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COMPARING TWO METHODS OF NON-COMPLIANCE
CLASS II THERAPY:
THE DISTAL JET
AND THE SMD (FROG)
Larrissa K. Cali, 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
0
Abstract
Purpose:
The objective of this study was to compare the
dental effects of the Distal Jet and the Frog, two types of
molar distalizers.
The position of the upper second molars
was also evaluated to determine if second molar eruption
affected the dental changes caused by the distalization
appliances or the rate of distalization.
Materials and Methods:
The investigation was a
retrospective, clinical study of 79 Distal Jet patients
with a mean initial age of 13.6 years and 29 Frog patients
with a mean age of 11.5 years.
The Frog and Distal Jet
samples were matched according to initial age and gender.
Pretreatment (T1) and postdistalization (T2) lateral
cephalograms were traced and analyzed with the pitchfork
analysis.
The long axes of the upper first molar and upper
incisor were measured relative to the functional occlusal
plane to evaluate angular changes in these teeth.
Variations in design of the Distal Jet appliance were
assessed by comparing the original tube and piston design
to the Bowman modification.
The dental effects and rate of
the distalization appliances were compared when second
molars were erupted or unerupted.
Independent t-tests were
used to assess differences between groups.
1
Results:
The original tube and piston design of the Distal
Jet exhibited a significantly significant greater amount of
horizontal molar movement over a shorter period of time.
Patients treated with the Frog and both appliance designs
of the Distal Jet exhibited a general trend for mesial
movement of the maxilla, mandible, and dentition.
The
Distal Jet produced significantly more molar distalization
than the Frog in a shorter period of time.
Greater mesial
movement of the lower incisors and lower molars was seen in
the Distal Jet group when compared to the patients treated
with the Frog.
More incisor anchorage loss was observed
when distalizer therapy was initiated after second molars
erupted.
Conclusions:
The original design of the Distal Jet
appliance produces greater distal maxillary molar movement
in a shorter period of time when compared to the Bowman
modification.
The Distal Jet and the Frog are effective at
correcting Class II malocclusions although the Distal Jet
is a more efficient means of molar distalization.
Molar
distalization after second molar eruption causes more
incisor anchorage loss than that produced when second
molars are unerupted.
2
COMPARING TWO METHODS OF NON-COMPLIANCE
CLASS II THERAPY:
THE DISTAL JET
AND THE SMD (FROG)
Larrissa K. Cali, 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
3
COMMITTEE IN CHARGE OF CANDIDACY:
Professor Rolf G. Behrents,
Chairperson and Advisor
Professor Eustaquio Araujo
Associate Clinical Professor Donald R. Oliver
i
ACKNOWLEDGEMENTS
I would like to thank Dr. Behrents for allowing me to
be a part of the orthodontic program at Saint Louis
University.
I feel very blessed to have received my
orthodontic education at an institution that provides an
extraordinary clinical and didactic environment and the
opportunity to learn from so many incredible instructors.
Thank you to Dr. Behrents for sharing your vast expertise
in diagnosis and treatment planning and for guiding and
advising me on my thesis.
I would like to recognize Dr. Araujo for his
assistance on my thesis.
He is an extraordinary clinician,
mentor, and individual and his guidance has left an
indelible impression.
I will be forever grateful for the
ways that he has shaped my life and future career.
Thank you to Dr. Oliver for his immeasurable support
and encouragement during the research process.
and attention to detail are incredible.
His memory
I am thankful that
I have had the opportunity to gain experience from such a
remarkable instructor and orthodontist.
A special thank you goes to Dr. Jay Bowman and Dr.
Kevin Walde for providing the records that were used in
this study.
They are exceedingly busy in their practices
ii
yet never hesitated to take the time to provide guidance
and assistance to me.
Thank you to Heidi Israel for her help with the
statistical analysis.
She has worked tirelessly even with
an extremely demanding schedule and I am grateful for the
time she made available to help me.
iii
TABLE OF CONTENTS
LIST OF TABLES............................................v
LIST OF FIGURES..........................................vi
CHAPTER 1:
INTRODUCTION..................................1
CHAPTER 2: REVIEW OF THE LITERATURE......................4
The Class II Problem Defined.........................4
Prevalence of Class II Malocclusions.................4
Class II Etiology....................................5
Class II Correction..................................6
The Role of Compliance in Treatment..................8
Appliances Requiring Minimal Compliance.............10
Fixed Functional and Bite Jumping Appliances........11
Herbst.........................................11
MARA...........................................14
Mandibular Protraction Appliance (MPA).........16
Forsus.........................................17
Jasper Jumper..................................19
Intraoral Molar Distalization Appliances............21
Magnets........................................22
NiTi Coil Springs..............................23
Pendulum.......................................24
Jones Jig......................................26
Distal Jet.....................................27
Simplified Molar Distalizer (SMD)..............38
Distalizing and Second Molars.......................40
Summary and Statement of Thesis.....................41
References..........................................42
CHAPTER 3: JOURNAL ARTICLE
Abstract............................................47
Introduction........................................49
Materials and Methods...............................51
Sample.........................................51
Data Collection................................53
Statistical Methods............................55
Results.............................................56
Discussion..........................................60
Conclusions.........................................67
References..........................................69
Appendix.................................................71
Vita Auctoris............................................73
iv
LIST OF TABLES
Table 3.1:
Sample characteristics of age-matched
Distal Jet and Frog samples...............58
Table 3.2:
Comparison of age-matched Distal Jet
and Frog samples..........................58
Table 3.3:
Comparison of patients on the basis
of second molar position..................60
Table 3.4:
Comparison of Distal Jet appliance
effects reported in the literature........65
Table A.1:
Description of cephalomeric variables
used in the pitchfork analysis............71
Table A.2:
Sample characteristics of Distal Jet
group according to appliance design.......72
Table A.3:
Comparison of original tube and
piston Distal Jet and Bowman modified
Distal Jet................................72
v
LIST OF FIGURES
Figure 2.1:
Diagram of the original bilateral
tube and piston design of the Distal
Jet..................................28
Figure 2.2:
Diagram of the Frog appliance........39
Figure 3.1:
Diagram of the variables included
in the pitchfork analysis............54
vi
CHAPTER 1:
INTRODUCTION
Many techniques and appliances are used to correct
Class II malocclusions.
All of the methods can be
successful at producing Class I occlusions in patients with
dental and/or skeletal problems.
Attempts have been made
to develop new techniques to make treatment better and more
efficient, decrease chair time, and reduce the need for
patient cooperation.
Class II malocclusion presents a frequent challenge to
orthodontists.
Many of the techniques aimed at correcting
Class II malocclusions such as headgear, removable
appliances, and interarch elastics, rely heavily on patient
compliance.
Acquiring cooperation from patients can be
difficult and when cooperation is lacking, longer treatment
times and inferior outcomes can result.
To limit the
reliance on patient compliance, clinicians have turned to
appliances such as molar distalizers to treat Class II
patients.
Distalizing appliances can be an effective means
to translate upper molars that are positioned forward into
a Class I relationship without the reliance on patient
cooperation.
Establishing the effects of various
appliances and determining which are most effective is
1
important for clinicians so that they can make educated
treatment decisions.
Maxillary molar distalizers are not without drawbacks.
They can be costly and uncomfortable.
The appliances can
break or fail requiring repair and increasing chair time.
Undesirable effects on the dentition can result.
The Distal Jet has been previously compared to several
different molar distalizing appliances.
It has proven to
be an effective and reliable method of molar distalization.
The Distal Jet has been touted as an appliance that
produces bodily movement of the maxillary molars.
The
ability to produce bodily molar movement has also been
attributed to the Frog, another appliance for molar
distalization but, to date, there is no published data
examining the effects of the Frog.
The purpose of this study is to compare and contrast
the dental effects of the Distal Jet and the Frog.
The
amount and rate of molar distal movement and tipping along
with the amount of anchorage loss will be considered.
The
goal of this investigation is to establish whether the Frog
appliance can be used effectively to correct Class II
dentitions and how it compares to the Distal Jet, an
established method of Class II treatment.
Additionally,
two types of Distal Jet appliances will be compared to
2
determine if there is a difference in the dental effects
they produce.
The effect of erupted second molars on the efficiency
and results of distalizer therapy have been examined and
the conclusions about their contribution in distalization
treatment are contentious.
In this study, the position of
second molars will be compared with the dental effects that
are produced to determine if these teeth play a significant
role in the amount of distalization or anchorage loss that
is observed.
3
CHAPTER 2:
REVIEW OF THE LITERATURE
The Class II Problem Defined
The goals of orthodontic treatment are aesthetics,
function, and stability.
Occlusal function is determined
by the relationship of the upper and lower teeth to each
other.
Angle, the father of modern orthodontics, is
credited with developing the first meaningful
classification of occlusal relationships in the 1890s.1
Angle suggested that the upper first molars were the key to
occlusion and that a Class II malocclusion exists when the
lower molars are positioned distally relative to the upper
molars.1
In Class I, or normal, occlusion, the mesiobuccal
cusp of the upper first molar occludes in the buccal groove
of the lower molar.
Orthodontists attempt to finish
orthodontic treatment with Class I occlusion whenever
possible.
Prevalence of Class II Malocclusions
Class II malocclusion is a common finding within the
general population and among orthodontic patients.
It is
characterized by the upper molars positioned forward of the
lower molars and a preponderance of upper incisors are
forward of the lower incisors in what is termed overjet.
4
The third National Health and Nutrition Examination
Survey (NHANES III) was conducted from 1988 to 1991 and
studied 7,000 individuals to provide estimates of
malocclusion in U.S. children and adults.
Rather than
looking at molar relationships, measurements of overjet
were used as an estimate of the prevalence of Class II
malocclusion.2
According to data from NHANES III, Class II
malocclusion, defined as 5 mm or more of overjet, occurs in
23% of children (ages 8-11), 16% of adolescents (ages 1217) and 13% of adults (ages 18-50).
Mildly increased
overjet, 3-4 mm, is as prevalent as what is considered an
ideal overjet of 1-2 mm.
Severe Class II malocclusion
occurs in 4% of the population and is more frequent in
African-Americans and Mexican-Americans than in Caucasians.2
This data indicates that the skeletal Class II jaw
relationship is the most common skeletal disharmony
occurring in the United States.
Class II Etiology
The nature of Class II malocclusions has been examined
extensively.
In 1981, McNamara evaluated the lateral
cephalometric radiographs of 277 children eight to ten
years of age with Class II malocclusions to determine the
maxillary and mandibular skeletal and dentoalveolar
positions and the vertical development of each patient.3
5
According to McNamara, those with Class II malocclusions
most frequently exhibit retrusion of the mandible.
The
position of the maxilla is more variable but tends to be
normally positioned.
If it is in an abnormal position, the
maxilla tends to exhibit skeletal retrusion more often than
protrusion, which was found in only a small percentage of
the subjects.
In patients that exhibited excessive
vertical development, maxillary retrusion was most commonly
occurring.
Excessive vertical development is found
frequently in Class II individuals and McNamara suggests
this may be due to abnormalities in respiratory function.
The results of this study indicate that the maxillary
dentition is less protrusive in Class II malocclusions than
what was reported in previous studies.
McNamara indicates
that lower incisors are typically normally positioned.
He
concluded that the Class II problem is complex and there
are 77 different combinations of morphological traits that
can result in a Class II malocclusion.3
Class II Correction
Proffit refers to a skeletal growth pattern that is
cephalocaudal, i.e., more growth occurs in the lower
extremities than in the upper.1
This same phenomenon takes
place in the face where the mandible exhibits accelerated
growth relative to that of the maxilla.
6
This trend is
referred to as differential growth and can contribute to
the correction of a Class II malocclusion.
Proffit
cautions, however, that it is unlikely to expect that
growth will supply more than 3-4 mm to the correction of a
Class II malocclusion.
Numerous methods have been
described for the correction of Class II malocclusions.
Some techniques affect only the dental arches while others
result in skeletal correction.
Extraction of teeth in both
dental arches or in the maxillary arch alone can also be
employed to modify occlusal relationships and reduce
overjet.1
This approach can be particularly helpful in
patients exhibiting dental crowding or protrusive soft
tissue profiles.
Class II treatments can involve extraoral
traction with headgear to modify the growth of the maxilla
and allow differential forward growth of the mandible and
to distalize or maintain the position of the maxillary
dentition.1
Multiple techniques act intraorally to deliver
distally-directed forces on the maxillary dentition and
mesially-directed forces in the mandible.1
either fixed or removable.
These can be
Examples include functional
appliances and intermaxillary (Class II) elastics.
Orthognathic surgery to reposition one or both jaws is an
effective method to treat Class II patients when soft
tissue aesthetics is a concern and in those individuals
7
where a severe occlusal and/or skeletal discrepancy exists.1
Each of these approaches has been used successfully in
Class II correction and all have inherent strengths and
shortcomings.
The Role of Compliance in Treatment
Studies investigating the role of patient compliance
in treatment are frequent in the orthodontic literature.
Many of the appliances used in the treatment of Class II
malocclusions such as headgears, removable functional
appliances, and intermaxillary elastics rely heavily on
patient cooperation for success.
Bos et al. studied
headgear compliance objectively with a timer device that
recorded temperature.4
Their findings indicate that
compliance with headgear is significantly overestimated by
orthodontists, patients, and parents of patients.
Often
times, subjective information from patients is the only
evidence of cooperation with appliances.5
False reports
regarding compliance and an inability to accurately measure
a patient’s level of cooperation make distinguishing
compliant patients from noncompliant ones difficult or
impossible.5
Prediction of patient compliance may be helpful to
forecast treatment issues in order to alter the treatment
plan and reduce the need for cooperation before problems
8
arise.
Unfortunately, “identifying characteristics that
predict cooperation with treatment is a difficult and
complex problem.”6
Several characteristics of patients
have been examined in an attempt to determine what drives a
patient to comply.
Several studies have shown that younger
patients comply more readily than older ones4,7,8 and that
girls are more compliant than boys.6
Other studies have
shown no relationship between gender and level of
compliance4 and some have found that boys are more compliant
than girls.7
Overall, the complexity of human behavior
makes it difficult to make useful predictions.5
It has been said that “patient cooperation is the
single most important factor every orthodontist must
contend with.”6
Motivating patients can be challenging and
when patient compliance is lacking, longer treatment times6,
9
and compromised outcomes6 may result.
The results of a
study by Skidmore, et al., indicate that orthodontic
treatment of patients with Class II molars takes longer
than Class I treatment.9
Correction of Class II
malocclusions is made more challenging by the use of
appliances that require cooperation such as headgear,
elastics and removable appliances.10
Conversely, patients
whose treatment is completed in a timely manner may be more
9
pleased with their orthodontic treatment and more likely to
refer other patients to their orthodontist.11
Because of the concerns regarding patient compliance,
orthodontists have sought treatment modalities that reduce
the need for patient compliance.
There are several
examples of appliances that require minimal cooperation yet
can be used successfully to correct a Class II
malocclusion.
Appliances Requiring Minimal Compliance
Appliances that do not rely on compliance to correct
Class II malocclusions can be classified into those that
reposition the mandible forward and utilize certain
functional or bite jumping elements for correction and
those that are focused only on maxillary molar
distalization.
The following is a partial listing of
appliances that are considered to require minimal patient
cooperation:
Fixed Functional Appliances
Herbst
MARA
MPA
Forsus
Molar Distalizers
Jones Jig
Pendulum
Distal Jet
Frog
10
Fixed Functional and Bite Jumping Appliances
Fixed functional appliances are attractive to
clinicians because they reduce the reliance on patient
cooperation.
Some common fixed functional appliances
include the Herbst, MARA, MPA and Forsus.
Herbst
The Herbst was introduced by Herbst in 1909.12
appliance was re-introduced in 1979 by Pancherz.
The
It
consists of bilateral telescope mechanisms which are each
made up of a tube attached to the upper first molar band
and a plunger attached to the lower first premolar band.
Alternatively, cast splints can be used instead of bands.
The length of the tube and plunger determines the amount of
mandibular advancement.
Pancherz recommends advancement of
the mandible until the incisors are in an edge-to-edge
relationship.13-15
Speech, mastication, and swallowing are
all carried out with the mandible in an anteriorly
protruded position.
Pancherz contends that Herbst
appliance therapy causes a redirection of maxillary growth,
mesial tooth movements in the mandible, distal tooth
movements in the maxilla, and possibly stimulates
mandibular growth.14
Pancherz has conducted several studies comparing the
skeletal and dental effects in Class II, division 1
11
patients treated with the Herbst compared with untreated
control groups.13,14
Patients were treated for six months
while the control group was followed for the same length of
time.13
The occlusion was analyzed via dental casts and the
skeletal effects were assessed using lateral cephalograms
taken before and after the examination period with the
teeth in centric occlusion and with the mouth wide open so
as to inspect the mandibular condyle.
All patients started
treatment with a full-cusp Class II molar relationship.
There were no significant differences between the treatment
group and the control group in any of the cephalometric
variables that were studied.
After treatment, all of the
cases exhibited successful correction to a Class I
relationship.
The overjet decreased 3.8 mm and the
overbite decreased 2.5 mm.
None of the patients showed a
difference in centric occlusion and centric relation
greater than 1.5 mm.
The control group exhibited no
changes in the same parameters.
The ANB angle was
significantly reduced in the Herbst group as compared to
the control group and this was attributed to a decrease in
the SNA angle and an increase in the SNB angle.
Lower
facial height was increased more in the treatment group.
The position of the upper incisors was not changed in
either of the groups but the lower incisors were
12
significantly proclined (5.4º) in the Herbst group and they
were unchanged in the control group.
Herbst treatment
resulted in a reduction in facial profile convexity while
the control group exhibited negligible profile changes.
There was a significant increase in mandibular length in
the Herbst group (3.2 mm) when compared with that of the
untreated controls (1.0 mm).
Pancherz asserts that the
improvement in sagittal molar and incisor relationships
seen after Herbst therapy is a consequence of equal
contributions of orthopedic and dentoalveolar changes.14
Molar correction is primarily a result of an increase in
mandibular length, distal movement of the maxillary molars
and mesial movement of the mandibular molars.14
Overjet
correction is a consequence of an increase in mandibular
length along with proclination of the lower incisors.
According to the research conducted by Pancherz, the
temporomandibular joints were unchanged in all of the
patients treated with Herbst appliances.
The mandible
exhibited greater skeletal effects than the maxilla
primarily due to an increase in length in combination with
an anterior displacement.
Intrusion of lower incisors and
eruption of the lower molars causes the occlusal plane to
tip downward.15
After Herbst treatment, patients exhibit
less increase in mandibular length that untreated
13
controls.15
The occlusal plane tips up anteriorly and the
upper molars are moved mesially and extruded.
Most of the
posttreatment changes occur in the first six months after
Herbst therapy.
When compared with removable functional appliances,
the Herbst has several advantages: it cannot be removed by
the patient, requires no patient cooperation, and has a
short active treatment time of approximately 6-8 months.15
The Herbst is indicated in patients with a Class II,
division 1 or division 2 malocclusions.
It is most
effective in the permanent dentition approximately at the
pubertal growth peak.
Herbst therapy is not suggested for
use in the deciduous or mixed dentition and should not be
utilized for nongrowing patients as the effects of
treatment would be limited to the dentition.15
MARA
The Mandibular Anterior Repositioning Appliance (MARA)
was introduced by Ormco in 1998 after being developed and
tested by Toll and Eckhart.1
The appliance consists of
stainless steel crowns on the upper and lower first molars
attached to a TPA and lower lingual holding arch,
respectively.
Horizontal bars protrude from the upper and
lower molar crowns on the buccal which creates occlusal
interferences causing the mandible to protrude forward into
14
a Class I occlusion.
Shims can be used to incrementally
increase the activation.
According to Pangrazio-Kulbersh et al., the MARA
produces significant dental and skeletal effects.16
Their
sample of 30 Class II patients treated with the MARA was
compared to a matched sample of untreated controls from the
Michigan Elementary and Secondary School Growth Study and
to a previous study investigating the effects of the Herbst
and Frankel II appliances.
The results indicated that the
MARA produces no orthopedic effect in the maxilla.
On the
other hand, the greatest difference between the treatment
and control groups was in mandibular skeletal measurements
indicating enhanced mandibular growth.
The maxillary
molars were moved distally and the lower molars and
incisors were moved forward.
were not observed.
Vertical dental movements
Significant increases in the anterior
and posterior face heights were observed in the treatment
group.
The MARA produces effects similar to those of the
Herbst and has a greater dental effect than the Frankel II.
The Herbst has a greater effect on maxillary growth and
exhibits greater intrusive effects on the dentition when
compared to the MARA.
The authors concluded that 47% of
the Class II correction produced by the MARA is orthopedic
while 53% can be accounted for by dental alterations.16
15
Advantages of the MARA in comparison to the Herbst
include enhanced aesthetics, disengagement does not occur,
and breakage is not as common.12
Additionally, the MARA can
be used with full fixed appliances.12
Disadvantages include
the requirement of molar crowns which increase the facial
height and can cause mobility of the molars.12
Mandibular Protraction Appliance (MPA)
The Mandibular Protraction Appliance (MPA) was
introduced in 1995 by Coelho.12
fabricated by the orthodontist.12
It was designed to be
The original appliance
has been redesigned four times to facilitate construction
and installation and to improve on the functionality.17,18
The most recent advancement, the MPA IV, consists of a tube
that connects to the maxillary molar at the headgear tube
and a piston that connects to the lower archwire at a helix
distal to the canine bracket.19
A comparative study of the Herbst and MPA was
conducted by Alves and Oliveira to evaluate the skeletal,
dental, and soft tissue effects of the two appliances.19
The study included 43 adolescents divided into three
groups:
12 subjects with a mean age of 12 years and 4
months treated with the Herbst for 8.7 months; 15 subjects
with a mean age of 13 years and 2 months treated with the
MPA for 8.3 months; and group 3 consisted of 16 subjects
16
with a mean age of 10 years 4 months who received no
orthodontic treatment.
Lateral cephalograms were taken of
each patient in the treatment groups before treatment and
after appliance removal.
Patients in the control group had
two radiographs within the 10 month interval they were
followed.
Results of the study indicated that both the
Herbst and MPA result in greater increases in mandibular
length, protrusion of the lower incisors, and retrusion of
the upper lip when compared with the untreated controls.
Patients treated with the MPA exhibited significantly more
mandibular sagittal change than those in the Herbst group.19
Forsus
Vogt is credited with development of the Forsus
Fatigue Resistant Device (FRD).20
The Forsus consists of a
push rod with a hook on the mesial end that is crimped onto
the lower archwire distal to the canine or first premolar
brackets.21
The distal end of the push rod inserts into a
telescoping cylinder that is made up of an inner and outer
sliding tube surrounded by an open-coil spring.
The distal
end of the cylinder is then attached to the maxillary first
molar headgear tube with an L-pin or clip feature.
When the spring is compressed it delivers about 200 g
of force.21
Generally, the springs are not fully compressed
making the force level more comparable to interarch
17
elastics.
The force of the spring places a distal and
intrusive force on the upper maxillary molars using the
lower arch as anchorage.
A study of the Forsus appliance evaluated the skeletal
and dental effects of the device.20
A questionnaire was
also used to assess patient satisfaction with the
appliance.
The sample was made up of 13 growing Class II
patients with an average age of 14.2 years treated for four
months with the Forsus.
Lateral cephalograms were taken
before treatment and upon removal of the appliance.
Results indicated that the upper molars were moved distally
and the lower molars were moved mesially, improving the
Class II molar relationship by ¾ of a cusp width.
Sixty-
six percent of the correction was shown to be a result of
dental effects.
The upper anterior teeth were retroclined
by 5.3º while the lower teeth were proclined 9.6º, reducing
the overjet by 4.6 mm.
The overbite decreased 1.2 mm owing
to intrusion and protrusion of the lower incisors.
The
occlusal plane rotated 4.2º and the upper and lower dental
arches were broadened during treatment.
More dental
expansion occurred in the upper arch in comparison.
A
questionnaire provided to patients two months into
treatment indicated that the Forsus appliance did not cause
pain or issues with sleep but patients reported minor
18
eating and speech problems, limited mouth opening, change
in appearance and soft tissue discomfort.
reportedly an issue.
Oral hygiene was
Two-thirds of the patients preferred
the Forsus to the previous Class II appliance that was
being used (headgear, activator, or interarch elastics).20
According to Vogt, the Forsus can be used in the place
of Class II elastics or the Herbst appliance.21
It is
indicated in patients with convex profiles but should not
be used in Class II patients with protrusive maxillae or
normal mandibles.
21
Jasper Jumper
Jasper introduced a flexible fixed force module called
the Jasper Jumper in 1987.
The appliance is composed of a
stainless steel spring that is covered by an opaque plastic
covering.22
It is most commonly attached with a ball pin
through the headgear tube of the first maxillary molar
posteriorly and anteriorly it is connected to the lower
arch wire.
The lower premolar brackets are removed to
allow increased movement.
Alternatively, the appliance can
be attached with “outriggers” (sectional bypass wires) in
the lower arch to allow the premolars bonds to remain in
place.22
The role of relative contributions of dental and
skeletal changes to the overall treatment effects of Jasper
19
Jumpers is controversial.
Cope et al.23 and Covell et al.24
suggest that the primary effect of Jasper Jumpers on Class
II correction is dentoalveolar. Cope et al. demonstrated
limited posterior displacement of the maxilla and only
posterior rotation of the mandible, no significant effect
on horizontal mandibular growth.
Covell et al. found that
forward maxillary growth was restricted but discovered no
significant effect on mandibular growth.
On the contrary,
a study by Stucki and Ingervall indicated a slight
retrusive effect on the maxilla and a significant increase
in mandibular prognathism.25
The findings of Weiland and
Bantleon also suggest a considerable orthopedic effect,
concluding that 40% of the Class II correction is a result
of skeletal changes while 60% is due to dentoalveolar
alterations.26
They indicate that the skeletal correction
occurred mainly in the mandible with the appliance
producing an increase in mandibular growth and a mild
reduction in maxillary horizontal development.
The various studies that have investigated the effects
of Jasper Jumpers tend to agree on the dentoalveolar
changes that are produced by the appliance.
The maxillary
incisors are retracted and extruded while the mandibular
incisors are proclined and intruded.23-25
The maxillary
molars undergo distalization whereas the mandibular molars
20
are moved mesially.23-26
In addition, the Jasper Jumper
produces expansive forces on the maxillary teeth.22
All of
the studies showed a corrected Class I occlusion at the end
of Jasper Jumper therapy in every patient.23-26
In comparison with the Herbst, the Jasper Jumper has
several advantages.22
The amount of force is more easily
controlled and the flexible modules offer increased patient
comfort.
Eating and brushing are less complicated with the
Jasper Jumper.
The most noteworthy drawbacks to the
appliance are breakage, which occurs in 9% of the patients
according to Stucki and Ingervall25 and undesired tooth
movements.
Intraoral Molar Distalization Appliances
Maxillary molar distalizers have been developed as a
minimal compliance method for Class II patients with
reasonably good skeletal relationships and only mild or
moderate space discrepancies in the maxillary arch.
Molar
distalizers are intra-arch appliances that often rely on
the palatal vault and upper premolars and anterior teeth to
provide anchorage for the distalization force.
Proffit
asserts that up to 6 mm of distal movement can be created
with distalization.1
Even so, it is difficult to move
maxillary molars bodily and to maintain the molar position
after the molars have been distalized and the rest of the
21
maxillary dentition is retracted.
Often times, the
treatment approaches to retract anterior teeth after
distalization require cooperation from the patient.
Numerous appliances have been developed to distalize
maxillary molars.
Magnets
Gianelly first described the use of repelling magnets
for maxillary molar distalization in 1988.
The magnets are
attached on the upper fixed appliance in the buccal around
the area of the first or second premolar and the first
molar.27
In a study with ten consecutively treated patients
with a mean age of 13.4 years, Bondemark and Kurol used
intra-oral photographs, lateral radiographs and dental
casts acquired pretreatment and after molar distalization
to evaluate the dental effects produced.28
They found that
magnets were successful at distalizing upper molars to a
Class I relationship in all of the patients with a mean
treatment time of 16.6 weeks.
On average, the upper molars
were moved distally 4.2 mm, tipped distally 8.0º, and
rotated disto-buccally.
Anchorage loss of roughly 1.5 mm
was demonstrated by mesial movement of premolars, canines,
and incisors.
The upper incisors moved forward 1.8 mm and
were tipped forward 6º.
Gianelly, et al. indicated that
22
80% of the space created with molar distalization using
magnets is attributable to distal movement of the molars.27
This method does not require patient compliance and
can be successful at correcting Class II molars into a
Class I relationship in a relatively short period of time
(mean of 16.6 weeks, according to Bondemark and Kurol28).
Nevertheless, the magnets are costly, lack corrosion
resistance, and produce a great deal of distal molar
tipping when bodily movement is more desirable.28
They also
require frequent activation to maximize the force.
Weekly
activation has been recommended by Gianelly.27
NiTi Coil Springs
NiTi coils have been used as a compliance-free method
of distalizing upper molars.
The appliance consists of a
Nance button attached to the first premolars for anchorage
control and 100 g coil springs positioned on the upper
archwire between the first premolars and first molars.29
An
uprighting spring can be used in the vertical slots of the
first premolars for anchorage augmentation.
A comparison of NiTi coil springs and magnets was
performed to evaluate the dental effects of the two
methods.30
The study involved 15 Class II patients
evaluated cephalometrically and through dental model
analysis.
Each patient received a modified Nance appliance
23
attached to the upper first premolars along with magnetic
devices on the right side and Ni-Ti open coil springs on
the left.
Coil springs produced significantly more distal
molar movement than was found with the magnets.
The amount
of distal crown tip and distopalatal rotation produced by
both techniques was not significant.
All of the patients
were successfully treated to a Class I molar relationship
in 3 months, however, the NiTi coil springs were more
effective and required less frequent activation.30
Pendulum
The Pendulum appliance was first described by Hilgers
in 1992.
It utilizes a Nance appliance with auxiliary
wires that can be soldered to bands on the premolars or
deciduous molars or bonded to the occlusal surfaces of the
teeth.
Increasing the number of teeth in the anchorage
unit, increases stability of the appliance.32
Two .036 inch
TMA springs extend from the distal aspect of the acrylic
button and when activated and inserted into the first
maxillary molar lingual sheaths, provide the distalization
force.
If the upper arch requires expansion, an expansion
screw can be added to the center of the Nance button.
This
appliance is referred to as the Pend-X.
Byloff and Darendeliler evaluated the Pendulum
appliance utilizing 200-250 g of distalization force to the
24
upper first molars in 13 patients with dental Class II
malocclusions.31
The dental and skeletal effects were
assessed with pretreatment and postdistalization
cephalometric radiographs.
weeks on the average.
Pendulum therapy lasted 16.6
During this time, the maxillary
first molar was moved distally 3.39 mm and tipped distally
14.5º.
The rate of molar distal movement was 1.02 mm per
month.
The upper molars were intruded and second premolars
were extruded.
The maxillary second premolars moved
mesially 1.63 mm.
The upper incisors moved anteriorly and
tipped labially but incisor anchorage loss was minimal.
The Pendulum did not have any orthopedic effects.31
A study by Ghosh and Nanda used a larger sample size
(41 subjects) to evaluate the dental effects of the
Pendulum appliance.33
Their analysis used lateral
cephalometric radiographs and dental models.
They found
that the mean amount of maxillary molar distalization was
3.37 mm with mean distal molar tipping of 8.36º.
The first
premolars were moved mesially 2.55 mm on average and tipped
mesially 1.29º.
Intrusion of the first molar was not
statistically significant however the first premolar
extruded 1.7 mm.
Transverse molar widths were increased
during appliance therapy.
The results of the study
indicated a mesiobuccal rotation of the first molar which
25
is favorable in Class II treatment and according to the
authors, may be caused by the arc created by the spring
when it moves distally.33
The Pendulum appliance has the benefits of minimal
reliance on patient compliance and simple construction and
activation.33
It can be used to increase maxillary
transverse width when necessary.
The large amount of molar
tipping should be considered when planning treatment using
this appliance.
Jones Jig
The Jones Jig, developed by Jones, uses an open-coil
NiTi spring in a jig assembly to provide distalization
force to the maxillary first molars.
A modified Nance
button with auxiliary wires attached to the upper first or
second premolars or the deciduous molars acts as the
anchorage unit.
The Jones Jig provides 70-75 g of force
when it is activated by compression of the NiTi coil
spring.34
Evaluations of the Jones Jig demonstrate a dental
Class II correction with orthopedic alterations.
As with
other intraoral molar distalizers, the maxillary first
molars are moved distally which results in anchorage loss
that is revealed by mesial movement and tipping of the
maxillary premolars.35-36
Gulati, et al showed that the
26
appliance causes significant distal tipping and
distopalatal rotation of the upper first molars.35
The
appliance causes maxillary molar extrusion and an increase
in the mandibular plane angle.35
According to Jones and
White, Class II malocclusion caused by maxillary molar
rotation alone can be corrected in 90-120 days while true
Class II molar relationships can be corrected in 120-180
days.34
Distal Jet
The Distal Jet was developed by Carano and Testa in
1996 (Figure 2.1).
The original design of the appliance
consists of a bilateral piston and tube assembly.
The .036
inch internal diameter tubes are embedded in an acrylic
Nance button in the palate.
A wire extends from the tube,
like a piston, runs posteriorly parallel to the occlusal
plane, and ends in a bayonet bend that is inserted into the
lingual sheath on the first molar band.
Each tube has a
NiTi open-coil spring and screw-clamp that provides the
distalization force.
The appliance is supported by an
anchor wire from the Nance button to bands on the second
premolars.
Every four to six weeks, the coil spring is
reactivated by moving the screw-clamp distally to compress
the spring.
The clamp is locked in place by tightening the
mesial set-screw with a small Allen wrench.
27
In 1996,
Carano and Testa recommended 160 g NiTi coil springs for
children and 250 g springs for adults.37
Alternatively,
stainless steel springs can be used in the place of NiTi.
One advantage of the Distal Jet is the ability to convert
the appliance to a Nance holding arch after the desired
molar position has been obtained.
A solid extension is
formed by flowing light-cured acrylic around the coil
spring, set-screw, and the distal bayonet bend.
The
premolar supporting wires can be sectioned at the Nance
button with a high speed to allow retraction of the
anterior teeth.
Figure 2.1: Diagram of the original bilateral tube
and piston design of the Distal Jet (photo used by
permission of Dynaflex)
28
Several modifications have been made to improve the
ease of use and functionality of the Distal Jet.38
A
variation that includes two set screws in the activation
collar makes the transition to a Nance holding arch easier,
cleaner, and more reliable.38 The mesial set screw is still
used during the active distalization phase but when distal
movement is completed, the collar is moved mesially so that
the spring can be pulled from the wire with a plier.
The
collar is then locked into place at the junction of the
tube and wire.
The mesial set screw is tightened onto the
tube and the distal set screw is tightened onto the wire to
lock the tube and piston together.
With the Bowman modification, the tube and piston
arrangement was replaced with a rigid tracking wire.
This
variation simplifies the conversion to a holding arch
following distalization.
The coil springs are left in
place, the hex screws are locked, and the premolar
supporting wires are sectioned.
Variations can be included such as helical loops in
the bayonet wires to produce distal maxillary molar
rotation or to upright mesially tipped molars.38
Limited
maxillary expansion can be accomplished by embedding a
jackscrew in the Nance palatal button.38
The terminal ends
of the Distal Jet can be adjusted to provide molar rotation
29
correction.39
Carano, et al. recommend rotation correction
before activating the appliance for distalization.39 A
variation on the design of the Distal Jet can be used to
upright lower molars that have tipped mesially.40
Carano
and associates contend that the appliance is comfortable,
uncomplicated to insert, and has an insignificant extrusive
component.39
Some advantages of the Distal Jet are good esthetics,
comfort, and ease of insertion and activation.41
Carano and
Testa indicate that the Distal Jet can produce bodily
movement of the maxillary molars because the line of force
is through the center of resistance of the first molar.37
It can be used for both unilateral and bilateral Class II
correction.41
Bowman advocates overcorrection of the
maxillary molar to a super Class I by 2 mm as has been
suggested by Hilgers.
Additionally, it has been suggested
that auxiliaries such as headgear or elastics can be used
if there is an increase of more than 1 mm in overjet during
distalization, an idea that was first proposed by
Gianelly.28
Two studies have examined the forces and moments
created by the Distal Jet during molar distalization.43,44
Kinzinger and Diedrich conducted an in vitro study of three
lab-fabricated appliances using a 3D metering device.43
30
Their results indicate that the Distal Jet produces
distalizing forces with uprighting moments.
There are
forces and moments that are buccally directed and, because
the force is palatal to the center of rotation, it acts to
rotate the first molars mesio-palatally.
The forces remain
uniform because the coil is reactivated frequently.
They
relate that if a patient’s palate is shallow, the amount of
molar distal tipping can be increased because of the
inability to direct the line of force through the molar’s
center of resistance.
Uprighting activation can be used to
compensate for distal tip of the molar and a toe-in bend
can be used to counteract the rotational moment.
The
authors, however, indicate that these adjustments cause an
increase in friction which therefore would hinder the
distal movement of the molar and should not be used.
They
recommend overcorrection to a super Class I so that
uprighting can occur.
They also advocate the use of a TPA
or bihelix to rotate the molars.43
Nishii, et al. scanned and superimposed pre- and postdistalization casts to evaluate the effects of the Distal
Jet on the maxillary teeth 3-dimensionally.44
Their results
indicate a mean maxillary first molar distalization of 2.4
mm, distal tip of 1.8º, lateral expansion of 1.2 mm, and
vertical extrusion of 0.5 mm.
The second premolars moved
31
mesially 1.4 mm, expanded laterally by 0.3 mm, and extruded
0.5 mm.
The upper incisors moved mesially 2.4 mm and
tipped mesially 4.5º while extruding 0.3 mm.
Measurements
of pre- and post-distalization cephalograms indicated no
significant skeletal changes but the Y-axis, lower face
height, and mandibular plane were increased.
The monthly
mean molar distalization rate was 0.4 mm.44
A study of the Distal Jet was conducted by Ngantung,
et al. to evaluate the effects of the appliance on the
maxillary teeth and the outcomes following orthodontic
treatment.41
Pre-treatment, post-distalization, and post-
treatment lateral cephalograms of 21 female and 12 male
patients with a mean age of 12.8 years were used. Bands
were cemented on the maxillary first molars and second
bicuspids.
All of the subjects had full fixed appliances
during distalization and Jasper Jumpers were used to
maintain the molar distalization.
The maxillary molar
distalization phase averaged 6.7 months in length while
mean total treatment time was 25.7 months.
The maxillary
first molars were distalized 2.1 mm and were distally
tipped 3.3º while the second premolars moved mesially 2.6
mm and were distally tipped 4.3º.
The distal tipping of
the second premolars is in contrast to that found with the
Pendulum and Jones Jig which tip the premolars mesially.
32
The maxillary second molars were also moved distally 2.6
mm.
The maxillary incisors exhibited anchorage loss from
the distalization force.
The upper incisor to SN increased
12.2º and overjet was increased by 1.7 mm.
They found an
increase in lower anterior face height of 2.4 mm and the
upper and lower lips to E plane increased during the
distalization phase.
At the end of treatment, the
maxillary first and second molars were positioned mesially,
tipped mesially, and extruded.
An interesting finding was
that the maxillary first molars finished treatment more
mesially than when they started.
The maxillary second
premolars were positioned distally and tipped mesially.
The upper incisor was uprighted and extruded.
The final
angulation of the upper incisors was nearly ideal. The
upper and lower lips to E plane decreased.
The
investigators concluded that the Distal Jet generated less
tipping of maxillary molars and better bodily movement when
compared to the Pendulum and Jones Jig.
According to the
authors, reduction of distalization force is not effective
in deterring anchorage loss (the Jones Jig utilizes 75 g of
force, while the Distal Jet uses 240 g).
They indicate
that the Distal Jet should not be used on patients with
full profiles, high FMAs, anterior open bites, or
significant crowding.41
33
Bolla et al. assessed the effectiveness of the Distal
Jet used independent of multibracket appliances.45
In their
study, the bicuspids and canines were retracted one tooth
at a time using .017 x.025 NiTi sectional wires and power
chain.
A utility arch was used for incisor retraction.
In
five months, the upper first molars moved distally 3.2 mm
and tipped distally 3.1º.
The upper first premolars moved
mesially 1.3 mm and tipped distally by 2.8º.
They found no
significant change in upper incisor position, overjet,
lower facial height, or mandibular plane angle.
Seventy-
one percent of the space created during distalization was
from distal molar movement while 29% was from anchorage
loss.
The distalization force was increased from 180 g to
240 g if the patient had second molars.45
There are several studies comparing the Distal Jet to
other methods of Class II correction in terms of
efficiency, degree of undesired side effects.46
Chiu, et
al. compared the dental and skeletal effects of the Distal
Jet and Pendulum.
The Distal Jet group had concurrent full
fixed appliances during molar distalization while fixed
appliances were delayed in the Pendulum group until the
distalization had been completed.
The study consisted of
two groups of 32 Class II division 1 patients with a mean
age of 12 years 3 months in the Distal Jet group and 12
34
years 6 months in the Pendulum group.
were analyzed at three time points:
Lateral cephalograms
pretreatment,
postdistalization and posttreatment for skeletal and dental
differences.
During treatment in both groups, the
mandibular plane angle opened, increasing lower anterior
facial height.
The authors point out that this effect of
the Distal Jet and the Pendulum on the vertical dimension
has been observed in other studies.
In the Pendulum group,
molar distalization was significantly greater but the
molars were also tipped distally to a greater degree.
Nevertheless, when the amount of distal movement was
considered, the Distal Jet was equally as likely to tip the
molars (each mm of distal movement corresponded to 1.8º of
distal tip).
Less anchorage loss, when measured at the
first premolars, was found in the Pendulum group.
The
maxillary incisors in the Distal Jet group exhibited more
flaring and intrusion and the overjet was increased
significantly more than in the Pendulum group.
The
investigators attribute the differences in premolar
anchorage loss to the fact that the Pendulum utilizes four
premolars instead of two in the anchorage unit.
They
credit the incisor anchorage loss to the use of full fixed
appliances in the Distal Jet group.
The Pendulum was shown
to be more efficient (distalization took seven months
35
instead of ten).
On the whole, during treatment, the
maxillary molars finished in a more mesial location than
their original position in the Distal Jet group but the
overall molar correction was the same in both groups.46
Bolla et al. conducted a study evaluating the nature
of maxillary molar movement and degree of anchorage loss
with the Distal Jet with the intention of comparing it to
other molar distalizers.47
The sample consisted of 20
subjects with a mean age of 12.6.
Pre- and post-
distalization lateral cephalograms and dental models were
analyzed.
The results indicated that the average
distalization phase took five months to distalize molars
3.2 mm and distally tip them 3.1º.
First bicuspids were
moved mesially 1.3 mm and tipped distally 2.8º.
The first
molars were extruded 0.5 mm while the first premolars were
extruded 1.1 mm.
The maxillary incisors and overjet were
not significantly changed and there was an insignificant
increase in lower anterior facial height.
The molars were
expanded laterally and mildly rotated mesio-palatally.
Other appliances such as the Pendulum, Jones Jig,
Greenfield appliance and sagittal appliance display a more
advantageous distal rotation of the upper molars but also
exhibit molar constriction which is unfavorable in Class II
treatment.
They noted that if recovery from tipping is
36
taken into account, the total space created by the
Pendulum, Distal Jet with fixed appliances, and Distal Jet
alone is approximately the same.47
A literature review was conducted by Kinzinger et al.
to assess the treatment effects of several appliances that
use intramaxillary anchorage for distalization.48
After
reviewing 85 articles, 22 were included in the analysis.
The longest linear amount of molar distalization was found
with the Pendulum which also exhibited the greatest amount
of tipping.
Vertical movements of molars were minimal with
the least amount of vertical side-effects found with the
Distal Jet, the Pendulum exhibited the greatest amount of
intrusion and the Jones Jig had the highest amount of
extrusion.
The Jones Jig and Pendulum displayed the
smallest amount of premolar anchorage loss.
The smallest
amount of premolar tipping was found with the Distal Jet
and Pendulum while the Jones Jig demonstrated the most
tipping.
The incisors were mesialized the most and
displayed the largest protrusion with the Distal Jet that
utilized two anchorage teeth.
The Jones Jig showed the
least amount of incisor mesialization.
The highest
effective molar distalization was found with the Pendulum
but the authors point out that there is also a significant
amount of distal tipping therefore subsequent uprighting
37
reduces the space.
The First Class appliance and the
Distal Jet had the highest efficiency (greatest amount of
distalization with the least amount of anchorage loss).
The authors recommend that the anchorage unit have as many
teeth as possible and indicate that deciduous molars can
act as anchorage but will perform this task with lesser
quality than that provided by premolars.
They point out
that anchorage loss is more marked in the incisors than in
the first premolars with maxillary distalizers.48
Simplified Molar Distalizer (Frog)
The Simplified Molar Distalizer (SMD), or Frog, was
introduced by Walde in 2003 (Figure 2.2).49
The design of
the Frog consists of a modified Nance button with embedded
.028-inch stainless steel wires that are bonded to either
two or four premolars or deciduous molars.
The appliance
also includes an expansion screw and a removable spring
bent from a .032-inch stainless steel or TMA wire with
adjustment loops used for fine tuning and double back bends
for insertion into the lingual sheaths of the upper first
molar bands.
The appliance is activated by inserting the
activation tool into the head of the screw and rotating it
counterclockwise.
Each 360º rotation of the screw opens
the appliance approximately 0.5 mm and the appliance can be
reactivated at four-to-eight-week intervals.
38
Multiple
turns of the screw can be made at each patient visit.
According to Walde, the Frog can produce 1-2 mm of
maxillary molar movement per month.
Conversion to a Nance
holding arch is accomplished by sealing the screw with
acrylic or composite resin and severing the connections to
the premolars from the Nance button.
Figure 2.2: Diagram of the Frog appliance (photo used
by permission of Dynaflex)
Walde relates that there are several advantages of the
Frog which include easy assembly and activation, threedimensional molar control, and an easily removable and
adjustable distalizing spring.
It can be used for
bilateral or unilateral molar distalization and when second
molars are fully erupted. There is minimal requirement for
39
patient cooperation and the appliance has an aesthetic
appearance.
Walde maintains that appliance placement is
critical and correct placement will result in bodily molar
movement.
The appliance should be positioned approximately
at the trifurcation of the upper molars which is generally
10-12 mm from the occlusal surface.
According to Walde,
this position places the distalization force at the center
of resistance of the molars for bodily tooth movement.
If
the appliance is placed too far occlusally more crown
tipping will occur, too far apically, more root tipping
will occur.49
Distalizing and Second Molars
Several studies have investigated the influence of
erupted second molars on the amount and rate of
distalization, the amount of molar tipping, and the degree
of anchorage loss.
The results are controversial.
Some
studies have concluded that the position of the second
molars has no effect on the amount of distal molar
movement, molar tipping, or anchorage loss.33,34,50
Some have
noted that distal molar movement appears to be more
efficient before second molar eruption.32
According to
Bolla et al, there is less molar tipping and less loss of
anchorage when second molars are partially or completely
40
erupted but there is no significant difference in the
amount of distalization.45,47
Summary and Statement of Thesis
The purpose of this investigation is to compare and
contrast the dental effects of two maxillary molar
distalizers:
the Distal Jet and the Frog.
Multiple
studies have investigated the dental effects of the Distal
Jet but studies of the Frog have not been reported.
Comparisons will be made based on the amount and rate of
maxillary molar distal movement and the degree of distal
tipping.
Anchorage loss will be determined from the amount
of anterior movement of incisors and the extent of labial
tipping.
The original Distal Jet design will be compared
to a modification made by Bowman that replaces the tube and
piston arrangement with a rigid wire.
The modification has
been said to significantly diminish anchorage loss.51
The
eruption of second molars will be evaluated to determine if
there is an effect on the amount of molar distalization or
anchorage loss.
41
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Cope JB, Buschang PH, Cope DD, Parker J, Blackwood HO.
Quantitative evaluation of craniofacial changes with
Jasper Jumper therapy. Angle Orthod. 1994;64:113-122.
24.
Covell DA, Trammell DW, Boero RP, West R. A
cephalometric study of class II Division 1
malocclusions treated with the Jasper Jumper
appliance. Angle Orthod. 1999;69:311-320.
25.
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;20:271281.
26.
Weiland FJ, Bantleon HP. Treatment of Class II
malocclusions with the Jasper Jumper appliance--a
preliminary report. Am J Orthod Dentofacial Orthop.
1995;108:341-350.
27.
Gianelly AA, Vaitas AS, Thomas WM. The use of magnets
to move molars distally. Am J Orthod Dentofacial
Orthop. 1989;96:161-167.
28.
Bondemark L, Kurol J. Distalization of maxillary first
and second molars simultaneously with repelling
magnets. Eur J Orthod. 1992;14:264-272.
29.
Gianelly AA, Bednar J, Dietz VS. Japanese NiTi coils
used to move molars distally. Am J Orthod Dentofacial
Orthop. 1991;99:564-566.
30.
Erverdi N, Koyutürk O, Küçükkeles N. Nickel-titanium
coil springs and repelling magnets: a comparison of
two different intra-oral molar distalization
techniques. Br J Orthod. 1997;24:47-53.
31.
Byloff FK, Darendeliler MA. Distal molar movement
using the Pendulum appliance. Part 1: Clinical and
radiological evaluation. Angle Orthod. 1997;67:249260.
44
32.
Hilgers JJ. The Pendulum appliance for Class II noncompliance therapy. J Clin Orthod. 1992;26:706-714.
33.
Ghosh J, Nanda RS. Evaluation of an intraoral
maxillary molar distalization technique. Am J Orthod
Dentofacial Orthop. 1996;110:639-646.
34.
Jones RD, White JM. Rapid Class II molar correction
with an open-coil jig. J Clin Orthod. 1992;26:661-664.
35.
Gulati S, Kharbanda OP, Parkash H. Dental and skeletal
changes after intraoral molar distalization with
sectional jig assembly. Am J Orthod Dentofacial
Orthop. 1998;114:319-327.
36.
Runge ME, Martin JT, Bukai F. Analysis of rapid
maxillary molar distal movement without patient
cooperation. Am J Orthod Dentofacial Orthop.
1999;115:153-157.
37.
Carano A, Testa M. The Distal Jet for upper molar
distalization. J Clin Orthod. 1996;30:374-380.
38.
Bowman SJ. Modifications of the Distal Jet. J Clin
Orthod. 1998;32:549-556.
39.
Carano A, Testa M, Bowman SJ. The Distal Jet
simplified and updated. J Clin Orthod. 2002;36:586590.
40.
Carano A, Testa M, Siciliani G. The Distal Jet for
uprighting lower molars. J Clin Orthod. 1996;30:707710.
41.
Ngantung V, Nanda RS, Bowman SJ. Posttreatment
evaluation of the Distal Jet appliance. Am J Orthod
Dentofacial Orthop. 2001;120:178-185.
42.
Bowman SJ. Class II combination therapy (Distal Jet
and Jasper Jumpers): a case report. J Orthod.
2000;27:213-218.
43.
Kinzinger GSM, Diedrich PR. Biomechanics of a Distal
Jet appliance. Theoretical considerations and in vitro
analysis of force systems. Angle Orthod. 2008;78:676681.
45
44.
Nishii Y, Katada H, Yamaguchi H. Three-dimensional
evaluation of the Distal Jet appliance. World J
Orthod. 2002;3:321-327.
45.
Bolla E, Doldo T, Giorgetti R. Distal movement of
maxillary canines and premolars with sectional
mechanics following Distal Jet application to molars.
Prog Orthod. 2004;5:72-89.
46.
Chiu PP, McNamara JA, Franchi L. A comparison of two
intraoral molar distalization appliances: Distal Jet
versus Pendulum. Am J Orthod Dentofacial Orthop.
2005;128:353-365.
47.
Bolla E, Muratore F, Carano A, Bowman SJ. Evaluation
of maxillary molar distalization with the Distal Jet:
a comparison with other contemporary methods. Angle
Orthod. 2002;72:481-494.
48.
Kinzinger GSM, Eren M, Diedrich PR. Treatment effects
of intraoral appliances with conventional anchorage
designs for non-compliance maxillary molar
distalization: a literature review. Eur J Orthod.
2008;30:558-571.
49.
Walde KC. The simplified molar distalizer. J Clin
Orthod. 2003;37:616-619.
50.
Byloff FK, Darendeliler MA, Clar E, Darendeliler A.
Distal molar movement using the Pendulum appliance.
Part 2: The effects of maxillary molar root uprighting
bends. Angle Orthod. 1997;67:261-270.
51.
Bowman SJ. Class II combination therapy: Molar
distalization and fixed functional. In: Current
Concepts in Clinical Orthodontics, Elsevier, in press.
46
CHAPTER 3:
JOURNAL ARTICLE
Abstract
Purpose:
The objective of this study was to compare the
dental effects of the Distal Jet and the Frog, two types of
molar distalizers.
The position of the upper second molars
was also evaluated to determine if second molar eruption
affected the dental changes caused by the distalization
appliances or the rate of distalization.
Materials and Methods:
The investigation was a
retrospective, clinical study of 79 Distal Jet patients
with a mean initial age of 13.6 years and 29 Frog patients
with a mean age of 11.5 years.
The Frog and Distal Jet
samples were matched according to initial age and gender.
Pretreatment (T1) and postdistalization (T2) lateral
cephalograms were traced and analyzed with the pitchfork
analysis.
The long axes of the upper first molar and upper
incisor were measured relative to the functional occlusal
plane to evaluate angular changes in these teeth.
Variations in design of the Distal Jet appliance were
assessed by comparing the original tube and piston design
to the Bowman modification.
The dental effects and rate of
the distalization appliances were compared when second
47
molars were erupted or unerupted.
Independent t-tests were
used to assess differences between groups.
Results:
The original tube and piston design of the Distal
Jet exhibited a significantly significant greater amount of
horizontal molar movement over a shorter period of time.
Patients treated with the Frog and both appliance designs
of the Distal Jet exhibited a general trend for mesial
movement of the maxilla, mandible, and dentition.
The
Distal Jet produced significantly more molar distalization
than the Frog in a shorter period of time.
Greater mesial
movement of the lower incisors and lower molars was seen in
the Distal Jet group when compared to the patients treated
with the Frog.
More incisor anchorage loss was observed
when distalizer therapy was initiated after second molars
erupted.
Conclusions:
The original design of the Distal Jet
appliance produces greater distal maxillary molar movement
in a shorter period of time when compared to the Bowman
modification.
The Distal Jet and the Frog are effective at
correcting Class II malocclusions although the Distal Jet
is a more efficient means of molar distalization.
Molar
distalization after second molar eruption causes more
incisor anchorage loss than that produced when second
molars are unerupted.
48
Introduction
Persons with Class II malocclusions represent a
significant proportion of the population.
According to
NHANES III, which classified individuals as Class II when 5
mm or more overjet was displayed, Class II malocclusion
occurs in 23% of children, 16% of adolescents, and 13% of
adults.1
Multiple techniques for correction of Class II
malocclusions are employed in orthodontic practices.
These
include fixed and removable appliances, extraction of
teeth, and orthognathic surgery.2
Difficulty acquiring patient compliance has resulted
in decreased success and more challenging orthodontic
treatment when some of the methods for Class II correction,
such as headgears, removable appliances, and intermaxillary
elastics are utilized.3
A lack of patient compliance can
result in increased treatment time.4,5
Minimal compliance techniques, such as maxillary molar
distalization appliances, have been utilized to reduce the
problems associated with methods that require cooperation.
Examples of these appliances include the Pendulum, Jones
Jig, Distal Jet, magnets, and NiTi coil springs.
These
appliances are effective at translating Class II maxillary
molars into Class I occlusion but can result in undesirable
49
side effects such as maxillary molar tipping and incisor
proclination.
The Distal Jet was developed by Carano and Testa in
1996.
The appliance derives its force from a bilateral
tube and piston assembly that is embedded in a Nance
acrylic button that serves to resist the forces produced
during distalization.
Several modifications have been made
to the original design in an attempt to improve the
efficiency of the appliance.
Several studies have examined
the effects of the Distal Jet7,8,9,10 and compared them to
other molar distalizing appliances.11,12,13
The Frog was developed by Walde.
It was introduced in
2003.14 The Frog derives its distalization force from an
expansion screw that is embedded in a Nance palatal button.
Stainless steel wires are bonded to the upper first and
second premolars.
There are no published reports on the
effects of the Frog on the maxillary dentition.
The purpose of this study is to examine the effects of
the Distal Jet and Frog on the dentition and compare the
appliances with regard to the amount and rate of maxillary
molar distalization and the degree of unwanted side
effects.
Further, the position of upper second molars will
be evaluated to determine if their presence affects the
magnitude or quality of molar distalization.
50
Materials and Methods
Sample
Class II patients treated with non-implant supported
molar distalization appliances were evaluated in this
study.
Two groups of subjects treated with either the
Distal Jet (AOA) or the Frog (Forestadent) appliance (78
Distal Jet and 29 Frog) were selected from the offices of
two practicing orthodontists.
Dr. Jay Bowman (Kalamazoo,
MI) supplied the Distal Jet sample while the Frog sample
was obtained from the office of Dr. Kevin Walde
(Washington, MO).
The Distal Jet sample was further
classified according to appliance design and whether the
upper anterior teeth had brackets placed prior to
distalization therapy.
Of the 78 Distal Jet patients, 16
had the original tube and piston design of the Distal Jet.
These patients had bands on the first premolars and the
upper incisors were bonded prior to distalization. The
balance of the sample had the Bowman modification of the
Distal Jet in which the tube and piston is replaced with a
rigid wire and two locking collars.
Of those 63 patients
with the Bowman modified Distal Jet, 24 had incisor
brackets placed before distalization.
The balance of the
sample (39) was not bracketed prior to Distal Jet
activation.
Further, in 19 of these 39 patients, occlusal
51
rests on the first premolars were utilized instead of
premolar bands.
The entire sample of Frog patients had
brackets bonded to the upper incisors prior to
distalization and anchor wires were used in the distal
embrasures of the upper first and second premolars.
All of
the patients (Distal Jet and Frog) had the lower arch fully
bonded during distalizer therapy.
Lateral cephalograms
taken before treatment was initiated (T1) and immediately
following the molar distalization phase (T2) were acquired.
Additionally, patient records were examined for information
regarding each patient’s age, gender, length of distalizer
therapy, and total treatment time.
The inclusion criteria
utilized for patient selection were:
Pre-treatment Class II malocclusion
No permanent teeth extracted (excluding third
molars)
Diagnostic quality lateral cephalograms before
treatment and immediately following molar
distalization
No other means of molar distalization utilized
between T1 and T2
Bilateral distalization
Variation in treatment mechanics was minimized by
using samples from only two practitioners.
The upper first
molars were corrected to a Class I or super Class I
52
relationship in all of the patients.
Other Class II
appliances such as Jasper Jumpers, Forsus, or Class II
elastics were utilized in some of the patients following T2
in order to maintain the position of the distalized molars
during subsequent retraction of the upper teeth.
Data Collection
The pretreatment and postdistalization cephalometric
radiographs were either traced electronically using Dolphin
imaging software (Frog sample) or hand-traced on acetate
(Distal Jet) by the same investigator.
The electronic
radiographs were then printed and hand-traced on acetate.
Pre-treatment (T1) and post-distalization (T2) tracings
were superimposed using the Pitchfork analysis as described
by Johnston.14
The pitchfork analysis allows the maxillary and
mandibular translatory growth changes relative to the
cranial base and the dental changes relative to the basal
bone to be measured (See Fig. 3.1 and Appendix, Table A.1).
The sum of the maxillary and mandibular skeletal changes,
ABCH, represents the net effect of skeletal growth.
When
the value for the ABCH is summed with the change in upper
and lower first molar movements, the overall change in
molar relationship can be determined.
The analysis also
allows the change in upper and lower incisors to be
53
measured and when this value is added to the ABCH, the
change in overjet can be determined.
Each measurement is
given a sign relative to its impact on the Class II
malocclusion:
positive if it tends to improve the Class II
relationship or reduce overjet, negative if it worsens the
Class II relationship or increases overjet.
All
measurements are made along the mean functional occlusal
plane, an average of the T1 and T2 functional occlusal
planes, defined by the premolars and first molars.
Measurements were carried out with digital calipers
(Mitutoyo), as suggested by Johnston, to the nearest tenth
of a millimeter.14
Figure 3.1: Diagram of the variables included in the
pitchfork analysis. Skeletal and dental changes are
measured relative to the basal bone.14
54
Because maxillary molar distalizers are likely to
produce angular changes of the upper first molars and upper
incisors, the angulations of these teeth were measured by
hand relative to the occlusal plane.
The upper second
molars were classified as unerupted if they were at the
level of the CEJ of the upper first molar or higher and
erupted if they were below the level of the upper first
molar CEJ.
The sample of patients treated with the Frog was
matched with Distal Jet patients on the basis of age.
The
angular changes of upper first molars and incisors and
results of the Pitchfork analysis were compared.
The
Distal Jet sample was compared according to the version of
the appliance used (original tube and piston version or the
Bowman modification).
Dental changes produced by
distalization therapy along with the time required for
distalization and the rate of distalization were compared
when second molars were erupted or unerupted.
Statistical Methods
SPSS 15.0 for Windows (IBM) was used for statistical
analysis of the data.
Levene’s test was used to assess the
equality of variances before performing the independent
two-sample t test to evaluate differences between the
55
groups.
Differences between groups were considered
statistically significant when p < .05.
Intra-examiner reliability was tested by random
selection of 10% of the original sample which was retraced
and superimposed.
All of the measurements were carried out
again and evaluated with the Cronbach’s Alpha test.
The
intraclass correlation coefficient was 0.938.
Results
Cephalometric comparison of the original design (Group
1)and the Bowman modification (Group 2) of the Distal Jet
(See Appendix Table A.2 and Table A.3) revealed minimal
differences.
The pitchfork analysis demonstrated that the
maxilla moved mesially relative to the cranial base (0.26
mm in Group 1 and .019 mm in Group 2).
The mandible also
exhibited mesial movement of 0.74 mm in Group 1 and 0.57 mm
in Group 2, on average.
The apical base change was 0.44 mm
in Group 1 and .37 mm in Group 2.
In both groups the upper
molar was distalized and tipped distally, the upper incisor
was moved mesially and tipped labially, and the lower first
molar and lower incisor moved mesially.
Group 1 exhibited
2.7 mm of distal molar movement and 4.7º of distal tipping.
The upper incisor moved forward 3.2 mm and was flared
11.2º.
The total change in molar position was 4.3 mm with
the lower molar moving forward 1.1 mm.
56
The lower incisor
moved forward 1.9 mm and the change in overjet was 0.7 mm.
In Group 2, there was 3.9 mm of distal molar movement with
4.6º of distal tipping.
The upper incisor moved forward
3.9 mm and tipped 8.6º.
The lower molar and lower incisor
were moved mesially, 0.8 mm and 2.1 mm, respectively.
The
total molar change was 5.1 mm while the overjet increased
0.6 mm.
The total treatment time was 27.5 months in Group
1 and 30.0 months in Group 2.
The time required for
distalization was 7.0 months in Group 1 and 7.7 months in
Group 2.
The amount of distal molar movement per month was
.41 mm in Group 1 and 0.53 mm in Group 2.
Statistically
significant differences were found in the amount of molar
distalization (U6) and rate (mm of molar
distalization/month) of distalization.
These differences
were considered to be minimal so these groups were
combined.
The group of patients treated with the Frog appliance
was matched according to age to the Distal Jet group
without regard to the version of Distal Jet appliance used
(Table 3.1).
The pitchfork analysis revealed a trend
toward mesial movement of the maxilla and mandible in the
Distal Jet and the Frog samples (Table 3.2).
The ABCH was
0.6 mm in the Distal Jet group and 0.4 mm in the Frog
group, on average.
The maxilla and mandible moved forward
57
Table 3.1: Sample characteristics of age-matched Distal Jet
and Frog samples
Table 3.2: Comparison of age-matched Distal Jet and Frog
samples
58
Selected variables were compared when patients had
second molars erupted or unerupted in order to determine if
the presence of second molars affected the amount or rate
of molar distalization, degree of molar tipping, or the
amount of anchorage loss at the incisors (Table 3.3).
Distal Jet and Frog patients were classified according to
the amount of eruption noted on the lateral cephalograms.
Molars were considered unerupted if they were at or above
the level of the CEJ and erupted if they were below the
level of the CEJ.
Of the total sample of patients, 58 were
deemed to have erupted second molars while in 50 of the
patients, second molars were unerupted.
The amount of
molar distalization and degree of molar distal tipping were
3.5 mm and 5.3º, respectively on average, if the second
molars were unerupted and 3.3 mm and 3.9º when they were
erupted.
In the group with unerupted second molars, the
upper incisors moved mesially 2.4 mm and tipped labially
8.1º.
The amount of overjet increased by 0.3 mm.
The time
required for distalization was 7.3 months, on average, in
this group and the rate of distalization was 0.5 mm/month.
The patients with second molars erupted exhibited 3.2 mm of
mesial incisor movement and 8.9º of incisor flaring.
amount of overjet was increased by 1.0 mm.
The
It took 7.7
months, on average, to distalize the molars and there was
59
0.4 mm/month of distal molar movement.
The only
statistically significant difference between the groups was
found in the amount of mesial movement of the upper
incisors.
Table 3.3: Comparison of patients on the basis of second
molar position
Discussion
In previous published studies the Distal Jet appliance
has been compared to many various techniques used to
distalize molars including the Pendulum, Jones Jig,
magnets, and NiTi coil springs.
The Distal Jet has proven
to be an effective, reliable method of Class II correction.
The present retrospective study compares the dental and
skeletal effects in 78 patients treated with the Distal Jet
appliance and 29 patients treated with the Frog.
60
To date,
there are no published studies that examine the effects of
the Frog.
Distal Jet and Frog patients that were matched
according to age and gender were compared (Table 3.2).
In
both groups, skeletal changes were observed with a trend
for mesial movement of the maxilla and mandible relative to
the cranial base which is the normal growth pattern.
The
skeletal changes seen between the groups were not
statistically significant as would be expected.
The trend for dental changes produced by the molar
distalizers in this investigation agrees with the results
of previous studies.
The maxillary molars were moved
distally and tipped distally due to the line of force
acting below the center of rotation.
Anchorage loss was
observed in the form of upper incisor mesial movement and
flaring.
Both appliances were effective at moving the maxillary
molars into a Class I relationship.
The Distal Jet group
exhibited 3.6 mm of distal maxillary molar movement and
4.7º of molar distal tipping, on average.
The Frog
appliance translated the maxillary molar a mean of 2.6 mm
with 4.4º of tipping.
The amount of maxillary molar
movement and the change in molar relationship was
statistically significant.
Since the pretreatment
61
characteristics of the patients were not examined, this
difference could be explained by a greater Class II molar
discrepancy in the Distal Jet group at the start of
treatment.
When employing molar distalizers, clinicians
will typically activate the appliance until the upper molar
is in a Class I or super Class I relationship at which time
the appliance is converted into a holding arch to help
maintain the distalized molar position.
If the Class II
relationship in the Distal Jet group was more severe at the
beginning of treatment, greater amounts of molar
distalization would be required to correct the
relationship.
The lower molar and lower incisor moved mesially in
both samples.
This trend can be explained because the
lower arch was bonded in all of the patients and
orthodontic appliances cause a general mesial migration of
teeth.
The amount of lower molar and lower incisor
movement between the groups was considered statistically
significant.
In the Distal Jet group, the lower molars
were moved forward 1.2 mm and the lower incisors moved
forward 2.7 mm while in the Frog group they translated 0.7
mm and 1.0 mm, respectively.
This difference could be
explained by a difference in treatment technique,
dissimilar appliances used in the two practices, or the
62
amount of pretreatment crowding.
The increased mesial
movement of the lower incisor in the Distal Jet group would
explain the favorable change in overjet because the
postdistalization position of the lower incisor would
assist with the Class II correction to a greater degree.
The change in overjet was found to be statistically
significant.
Anchorage loss was examined at the level of the upper
incisor.
The Distal Jet group exhibited 2.9 mm of upper
incisor movement and 8.6º of flaring.
There was 2.2 mm of
incisor translation and 6.7º of tipping displayed in the
Frog patients.
These differences were not considered
statistically significant.
Anchorage loss in the form of
mesial movement of the upper premolars was not considered
in the present study.
The total treatment time and the rate of distalization
were statistically significant when the two groups were
compared.
Patients were in treatment for 27.4 months in
the Distal Jet group and 33.8 months in the Frog group.
The differences in treatment time could be explained
because of varied treatment philosophies and mechanics of
the two practitioners.
The rate of distalizer therapy was
0.5 mm/month in the Distal Jet group and 0.4 mm/month in
63
the Frog group.
This difference was found to be
statistically significant.
When comparing the effects of the Distal Jet appliance
found in the present study with published studies on the
Distal Jet, previous studies have demonstrated 2.1-3.4 mm
of molar distalization (Table 3.4).6,8,10,15,16
The present
study found a similar but slightly greater amount of molar
distalization (3.6 mm).
In previous studies, the degree of
distal molar tipping ranges from 1.8-5º.6,8,10,15,16
In this
investigation, 4.7º of distal molar tipping was found.
This value is on the high side of the range seen in other
studies which would be expected given the greater amount of
molar distalization.
The amount of upper incisor movement
and degree of tipping reported in other studies varies
considerably.
Some studies found a very small,
insignificant amount of incisor movement11,16 while others
reported incisor anchorage loss values greater than what
was found in the current investigation.6,10,15
The results of
the various studies are not directly comparable as the
upper incisors were variably bonded or unbonded during
distalization therapy.
Edgewise appliances can affect the
amount of incisor movement making the anchorage loss not
completely attributable to the distalization appliance.
The present study used patients that had orthodontic
64
65
Table 3.4:
literature
Comparison of Distal Jet appliance effects reported in the
brackets placed before distalization which would be
expected to affect the amount of incisor movement. Time
required for distalization, ranged from 5-10 months in
previous studies.6,8,10,15,16
In the present study, the Distal
Jet therapy took 7.3 months on average, a value that is
comparable to published reports.
The rate of distal
movement in this study was 0.5 mm/month, a value that is
greater than that found in Chiu, et al.10 but less than that
found in Bolla, et al.11
The position of maxillary second molars and their
effect on molar distalization and anchorage loss was
evaluated in this study (Table 3.3). Other studies have
presented conflicting results regarding the effect of
second molars during distalizer therapy.
Some studies have
indicated that there is no effect on molar distalization or
anchorage loss when second molars are erupted or
unerupted.17,18,19
Other studies report that distalization is
more effective before the second molars are erupted.20
Bolla, et al., indicate that when second molars are
partially or completely erupted there is less molar tipping
and loss of anchorage during molar distalization but there
is no significant difference in the amount of molar
distalization.9,11
In the present study, the amount and
66
degree of molar tipping, the amount of incisor movement,
the total treatment time, and the rate of distalization
were compared when second molars were above the level of
the CEJ (unerupted) and below the level of the CEJ
(partially or completely erupted).
The only statistically
significant difference was found in the amount of
horizontal movement of the upper incisor (i.e., anchorage
loss).
In the group with unerupted second molars, the
incisors exhibited 2.4 mm of incisor translation while in
the group with partially or completely erupted second
molars, the incisors moved 3.2 mm.
A possible explanation
for the greater amount of anchorage loss exhibited when
second molars are erupted is because two teeth instead of
one are being distalized, the reciprocal force on the
incisors is greater resulting in greater mesial movement.
Conclusions
The results of the present study indicate:
1. The Bowman modified Distal Jet produces
significantly more maxillary molar distalization
when compared to the original design.
2. The Distal Jet produces greater distal maxillary
molar movement in a shorter period of time.
67
3. Undesirable side effects (distal molar tipping and
anchorage loss) are observable with both distalizer
therapies.
4. More anchorage loss is observed in patients with
erupted second molars.
5. The Distal Jet appliance and the Frog are effective
therapies in the correction of Class II
malocclusions although the Distal Jet may be
slightly more efficient.
68
References
1.
Proffit WR, Fields, HW, 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.
Proffit WR, Fields HW, Sarver DM. Contemporary
Orthodontics. 4th ed. St. Louis, MO: Mosby Elsevier,
2007.
3.
McSherry PF, Bradley H. Class II correction-reducing
patient compliance: a review of the available
techniques. J Orthod. 2000;27:219-225.
4.
Nanda RS, Kierl MJ. Prediction of cooperation in
orthodontic treatment. Am J Orthod Dentofacial Orthop.
1992;102:16-21.
5.
Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors
influencing treatment time in orthodontic patients. Am
J Orthod Dentofacial Orthop. 2006;129:230-238.
6.
Ngantung V, Nanda RS, Bowman SJ. Posttreatment
evaluation of the Distal Jet appliance. Am J Orthod
Dentofacial Orthop. 2001;120:178-185.
7.
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Appendix
Table A.1: Description of cephalomeric variables used in
the pitchfork analysis. Values are given signs relative to
their impact on Class II correction: positive if they
would assist in the correction (i.e., forward displacement
of the mandible or mandibular dentition) and negative if
they would hinder correction (i.e., forward displacement of
the maxilla or maxillary dentition). Measurements are made
parallel to the mean functional occlusal plane (MFOP)
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Table A.2: Sample characteristics of Distal Jet group
according to appliance design
Table A.3: Comparison of original tube and piston Distal
Jet and Bowman modified Distal Jet
* signifies significance at p > 0.05
**signifies significance at p < 0.01
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VITA AUCTORIS
Larrissa Cali was born on October 20, 1978 in
Cleveland, Ohio.
She attended The Ohio State University in
Columbus, Ohio for her undergraduate studies and received a
Bachelor of Science in Agriculture.
She relocated to
Cleveland and was married to Lucas Cali in May 2004.
She
attended Case Western Reserve University where she earned
her DMD degree in 2008.
Following graduation from dental
school, she began the orthodontic residency program at
Saint Louis University in pursuit of a Masters Degree in
Dentistry.
Upon graduation, she will move to Texas to
begin her orthodontic career.
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