after being developed by Eckhart and Toll.12 It consists of upper and lower
first molar stainless steel crowns that produce an interference with one another in order to
protract the mandible.13 Many studies have looked at the effects of the MARA11,14-16 and
compared them to other fixed functional appliances.15 The overall skeletal effects appear
to include a short-term restraint of the maxilla and increase in mandibular length.15,16
The dental effects include mesial movement in the upper and lower molars.16 The upper
and lower incisors have generally moved forward with lower incisor proclination.15,16
The Forsus Fatigue Resistant Device was developed by Vogt as a fixed Class II
corrector.17 It is a prefabricated interarch push spring that is comprised of a push rod that
inserts into a telescoping cylinder.18 The push rod is attached to the lower archwire either
distal to the canine or first premolar bracket and the telescoping cylinder inserts into the
upper molar headgear tube.18 In the previous studies of the Forsus8,9,17 the effects of the
appliance have been compared to intermaxillary elastics8 and control samples,9 however,
only two timepoints have been analyzed. Prior investigations have shown mesial
movement of both the maxilla and mandible.8,9,17 The upper and lower molars have also
been shown to move mesially.8,9,17 Also, existing literature shows a trend toward lower
incisor proclination.8,9,17
In both the Forsus and MARA, skeletal and dental effects for Class II correction
have been observed.8,9,11,14-17 However, there has not been a study that has compared
these appliances side by side. The purpose of this study is to compare the skeletal and
dentoalveolar effects of the MARA and Forsus to one another at three time points.
Moreover, this study will evaluate the undesirable side effects, including lower incisor
29
proclination and upper molar tipping between the Forsus and MARA. Furthermore, the
duration of each treatment will be recorded because of the significance with treatment
time and cooperation.19
Materials and Methods
Sample
In this study Class II patients were treated non-extraction with fixed interarch
Class II correctors. The subjects were from two private practices, one that treated with
the MARA (Ormco) and the other treated with the Forsus (3M Unitek) (25 MARA and
25 Forsus). Lateral cephalograms were taken before treatment (T1), after interarch
appliance removal (T2), and at the completion of fixed therapy (T3). The mean start age
for the MARA sample was 12.7 ± 0.8 years and the Forsus sample had a mean start age
of 12.1 ± 1.3 years.
In the Forsus sample the median duration of treatment from T1-T2 was 21 months
(IQR = 18.5 to 27 months) as shown in Table 3.1. During this period, the subjects were
fully bonded; the Forsus was applied at the end of the leveling and aligning stage. The
range that the Forsus was applied during T1-T2 was between 2 to 11 months, with a
median of 5.5 months. In both the upper and lower arches, 0.019 x 0.025-inch stainlesssteel archwires were placed during Forsus treatment and consistently cinched back in the
mandibular arch. After the Forsus was removed, T2, the subjects were in the finishing
stages and the Class I correction was maintained. The median duration from T2-T3 in the
Forsus was 6 months (IQR = 4 to 7 months). The total median treatment time, T1-T3,
was 26 months in the Forsus group (IQR = 23 to 32 months).
30
In the MARA sample the median duration of treatment from T1-T2 was 13
months (IQR = 11 to 16 months) as shown in Table 3.1. During this time, the MARA
was placed, but the subjects were not fully bonded. In all of the MARA subjects, a lower
lingual holding arch was used. After the MARA was removed, T2, the patients were
fully bonded for a median duration of 19 months (IQR = 14 to 24 months). During this
time period, the patients were leveled and aligned and then finished while maintaining the
Class I occlusion. The median duration of the comprehensive treatment in the MARA
group was 33 months (IQR = 26 to 36.5 months).
Table 3.1 Median Treatment Duration and Inter-quartile Range (months)
Appliance
Forsus
MARA
T1-T2
21
(18.5 to 27)
13
(11 to 16)
T2-T3
6
(4 to 7)
19
(14 to 24)
T1-T3
26
(23 to 32)
33
(26 to 36.5)
In addition to treatment duration, the subjects’ gender, age, and cervical vertebral
maturation stage20 at start age was recorded, so that the subjects could be matched based
on gender, age and cervical vertebral stage at start age (Table 3.2). The cervical vertebral
stage was recorded at start age using the cervical vertebral maturation (CVM) method.21
The median value for the CVM stage at T1 or start age was 2 (range of 1 to 4). The
inclusion criteria for the subjects selected was the following: (1) initial Class II
malocclusion, (2) no permanent teeth extracted, (3) lateral cephalograms of diagnostic
quality taken at three time points and (4) correction of Class II malocclusion to Class I or
super Class I occlusion. The treatment variability was also reduced by using samples that
were only treated by one practitioner. After the removal of the Forsus or MARA (T2)
31
other Class II correctors, such as Class II elastics, may have been used in some patients in
order to maintain the Class I occlusion.
Table 3.2: Age, gender and cervical vertebral maturation stage- matched Forsus and
MARA samples
Appliance
Males
Mean Start
Age (yrs)
Females
Forsus
12
13
12.7 ± 0.8
(11.6 - 15)
MARA
12
13
12.1 ± 1.3
(9.3 – 15.3)
Median
CVM
Stage T1
2
2
Data Collection
The pre-treatment, appliance removal, and post-treatment cephalograms were
digital radiographs. The magnification of the MARA sample was 0% while the Forsus
had a magnification of 14%, which was adjusted for in the measurements. These were
printed on photo quality paper and hand-traced on acetate paper using a 0.3 mm pencil.
Measurements were performed using a digital caliper to the nearest tenth of a millimeter
as recommended by Johnston.22 Superimpositions were performed between pretreatment (T1) and appliance removal (T2) and between appliance removal (T2) and posttreatment (T3) using the Pitchfork analysis explained by Johnston.22
The pitchfork analysis presents the changes in molar and incisor relationships as
an algebraic sum of skeletal growth relative to the cranial base and dental movements
relative to basal bone. The measurements are given a sign of positive or negative
depending on the impact on the Class II relationship: a positive sign is used when the
Class II molar relationship or overjet is improved and a negative sign is used when it is
32
worsened. The apical base change (ABCH) is the total amount of the maxillary and
mandibular skeletal growth changes and signifies the overall effect of skeletal growth.
The change in molar relationship is determined when the ABCH is added to the changes
in upper and lower first molar movements. The change in overjet is found when the
ABCH is summed with the changes in upper and lower incisor movements. These
measurements are all made relative to the mean functional occlusal plane, which is
determined from the average of T1, T2 and T3 functional occlusal planes. The functional
occlusal plane is based on the first molars and premolars and the incisors are
disregarded.22
Max + Mand = ABCH
ABCH + U6 + L6 = 6/6
ABCH + U1 + L1 = 1/1
Figure 3.1: Pitchfork analysis diagram, adapted from Johnston.22
33
Because Class II interach appliances often produce angular changes to upper and
lower incisors, the angles of these teeth were measured by hand relative to the mean
functional occlusal plane. Also, the amount of tipping of the upper and lower molars was
measured by subtracting the amount of root movement from crown movement.
Statistical Methods
The data was statistically analyzed using SPSS 17.0 for Windows (IBM). An
independent two-sample t-test was performed to analyze the differences between the two
groups. A Levene’s test was also done to evaluate the equality of variances. Differences
among the groups were regarded as statistically significant at p < 0.05.
Results
Forsus and MARA Treatment Effects (T1-T2)
During the treatment phase of the Forsus (Figure 3.2), the maxilla moved
mesially 1.7 mm and the mandible moved mesially 4.8 mm, resulting in an apical base
change of 2.9 mm. The upper molars tipped mesially because the crowns moved
mesially 0.7 mm, while the roots moved mesially 0.4 mm. The lower molars tipped
distally because crowns and roots moved mesially 1.7 mm and 2.4 mm, respectively;
tipping distally 0.6 mm. The total molar correction (ABCH + U6 + L6) was 3.8 mm.
The upper incisor distalized 1.1 mm, while the lower incisor moved mesially 1.4 mm.
The overjet correction (ABCH + U1 + L1) was 5.6 mm. The upper incisor was
retroclined 4.3 degrees and the lower incisors proclined 4.2 degrees.
34
Figure 3.2: Pitchfork treatment changes from T1-T2 in Forsus Sample
In the MARA treatment period (Figure 3.3), the maxilla moved mesially 2.8 mm
and the mandible moved mesially 5.1 mm, with an apical base change of 2.3 mm. The
upper molars tipped distally because the crown was distalized 0.3 mm and the root had no
movement. The lower molar crowns and roots moved mesially 0.5 mm, so no tipping
was observed. Total molar correction was 3.1 mm. The upper incisor had no movement,
while the lower incisor moved mesially 0.2 mm. The overjet correction was 2.6 mm.
Both the upper and lower incisors were proclined 1.4 degrees.
35
Figure 3.3: Pitchfork treatment changes from T1-T2 in MARA Sample
Between the Forsus and MARA a few findings were statistically significant
during T1-T2 including the following: lower incisor angulation, lower molar tipping and
lower molar root movement. The lower incisor was proclined 2.8 degrees greater in the
Forsus than the MARA. The lower molar had 0.6 mm greater distal tipping in the Forsus
than the MARA. Also, the lower molar root movement was 1.9 mm greater in the Forsus
than the MARA. The comparisons between the Forsus and MARA during T1-T2 can be
seen in Table 3.3.
36
Table 3.3: T1-T2 Pitchfork comparison of Forsus and MARA
Forsus
Mean
2.9
T1-T2
ABCH (mm)
MAX (mm)
MAND (mm)
U6 Crown (mm)
U6 Root (mm)
U6 Tipping (mm)
L6 Crown (mm)
L6 Root (mm)
L6 Tipping (mm)
6/6 (mm)
U1 (mm)
L1 (mm)
1/1 (mm)
U1 Angle (°)
L1 Angle (°)
NS, Not significant
*P < 0.05
-1.7
4.8
-0.7
-0.4
-0.3
1.7
2.4
-0.6
3.8
1.1
1.4
5.6
4.3
4.2
SD
1.8
2.1
3.3
2.1
1.8
1.7
1.5
1.8
1.0
2.1
2.3
2.3
3.6
8.9
7.9
MARA
Mean
SD
2.3
2.2
-2.8
5.1
0.3
0.0
0.3
0.5
0.5
0.0
3.1
0.0
0.2
2.6
-1.4
1.4
2.7
3.8
1.6
1.5
1.5
1.3
1.1
1.4
2.3
1.7
1.9
2.1
7.4
4.2
Significance
0.507
NS
0.600
0.236
0.125
0.335
0.817
0.249
0.012
0.045
0.789
0.095
0.574
0.122
0.534
0.016
NS
NS
NS
NS
NS
NS
*
*
NS
NS
NS
NS
NS
*
Forsus and MARA Post-Treatment Effects (T2-T3)
In the Forsus post-treatment phase (Figure 3.4), the maxilla move distally 0.2
mm, while the mandible moved mesially 0.3 mm, resulting in an apical base change of
0.5 mm. The upper molars tipped mesially because the crowns moved mesially 0.4 mm,
while the roots moved distally 0.2 mm. The lower molars tipped distally because crowns
and roots moved distally 0.7 mm and 0.2 mm, in that order. The total molar correction
was -0.7 mm. The upper incisor moved mesially 0.4 mm and the lower incisor moved
mesially 0.2 mm. The overjet correction was 0.3 mm. The upper incisor was proclined
1.7 degrees and the lower incisors proclined 0.7 degrees.
37
Figure 3.4: Pitchfork treatment changes from T2-T3 in Forsus Sample
In the MARA sample (Figure 3.5), the maxilla moved mesially 1.1 mm and the
mandible moved mesially 3.3 mm, with an overall apical base change of 2.2 mm. The
upper molars tipped mesially, with 2.3 mm mesial crown movement and 0.6 mm mesial
root movement. The lower molars tipped distally because the crowns moved mesially 0.2
mm, but the roots moved mesially 1.3 mm. There was no molar correction during this
period. The upper incisor moved mesially 0.2 mm, while the lower incisor distalized 1.3
mm. The overjet correction was 0.7 mm. The upper incisor was proclined 2.2 degrees
and the lower incisors retroclined 1.2 degrees.
38
Figure 3.5: Pitchfork treatment changes from T2-T3 in MARA Sample
The statistically significant variables found during T2-T3 between the Forsus
and MARA were the treatment duration, apical base change, maxillary and mandibular
skeletal movements, upper and lower molar tipping, and lower incisor movement. The
post-treatment duration was 13.6 months longer in the MARA than the Forsus. The
apical base change was 1.7 mm greater in the MARA than the Forsus. The maxilla
moved mesially 1.3 mm greater in the MARA than the Forsus. The mandible moved
mesially 3.0 mm greater in the MARA than the Forsus. The upper molars tipped
mesially 1.3 mm greater in the MARA than the Forsus and the lower molars tipped
distally 0.6 mm greater in the MARA than the Forsus. Finally, the lower incisor
movement was distalized 1.5 mm greater in the MARA than the Forsus. The
comparisons between the Forsus and MARA during T2-T3 can be seen in Table 3.4.
39
Table 3.4: T2-T3 Pitchfork comparison of Forsus and MARA
Forsus
Mean
T2-T3
ABCH (mm)
MAX (mm)
MAND (mm)
U6 Crown (mm)
U6 Root (mm)
U6 Tipping (mm)
L6 Crown (mm)
L6 Root (mm)
L6 Tipping (mm)
6/6 (mm)
U1 (mm)
L1 (mm)
1/1 (mm)
U1 Angle (°)
L1 Angle (°)
NS, Not Significant
*P < 0.05
0.5
0.2
0.3
-0.4
0.2
-0.5
-0.7
-0.2
-0.5
-0.7
-0.4
0.2
0.3
-1.7
0.7
SD
1.3
2.0
2.7
1.8
1.7
1.1
1.3
1.8
1.2
1.1
1.3
1.1
1.6
4.7
3.6
MARA
Mean
2.2
-1.1
3.3
-2.4
-0.6
-1.8
0.2
1.3
-1.1
0.0
-0.2
-1.3
0.7
-2.2
-1.2
SD
2.8
3.2
5.1
2.4
1.8
2.0
1.8
2.3
2.0
1.6
1.2
2.7
1.8
5.8
5.2
Significance
0.003
0.005
0.001
0.060
0.664
0.005
0.132
0.067
0.021
0.172
0.446
0.001
0.854
0.346
0.150
*
*
*
NS
NS
*
NS
NS
*
NS
NS
*
NS
NS
NS
Forsus and MARA Overall Treatment Effects (T1-T3)
The overall treatment effect (Figure 3.6) in the Forsus showed the maxilla moved
mesially 1.6 mm and the mandible moved mesially 5.1 mm, resulting in an apical base
change of 3.4 mm. The upper molars tipped mesially because the crowns moved
mesially 1.2 mm, while the roots moved mesially 0.2 mm. The lower molars tipped
distally because the crowns moved mesially 0.9 mm, while the roots moved mesially 2.1
mm. The total molar correction was 3.2 mm. The upper incisor distalized 0.7 mm, while
the lower incisor moved mesially 1.5 mm. The overjet correction was 5.8 mm. The
upper incisor was retroclined 2.6 degrees and the lower incisors proclined 4.9 degrees.
40
Figure 3.6: Pitchfork treatment changes from T1-T3 in Forsus Sample
In the MARA (Figure 3.7), the maxilla moved mesially 3.9 mm and the mandible
moved mesially 8.4 mm, with an apical base change of 4.5 mm. The upper molars
tipped mesially because the crowns and roots moved mesially 2.1 mm and 0.6 mm,
respectively. The lower molars tipped distally because the crowns moved mesially 0.8
mm, while the roots moved mesially 1.9 mm. The total molar correction was 3.1 mm.
The upper incisor mesialized 0.2 mm and the lower moved distally 1.1 mm. The overjet
correction was 3.2 mm. The upper incisor was proclined 3.6 degrees and the lower
incisors proclined 0.2 degrees.
41
Figure 3.7: Pitchfork treatment changes from T1-T3 in MARA Sample
The overall treatment effects between the Forsus and the MARA can be seen in
Table 3.5. The only variables that were significant in the overall treatment results were
the apical base change and the maxillary and mandibular skeletal movements. In the
MARA the maxilla and mandible moved mesially significantly more than in the Forsus
by 2.3 mm and 3.3 mm, respectively. Also, the MARA sample had 1.1 mm greater apical
base change than the Forsus.
42
Table 3.5: T1-T3 Pitchfork comparison of Forsus and MARA
T1-T3
ABCH (mm)
MAX (mm)
MAND (mm)
U6 Crown (mm)
U6 Root (mm)
U6 Tipping (mm)
L6 Crown (mm)
L6 Root (mm)
L6 Tipping (mm)
6/6 (mm)
U1 (mm)
L1 (mm)
1/1 (mm)
U1 Angle (°)
L1 Angle (°)
NS, Not significant
*P <0.05
Forsus
Mean
3.4
-1.6
5.1
-1.2
-0.2
-0.9
0.9
2.1
-1.1
3.2
0.7
1.5
5.8
2.6
4.9
SD
1.8
2.2
3.2
2.2
1.4
1.9
2.1
2.6
1.6
2.1
2.6
2.2
3.1
9.4
8.0
MARA
Mean
4.5
-3.9
8.4
-2.1
-0.6
-1.5
0.8
1.9
-1.1
3.1
-0.2
-1.1
3.2
-3.6
0.2
SD
4.2
3.0
6.2
2.6
2.1
1.7
2.1
2.2
1.9
2.7
2.1
3.5
2.3
7.3
6.5
Significance
0.003
*
0.017
*
0.005
*
0.542
NS
0.340
NS
0.672
NS
0.745
NS
0.560
NS
0.486
NS
0.273
NS
0.135
NS
0.071
NS
0.262
NS
0.738
NS
0.284
NS
Discussion
This study was performed to observe the skeletal and dental effects of the Forsus
and MARA in Class II malocclusions. This study adds to the existing literature by
comparing the two appliances alongside one another. Also the current study expands on
previous investigations by evaluating the Forsus and MARA at three timepoints. In the
past, the Forsus has only been analyzed at two timepoints. Comparisons of the Forsus
and MARA appliance effects from this study to those reported in existing literature can
be seen in Table 3.6 and Table 3.7. The subsequent discussion is organized into five
sections: maxillary skeletal, mandibular skeletal, maxillary dental, mandibular dental and
overall effects.
43
Table 3.6: Comparison of the Forsus appliance effects reported in the literature:
Pre-treatment to Post-treatment. Positive sign indicates an improvement in Class II
correction (mesial movements in mandible and distal movements in maxilla) Negative
sign indicates worsening of Class II malocclusion (distal movements in mandible and
mesial movements in maxilla)
Author(s)
Jones et
al.8
Franchi et
al.9
Present
study
ABCH
(mm)
2.6
MAX
(mm)
-1.7
MAND
(mm)
4.4
U6
(mm)
-1.2
L6
(mm)
1.8
6/6
(mm)
3.2
U1
(mm)
-0.7
L1
(mm)
1.2
1/1
(mm)
3.2
U1
(°)
-3.7
L1
(°)
6.3
N/A
N/A
N/A
-1.0
2.4
3.4
1.1
2.3
5.4
1.2
6.1
3.4
-1.6
5.1
-1.2
0.9
3.2
0.7
1.5
5.8
2.6
4.9
Table 3.7: Comparison of the MARA appliance effects reported in the literature:
Pre-treatment to Post-treatment. Positive sign indicates an improvement in Class II
correction (mesial movements in mandible and distal movements in maxilla) Negative
sign indicates worsening of Class II malocclusion (distal movements in mandible and
mesial movements in maxilla)
Author(s)
Siara-Olds
et al.15
Ghislanzo
ni et al.16
Present
study
ABCH
(mm)
MAX
(mm)
MAND
(mm)
U6
(mm)
L6
(mm)
6/6
(mm)
U1
(mm)
L1
(mm)
1/1
(mm)
U1
(°)
L1
(°)
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0.8
-0.7
0.3
N/A
N/A
N/A
-2.0
3.1
3.9
-1.0
1.4
3.1
1.2
3.3
4.5
-3.9
8.4
-2.1
0.8
3.1
-0.2
-1.1
3.2
-3.6
0.2
Maxillary Skeletal Effects
In both the Forsus and MARA the maxilla came forward, which is an expected
pattern of normal growth.12 However, the overall treatment effects demonstrated that the
Forsus had significantly greater restraint of the maxilla than the MARA. This finding is
supported by Franchi et al., who observed that the Forsus had significant restriction on
the maxilla. In previous studies, the MARA has also displayed a restriction on the
maxilla, however, past investigators showed that this restriction was transient and was not
significant long term.15,16 In this study, the greater restraint of the maxilla observed from
44
the Forsus may be due to the simultaneous treatment with fully bonded appliances. In
this instance, the Forsus may have more of a “headgear effect” than the MARA because it
is not solely focusing its forces on the upper molar. Instead, the Forsus may be able to
distalize the entire maxillary dentition because it is tied together giving a greater
orthopedic effect.
Mandibular Skeletal Effects
Similar to the maxilla, the mandible also came forward in both groups, which was
anticipated.12 Furthermore, in both samples the mandible had the greatest contribution to
the molar correction. In the overall treatment effects, the MARA portrayed a statistically
significant increase in mandibular protraction in comparison to the Forsus. In previous
investigations of the MARA, different methods have been used to measure mandibular
length, so it is difficult to compare the present results to the existing literature. However
in a study by Jones et al., who also used the pitchfork analysis for the Forsus, the
mandibular skeletal findings were similar. The results of this study may be explained
because of the MARA’s greater functional effect with respect to the Forsus. This is
probably due to the rigid design of the MARA in comparison to the Forsus. However,
the increase in mandibular protraction in the MARA may also be due to the difference in
treatment duration between the groups. The overall median treatment time for the Forsus
was 26 months while the MARA was 33 months. The difference in time could allow for
more mandibular growth in the MARA group versus the Forsus group. 8
45
Maxillary Dental Effects
The overall movement of the maxillary dentition was not significant between the
MARA and the Forsus, however during the period of post-treatment effects the MARA
had significantly greater mesial tipping of the upper molar. This relapse of the upper
molar could be due to the greater force placed on the upper molar by the MARA during
the treatment period, which caused more tipping rather than bodily movement in molar
correction. In general in the MARA and the Forsus groups, the upper molar crowns
moved mesially much like previous studies.8,9,16 Similar to the study by Franchi et al.,
the upper incisors in the present Forsus group were slightly distalized and more upright,
but not to a significant amount in comparison to the MARA.9
Mandibular Dental Effects
Between the Forsus and the MARA the overall mandibular dental treatment
effects were not statistically significant. However, there were significant findings during
the treatment
(T1-T2) and post-treatment (T2-T3) phase. During the appliance
treatment phase, the Forsus group had a significantly greater amount of lower incisor
proclination in comparison to the MARA group, which was observed in previous Forsus
investigations.8,9,17 However, it is important to recognize that some of the lower incisor
proclination may depend on the amount of crowding in each sample. The level of
crowding was not recorded and could be a limitation of the study. Also, the lower molar
root moved mesially significantly more in the Forsus group than in the MARA group,
which suggests more bodily movement of the lower molar in the Forsus group. During
the post-treatment phase there was significantly more distal movement of the lower
46
incisors in the MARA in comparison to the Forsus. This could be due to the techniques
used by each practitioner after the compliance-free appliance. For instance, the distal
movement of the lower incisors in the MARA group during post-treatment phase could
have been a result of interproximal reduction used by the practitioner. Also during the
post-treatment phase the MARA demonstrated significantly greater lower molar distal
tipping in comparison to the Forsus. This may be deceiving because the lower molar
crown moved mesially in the MARA group; however, the root moved mesially more than
the crown. The overall treatment effect (T1-T3) seen among the two groups was mesial
movement of the lower molars. The lower incisors showed more mesial movement and
proclination in the Forsus group, but not to a significant degree in comparison to the
MARA group. Earlier studies of the Forsus demonstrated greater amounts of lower
incisor proclination with 6.1 to 6.3 degrees, in comparison to 4.9 degrees of proclinaton
in the present study. This variation between the present study and previous studies may
be due to the average amount of overjet and molar correction needed in each sample at
the start.
Overall Effects
The overall treatment effects show that most of the molar correction in both the
Forsus and MARA came from skeletal effects. There was 132% and 106% improvement
in molar relationship from skeletal effects in the MARA and Forsus groups, respectively.
The largest contribution to the skeletal changes came from the mandible in both groups.
However, because of a lack of a control sample in this study the contribution of natural
growth to this mandibular change cannot be quantified. The dental effects negatively
47
affected the molar relationship, mostly because the maxillary molar moved forward in the
Forsus and MARA samples.
Conclusions
1) The Forsus and MARA are both acceptable compliance-free appliances for
Class II correction.
2) The Forsus has a greater restraint on the maxilla when compared to the
MARA.
3) The MARA produces significantly greater forward displacement of the
mandible than the Forsus.
4) The Forsus may produce greater lower incisor proclination than the MARA in
correction of the overjet.
5) Most of the molar correction is attained from mandibular skeletal effects in
both groups.
48
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50
Appendix
Table A.1: Description of pitchfork analysis variables. These measurements are made
relative to the mean functional occlusal plane (MFOP). Positive sign indicates an
improvement in Class II correction (mesial movements in mandible and distal
movements in maxilla) Negative sign indicates worsening of Class II malocclusion (distal
movements in mandible and mesial movements in maxilla)22
Variable
Skeletal Change
Abbreviation
ABCH
Maxilla
Max
Mandible
Mand
Upper Molar
U6
Lower Molar
L6
Molar Relation
6/6
Upper Incisor
U1
Lower Incisor
L1
Overjet
1/1
51
Definition
The accumulation of maxillary
and mandibular growth relative
to cranial base,
ABCH= Max + Mand
Maxillary displacement relative
to cranial base
Mandibular displacement
relative to cranial base
Upper first molar displacement
relative to basal bone,
measurement is taken at the
mesial contact point
Lower first molar displacement
relative to basal bone,
measurement is taken at the
mesial contact point
The change in molar
relationship is determined by
adding the ABCH to the upper
and lower molar movements,
ABCH + U6 + L6 = 6/6
Upper incisor displacement
relative to basal bone,
measurement is taken at the
incisal edge
Lower incisor displacement
relative to basal bone,
measurement is taken at the
incisal edge
The change in overjet is
determined by adding the
ABCH to the upper and lower
incisor movements,
ABCH + U1 + L1 = 1/1
Vita Auctoris
Shereen Azizollahi was born on September 6, 1983 in Los Angeles, California to
Arsalan Azizollahi and Nasrin Azizollahi. She is the younger of two children.
She grew up in Irvine, California and graduated from University High School in
June of 2001. She attended the University of California Los Angeles for her
undergraduate studies where she received a Bachelor in Science in Biology in 2005. She
attended the University of Southern California where she earned her Doctorate of Dental
Surgery degree in 2009. Subsequently, she began the orthodontic residency program at
Saint Louis University where she expects to receive a Master of Science in Dentistry
(Research) degree. During her orthodontic residency she married Jonathan Falakassa in
June 2011. Upon graduation, she will move to Miami, Florida to begin her orthodontic
career.
52