Download EVALUATION OF FINAL EFFECTS OF CONVENTIONAL VERSUS

EVALUATION OF FINAL EFFECTS OF CONVENTIONAL VERSUS
IMPLANT SUPPORTED DISTAL JET FOLLOWED BY COMPREHENSIVE
ORTHODONTIC TREATMENT!
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Krystal M. Baumgartner, D.D.S.!
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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
2012
Abstract
Purpose:
The objective of this study is to evaluate and
compare the final treatment dental and skeletal effects of
the conventional Distal Jet and the miniscrew implant (MI)
supported Horseshoe Distal Jet appliance.
Materials and Methods:
Lateral cephalometric radiographs
were obtained on 54 subjects to perform this retrospective
study.
The subjects were divided into two groups based on
the type of Distal Jet used.
Group 1 consisted of 27
subjects treated with a tooth-supported Distal Jet and
Group 2 was comprised of 27 subjects treated with a
miniscrew implant (MI) supported Horseshoe Jet.
Following
the Distal Jet appliance, all patients underwent full
comprehensive orthodontic treatment.
Pre- and post-
treatment radiographs were hand-traced and measurements
were analyzed with the pitchfork analysis.
Angular changes
in the upper first molar and upper incisor were evaluated
by measuring the long axes of the teeth relative to the
mean functional occlusal plane.
Information about
treatment time was used to determine if there is a
difference in the amount of time required to treat the
patients.
Independent t-tests were used to compare
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skeletal/dental effects and treatment time between the
groups.
Results:
Both groups showed a forward movement of the
maxilla and mandible.
At the end of comprehensive
orthodontic treatment, the upper molar in both groups had
experienced distal movement. The difference in lower molar
change was significant with the tooth-supported group
having a greater contribution to molar correction with more
mesial movement.
The change in upper incisor movement and
angulations among the two groups was not significant.
Group 2 had a distal movement of the lower incisors that
was a significant difference from the mesial movement seen
in Group 1.
Treatment time in Group 1 was 1.6 months
longer compared to Group 2.
Conclusions:
(1) In comparing Class II treatment with the
tooth-supported versus the miniscrew implant supported
Distal Jet followed by fixed orthodontic appliances, no
advantage of one appliance over the other was demonstrated.
(2) The final effects of Class II molar correction and
overjet in the groups showed no significant difference.
(3)Difference in total treatment time with the two types of
Distal Jet is not significant.
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EVALUATION OF FINAL EFFECTS OF CONVENTIONAL VERSUS
IMPLANT SUPPORTED DISTAL JET FOLLOWED BY COMPREHENSIVE
ORTHODONTIC TREATMENT
!
!
!
!
Krystal M. Baumgartner, 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
2012
!
COMMITTEE IN CHARGE OF CANDIDACY:
Professor Eustaquio A. Araujo
Chairperson and Advisor
Professor Rolf G. Behrents
Associate Clinical Professor Donald R. Oliver
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ACKNOWLEDGEMENTS
I would like to express my gratitude and appreciation to
the following individuals:
Dr. Araujo, for his continual support, patience, and
encouragement not only as my committee advisor but
throughout my residency.
His vast knowledge, clinical
skills, and passion about orthodontics have been invaluable
to my education and experience.
The things I have learned
from him will stay with me throughout my life and career.
I am sincerely grateful for all his kind words and
confidence he gave me.
Dr. Behrents, for allowing me to be a part of the
orthodontic program at Saint Louis University, and for his
assistance on my thesis.
I appreciate the chance to be a
resident at an institution that provides a remarkable
clinical and didactic experience.
His orthodontic
knowledge and dedication to the residents have played a
large role in guiding me throughout my residency.
Dr. Oliver, for his commitment and care in all the
phases of my orthodontic education.
His dedication and
encouragement in the classroom carried to my clinical
experience.
His knowledge and skill allowed me to develop
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as a clinician and will continue to influence me in my
orthodontic career.
Dr. Bowman, for providing the records that were used
in this study.
He was very informative and always
available to answer all of my questions in assisting me
with gathering information.
I appreciate his generosity in
giving me his time and sharing his knowledge with me.
A special thank you to Heidi Israel in assisting me
with the statistical analysis.
Despite her demanding
schedule, she was willing to take time in helping me gain
data and providing explanations to me whenever needed.
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TABLE OF CONTENTS
List of Tables……………………………………………………………………………………………………………………v
List of Figures………………………………………………………………………………………………………………vi
CHAPTER 1: INTRODUCTION……………………………………………………………………………………………1
CHAPTER 2: REVIEW OF THE LITERATURE
The Class II Malocclusion………………………………………………………………………………………4
Prevalence of Class II Malocclusion………………………………………………5
Etiology of Class II Malocclusion……………………………………………………6
Class II Correction…………………………………………………………………………………………7
The Role of Compliance in Treatment…………………………………………………………11
Maxillary Distalizers Requiring Minimal Compliance…………………12
NiTi Coil Springs……………………………………………………………………………………………13
Jones Jig…………………………………………………………………………………………………………………13
Pendulum……………………………………………………………………………………………………………………15
Distal Jet………………………………………………………………………………………………………………16
Miniscrew Implants as Anchorage……………………………………………………………………19
Implant Supported Distalizers…………………………………………………………………………20
Distal Jet……………………………………………………………………………………………………………………………22
Tooth-Supported Distal Jet……………………………………………………………………22
Miniscrew Implant Supported Horseshoe Distal Jet…………25
Measuring Class II Correction…………………………………………………………………………28
Statement of Thesis……………………………………………………………………………………………………30
References……………………………………………………………………………………………………………………………31
CHAPTER 3: JOURNAL ARTICLE
Abstract…………………………………………………………………………………………………………………………………37
Introduction………………………………………………………………………………………………………………………40
Materials and Methods………………………………………………………………………………………………42
Sample…………………………………………………………………………………………………………………………42
Data Collection…………………………………………………………………………………………………44
Statistical Methods………………………………………………………………………………………47
Results……………………………………………………………………………………………………………………………………48
Discussion……………………………………………………………………………………………………………………………52
Skeletal Changes………………………………………………………………………………………………53
Dental Changes……………………………………………………………………………………………………54
Conclusions…………………………………………………………………………………………………………………………57
Appendix…………………………………………………………………………………………………………………………………59
References……………………………………………………………………………………………………………………………60
Vita Auctoris……………………………………………………………………………………………………………………
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LIST OF TABLES
Table 2.1:
Tooth-Supported Distalizers………………………………………14
Table 2.2:
Implant-Supported Distalizers…………………………………22
Table 3.1:
Characteristics of sex and age-matched
samples……………………………………………………………………………………………43
Table 3.2:
Samples defined at pre-treatment…………………………47
Table 3.3:
Comparisons of sex and age-matched
individuals with tooth-supported and MI
supported Distal Jet appliances……………………………51
Table A.1:
Description of pitchfork analysis
cephalometric variables…………………………………………………61
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LIST OF FIGURES
Figure 2.1:
Original Distal Jet……………………………………………………………17
Figure 2.2:
Bowman Modification Distal Jet………………………………23
Figure 2.3:
Miniscrew implant supported Distal Jet…………27
Figure 3.1:
Pitchfork analysis diagram…………………………………………46
Figure 3.2:
Pitchfork summary of treatment changes…………50
vi
CHAPTER 1:
INTRODUCTION
Class II malocclusions are frequent in the general
population and they present a constant challenge to
orthodontists in searching for ideal and efficient
treatment methods.
There are many treatment approaches and
appliances available that are capable of correcting the
Class II molar relation whether it is a result of dental or
skeletal aberrations.
The orthodontist’s decision about
which appliance to use often depends on the skeletal or
dental discrepancy as well as the treatment objectives and
patient compliance.
Many removable and fixed appliances are used for
treating Class II malocclusions.
In choosing the most
efficient appliance for a specific problem one needs to
consider the objectives of treatment, the developmental
stage of the patient, the side effects of the appliance
prescribed, as well as patient compliance.
The need for compliance from the patient is a
significant component of many Class II treatment
approaches.
Poor cooperation leads to longer treatment
times and less than ideal outcomes.
For this reason,
clinicians have tried to develop methods that do not rely
on patient compliance.
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When the Class II malocclusion is a result of the
maxillary first molars being positioned too far mesially in
the dental arch, a mode of correction can be either to hold
the molars in an effort to restrict their forward movement,
to restrict forward growth of the maxilla, or to move the
molars distally.
This has been done traditionally with
headgears and/or elastics as well as functional appliances.
In an effort to avoid the needed cooperation required for
successful headgear use a number of “distalizing”
appliances have been developed (e.g.’s NiTi coil springs,
Jones Jig, Pendulum, and the Distal Jet).
A drawback of Class II distalizers, however, has been
unwanted side-effects. Specifically the anterior anchorage
loss and tipping of the incisors that result from
distalizing the maxillary molars; necessitating time to
correct after the distalization is complete.
It also
usually requires compliance in terms of wearing elastics.
Miniscrew implants (MI) placed in the maxilla have been
used in order to eliminate or lessen these such sideeffects.
Instead of the reactive forces acting on the
anterior maxillary dentition, the forces are distributed to
the miniscrew implants and, in turn, to the supporting
bone.
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The Class II malocclusion is a common and important
problem in orthodontics.
Various approaches have been used
over more than 100 years to attempt correction.
In the
last 40 years, distalizing appliances have been introduced
to cause distal movement of the maxillary molars.
More
recently, miniscrew implants have been added as anchorage
for more efficiency and effectiveness.
In regards to
distalizing appliances, skeletal anchorage is expected to
decrease the amount of anchorage loss during maxillary
molar distalization and subsequent retraction of the
anterior teeth.
This study will compare the final effects of a toothsupported Distal Jet and a miniscrew supported Distal Jet
followed by fixed orthodontic appliances in correcting a
Class II malocclusion.
The skeletal and dental changes
will be evaluated, and it will further investigate the
difference in treatment time.
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CHAPTER 2:
REVIEW OF THE LITERATURE
Class II Malocclusion
Important goals that orthodontists aim to accomplish
in their treatment include aesthetics, balance, function,
and stability.
A normal dental occlusion has been
described for the human dentition and such serves as a goal
of orthodontic treatment.
In the 1890s, Angle’s
classification of malocclusion not only subdivided the
major types of malocclusion but also included the first
clear and simple definition of normal occlusion in the
natural dentition.
Angle stated that the upper first
molars were the key to occlusion.
A Class I molar
relationship was defined as having the upper and lower
first molars related so that the mesiobuccal cusp of the
upper molar occludes in the buccal groove of the lower
molar.1
Furthermore, a Class II relationship was described
as the lower molar distally positioned relative to the
upper molar to the extent of more than one-half the width
of one cusp.
Angle’s classification addresses the dental
component of the Class II malocclusion, however, the
malocclusion may also have a craniofacial component.
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Prevalence of Class II Malocclusion
The third National Health and Nutrition Examination
Survey (NHANES III) collected data on children in the
United States and reported the prevalence of
malocclusion and orthodontic treatment need.
It was
carried out from 1988 to 1994 and studied 14,000
individuals in order to make estimates for approximately
150 million persons based on the sampled racial/ethnic and
age groups.
The NHANES study, for their examination
purposes and ease of application, redefined the Class II
malocclusion as the presence of 5 mm or more overjet.
By
this definition that study found the incidence of
“Class II” as 23% of children, 15% of youths, and 13% of
adults.1,2
With increasing age and mandibular growth, the
amount of overjet usually decreases.
Therefore, the
prevalence of the Class II malocclusion, by this
definition, also decreases.
A study done by Thilander et
al3 on Colombian children and adolescents found that the
prevalence increases with age until the late mixed
dentition where it occurred in 24.9% of the sample, and
then decreases to 18.5% in the permanent dentition.
The prevalence of Class II problems in different
racial groups has been reported in the literature and
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varies in these studies from 12 – 40% of the population
sampled.4
It is evident that there is much variation and
there are certain groups of the population that have a
greater tendency for certain malocclusions.
With regards
to male versus female prevalence, sex generally has little
effect on dental and skeletal positions.5
As is seen, the
Class II problem is present in a large percentage of the
population and is therefore commonly seen by orthodontists.
Etiology of Class II Malocclusions
A Class II molar relationship, upon which Angle
developed his classification, can be the result of many
skeletal and dental combinations.
Most of the studies
conducted to investigate the cause and source of the Class
II malocclusion have compared Class II individuals to
normal Class I individuals or existing cephalometric
standards.
In 1981, McNamara6 performed a cross-sectional
lateral cephalometric evaluation of the distribution of
specific relationships in 277 subjects eight to ten years
of age with a Class II malocclusion.
The four major
components that can contribute to the anteroposterior
differences in a Class II individual that were measured and
analyzed in this study were maxillary skeletal position,
maxillary dentoalveolar position, mandibular dentoalveolar
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position, and mandibular skeletal position.
It is a
variation in one of these, or a combination, that may
result in a Class II malocclusion.6
The findings led to the
conclusion that a Class II malocclusion is not a single
clinical entity, but rather a result of numerous
combinations of skeletal and dental components.
McNamara
stated that the most commonly occurring factor in Class
II’s is the retrusion of the mandible and not the
protrusion of the maxilla.6
For many patients, however, maxillary molar
distalization is the chosen strategy for correction of the
Class II malocclusion.
These situations in which treating
the maxillary arch is indicated for a Class II patient,
distalizing the molars can gain space and correct posterior
tooth malpositions.7
Class II Correction
As described, there are a variety of dental and
skeletal components that contribute to the problem and
therefore to the decision-making process when planning
treatment for a patient having a Class II malocclusion.
Among the factors to consider are the profile, facial,
skeletal and dental relationships in order to achieve the
goals of treatment.
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As mentioned previously, the prevalence of the Class
II malocclusion decreases with increasing age.
When
Proffit1 describes the variability in the pattern of growth
he states that it is a reflection of a “cephalocaudal
gradient of growth.”
This refers to the fact that there is
more growth of the lower limbs than the upper limbs during
postnatal life.
This applies to the mandible which is
farther away from the brain than the maxilla and therefore
grows more and later in development.
Proffit states that
growth can usually only correct 3-4 mm of the Class II
malocclusion.
Unfortunately the advantage of the
differential growth of the mandible does not affect every
individual in the same manner.
The chin in Class II,
division 1 individuals is located relatively more
posteriorly than in normal occlusion with a steeper
mandibular plane angle.8
As a result of this growth pattern
in which the mandible grows in a downward instead of
forward direction, later growth may not aid in the sagittal
discrepancy correction.
Many orthodontists use functional appliances to
attempt to take advantage of growth in an adolescent.
The
intent of the treatment would be to hold the mandible in a
forward position during the growth period while restraining
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the maxilla in order to achieve a better profile and aid in
dental correction.
These appliances have been shown to be
efficient in correcting the molar relationship and the
sagittal maxillomandibular skeletal differences in Class II
subjects.9
Extraoral traction, or headgear, was reintroduced in
the late 1940s and became a popular and effective method of
Class II correction.1
It was used to cause distal movement
of the maxillary molars in order to guide them in a Class I
position.
Headgear was thought by some to only cause
dental movement until studies proved otherwise.
In 1963,
Wieslander and co-workers10 collected cephalometric records
on 30 subjects in the mixed dentition with a
Class II
malocclusion that were treated with Kloehn-type cervical
pull headgear. They were then compared to normal Class I
children of the same age, sex and treatment time period.
The use of cervical pull headgear in the mixed dentition
period was shown to not only affect the maxilla, but also
the surrounding bony structures in direct contact with the
maxilla.
In addition to retracting the maxillary molars,
headgear was shown to have an orthopedic effect.
This
appearance may cause a posterior change in the position of
the pterygomaxillary fissure, a smaller amount of forward
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movement of the anterior nasal spine, and a tipping of the
anterior part of the palatal plane in a downward
direction.10
Many times in orthodontic treatment, extraction of
teeth are done to achieve ideal treatment results.
The
patient’s skeletal relationship, dental malocclusion, and
facial profile help guide the orthodontist into making an
extraction decision.
When extractions are indicated in
order to aid in Class II correction the spaces created by
extracting teeth are used to alleviate crowding and
compensate for the Class II relation.1
Severe disharmonies of mandibular retrusion or
maxillary protrusion have been treated with surgical
procedures with success.
Surgery may have to be performed
in order to accomplish an ideal result if the skeletal
discrepancy is severe enough where dentoalveolar treatment
and/or camouflage will not meet treatment goals.
All of
the mentioned treatment options have been successful in
treating Class II malocclusions and have their own
strengths and shortcomings.
Consequently, careful
treatment planning is a must when deciding which modality
to employ.
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The Role of Compliance in Treatment
When patient compliance is a factor in orthodontic
treatment, predictability of the outcome and treatment time
may become difficult.
Treatment involving headgear, inter-
maxillary elastics, or other removable appliances can only
be effective if the patient meets the requirements of
wearing such appliances and for the appropriate time.
Studies have investigated treatment cooperation.
Common
findings among them have been that younger patients (≤12
years old) are more cooperative, and boys commonly have
longer treatment times.11,12,13,14
Skidmore et al investigated
factors influencing treatment time in orthodontic patients.
They found that patients with at least one entry in their
records of poor elastic wear increased treatment duration
by a mean of 1.4 months.13
Treatment of Class II malocclusion often involves
distalizing maxillary molars which is especially dependent
on patient compliance.
For this reason, the orthodontist
may have to find an alternative treatment when there is a
lack of progress in treatment due to the patient’s noncompliance with wearing an appliance.
The development of
non-compliance approaches attempts to remove some of the
patient-determined variable factors that may affect
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treatment time and the quality of the result.15
Unfortunately, they do not come free of drawbacks that may
include appliance breakage and relatively high costs for
appliance construction.15
Maxillary Distalizers Requiring Minimal Compliance
Careful treatment planning is crucial, and the
position of the anterior teeth in relation to the soft
tissue profile must be assessed.
In patients with a
Class II malocclusion and maxillary dental protrusion,
moving the upper molars posteriorly followed by anterior
retraction is a frequently used option.1
After deciding
that maxillary molar distalization is the treatment of
choice, the next decision is to choose the appliance
to
accomplish this goal.
Because cooperation has been an increasing problem,
intraoral distalizing appliances that do not rely on the
patient have become popular.
Intraoral, dental-borne
distalizers generally consist of an anchorage unit such as
the premolars or deciduous molars, an acrylic Nance button,
and an active unit.16
The Nance button is anchored against
the palatal mucosa of the palate which, in theory, resists
displacement.
However, in clinical use anterior anchorage
is lost and soft tissue irritation often results.1
12
It is
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challenging to move maxillary molars bodily distal, and
additionally challenging to maintain their position when
retracting the anterior teeth.
There is an assortment of
tooth-borne appliances that achieve distalization, however
there is slight variation in the mode of anchorage, molar
movement tactics, and the effects of each appliance (Table
2.1).
NiTi Coil Springs
Intra-arch NiTi coil springs combined with an
anchorage unit have been used as a non-compliance method to
Gianelly et al17 used super-
distalize maxillary molars.
elastic intra-arch NiTi coil springs distal to upper first
premolars that were cemented to a modified Nance appliance
to achieve this movement.
Additional anchorage was
achieved by the use of uprighting springs applied to the
first premolars.
Gianelly reported an average of 1-1.5 mm
of molar distalization in one month with 8-10 mm activation
of the 100 g NiTi springs.17
Jones Jig
The Jones Jig18 is comprised of an active component and an
anchorage unit.
The active arm, or so-called Jig assembly,
is made up of a .030 inch wire that holds a nickel-titanium
coil spring and sliding hook.
13
A Nance holding arch
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Table 2.1: Tooth-Supported Distalizers
Author
Appliance
Molar
Crown
Distal
Movement
(mm)
Molar
Crown
Tipping
Anchorage
Loss (mm)
__
__
__
1.00
__
__
( ̊)
Premolar
Tipping
( ̊)
Gianelly17, 1991
NiTi Coils
Bondemark et al19,
1994
Supercoils
11.5/mo
3.20
Ghosh & Nanda20,
1996
Pendulum
3.37
8.36
2.55
1.29
Huerter21, 1999
Distal Jet
3.1
5.6
2.1
1.3
Patel22, 1999
Distal Jet
1.9
2.2
2.8
-3
Bondemark23, 2000
NiTi Coils
2.50
8.80
1.20
2.10
Brickman et al24,
2000
Jones Jig
2.51
7.53
2.00
4.76
Kinzinger et al25,
2004
Pendulum K
3.14
3.07
__
__
Bussick &
McNamara26, 2000
Pendulum
5.7
10.6
1.8
1.5
Chiu16, 2001
Distal Jet
3.0
5.0
2.5
0.3
Gutierrez27, 2001
Distal Jet
2.6
4.7
__
__
Lee28, 2001
Distal Jet
3.2
2.8
2.0
-2.3
Ngantuang et al29,
2001
Distal Jet
2.1
3.3
2.6
-4.3
Bolla30, 2002
Distal Jet
3.2
3.1
1.3
-2.8
Chiu et al16, 2005
Hilgers
Pendulum
Pendulum K
6.1
10.7
1.4
-1.7
3.85
4.18
1.08
-0.50
Kinzinger et al7,
2005
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attached to either the first or second premolars or the
primary molars with an acrylic palatal button makes up the
anchorage unit.
The appliance is inserted into the
maxillary first molar at both the arch wire slot and
headgear tubes.31
To activate the appliance the open-coil
NiTi springs are compressed and tied back to the premolars
in order to deliver a force of 70-75 g.15
According to
Jones, rotated Class II corrections require 90-120 days to
correct with the Jones Jig while true Class II molar
relationships may take 120-180 days correct.
Pendulum
The Pendulum is a non-compliance appliance that is
used for Class II malocclusion correction.
In 1992,
Hilgers explained this new mechanism as a way to deliver a
light, continuous, distal force to the maxillary first
molars.32
The Pendulum has a large Nance acrylic button
against the palate for anchorage in combination with
.032 inch TMA springs attached to the upper first molars.
When activated, the appliance produces a broad, swinging
arc of force from the midline of the palate to the
maxillary molars.
If the upper arch is narrow and
expansion is indicated, a mid-palatal jackscrew can be
15
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incorporated into the Nance button of the appliance.
The
form of the Pendulum appliance with an expansion screw is
referred to as the “Pend-X.”32
The Pendulum has the advantage of being a noncompliant means of correcting a Class II molar
relationship.
It is easy to fabricate and insert,
requiring only a single activation that can be adjusted via
the activation springs, and is easily accepted by the
patient.20
An inherent drawback, however, is anchorage loss
that occurs with the premolars and anterior teeth as a
result of the treatment.
Distal Jet
The Distal Jet is an appliance used for Class II
correction independent of patient compliance (Fig 2.1.)
It
was introduced in 1996 by Carano and Testa33 as a method for
distalizing maxillary molars without the disadvantages of
tipping or rotation.
The Distal Jet is composed of
bilateral .036 inch tubes attached to a palatal Nance
button.
A NiTi coil spring and a screw clamp are placed
over each of the tubes.
Springs of either 150 g for
children or 250 g for adults are customarily used.
Wires
attached to the Nance go through the tubes and end in a
bayonet bend in order to be inserted into the lingual
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sheaths of the first molar bands.
Wires extending from the
Nance button are soldered to premolar or deciduous molar
bands to act as tooth-borne anchorage. The Distal Jet can
be re-activated once a month by sliding the clamp closer to
the first molar tube.
Once the desired position of the
molars is achieved, the appliance can be converted into a
Nance retention device by covering the spring apparatus
with composite or acrylic and cutting off the wires to the
premolars.33
Fig 2.1: Original Distal Jet (Permission from Dynaflex)
The Distal Jet is advantageous in that it allows near
translatory distal movement of the maxillary molars.
This
is possible because the line of force is applied near the
center of resistance of the molars.
17
The force is applied
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palatal to the center of resistance so a resulting drawback
is mesial-palatal and distal-facial rotation.34
Several modifications and updates have been made to
the Distal Jet since its introduction in order to make it
easier to re-activate and to allow for better patient
comfort and oral hygiene.
Among the updates stated by
Carano in 200235 are a new lock for improved function, a
larger and more durable screw and activation wrench, a
return to a single-screw design, and a longer barrel of the
lock that allows for easier adjustments in order to correct
molar rotations.
These changes enabled the Distal Jet to
be simple and efficient for the orthodontist and patient.35
While the introduction of the numerous non-compliance
distalizers, of which the three above are examples, has
introduced many advantages for maxillary molar
distalization in orthodontic treatment, these methods are
not free of shortcomings.
Runge et al performed an
analysis of rapid maxillary molar distal movement without
patient cooperation using the Distal Jet and stated:
The common finding of the significant mesial
movement of the anchorage unit raises the
question of true value in the “non-compliance”
appliance category. To create excess overjet in
a Class II case that has to be subsequently
recovered introduces an element of insufficiency
into the treatment.31
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Miniscrew Implants as Anchorage
Orthodontic anchorage is the foundation for successful
tooth movement and is defined as the resistance to unwanted
tooth movement.36
Skeletal anchorage by either direct or
indirect anchorage is a way to achieve desired movements
while avoiding unwanted side-effects and not depending on
compliance.
According to Proffit, anchorage involving
implants largely improves the amount of true distal
movement of the maxillary dentition that can be achieved,
and allows for distalization of both the first and second
molars.
He also states that in some patients, up to 6 mm
of distalization has been achieved using implant anchorage.1
The concept of osseointegration was introduced in the
1960s by Branemark, who found that bone was compatible with
and had a high affinity for titanium.37
Retromolar and
palatal osseointegrated implants were able to act as either
direct or indirect anchorage during orthodontic
treatment.37,38,39
These applications made it possible to
apply orthodontic forces to accomplish tooth movement with
less to no adverse effects.
A temporary anchorage device (TAD) is defined by Cope40
as a device that is temporarily fixed to bone for the
purpose of enhancing orthodontic anchorage either by
19
!
supporting the teeth of the reactive unit or by completely
eliminating the need for a reactive unit, and then is
removed after use.
They can be fixed to the bone
mechanically by being cortically stabilized, or they can be
biochemically fixed by osseointegration.
An additional
category of anchorage where there is zero anchorage loss,
infinite anchorage, is made possible due to the
incorporation of dental implants and TADs.40
Implants, specifically miniscrew implants or TADs,
have since been used for a variety of procedures in
orthodontics including space closure, retraction,
intrusion, extrusion, and distalization.
The use of
implants in orthodontics has allowed efficiency in
treatment due to the stable anchorage and also because
there are less if any corrections that need to be made due
to anchorage loss.
There is also enhanced predictability
since patient compliance is often not a factor involved in
accomplishing the treatment with implant-supported
anchorage.
Implant Supported Distalizers
A systematic review of the literature was done by
Fudalej41 in order to access studies on appliances
reinforced with temporary skeletal anchorage devices.
20
The
!
findings suggested that distalizing appliances that used
skeletal anchorage had reduced unwanted side-effects
compared to tooth-borne appliances.
When miniscrew
implants or miniplates were used as anchorage there was an
increased amount of molar distalization while the maxillary
incisors remained stable.41
A rationale for the greater
movement is that there is a greater force applied to the
molars with a bone anchored system because the miniscrews
stay relatively stable in the bone.
The distal force
applied to molars in tooth-borne appliances, in contrast,
is dissipated among the anchor teeth causing mesial
movement.
Even though the miniscrew supported appliances
cause greater initial distalization, comprehensive
treatment to retract anterior teeth and close spaces
usually result in comparable amounts of distalization.
Most of the studies in the review used non-integrated
temporary skeletal anchorage devices (TSAD).
Advantages of
these compared to osseointegrated TSADs include immediate
loading, simpler surgery, lower cost, and less discomfort
for the patient.41
Temporary skeletal anchorage devices
have been incorporated into several distalizing appliances
in order to lessen or eliminate the anchorage loss that
results using the conventional appliance. Table 2.2
summarizes the effects of some of these appliances.
21
!
Table 2.2: Implant-Supported Distalizers
Author
Appliance
Molar
Crown
Distal
Movement
(mm)
3.9
Molar
Crown
Tipping
( ̊)
Incisor/premolar
movement (mm)
"
Gelgor42,
2004
Kircelli43,
2006
Escobar44,
2007
Kinzinger34,
2009
Oberti45,
2009
NiTi Coil
Springs
Pendulum
8.8
Incisors: 0.5 mesial
6.4
10.9
Pendulum
6.0
11.3
2nd pm: 5.4 distal,
1st pm: 3.8 distal
2nd pm: 4.85 distal
Distal Jet
3.92
__
!
!
!
!
!
!
!
Dual-Force
Distalizer
5.9
5.6
2nd pm: 1.87 distal,
1st pm: 0.78 mesial
2nd pm: 4.26 distal
Distal Jet
Tooth-Supported Distal Jet
The Distal Jet has become a popular appliance among
the options for Class II correction due to its numerous
advantages.
It can be used for unilateral or bilateral
correction, is relatively simple to insert, is well
tolerated and esthetic, and does not rely on patient
compliance.
The Bowman Modification of the Distal Jet appliance
replaces the tube/piston assembly with a U-shaped tracking
wire (Fig 2.2.)46
This is supported by bands on the
maxillary first molars and is either banded to, or rests
on, the premolars.
The occlusal rests are bonded in place
22
!
and may act as a bite opening mechanism during
distalization.
There are two sets of collars bilaterally
on the tracking wire.
The mesial collar is moved distally
against the super elastic coil spring to cause activation.
The distal collar is released only 1/8 a turn in order to
allow distal translation of the molars.
When activation is
complete the distal stop collars on the tracking wire are
locked.
This allows for easy conversion to a Nance holding
arch since the coil springs do not have to be removed.46
Fig 2.2: Bowman Modification Distal Jet with tracking wire and collars
(photo courtesy of Dr. S. Jay Bowman)47
Bolla et al30 performed a retrospective study on 20
subjects that were treated with the Distal Jet to correct a
Class II dental malocclusion.
The aim was to analyze the
effects of the Distal Jet alone, without fixed orthodontic
appliances bonded to the teeth.
23
Generally, the Distal Jet
!
studies include subjects that simultaneously have brackets
bonded to the maxillary dentition during distalization.
An
early report by Gutierrez27 stated that there was greater
distal movement of the upper first molar when the Distal
Jet was used alone (3.7 mm vs 2.6 mm).
There were 7.3⁰ of
distal tipping of the molar which was more than the 4.7⁰
that occurred when distalization occurred with appliances
in place.
A more dramatic finding was the amount of upper
incisor proclination that resulted from using the Distal
Jet with brackets in place compared to the Distal Jet alone
(12.3⁰ vs 2.2⁰).27’30
!
The investigation by Bolla on the effects of the
Distal Jet alone obtained results from measuring pre- and
post-distalization lateral cephalometric radiographs and
dental casts.
The measurements were comparable to other
reports in the literature on the Distal Jet and can be
found in Table 2.1.
Ngantung et al29 did an evaluation on the Distal Jet
appliance in order to investigate not only postdistalization effects, but also post-treatment effects.
The thirty-three patients were treated with the Distal Jet
during full-bracketed appliance therapy.
Post-
distalization effects can be found in Table 2.1 among the
24
!
results of the similar distalizing appliances.
The post-
treatment effects showed a 1.82 mm net mesial movement of
the upper first molar.
The Class I molar relationship that
was achieved with distalization was sustained due to the
4.8 mm net mesial change of the lower first molar.
Ngantung stated that it was difficult to differentiate the
effects of treatment from the effects of growth.29
The
maxillary incisor to SN angle increased an average of 5.3⁰
at the completion of treatment.
The mentioned studies come
to a similar conclusion about the tooth-supported Distal
Jet.
The appliance is successful at distalizing upper
first molars to correct a Class II malocclusion, but not
without adverse anchorage loss in the premolars and
incisors.
Miniscrew Implant Supported Horseshoe Distal Jet
Bowman described the miniscrew anchorage supported
Horseshoe Jet (Fig 2.3) as an appliance that relies solely
on palatal miniscrews for anchorage.
This form of the
Distal Jet is supported by skeletal anchorage.
Thus, it
removes dental or palatal vault anchorage and subsequent
anchorage loss.
The forces applied to cause distal
movement of the molars are the same as the original Distal
25
!
Jet, close to the center of resistance in order to cause
less unwanted tipping.47
Miniscrew implants can be incorporated into the
Horseshoe Jet by attaching the screws to hooks on the
anterior part of the tracking wire with steel ligature
wires.
The mechanism of attachment allows any screw size
to be used.
Successfully utilized screws have included
1.5 – 2 mm in diameter and 6 – 8 mm in length.
The
miniscrews are placed under local anesthesia in a palatal
position between the second premolar and first molar.
The
Horseshoe Jet is cemented into place and bonding adhesive
is applied or ligature wires are secured tightly to the
miniscrews.
The distal set screws are unlocked a quarter
turn to allow distal movement along the tracking wire.
Subsequently, the mesial set screws are unlocked and moved
toward the molars in order to activate the super-elastic
coil spring and then locked again.
Evaluation of the
distalization is noted every four weeks and re-activation
is performed at this time until the desired position is
achieved.
When distalization is complete, the distal set
screws are locked into place and the appliance acts as
anchorage control as the anterior teeth are retracted.47
26
!
Fig 2.3: Miniscrew implant supported Distal Jet (photo courtesy of Dr.
S. Jay Bowman)48
The goal of the miniscrew implant (MI) supported
Distal Jet is to diminish or lessen to a large degree the
anchorage loss experienced with conventional tooth-borne
distalizers.
It consists of only the horseshoe wire and
lacks the support arms to the premolars, therefore
utilizing pure skeletal anchorage.
The distal force is
applied to the molars and any reciprocal force is
dissipated to the miniscrews.
Since the premolars are not
attached to the appliance, they tend to follow the molars
due to the stretching and pulling of the transseptal
fibers.
Cautious miniscrew implant placement is necessary
in order to avoid any interference of roots with the
anticipated movements.
27
!
After the desired position of the molars is achieved,
the appliance is conveniently converted to an indirect MI
supported anchorage device by locking the distal-set
screws.
The appropriate retraction mechanics can then be
applied to the maxillary teeth.48
Measuring Class II Correction
It is beneficial to know if the orthodontic treatment
rendered to a patient was successful or not.
In order to
see the effects of treatment, the skeletal and dental
changes must be measured.
These measurements are
especially important when there was an attempt at
anteroposterior correction.
When a Class II malocclusion
is corrected with treatment it is beneficial to know where
the correction came from.
It may be a result of
restricting the maxilla, distalizing the maxillary molars,
forward movement of the mandibular dentition, forward
growth of the mandible, or a combination of these.
The
type of movement will depend on the orthodontist’s goals of
treatment and the treatment modality.
Cephalometric radiographs capture both skeletal and
dental information.
Johnston49 explains that the method of
measuring change due to treatment and/or growth involves
some form of superimposition that consists of registration
28
!
and orientation.
To measure only bodily displacement
without the component of remodeling, the registration and
orientation must be based on stable reference structures.
Johnston describes a method of cephalometric analysis that
accounts for anteroposterior change measured at the level
of the occlusion.
This ‘pitchfork diagram’ summarizes
correction of malocclusion by measuring the changes in
molar relationship and overjet.
The superimposition of the
cephalometric radiographs reveals a series of physical
displacements produced by growth and tooth movement:
displacement of maxilla relative to cranial base, movement
of maxillary dentition relative to maxillary basal bone,
translation of mandible relative to cranial base, and
movement of mandibular dentition relative to mandibular
basal bone.49
Measuring these changes on pre-treatment and
post-treatment cephalometric radiographs can show the
causes of the correction.
In the ‘pitchfork diagram’ the
displacements are given positive or negative values based
on the contribution to the Class II correction.
A positive
value is given to movements that correct a Class II, such
as forward mandibular growth, mesial mandibular molar
movement, or a reduction in overjet.
A negative value is
applied if the movement increases the Class II molar
relationship or increases the overjet.
29
The change in molar
!
relationship and overjet can then be discovered from the
algebraic sum of the skeletal and dental movements.
Johnston’s ‘pitchfork diagram’ is able to show treatment
changes with respect to both magnitude and source,
providing a summary of the various components of change
that occur at the occlusal plane.49
Statement of Thesis
The aim of this investigation is to compare the
effects of a tooth-supported Distal Jet and miniscrew
implant (MI) supported Distal Jet at the completion of
orthodontic treatment.
Several studies have investigated
the dental effects of a Distal Jet and similar appliances
immediately after distalization.
Numerous studies have
also reported findings on implant supported maxillary molar
distalizers.
Few have compared and contrasted the
difference in final treatment results between a toothsupported distalizer and implant supported distalizer.
The
current study will specifically examine the Distal Jet,
both tooth-supported and MI supported, with successive
fixed orthodontic appliances.
The final treatment results
will then be compared to examine if there are differences
in amount of maxillary molar distal movement or distal
tipping, anterior movement of incisors, and treatment time.
30
!
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17. Gianelly AA, Bednar J, Dietz VS. Japanese NiTi coils
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18. Jones RD, White JM. Rapid Class II molar
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19. Bondemark L, Kurol J, Bernhold M. Repelling magnets
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20. Ghosh J, Nanda RS. Evaluation of an intraoral
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21. Huerter GWJ. A retrospective evaluation of maxillary
molar distalization with the Distal Jet appliance.
Saint Louis University;1999. Masters Degree Thesis.
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22. Patel AN. Analysis of the Distal Jet appliance for
maxillary molar Distalization. University of
Oklahoma;1999. Masters Degree Thesis. Oklahoma City,
OK.
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23. Bondemark L. A comparative analysis of distal
maxillary molar movement produced by a new lingual
intra-arch Ni-Ti coil appliance and a magnetic
appliance. Eur J Orthod. 2000;22:683–95.
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24. Brickman CD, Sinha PK, Nanda RS. Evaluation of the
Jones Jig appliance for distal molar movement. Am J
Orthod Dentofacial Orthop. 2000;118:526–34.
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25. Kinzinger G, Syrée C, Fritz U, Diedrich P. Molar
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in the initial phase. J Orofac Orthop. 2004;65:389–
409.
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26. Bussick TJ, McNamara JA Jr. Dentoalveolar and
skeletal changes associated with the pendulum
appliance. Am J Orthod Dentofacial Orthop. 2000;117:
333–43.
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27. Gutierrez VME. Treatment effects of the Distal
Jet appliance with and without edgewise therapy.
Saint Louis University;2001. Masters Degree Thesis.
St. Louis, MO.
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28. Lee S. Comparison of the Treatment Effects of Two
Molar Distalization Appliances. Saint Louis
University;2001. Masters Degree Thesis. St. Louis,
MO.
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29. Ngantung V, Nanda RS, Bowman SJ. Posttreatment
evaluation of the distal jet appliance. Am J Orthod
Dentofacial Orthop. 2001;120:178–85.
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30. 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;72:481–94.
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31. Runge ME, Martin JT, Bukai F. Analysis of rapid
maxillary molar distal movement without patient
cooperation. Am J Orthod Dentofacial Orthop.
1999;115:153–57.
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32. Hilgers JJ. The pendulum appliance for Class II
non-compliance therapy. J Clin Orthod. 1992;26:706–
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33. Carano A, Testa M. The distal jet for upper molar
distalization. J Clin Orthod. 1996;30:374–380.
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34. Kinzinger GSM, Gülden N, Yildizhan F, Diedrich PR.
Efficiency of a skeletonized distal jet appliance
supported by miniscrew anchorage for noncompliance
maxillary molar distalization. Am J Orthod
Dentofacial Orthop. 2009;136:578–86.
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35. Carano A, Testa M, Bowman SJ. The distal jet
simplified and updated. J Clin Orthod. 2002;36:586–
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36. Justens E, De Bruyn H. Clinical outcome of miniscrews used as orthodontic anchorage. Clin Implant
Dent Relat Res. 2008;10:174–80.
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37. Wahl N. Orthodontics in 3 millennia. Chapter 15:
Skeletal anchorage. Am J Orthod Dentofacial Orthop.
2008;134:707–10.
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38. Roberts E. Rigid endosseous implants for orthodontic
and orthopedic anchorage. Angle Orthod. 1989;59:24756.
39. Wehrbein H, Merz BR, Diedrich P, Glatzmaier J. The
use of palatal implants for orthodontic anchorage.
Design and clinical application of the orthosystem.
Clin Oral Implants Res. 1996;7:410–16.
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40. Cope JB. Temporary anchorage devices in orthodontics:
A paradigm shift. Sem Orthod. 2005;11: 3–9.
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41. Fudalej P, Antoszewska J. Systematic review:
Are orthodontic distalizers reinforced with the
temporary skeletal anchorage devices effective? Am J
Orthod Dentofacial Orthop. 2011;139:722–29.
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42. Gelgör IE, Büyükyilmaz T, Karaman AIY, Dolanmaz D,
Kalayci A. Intraosseous screw-supported upper molar
distalization. Angle Orthod. 2004;74:838–50.
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43. Kircelli BH, Pektaş ZO, Kircelli C. Maxillary molar
distalization with a bone-anchored pendulum
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44. Escobar SA,
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Tellez PA, Moncada CA, Villegas CA,
Oberti G. Distalization of maxillary
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45. Oberti G, Villegas C, Ealo M, Palacio JC, Baccetti,
T. Maxillary molar distalization with the dual-force
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study. Am J Orthod Dentofacial Orthop. 2009;135:282–
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46. Kinzinger GSM, Diedrich PR, Bowman SJ. Upper molar
distalization with a miniscrew-supported Distal Jet.
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47. Bowman SJ. Distal Jets refined: Bowman modification
and Horseshoe Jet. AOAppliances. 2008;1–5.
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48. Bowman SJ. Miniscrew implant molar distalization:
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Orthodontic Implants, Miniscrew Implants and Mini
Plates. (Mosby Ltd.:In Press).
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49. Johnston LE Jr. Balancing the books on orthodontic
treatment: an integrated analysis of change. Br J
Orthod. 1996;23:93–102.
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CHAPTER 3:
JOURNAL ARTICLE
Abstract
Purpose:
The objective of this study is to evaluate and
compare the final treatment skeletal and dental effects of
the conventional tooth-supported Distal Jet and the
miniscrew implant (MI) supported Horseshoe Distal Jet
appliance using lateral cephalometric radiographs of
previously treated patients.
Information about treatment
time will be used to determine if there is a difference in
the amount of time required to treat patients with the
different appliances.
Materials and Methods:
Lateral cephalometric radiographs of
Class II patients treated with the Distal Jet appliance
were obtained from a single practice.
The sample was
divided into two groups of 27 patients based on the type of
Distal Jet used for treatment.
The subjects were placed in
either a tooth-supported Distal Jet group or a miniscrew
implant (MI) supported Horseshoe Distal Jet1 group.
inclusion criteria for subject selection were:
The
(1) pre-
treatment Class II malocclusion, (2) no permanent teeth
extracted (excluding third molars), (3) diagnostic quality
lateral cephalometric radiographs pre- and post-treatment,
37
!
(4) the use of the Distal Jet for molar distalization,
followed by fixed orthodontic appliances, and (5) bilateral
distalization.
Pre-treatment (T1) and post-treatment (T2) lateral
cephalometric radiographs were obtained for each subject.
The pre-treatment and post-treatment tracings were then
superimposed using the Pitchfork analysis and measured with
electronic vernier calipers.2
The angular changes of the
first molars and anterior incisors were measured relative
to the mean functional occlusal plane.
An independent two-
sample t-test was performed to compare the two groups and
differences were considered statistically significant at
p < .05.
Results:
The tooth-supported Distal Jet group and the MI
supported Distal Jet group both showed a mesial trend in
movement of the maxilla and mandible.
At the end of
comprehensive orthodontic treatment, the upper molar in
both groups had a slight distal movement. The difference in
lower molar change was significant with the tooth-supported
Distal Jet group having a greater contribution to molar
correction with more mesial movement.
The difference in
overall molar correction was insignificant.
The change in
upper incisor movement and angulations between the two
38
!
groups was not significant.
The MI supported group had a
distal movement of the lower incisors which was a
significant difference from the mesial movement of the
tooth-supported group.
The overjet change was very similar
between the groups and of no significance.
Treatment time
in the tooth-supported group was 1.6 months longer than the
MI supported group.
Conclusions:
(1) Class II treatment with the tooth-
supported Distal Jet or miniscrew implant supported Distal
Jet followed by fixed orthodontic appliances does not show
any advantage for either maxillary molar distalizing
appliance.
(2) The final effects of Class II molar
correction and overjet in the groups were similar with no
significant difference.
(3)Difference in total treatment
time with the two types of Distal Jet is not significant.
39
!
Introduction
Class II malocclusions are frequent in the general
population.
In 1998, the third National Health and
Nutrition Examination Survey3 reported that a
Class II malocclusion occurred in 23% of children, 15% of
youths, and 13% of adults.4
Class II malocclusions are treated by several
different techniques.
The choice of treatment method is
dependent on many factors, some of which include:
the
patient’s age, the amount of jaw discrepancy, the severity
of the Class II molar relationship, the amount of space
available in the arch, and the compliance of the patient.
In treating Class II malocclusions, molar distalization has
been among the preferred methods of non-extraction
treatment.
There are several means of distalizing
treatments, with both patient compliance non-compliance
methods.
The methods that are independent of patient
compliance are usually more favorable due to greater
predictability.
The Distal Jet is a fixed appliance that is
independent of patient compliance.
The conventional Distal
Jet customarily utilizes bands on the maxillary first
molars and first premolars, with a palatal Nance button.
40
!
Due to the dentoalveolar support of the appliance, the
distalization of the first molars results in opposite tooth
movements anterior to the first molars.
The literature
reports that the effects of the Distal Jet include:
first
molar distalization and distal tipping, mesial movement and
mesial tipping of the first and/or second premolars,
incisor proclination, an increase in lower anterior face
height, and a minor increase in FMA.5
Some of these effects
have to be compensated for after distalization in order to
achieve ideal results.
The miniscrew implant (MI) supported Horseshoe Distal
Jet described by Bowman1 introduces an anchorage strategy
where the reciprocal forces from distalizing the molars are
placed on the MI and supporting bone instead of the
dentition.
Therefore, there should be less anchorage loss
in anterior teeth and incisor proclination.
If few or no
dental compensations are produced after distalization,
overall treatment time is expected to be shorter.
This study will focus on evaluating the final
treatment differences between two groups of Class II
patients treated with either a tooth-supported Distal Jet
or a miniscrew implant supported Horseshoe Distal Jet.
41
!
Materials and Methods
Sample
The data in this retrospective clinical study was
obtained from lateral cephalometric radiographs of Class II
patients treated with Distal Jet appliances.
The sample
was divided into two groups based on the type of Distal Jet
used for treatment (Table 3.1).
The subjects were placed
in either a tooth-supported Distal Jet group (Group 1) or a
miniscrew implant (MI) supported Horseshoe Distal Jet6 group
(Group 2).
The patients were selected from the office of a
single practicing orthodontist and the lateral
cephalometric radiographs were from the same imaging
device.
The inclusion criteria for subject selection were:
(1) pre-treatment Class II malocclusion, (2) no permanent
teeth extracted (excluding third molars), (3) diagnostic
quality lateral cephalometric radiographs pre- and posttreatment, (4) the use of the Distal Jet for molar
distalization, followed by fixed orthodontic appliances,
and (5) bilateral distalization.
42
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Table 3.1:
Characteristics of sex and age-matched samples
!
Males
Females
Mean Initial Age
"
Tooth Supported
10
17
13 y 2 mo
"
MI Supported
10
17
12 y 8 mo
Group 1 was composed of 27 patients (17 females, 10
males) treated with the conventional Distal Jet.
The
distalization was accomplished with the Bowman modification6
of the Distal Jet where the tube and piston is replaced
with a rigid tracking wire and two locking collars.
Group 2 consisted of 27 patients (17 females, 10 males)
treated with the MI supported Horseshoe Distal Jet.
Brackets were bonded to the lower arch in both groups
during distalization to initiate leveling.
Once the desired amount of distalization was achieved
in the Bowman modification, the Distal Jet was converted
into a holding arch by locking the distal set screws along
the tracking wire and sectioning the wires attached to the
premolars.
The original Distal Jet was converted to a
modified Nance holding arch by cutting the wires attached
to the premolars and removing the open coil spring.
supported Horseshoe Jet was simply converted into an
indirect MI supported anchorage system by locking the
43
The MI
!
distal-set screws.
It then provided skeletal anchorage for
subsequent retraction mechanics of the maxillary anterior
teeth.
Class II elastics were utilized when required.
Data Collection
Pre-treatment (T1) and post-treatment (T2) lateral
cephalometric radiographs were obtained for each subject.
Each radiograph was hand-traced on acetate paper with a
0.3 mm pencil by a single investigator.
The pre-treatment
and post-treatment tracings were then superimposed using
the Pitchfork Analysis.
This method described by Johnston2
is a cephalometric analysis that accounts for
anteroposterior change measured at the level of the mean
functional occlusal plane.
The mean functional occlusal
plane is constructed by averaging the T1 and T2 functional
occlusal planes.
This ‘pitchfork diagram’ (Figure 3.1)
summarizes correction of malocclusion by measuring the
changes in molar relationship and overjet.
The
superimposition of the cephalometric radiographs reveals a
series of physical displacements produced by growth and
tooth movement:
displacement of the maxilla relative to
cranial base, movement of maxillary dentition relative to
maxillary basal bone, translation of mandible relative to
cranial base, and movement of mandibular dentition relative
44
!
to mandibular basal bone.2
Measuring these changes on pre-
treatment and post-treatment cephalometric radiographs can
show the components of the correction.
In the ‘pitchfork
diagram’ the displacements are given positive or negative
values based on the contribution to the Class II
correction.
A positive value is given to movements that
correct a Class II, and a negative value is applied if the
movement increases the Class II molar relationship or
increases the overjet.
The change in molar relationship
and overjet can then be discovered from the algebraic sum
of the skeletal and dental movements.
Johnston’s
‘pitchfork diagram’ is able to show treatment changes with
respect to both magnitude and source, providing a summary
of the various components of change that occur at the mean
functional occlusal plane.
The measurements were carried
out with electronic vernier calipers to the nearest tenth
of a millimeter.2
The dental and skeletal anteroposterior changes were
measured and accounted for using the Pitchfork analysis.
The Distal Jet also causes angular changes in the first
molars and anterior teeth during maxillary molar
distalization.
The angulations were measured by hand
relative to the mean functional occlusal plane.
45
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MAX + MAND = ABCH
ABCH + U6 + L6 = 6/6
ABCH + U1 + L1 = 1/1
Fig 3.1: Pitchfork analysis diagram, adapted from Johnston2
Pre-treatment lateral cephalometric radiographs were
evaluated for eruption of maxillary second molars, presence
of mandibular primary second molars, angular measurements
(SNA, SNB, ANB) to determine initial severity of skeletal
Class II, and interincisal angle (Table 3.2).
46
!
Table 3.2:
Samples defined at pre-treatment
Group 1
Group 2
Subjects with MAX 2nd
molars erupted
14
21
Subjects with MN primary
2nd molars present
4
6
Mean SNA (⁰)
80.85
83.15
Mean SNB (⁰)
77.26
78.56
Mean ANB (⁰)
3.63
4.59
Interincisal Angle (⁰)
134.19
131.15
Statistical Methods
Analysis was completed using statistical software SPSS
20.0 for Windows.
Levene’s test was used before the
comparison of means to assess the equality of variances.
An independent two-sample t-test was performed on the two
groups and differences were considered statistically
significant at p < .05.
The Cronbach’s Alpha test was performed to evaluate
intra-examiner reliability.
The lateral cephalometric
radiographs from 10% of the original sample were re-traced
47
!
and superimposed.
The intraclass correlation coefficients
of the measurements ranged from 0.68-0.92.
Results
The final treatment effects of the tooth-supported
Distal Jet and the MI supported Horseshoe Distal Jet can be
found in Table 3.2.
The pitchfork analysis for the tooth-
supported Distal Jet (Group 1) revealed a mean measurement
of -2.48 mm for the maxilla.
This indicates a forward
movement of the maxilla relative to the cranial base.
The
MI supported Horseshoe Jet (Group 2) had a mean measurement
of -3.10 for the maxilla.
Both groups had mesial movement
of the maxilla and the small difference between the two
groups was not significant.
The mean change of the mandible after treatment was a
forward movement for both groups.
Group 1 had a 3.58 mm
change and Group 2 showed a 4.03 mm change.
The difference
in the amount of mesial movement between the groups was
significant, however, the reliability score for this
measurement was low.
The mean apical base change (ABCH), or the
growth/displacement of the mandible relative to the
maxillary basal bone, exhibited a positive contribution to
48
!
the anteroposterior correction in both groups.
The
difference between the tooth-supported group (1.09 mm) and
MI supported group (3.23 mm) was statistically significant.
There was distal movement and distal tipping of the
upper molar in both groups (0.25 mm, 0.52⁰ in Group 1 and
0.45 mm, 2.00⁰ in Group 2.)
These results were similar and
not significant.
There was a significant difference in the amount of
lower molar measurement between the two groups.
The tooth-
supported group had a mesial movement (mean 1.25 mm) and
the MI supported group showed a distal movement (mean
-0.52 mm).
The mean total molar correction was not
significant at 2.59 mm in Group 1 and 3.15 mm in Group 2.
The upper incisor mean change was a 0.42 mm in Group 1
and -0.27 mm Group 2.
These results show a slight distal
movement in the tooth-supported group and a mesial movement
in the MI supported group, but the small difference was not
significant.
There was upper incisor proclination in both
groups (5.15⁰ in Group 1 and 7.93⁰ in Group 2.)
The difference in lower incisor change between groups
was significant.
Group 1 had a mean change of 0.91 mm
while Group 2 had a mean change of -0.31.
49
The lower
!
incisor moved forward in Group 1, whereas it moved distal
in Group 2.
The amount of overjet correction was similar
among the groups and not significant (2.42 mm in Group 1,
2.63 mm in Group 2).
The mean treatment time for the tooth-supported group
was 30.11 months and 28.48 months for the MI supported
group.
The 1.6 month longer treatment in the tooth-
supported groups is insignificant.
Fig 3.2: Pitchfork summary of treatment changes.
(A) Treatment changes in Group 1
(B) Treatment changes in Group 2
50
!
Table 3.3:
Comparison of sex and age-matched individuals with Tooth-
Supported and MI Supported Distal Jet appliances
Tooth-supported
Distal Jet
MI supported
Distal Jet
Mean
SD
Mean
SD
Sig
ABCH (mm)
1.09
1.97
3.23
2.89
.003*
MAX (mm)
-2.48
1.99
-3.10
1.86
.241
MAND (mm)
3.58
3.20
6.33
4.03
.008*
U6 (mm)
0.25
1.53
0.45
2.15
.703
L6 (mm)
1.25
1.68
-0.52
1.70
.000*
U6/L6 (mm)
2.59
1.21
3.15
1.81
.186
U1 (mm)
0.42
2.26
-0.27
3.22
.365
L1 (mm)
0.91
1.81
-0.31
2.47
.043*
U1/L1 (mm)
2.42
2.51
2.63
2.46
.750
Distal Tipping
of U6 (⁰)
0.52
3.69
2.00
4.10
.169
Flaring of
U1 (⁰)
5.15
8.72
7.93
10.96
.307
Treatment Time
(months)
30.11
4.80
28.48
4.29
.194
* Statistically significant: p value ≤0.05
51
!
Discussion
The Distal Jet appliance has been shown to be a
successful and efficient method of distalizing maxillary
molars to correct a Class II malocclusion.
The literature
reports that it is capable of causing almost pure
translatory distal movement of the upper molars.7
The
inherent shortcoming to the conventional appliance is the
anchorage loss that occurs due to the reciprocal forces
from the distalization.
The majority of previous studies done on the Distal
Jet provide post-distalization data.
The data in this
present study are from pre- and post-treatment
cephalometric tracings of a tooth-supported Distal Jet
(Group 1, mean initial age 13y 2mo) and a MI supported
Distal Jet (Group 2, mean initial age 12y 8mo.)
The
amount of distalization produced immediately after the
Distal Jet was not compared.
Instead, the final results of
comprehensive treatment (Table 3.2) utilizing two forms of
the Distal Jet appliance to correct the Class II
relationship were evaluated to determine if there are
differences in skeletal effects, dental effects and
treatment time.
It should be noted that, when necessary,
Class II elastics were utilized in both groups during
52
!
treatment to help correct or maintain position of molars
during anterior tooth retraction.
Gianelly8 suggests that
if overjet increases greater than two millimeters during
distalization with the Distal Jet the addition of headgear
or elastics should be initiated.
Skeletal Changes
In this study the mean maxillary movement relative to
the cranial base (MAX) was -2.48 mm for the tooth-supported
group and -3.10 for the MI supported group.
The negative
value in the pitchfork analysis indicates a forward
movement of the maxilla in both groups.
This is
representative of the normal pattern of growth for the
maxilla.
The amount of maxillary change was similar for
the groups and not significant.
In the pitchfork analysis the mandibular change
relative to the cranial base (MAND) is calculated from the
measurements of MAX and ABCH.
The mandible had a mesial
movement in both groups (Group 1, 3.58 mm; Group 2,
6.33 mm), and the differences were significant.
Again,
this follows the normal forward pattern of
growth/displacement for the mandible.
The ABCH difference
was also significant at 1.09 mm for Group 1 and 3.23 mm for
Group 2.
A positive number denotes that the mandible
53
!
outgrows the maxilla.
The greater apical base change in
Group 2 may be related to the greater mean initial ANB
angle compared to Group 1 pre-treatment (Group 1 ANB: 3.63⁰,
Group 2 ANB: 4.59⁰).
Although the results showed
significance, the intraclass correlation coefficient for
the MAND measurements was low and therefore these
comparisons may be unreliable.
Dental Changes
Distal movement and distal tipping of the upper molars
in both groups (0.25 mm, 0.52⁰ in Group 1 and 0.45 mm, 2.00⁰
in Group 2) were noted.
The angular measurements were
measured relative to the mean functional occlusal plane.
It must be noted that these measurements reflect the amount
of movement after comprehensive treatment instead of postdistalization.
The amount of maxillary molar distalization that took
place in past studies of the Distal Jet ranged from 1.9 –
3.2 mm with 2.2⁰ – 5.6⁰ of distal tipping.5,9-14
The findings
in this study (Group 1: 0.25 mm, 0.52⁰; Group 2: 0.45 mm,
2.00⁰ ) represent the position of the molars after
retraction of the anterior teeth, where the upper molars
tend to move mesially.
54
!
The difference in the amount of upper molar movement
between the two groups was not significant.
A control
group with an average initial age of 9-12 years in a
previous study was analyzed with the pitchfork analysis
over a two-year time period.15
The amount of upper molar
movement in this untreated group was a mean of -1.1 mm,
signifying a mesial movement.
When compared to the results
of this study, the upper molars in the Distal Jet groups
were located in a slightly more distal position.
The lower molar moved mesially (mean 1.25 mm) in
Group 1, but moved distally (mean -0.52 mm) in Group 2.
This difference was significant.
The lower molar movement
in the MI supported group was in accordance with the lower
molar movement of the previously mentioned control group
(mean -0.6 mm).15
Class II elastics may have been needed to
a greater extent in the tooth-supported Distal Jet group to
control the amount of anterior tooth mesial movement, and
therefore, may have contributed to the significantly
greater amount of mesial lower molar movement.
The amount
of initial crowding or spacing and stage of dental
development may also play a role in the movement of the
lower molar.
55
!
The total Class II mean molar correction was 2.59 mm
in Group 1 and 3.15 mm in Group 2.
The MI supported
Horseshoe Jet showed slightly greater amount of molar
change, however not significant.
This could be due to the
slightly greater amount of distal movement of the upper
molar in the MI group and the fact that there is skeletal
anchorage during retraction.
The amount of anchorage loss is commonly measured in
the anterior teeth.
The direct amount of anchorage loss is
difficult to quantify in a post-treatment study since the
anterior teeth have been orthodontically retracted into the
created spaces.
There was a distal movement (mean 0.42 mm)
of the upper incisor in Group 1, and a mesial movement
(mean -0.27 mm) in Group 2.
More retraction occurred in
Group 1 compared to Group 2, but the differences will not
significant.
There was upper incisor proclination in both
groups (5.15⁰ in Group 1 and 7.93⁰ in Group 2) and these
differences were also not significant.
The lower incisor moved mesial in Group 1 (mean
0.91 mm) and distal in Group 2 (mean -0.31 mm).
These
differences were considered significant and may be due to
the amount of initial crowding and overjet, or the amount
of Class II elastic wear.
56
!
Group 1 had 2.42 mm total overjet correction, and
Group 2 had 2.63 mm of correction.
Even though there was
more overjet correction in the MI supported group, the
upper incisors moved mesial more and flared more than the
tooth-supported group, but the differences were
insignificant.
This may be influenced by the initial
amount of flaring and the amount of retraction
accomplished.
The mean treatment time for the tooth-supported group
was 30.11 months and 28.48 months for the MI supported
group.
The treatment time was approximately 1.6 months
shorter for the MI supported group, a difference not
considered significant.
Conclusions
1. Class II treatment with the tooth-supported Distal
Jet or miniscrew implant supported Distal Jet
followed by fixed orthodontic appliances does not
demonstrate any advantage for either maxillary molar
distalizing appliance.
2. The final effects of Class II molar correction and
overjet in the groups were similar with no
significant difference.
57
!
3. Difference in total treatment time with the two
types of Distal Jet is not significant.
58
!
Appendix
Table A.1: Description of pitchfork analysis cephalometric
variables
Abbreviation
Definition
ABCH
Mandibular displacement relative
to maxillary basal bone, measured
at D point (geometric center of
symphysis)
Skeletal Change
Maxilla
MAX
Mandible
MAND
Upper Molar
Lower Molar
Molar Change
Upper Incisor
Lower Incisor
Overjet
Maxillary displacement relative
to cranial base, measured at wing
point
Mandibular displacement relative
to cranial base (ABCH-MAX)
U6
Maxillary first molar
displacement relative to the
basal bone, measured at mesial
contact point
L6
Mandibular first molar
displacement relative to the
basal bone, measured at mesial
contact point
6/6
Molar relation change, measured
by registering on mesial contact
points of U6 and measuring the
separation of mesial contact
points of L6
U1
Maxillary incisor displacement
relative to basal bone, measured
at incisal edge
L1
Mandibular incisor displacement
relative to basal bone, measured
at incisal edge
1/1
Overjet correction, measured by
registering on incisal edges of
U1 and measuring the separation
of incisal edges of L1
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References
1.
Bowman SJ. Miniscrew implant molar distalization:
Evolution of the horseshoe Jet. Papadopoulos MA (Ed).
Skeletal Anchorage in Orthodontic Treatment of Class
II Malocclusion: Contemporary Applications of
Orthodontic Implants, Miniscrew Implants and Mini
Plates. (Mosby Ltd.:In Press).
2.
Johnston LE Jr. Balancing the books on orthodontic
treatment: an integrated analysis of change. Br J
Orthod. 1996;23:93–102.
3.
Proffit, W. R., Fields, H. W., Jr & Moray, L. J.
Prevalence of malocclusion and orthodontic treatment
need in the United States: estimates from the NHANES
III survey. Int J Adult Orthodon Orthognath Surg 13,
97–106 (1998).
4.
Proffit WR, Fields HW, Sarver DM. Contemporary
Orthodontics. 4th ed. St. Louis, MO: Mosby Elsevier,
2007.
5.
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;72:481–94.
6.
Bowman SJ. Distal Jets refined: Bowman modification
and Horseshoe Jet. AOAppliances. 2008;1–5.
7.
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;30:558–71.
8.
Gianelly AA, Bednar J, Dietz VS. Bidimensional
Technique: theory and practice. GAC International,
2000.
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9.
Huerter GWJ. A retrospective evaluation of maxillary
molar distalization with the Distal Jet appliance.
Saint Louis University;1999. Masters Degree Thesis.
St. Louis, MO.
10.
Patel AN. Analysis of the Distal Jet Appliance for
Maxillary Molar Distalization. University of
Oklahoma;1999. Masters Degree Thesis. Oklahoma City,
OK.
11.
Chiu PP, McNamara JA Jr, Franchi LA. Comparison of two
intraoral molar distalization appliances: Distal jet
versus Pendulum. Am J Orthod Dentofacial Orthop.
2005;128:353–65.
12.
Gutierrez VME. Treatment effects of the Distal
Jet appliance with and without edgewise therapy. Saint
Louis University;2001. Masters Degree Thesis. St.
Louis, MO.
13.
Lee S. Comparison of the Treatment Effects of Two
Molar Distalization Appliances. Saint Louis
University;2001. Unpublished Masters Degree Thesis.
St. Louis, MO.
14.
Ngantung V, Nanda RS, Bowman SJ. Posttreatment
evaluation of the distal jet appliance. Am J Orthod
Dentofacial Orthop. 2001;120:178–85.
15.
Rushforth CDJ, Gordon PH, Aird JC. Skeletal and Dental
Changes Following the Use of the Frankel Functional
Regulator. J. Orthod. 1999;26:127–34.
61
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VITA AUCTORIS
Krystal M. Baumgartner was born on February 13, 1984
in Bismarck, North Dakota.
She attended the University of
North Dakota in Grand Forks, North Dakota for her
undergraduate studies with a Biology/Pre-Dental major.
She
attended the University of Colorado School of Dental
Medicine where she earned her D.D.S. degree in 2009.
Following graduation from dental school, she moved to
Nashville, Tennessee where she completed a one year General
Practice Residency at Meharry Medical College.
In 2010,
she moved to St. Louis, Missouri to begin her graduate
orthodontic education at the Center for Advanced Dental
Education at Saint Louis University.
Dr. Baumgartner
expects to receive her Masters Degree in Dentistry
(Research) from Saint Louis University in December 2012.
62