Download CEPHALOMETRIC ASSESSMENT OF CLASS II NON-EXTRACTION RESISTANT DEVICE COMPARED TO

CEPHALOMETRIC ASSESSMENT OF CLASS II
NON-EXTRACTION
PATIENTS TREATED WITH THE FORSUS™ FATIGUE
RESISTANT DEVICE COMPARED TO
INTERMAXILLARY ELASTICS
Graham Jones, D.D.S.
An Abstract Presented to the Faculty of the Graduate School
of Saint Louis University in Partial Fulfillment
of the Requirements for the Degree of
Master of Science in Dentistry
2007
Abstract
Introduction: The Forsus™ Fatigue Resistant Device
(FRD) was tested as a compliance-free alternative to Class
II elastics.
Methods: A sample of 34 (14 females, 20
males) consecutively treated non-extraction FRD patients
ages 9 years, 0 months to 17 years, 0 months were matched
with a sample of 34 (14 females, 20 males) consecutively
treated non-extraction Class II elastics patients ages 9
years, 0 months to 17 years, 0 months based on four pretreatment variables (ANB, L1-GoMe, SN-GoMe, and treatment
duration).
Pre- and post-treatment cephalometric
radiographs were traced and analyzed using the pitchfork
analysis and a vertical cephalometric analysis. T-tests
were used to evaluate differences between groups.
Results:
No statistically significant differences were found in the
treatment changes between the groups.
There was a general
trend for mesial movement of the maxilla, mandible, and
dentition during treatment for both groups.
The mandibular
skeletal advancement and dental movements were greater than
those in the maxilla, which accounted for the Class II
correction.
groups.
Lower incisor proclination was seen in both
Vertically, both the maxillary and mandibular
molars exhibited eruption during treatment in both groups,
1
while lower incisor proclined with the incisal edge moving
closer to the lower border of the mandible.
Conclusions:
The Forsus™ FRD is an acceptable substitute for Class II
elastics for patients who appear to be non-compliant.
Greater forward displacement of the mandible compared to
the maxilla was the predominant factor in successfully
treated Class II patients with both Class II elastics and
the Forsus™ FRD appliance.
2
COMMITTEE IN CHARGE OF CANDIDACY:
Adjunct Professor Peter H. Buschang,
Chairperson and Advisor
Assistant Professor Ki Beom Kim,
Assistant Professor Donald R. Oliver
i
Dedication
I dedicate this project to my beautiful wife Erika,
whose love and support made the completion of this project
possible.
I am grateful for her unwavering devotion and
support throughout my education.
I also dedicate this to my son, Justus, who brings joy
to my life.
I express gratitude to my parents for their years of
love, support, and guidance throughout my life.
ii
Acknowledgements
I would like to acknowledge the following individuals:
Dr. Peter Buschang for chairing my thesis committee.
Thank you for your guidance, insights, and time.
You have
a devotion to learning and knowledge and you have taught me
much about myself and the world of scientific research.
Dr. Donald Oliver for serving on my thesis committee.
It has been a privilege to work with you.
I truly
appreciate your thought-provoking guidance and close
attention to detail, which makes you a great teacher and
orthodontist.
Dr. Ki Beom Kim for serving on my thesis committee.
Thank you for your guidance, insight, and encouragement.
iii
Table of Contents
List of Tables...........................................vi
List of Figures.........................................vii
CHAPTER 1: INTRODUCTION.......... ........................1
CHAPTER 2: REVIEW OF THE LITERATURE
The Class II Patient in Orthodontics.....................5
Class II Inter-arch Correction...........................9
Class II Elastics...................................10
Patient Compliance as a Factor in Treatment.........16
Non-compliance Inter-arch Appliances................18
The Herbst Appliance...........................18
The Mandibular Protraction Appliance...........22
The Mandibular Anterior Repositioning
Appliance......................................23
The Saif Spring................................26
The Jasper Jumper..............................27
The Eureka Spring..............................31
The Forsus™ Fatigue Resistant Device...........32
Comparing Class II Elastics with Fixed
Inter-arch Appliances.....................38
Summary and Statement of Thesis.........................39
References..............................................46
CHAPTER 3:
Abstract................................................51
Introduction............................................52
Materials and Methods...................................56
Sample..............................................56
Data Collection.....................................58
Statistical Methods.................................59
Results.................................................60
Cephalometric Comparison............................60
Pre-treatment..................................60
Post-treatment.................................60
Treatment Changes Measured by Pitchfork.............61
Vertical and Angular Treatment Changes..............62
Discussion..............................................63
Conclusions.............................................70
Acknowledgements........................................70
References..............................................71
iv
Figures.................................................75
Tables..................................................77
Vita Auctoris............................................82
v
List of Tables
Table 2.1:
Summary of the inter-maxillary noncompliance appliances.....................42
Table 2.2:
Summary of maxillary dental effects of
inter-arch appliances.....................43
Table 2.3:
Summary of mandibular dental effects of
inter-arch appliances.....................44
Table 2.4:
Summary of skeletal effects of inter-arch
appliances................................45
Table 3.1:
Sample Description........................77
Table 3.2:
Summary of Cephalometric Landmarks and
Definitions...............................78
Table 3.3:
Pre-treatment comparison of elastics and
Forsus™ groups for matched variables......79
Table 3.4:
Pitchfork analysis comparison of treatment
changes in elastics and Forsus™ groups....80
Table 3.5:
Comparison of pre and post-treatment
variables and treatment changes in
elastics and Forsus™ groups...............81
vi
List of Figures
Figure 2.1:
Diagram of Forsus FRD in place on a fully
banded/bracketed appliance................34
Figure 3.1:
Diagram of pitchfork analysis.............75
Figure 3.2:
Pitchfork summaries of treatment changes..76
vii
Chapter I: Introduction
Over the years in orthodontics, numerous techniques
and appliances aimed at producing predictable resolution of
Class II malocclusions have been introduced.
These
techniques vary in terms of their approach, complexity,
variability, and effectiveness.
Not surprisingly many
attempts have been made to develop newer appliances with
the aim to be more efficient or effective.
In the field of
healthcare, efficiency can be described as the production
of desired results with minimum waste of time, money,
effort, or skill.1
Similarly, efficacy can be defined as
the extent to which a specific intervention produces a
beneficial result under ideal conditions.1
Many techniques used for Class II correction have
significant shortcomings.
Some of the simplest and,
seemingly, most effective techniques rely heavily on
patient compliance.
Patient cooperation in treatment is
highly variable, unpredictable, and appears to be
decreasing among American patients.
Poor cooperation can
lead to poor treatment results and/or increased treatment
time.
Additional treatment time can be costly to both the
orthodontist and the patient.
Therefore, a number of
appliances have been designed in an attempt to eliminate,
1
or at least reduce, the need for patient compliance during
treatment.
Non-compliance appliances also have
shortcomings.
They may be expensive, uncomfortable to the
patient, unhygienic, prone to breakage, and they may have
unwanted side-effects.
As experience and material science progress, advances
might be expected to have occurred in the development of
Class II correction appliances.
However, as new appliances
are introduced, they must be thoroughly studied.
In order
to determine which appliances are most effective and
efficient in Class II correction, the practitioner needs to
know their dental and skeletal effects.
This study was designed to evaluate the effects of the
Forsus™ Fatigue Resistant Device (FRD) when compared to the
effects of Class II elastics.
The Forsus™ FRD is a three-
piece, telescoping system which incorporates a superelastic nickel-titanium coil spring.
The FRD attaches at
the maxillary first molar and on the mandibular archwire,
distal to either the canine or first premolar bracket.
As
the coil is compressed, opposing forces are transmitted to
the sites of attachment.
The properties of the spring,
theoretically, allow it to maintain a continuous force
without the possibility of fatigue.
Fatigue in this case
can be described as a fracture caused by repeated
2
application of stresses in the coil spring.
The result of
the forces produced by this device should serve to correct
Class II malocclusions.
The skeletal and dental effects
that are produced during Class II correction with this
device will be measured and compared to the effects of
Class II elastics.
Class II elastics were chosen as the
cooperation group because it represents a typical
compliance-reliant method of Class II correction.
The purpose of the following review is to describe the
challenge that Class II malocclusions pose to the
orthodontist and justify further study of the Forsus FRD as
an appropriate appliance in non-compliance situations. The
prevalence of Class II malocclusion in America and American
orthodontic practices will first be presented in order to
establish the significance of the Class II problem in
orthodontics.
Next, a review of the effects of Class II
elastics will be offered as a baseline to compare other
interarch appliances to.
The issue of compliance and the
sequelae of failure to comply with orthodontic instructions
will be examined as a justification for non-compliance
alternatives.
A review of the history of non-compliance
appliances will follow, in order to fully compare their
design, benefits, and problems.
Finally, a description of
the Forsus FRD and its potential benefits will be presented
3
in addition to a description of previous findings as relate
to this appliance.
It will be established that the Forsus
FRD is a viable, albeit not well researched, option in noncompliance Class II correction.
4
Chapter II: Review of the Literature
The Class II Patient in Orthodontics
The patient presenting with a Class II malocclusion
poses a significant problem in orthodontics in terms of
both the scope and the nature of the problem.
From 1989 to
1994 the National Health and Nutrition Estimates Survey III
(NHANES III) studied approximately 14,000 individuals and
was statistically designed to provide estimates of
approximately 150 million individuals of various racial and
ethnic groups.
The NHANES III data provides the best set
data regarding malocclusion in children and adults in
America.
According to NHANES III data, Class II
malocclusion (as based on overjet measurements greater than
4 mm) is present in approximately 11% of the US population
and comprises approximately one-fifth of all malocclusions.2
Prevalence of this relationship is 10.1% in whites, 11.8%
of blacks, and 6.5% of Hispanics.
This data also suggests
that the skeletal Class II pattern is the most common
skeletal disharmony among children and adults.
Data collected from 1966 to 1970 for the United Sates
National Health Survey suggest an even greater problem.
5
According to the study, which evaluated buccal segment
relationship rather than overjet, distoclusion was present
bilaterally in 16% of white youths and 6% of black youths
age twelve to seventeen.3
When unilateral distoclusion
subjects were included, the prevalence was 32% for
Caucasians and 18% for African Americans.
Distoclusion was
described as a situation where the lower molars occlude
with the upper molars in a location behind the normal
position3.
This categorization uses Angle’s definition of
Class II malocclusion.4
A study of occlusal relations reported in 1970 found
that 16.5% of Caucasian American children ages ten through
twelve had bilateral Class II malocclusion and 17.1% had
unilateral Class II malocclusion, for a total of 33.6% with
at least one side showing a Class II molar relationship.5
The same study found that 11.4% of African American
children within the same age range had a lower incidence of
Class II relationships, 7.6% bilateral and 3.8% unilateral.
Patients with Class II dental relationships often have
a corresponding skeletal disharmony.
Milacic and Markovic
examined the dental casts and cephalometric radiographs of
585 orthodontic patients and found that 51% of the patients
who had a Class II Angle relationship had a corresponding
Class II skeletal relationship.6
6
A Class II skeletal
relationship was classified as one having an ANB angle of 3
degrees or greater.
Beresford studied the occlusions and skeletal
relationships of 2000 patients aged six to eight-teen.7
According to his data, 73.7 percent of Angle Class II,
division 1 patients had a class II skeletal relationship.
Additionally, 56.7 percent of Angle Class II, division 2
patients possessed a Class II skeletal relationship.
It
should be noted that the skeletal classification was
determined clinically, not radiographically for this
sample.
The development of Class II malocclusion is complex
and multifaceted.
An array of skeletal and dental traits
can contribute in various ways to its development.
McNamara reviewed previous studies and evaluated the
characteristics of 277 children, eight to ten years of age,
with Class II dental relations.8
The review showed that
previous reports had found the maxilla to be retrusive,
normal, or protrusive, depending on the study.
Similarly,
the maxillary dentition had been reported to be normally
positioned or protrusive in Class II subjects.
The
mandible and/or mandibular dentition had been found to be
either normally positioned or retrusive.
7
Finally, there
had been a component of vertical excess reported as an
important characteristic in many Class II subjects.
McNamara’s sample of Class II children revealed that
77 different combinations of morphological characteristics
(maxillary skeletal position, maxillary dental position,
mandibular skeletal position, mandibular dental position,
and vertical dimension) exist which contribute to the
development of the problem.
Most commonly, the Class II
patients had retrusive mandibular skeletal position,
neutral maxillary and mandibular dental positions, and
excess vertical development.
Although the most common,
this combination accounted for only 10% of the sample.
Maxillary skeletal protrusion was rare.
The author
concluded that the Class II problem is multi-factorial and
often includes mandibular skeletal retrusion and excess
vertical development as the most important features.
Buschang and Martin longitudinally evaluated growth in
49 females and 50 males.9
This cephalometric report
provided the only published assessment of growth from
childhood through adolescence.
Vertical and
anteroposterior skeletal relationships were evaluated from
age six to fifteen in Class I and Class II subjects.
While
anteroposterior relationships (horizontal distance from ANS
to Pogonion) generally improved during childhood, they
8
tended to worsen during adolescence.
These changes were
primarily due to differences in horizontal growth of the
mandible.
Vertical skeletal changes, measured as the
vertical difference between Gonion and Pogonion, increased
in the majority of the subjects.
While an association
between vertical and anteroposterior changes was found, the
correlation was not strong.
Class II Inter-arch Correction
Currently, orthodontists have several methods at their
disposal to correct Class II malocclusions.
These include
fixed or removable intra-arch appliances, fixed or
removable inter-arch appliances, selective extraction
pattern, and surgical repositioning of one or both jaws.
Class II elastics are a typical inter-arch method used for
correction, but rely heavily on patient compliance for
their effectiveness.
Compliance in orthodontics is
variable and difficult to predict, therefore, a number of
compliance-free inter-arch appliances have been developed.
The effects of compliance-reliant Class II elastics will
first be reviewed, followed by a review of the problems
with compliance in orthodontics.
Next, a number of non-
compliant orthodontic appliances will be reviewed. The
published reports of their effects will be reviewed, and
9
the advantages and disadvantages of each appliance will be
presented.
The Forsus™ FRD will be described and its
potential benefits compared to the other non-compliance
appliances will be discussed.
Finally, the only published
report where the effects of a non-compliance appliance were
compared to the effects of Class II elastics will be
reviewed in order to justify the need for greater
investigation in this field.
Class II Elastics
The effects that Class II elastics typically produce
have been well described. Ellen et al. found that Class II
patients treated with Class II elastics and standard
edgewise orthodontics without headgear display mesial
movement of 4.1 mm and extrusion of 4.0 mm of the
mandibular molars.10 The mandibular incisors were proclined
7.9 degrees.
The maxillary incisors were extruded 3.7 mm
and retroclined 1.4 degrees. A 0.8 degree clockwise
rotation of the occlusal plane occurred and the lower
facial height increased 6.2 mm.
Pogonion and B-point moved
forward 1.6 mm and 1.1 mm, respectively.
Nelson et al. reported similar findings in a study of
patients treated with Class II elastics and Begg
orthodontics.11
Patients experienced 1.0 mm mesial growth
10
of the maxilla and 2.1 mm of mesial mandibular
displacement.
The incisal edge of the maxillary incisors
moved distally 3.7 mm, while the incisal edge of the
mandibular incisors moved mesially 1.0 mm.
overjet decreased 5.8 mm.
As a result,
Maxillary molars did not
experience significant movement, while mandibular molars
moved mesially 2.0 mm.
The resulting molar correction was
3.0 mm.
A later study by Nelson et al. again examined
patients treated with Begg appliances and Class II
elastics.12
These patients experienced 5.1 mm distal
movement of the maxillary incisors and 1.4 mm of mesial
movement of the lower incisors.
Overjet was reduced 6.7 mm
and lower face height increased 4.2 mm.
The maxilla and
mandible both experienced mesial movement during treatment,
1.3 mm and 1.6 mm, respectively.
A 1.3 degree increase in
the mandibular plane angle was also noted.
Gianelly et al. evaluated Class II patients treated
with Class II elastics and either Begg or edgewise
appliances.13
He showed that both edgewise and Begg groups
showed advancement of pogonion, 2.1mm and 1.6mm,
respectively.
SNA decreased in both groups (1.5 degrees
edgewise, 0.4 degrees Begg), while SNB increased 0.3
degrees in both groups.
Clockwise rotation of the
11
mandibular plane occurred in both groups (0.6 degrees
edgewise, 1.3 degrees Begg). Finally, an increase in
mandibular size was found in both groups (2.7 mm edgewise,
2.9 mm Begg); this was attributed to normal growth.
The
differences between the two groups were not statistically
significant.
Tovstein summarized the effects that Class II
elastics have on the occlusal plane in patients who
exhibited varying amounts of growth.14 While the occlusal
plane angle invariably increased during treatment, the
increases were less in patients who exhibited more growth
and greater in patients who grew less.
Furthermore, the
occlusal plane angle tended to return toward its previous
inclination after treatment in patients who grew more, but
exhibited little post-treatment change in patients who grew
less. Finally, he found that the changes in A- and B-points
were greater in the patients who exhibited the most growth,
suggesting that growth is an important factor in the
skeletal correction of Class II patients.
Hanes examined 38 Class II subjects who had Class II
elastics as the only mechanical strategy for Class II
correction.15
He found that the majority of the skeletal
correction came from posterior movements of A-point, rather
than anterior movements of B-point.
12
His subjects displayed
an average 2.5 mm posterior movement of A-point and a 0.9
mm posterior movement of B-point.
This posterior
displacement of B-point was due to a tendency for the
mandibular plane angle to increase an average of 0.8
degrees as the mandible rotated clockwise.
increased an average of 4.0 mm.
Facial height
Hanes found that the
posterior displacement of B-point was less in the group
treated with maxillary elastics than in a similar group
treated with cervical headgear.15
He concluded that,
typically, Class II elastics did not make the chin more
prominent in profile.
Bein discussed the theoretical forces that interact in
the dentition with the use of Class II elastics.16
His
calculations were based on average tooth sizes, inter-arch
distances, and typical elastic configurations.
When the
theoretical force vectors of four-ounce elastics were
analyzed, there was a 2.6 ounce extrusive force on the
lower molars, in addition to a 3.9 ounce mesial driving
force.
Furthermore, there was a tendency for distal
rotation of the mandibular molar roots and mesial rotation
of the maxillary molar roots, as the forces of the elastics
were transmitted through these teeth.
Zingeser, who evaluated vertical changes associated
with Class II elastic treatment, found a pronounced
13
vertical development of the mandibular dento-alveolus and
slight vertical development of the maxillary dentoalveolus.17
These vertical increases did not have a
significant effect on the mandibular plane due to the
concomitant counterclockwise rotation of the mandible that
normally occurs with growth, which tended to close the
mandibular plane.
Adams et al. experimentally studied the skeletal
effects of intermaxillary elastics placed in seven Macaca
Mulata monkeys.18
Cast splints were made to reduce the
amount of tooth movements, and forces ranging from 75 to
250 grams were applied.
Metallic bone markers and
histological markers were used to track the skeletal
effects.
Among the changes noted was a backward and
downward rotation of the maxilla.
The maxillary dentition,
including the second molars which were not included in the
splint, moved distally.
Areas of compression were found
between the maxillary tuberosity and the pterygoid process.
The mandible moved forward and rotated clockwise.
These
changes served to rotate the occlusal plane clockwise.
Animals in the mixed dentition showed increased bone
apposition in the posterior aspect of the mandibular
condyle.
Minimal or no changes were seen in the condyles
of the adult animals, although one adult experienced
14
pathologic resorption in the articular eminence of the
temporal bone, due to continuous compression of the joint.
Although various combinations of most of these effects
serve to correct Class II malocclusions, some of the
individual effects are considered undesirable in terms of
their result on facial esthetics.
For instance, clockwise
rotation of the occlusal plane can exaggerate the skeletal
appearance of the Class II relationship.11
This is
important because clockwise rotation appears to be a
commonly reported effect of class II elastics.10,11,19
Kanter
composed a list of adverse changes that may occur with the
use of elastics in Class II patients, including mesial
rotations of the mandibular molar crowns, steepening of the
occlusal plane, excessive labial inclination of the
mandibular incisors, and anterior displacement of the
entire mandibular dental arch.20
The unwanted side-effect
of lower incisor proclination is also commonly produced
with the use of Class II elastics.
This movement is
generally regarded as being unstable and, therefore,
undesirable.21
In spite of the undesirable side effects
produced, intermaxillary elastics can serve as a relatively
inexpensive and effective means to treat a Class II
malocclusion.
15
Patient Compliance as a Factor in Treatment
A major determining factor in the success of Class II
elastics during treatment is the willingness of the patient
to wear the elastics.
The effectiveness of elastics is
nearly entirely dependent on patient compliance.
Patient
compliance with a number of prescribed aspects of treatment
has been described as the major limiting factor in
orthodontic treatment.22
Shia examined 500 consecutive cases treated in his
office.23
He found that patient cooperation was the single
factor most likely to lengthen treatment time.
Skidmore et al. isolated nine factors that accounted
for 38% of the variation in treatment duration.24
factors, three were related to patient compliance.
Of these
One of
the factors that significantly contributed to increased
treatment duration was poor elastic wear.
Egolf et al. found that some of the factors that were
related to lack of compliance with headgear and Class II
elastics were personal and short-lived.25 These short-lived
factors included disrupting personal events and social
pressures.
Subjective and unexpected events were difficult
to predict and could extend treatment time if the treatment
plan was predicated on an assessment of the patient being
relatively compliant.
16
Patients may falsely report compliance or incorrectly
perceive that compliance has occurred.
Brandao et al.
instructed patients to wear headgear 14 hours per day.26
The amount of wear was recorded by the patients and,
unknown to the patients, monitored via a time recording
device within the headgear.
Although patients reported
themselves to be relatively compliant (with 13.6 hours of
headgear wear per day), the recordings revealed that
compliance was poor (5.6 hours per day).
Even after the
patients were told they were being monitored, compliance
only rose slightly (6.7 hours per day).
These findings
suggest that compliance was generally poor (less than half
of what was asked) and either misperceived or falsely
reported.
Patient compliance may be difficult to predict because
it is a complex psychosocial construct.
El-Mangoury noted
that patients who are good cooperators in some aspects,
such as oral hygiene may not necessarily be good
cooperators with elastic and headgear wear.27
The problem
is significant enough to warrant the development of several
“non-compliance” appliances.
These appliances, when
compared to standard treatment using Class II elastics, can
be more expensive, but their cost has been justified by the
17
notion that they can reduce treatment time while achieving
similar results.
Non-compliance Inter-arch Appliances
There are numerous examples in the orthodontic
literature of attempts to create an ideal Class II
correction appliance.
removable.
Initially, these appliances were
As the demand for compliance-free appliances
increased, some of the designs were altered so that the
removable appliances could be fixed in place.
The Herbst Appliance
The first and best established fixed Class II
correction appliance is the Herbst appliance.
Originally
designed as a removable appliance in 1909 by Emil Herbst, a
fixed version for sagittal orthodontic correction was
subsequently introduced and reports of its effects were
published in 1934.28
In 1979 Pancherz re-introduced the Herbst appliance in
the orthodontic literature.29 The Herbst appliance is
comprised of a plunger housed within a tube.
The tube is
typically attached to the maxillary first molar on each
side and the plunger is attached to the mandibular
dentition.
Methods of attachment include banded, crowned,
18
and acrylic splinted versions. The splinted Herbst is now
advocated by Pancherz as the preferred device.30
This
design incorporates cast splints that cover the maxillary
and mandibular molars and premolars and can include the
canines and anterior teeth. The anterior teeth can have
brackets placed which, in turn, can be ligated to the
splint.
In this way more teeth are included as anchorage.
This version is believed to be more hygienic, better
fitting, stronger, and less likely to require replacement
of bands over time.
The Herbst is typically used during
the initial six to eight months prior to full edgewise
orthodontic treatment.30
Although attempts have been made
to incorporate the Herbst into a single phase along with
fixed appliances, bracketing of mandibular canines and
premolars is not possible in conjunction with Herbst use.
In 1997, Pancherz reviewed the effects of Herbst
treatment.30
Effects included discernible mandibular
morphological changes and increased sagittal condylar
growth during treatment.
Effects described in the
maxillary complex of 45 Herbst subjects were similar to
those expected with high-pull headgear.
The upper molars
were intruded in 69% of the subjects (with a maximum value
of 3.5 mm of intrusion) and pushed distal in 96% of
subjects (with a maximum of 4.5 mm).
19
The occlusal plane
tipped downward up to a maximum of 7.5 degrees in 82% of
cases.
Overbite correction occurred due to eruption of the
mandibular molars, as well as intrusion and proclination of
the mandibular incisors.
These effects were largely
beneficial and comparable to the effects obtained in a
compliant patient wearing elastics and headgear.
A significant drawback of the Herbst appliance is its
tendency to procline the mandibular incisors.30,31
Whether
the banded, crowned, or splinted version is used, this
effect is difficult to control.
shown to be a problem.
Stability has also been
Post-treatment, it has been shown
that most of the mandibular morphological changes revert,
resulting in no long-term differences in mandibular growth
between patients treated with a Herbst and untreated
patients.30
The headgear effect appears to be fleeting as
well, as the maxillary molars extrude and move mesially.
The relapse of changes due to Herbst treatment all took
place within six months of appliance removal.30
In order to
maintain the benefits of the Herbst appliance, Pancherz
recommends finishing the patient with stable cuspal
interdigitations.30
In order to achieve this, treatment in
the mixed dentition should be avoided; rather treatment
should be reserved for the permanent dentition just after
the peak of pubertal growth.30
20
A report by Valant and Sinclair described the effects
of a splinted Herbst appliance in 32 consecutively treated
patients.31
According to this report, the Herbst exhibited
a slight headgear effect that served to decrease the SNA
angle 0.7 degrees, compared to a very slight increase of
this angle in a control group.
was more pronounced.
The effect on the mandible
A net 3.3 mm total mandibular length
increase in the Herbst group proved to be 1.3 mm greater
than the control group over the same time period.
Facial
height increased more in the Herbst group during treatment
than in the control group.
While maxillary incisors showed
minimal change, the mandibular incisors flared more during
Herbst treatment, even with the lower occlusal splint.
The
IMPA increased 2.4 degrees in the Herbst group and 0.4
degrees in the control group.
The Herbst group also showed
less vertical maxillary molar development (0.1 mm) during
treatment, compared to the control group (1.0 mm).
Maxillary molar movement was 1.5 mm in a distal direction,
with 6.4 degrees of distal crown tipping.
The mandibular
molars moved mesially 1.6 mm with no tipping.
Benefits of the Herbst include its effectiveness of
correcting Class II relationships and its non-compliance
nature.
Breakage, relapse of treatment results, potential
causation of a dual bite, cost of fabrication, and the need
21
for several initial appointments have plagued the Herbst
appliance.
The Mandibular Protraction Appliance (MPA)
The Mandibular Protraction Appliance (MPA) was
developed in 1995 as a less complicated and less expensive
alternative to the Herbst appliance.32
The original design
consisted of a set of in interlocking 0.032 inch stainless
steel wires that were intended to force the patient’s
mandible to be positioned forward.
A coiled spring was
also included in the device to prevent the wires from
interlocking.
If the patient attempts to force the
mandible into a retruded position, resistance in the
appliance is translated as a push force against the
maxillary molars and mandibular canines.32
Since its
inception, the MPA has undergone several transformations.
The most recent design more closely resembles the Herbst
appliance and consists of a 0.40 inch primary tube that
rests within a 0.045 inch tube.
The primary tube is
threaded into a loop on a lower 0.019 x 0.025 inch
stainless steel mandibular archwire.
Theoretically, the
MPA produces a set of forces similar to the Herbst
appliance.
While no studies have been published describing
the actual effects of the MPA, case reports suggest that it
22
can be an effective device in correcting Class II
malocclusions in both adolescents and adults.33
The
advantages of the MPA are its simple, chair-side
fabrication, reduced cost, non-compliance nature, and its
ability to be used in conjunction with nearly full, fixed
orthodontic appliances (the mandibular premolars cannot be
bonded).
The disadvantage of this device stems from its
non-rigid construction. Breakage and distortion of the
device are very likely because the diameter of stainless
steel wire used is neither rigid enough to resist
distortion, nor flexible enough to return to its predeformed state.
The Mandibular Anterior Repositioning Appliance (MARA)
The Mandibular Anterior Repositioning Appliance (MARA)
was introduced in 1998.
It was designed to encourage
patients to maintain their mandible in a forward position
by incorporating areas of occlusal interference.
Heavy
0.060 inch square steel bars run vertically from crowns
cemented on the maxillary molars and contact a second set
of 0.059 inch steel bars positioned horizontally on
mandibular molar crowns.
Additional advancements can be
accomplished with the addition of shim stocks.
As the
mandible is positioned forward there is the theoretic
23
potential for “growth stimulation” at the mandibular
condyle, similar to the effects hoped for when a removable
functional appliance is prescribed.
Additionally, as the
patient attempts to position the mandible posteriorly, push
forces are exerted distally against the maxillary molars
and mesially against the mandibular molars.
These forces
assist with the correction of Class II dental
relationships.
Based on cephalometric radiographs, Pangrazio-Kolbersh
et al. demonstrated the effects of the MARA on 12 boys and
18 girls (compared to a control group of twenty-one
untreated Class II subjects).34
Eruption of the molars was
assessed by measuring vertically from the Frankfort
Horizontal plane to the occlusal plane.
The maxillary
molars showed less eruption in the MARA group than in the
control group, at 0.1 mm per year compared to 0.9 mm of
eruption per year respectively.
Sagittal molar movements
were evaluated by measuring the distance from a vertical
reference line drawn perpendicular to Frankfort Horizontal.
The MARA group displayed an average of 1.1 mm distal
movement of the maxillary molars compared to a 1.3 mm
mesial movement of the maxillary molars in the control
group.
The mandibular molars moved mesially 1.2 mm on
average in the MARA group, while the control group showed
24
only 0.5 mm mesial movement.
The mandibular incisor moved
mesially 0.6 mm and the IMPA increased 3.9 degrees per year
in the MARA group, compared to 0.4 mm of distal movement
and a 0.3 degree IMPA increase in the control group.
The
MARA group showed greater increase in mandibular length, as
measured from condylion to gnathion, than the control
group.
The increases were 4.8 mm and 2.1 mm, respectively.
Anterior and posterior facial heights increased more in the
MARA group than in the control group.
Finally, the
occlusal plane angle increased 0.4 degrees and decreased
0.9 degrees in the MARA and control groups, respectively.
The effects of the MARA appear to be very similar to those
produced by the Herbst appliance, but with less headgear
effect on the maxilla and less mandibular incisor
proclination.
An advantage of the MARA is that full fixed
orthodontic appliances may be placed along with the MARA,
therefore reducing or eliminating the need for 2-phases of
treatment.
Allowing the MARA to remain in place following
Class II correction while fixed orthodontic treatment is
being performed may offer improvements in long term
stability.
Disadvantages of the MARA are related to the
necessity of stainless steel crown fabrication in order to
accommodate the appliance.
The crowns take additional time
25
and expense at a commercial laboratory.
The crowns can
also increase anterior face height slightly.
Because of
the time and additional appointments necessary for
fabrication, the MARA may not be a desirable mid-treatment
alternative for patients who cooperate poorly with Class II
elastic wear.
Like the other appliances reviewed, breakage
and the time and cost associated with repair pose
significant problems for its clinical application.
The Saif Spring
The Saif Spring was introduced in the late 1960s as a
fixed alternative to Class II elastics.
This nickel-
titanium spring system produces the same force vector as
Class II elastics.
It was designed to deliver 200-400
grams (approximately 6 to 13 ounces) of force. The low end
of this range of force is comparable to medium to heavy
elastics, and the high end may exceed the force recommended
for elastic use.
Breakage is a problem with this device.
It must also be replaced at varying intervals by the
orthodontist as the spring fatigues.
No data have been
presented to describe the actual effects of the Saif
Spring.35
26
The Jasper Jumper
The Jasper Jumper was introduced in 1994 as a fixed
Class II corrector that can be used in conjunction with
fixed appliances.
The Jasper Jumper consists of two vinyl
coated springs resting in the buccal sulcus.
This
appliance exerts different forces than Class II elastics;
it produces a distal and intrusive force against the
maxillary molar and a mesial and intrusive force against
the mandibular canine.
Cope et al. characterized the
dental and skeletal effects produced by the Jasper Jumper
in 31 Class II patients compared to a control group of
Class II adolescents.
The Jasper Jumper had a posterior
repositioning effect on the maxilla.36
ANS moved
posteriorly 0.9 mm per year and A-point was moved
posteriorly 0.6 mm per year.
There was no evidence of
increased condylar growth of the mandible with the Jasper
Jumper, although there was more clockwise mandibular
rotation produced than in the untreated control group.
Dentally, the Jasper Jumper moved both the upper incisors
and molars distally, 4.7 and 4.3 mm per year, respectively.
Compared to controls the Jasper Jumper group also showed
extrusion of the maxillary incisors and a tendency to
prevent eruption of the maxillary molars.
The mandibular
incisors displayed uncontrolled tipping, with the tip of
27
the incisor moving mesially 4.4 mm per year, and intruding
at a rate of 1.7 mm per year.
The lower molar moved
forward 3.8 mm by a combination of tipping and bodily
movements.
The lower molars were also extruded.
The net
effects of the Jasper Jumper were distal maxillary skeletal
and dental movements, mesial mandibular dental movements
due mostly to tipping, no additional mandibular growth over
control, and clockwise mandibular rotation.
Weiland and Bantleon published a report of seventeen
consecutively treated Jasper Jumper patients.37
When
compared to normal development, represented by the Bolton
standards, the Jasper Jumper patients showed slight
restriction of antero-posterior maxillary growth, 2.4 mm
more distal movement of the upper incisors, 0.8 mm more
mesial movement of the mandibular incisors, 1.6 mm more
mesial movement of the mandibular molar.
A 3.2 degree
clockwise rotation of the occlusal plane and 1.6 mm
advancement of Pogonion were found in the Jasper Jumper
group, which compared with 0.1° of counterclockwise
rotation and 0.8 mm of advancement in the control group.
The modest amount of increased mandibular length was
attributed to changes in the condyle-fossa relationship in
the temporal-mandibular joint.
28
The authors concluded the
net correction of the Class II malocclusion was 60% dental
and 40% skeletal.
A study by Stucki and Ingervall examined 26 patients
who had undergone Jasper Jumper treatment.38 Their findings
showed a 0.6 degree decrease in SNA, 0.8 degree increase in
SNB, and a 4.7 mm decrease in overjet.
Contrary to Cope,
et al.36, but in accordance with Weiland and Bantleon, they
reported an increase in mandibular length.37 The distance of
Pogonion to OLp (a line drawn from Sella, perpendicular to
the occlusal plane) distance increased 1.6 mm during
treatment.
Additionally, upper incisors were retroclined
1.6 mm and extruded 0.6 mm, the lower incisors were
proclined 6.4 degrees, lower molars moved mesially 2.6 mm
and extruded 0.7 mm, and the upper molars moved distally
0.9 mm and intruded 0.6 mm.
Contrary to the previously
described findings, the anterior face height was decreased
1.1 mm during treatment and the mandibular plane rotated
counterclockwise 1.2 degrees. No mention of occlusal plane
behavior was made.
Importantly, the patients treated with
the Jasper Jumper were not compared to untreated controls,
making it difficult to distinguish between the growth and
treatment effects.
Covell et al. examined 36 growing Class II patients
treated with the Jasper Jumper and fixed edgewise
29
treatment.39
These patients were compared to a control
group of untreated Class II patients.
The Jasper Jumper
group showed a significant reduction in the SNA angle (-1.6
degrees compared to +0.3 degrees in the controls), a 0.6
degree clockwise rotation of the occlusal plane (compared
to 1.4 degrees counterclockwise rotation in controls), and
a 5.3 degree increase in IMPA (compared with a 1.0 degree
decrease in controls).
and tipped distally.
The maxillary molars were intruded
Additionally, Jasper Jumper treated
patients experienced 2.6 mm forward (which was not compared
to control) and 0.9 mm extrusive movements of the
mandibular molars (compared to 0.4 mm in control).
No
significant changes in the mandibular plane angle or
horizontal mandibular growth were noted.
These findings,
with the exception of the lack of change in mandibular
plane angle, are in accordance with those of Cope et al.36
Both studies, which used appropriate controls, failed to
find the additional mandibular growth that was reported by
Weiland and Bantleon and Stucki and Ingervall whose
conclusions were drawn without the use of appropriate
controls.37,38
Covell et al. suggest that the differences in
mandibular length found between these studies may be due to
variations in superimposition technique.39
30
A forward
posture of the mandible may be misinterpreted as an
increase in mandibular length when using cranial
superimposition techniques.
Cope et al. and Covell et al.
who used separate cranial base, maxillary, and mandibular
structural superimpositions, found no increases in
mandibular length.36,39
Weiland and Bantleon, who reported
increased mandibular length, used only a cranial base
superimposition.37
The disadvantages of the Jasper Jumper include the
side effect of incisor proclination and the large inventory
of appliances required to accommodate the variety of
patients seen in a typical orthodontic practice.
breakage is also a problem.
Appliance
Other appliances, including
the Adjustable Bite Corrector, the Bite Fixer, and the
Klapper Superspring, are variations of the Jasper Jumper
design and might be expected to produce similar results.
The Eureka Spring
In 1996 the Eureka spring was introduced as a fixed
intra-arch Class II appliance.
It boasts better inventory
control and less breakage than the Jasper Jumper.40
The
design of the appliance incorporates an open coil spring
within a telescoping plunger assembly.
Because of the
telescoping aspect of the appliance, the mandible is
31
allowed to open up to 60 millimeters before the assembly
disengages.
This is a significant benefit over several
other, more rigid appliances which restrict mandibular
movement.40
A study of 37 consecutive patients treated with the
Eureka spring to correct Class II malocclusions described
the dental and skeletal effects.41
compared to any control group.
These effects were not
The maxillary incisors were
retroclined 2.9 degrees. The mandibular incisors did not
experience any change in angulation, but moved mesially
1 mm.
The occlusal plane rotated clockwise 2.3 degrees.
The maxillary molars moved distally 1.2 mm and intruded 0.9
mm.
The mandibular molars moved mesially 1.5 mm.
No
significant skeletal effects were produced.
The Forsus™ Fatigue Resistant Device
Recently, an innovative non-compliance appliance has
been developed to remedy some of the shortcomings that have
plagued previous appliances.
The Forsus™ Fatigue Resistant
Device (FRD) consists of a three piece, telescoping nickeltitanium spring that is attached to the headgear tube of
the maxillary molar band via an L-pin (See Figure 2.1).
The spring assembly is connected to the mandibular arch by
a push-rod, which attaches directly onto the mandibular
32
archwire either distal to the canine bracket or distal to
the first premolar bracket.
The FRD offers some advantages
over earlier non-compliance appliances.
First, it may be
assembled chair-side in a relatively short amount of time
because the device consists of only three parts.
Second,
the FRD is completely compatible with complete fixed
orthodontic appliances.
In contrast to other non-
compliance appliances, the FRD can be fabricated and
incorporated into the orthodontist’s pre-existing
appliance, with the only stipulation being that the
maxillary molar bands have headgear tubes.
crown fabrication is necessary.
No additional
This feature provides the
orthodontist a range of adaptability in treatment because
the FRD can be added to or removed from the patient’s full
appliances at any time.
In this manner, like the Saif
Spring, the FRD offers Class II correction alternative that
can be installed immediately for non-compliant patients.
Another potential positive result of this feature is that
the orthodontist can engage a full-sized wire into the
anterior brackets in an attempt to control the amount of
incisor tipping that takes place due to the Class II
corrective forces.
Finally, the manufacturer claims that
the FRD may be less prone to breakage than other
appliances.
The direct push-rod offers rigidity at the
33
point of attachment, while the fatigue-resistant spring
provides flexibility that is not possible with appliances
such as the Herbst and MARA.
Proprietary data suggest that
force levels of the spring are maintained at approximately
200 grams (equivalent to medium Class II elastics).42
If
the appliance does experience breakage, the portion that
breaks can be replaced during a single appointment.
Several other Class II correctors must be completely
replaced or repaired in a laboratory if broken.
1
3
2
Figure 2.1: Diagram of Forsus FRD in place on a fully
banded/bracketed appliance (modified from 3M)
1. L-pin through maxillary first molar tube
titanium spring 3. Push rod
34
2.
Nickel-
Like other non-compliance appliances, the FRD is not
free of drawbacks.
Breakage is not eliminated and the
spring and push-rod are bulky, with a potential for patient
discomfort and soft-tissue injury.
The FRD also requires a
moderate amount of inventory and additional expense.
The design of the Forsus™ FRD represents an
improvement of a previous, similar appliance, the Forsus™
Nitinol Flat Spring (NFS).
The Forsus™ NFS appliance,
designed in 2001, is composed of a set of nickel-titanium
bars attached to the first molar bands and the mandibular
archwire in the same fashion as the current Forsus™ FRD.
However, the first premolar bracket must be removed in
order to accommodate the Forsus™ Nitinol Flat Spring.
The effects of the Forsus™ NFS appliance were
described for a group of 16 Class II, division 1 patients
and compared to similar groups of Jasper Jumper patients
and untreated controls.43
The authors noted similar
skeletal changes in both treated groups.
These changes
included a decrease in the ANB angle due to retrusion of
maxilla and protrusion of the mandible. SNA decreased,
while SNB and Condylion-Gnathion increased.
Posterior face
height (S-Go) was increased and a significant clockwise
rotation of the mandible (increase in the y-axis) elongated
the anterior facial height. Dental changes included distal
35
movement, intrusion and retroclination of the upper
incisors.
The upper incisor to Sella-Nasion angle
decreased five degrees in both of the treated groups.
Intrusion, proclination, and mesial movement of the
mandibular incisors were noted. The IMPA increased 4.5
degrees in the Forsus™ NFS group and 6.5 degrees in the
Jasper Jumper group, while the lower incisor edge intruded
relative to the mandibular border 3 mm and 2.5 mm,
respectively.
The upper molars were distalized and
intruded, while the mandibular molars were moved mesially
and extruded. Overjet was decreased 3.7 mm in the Forsus™
NFS group and 3.2 mm in the Jasper Jumper group, no
decrease was found in the control group. Overbite was
decreased 1 mm in the Forsus™ NFS group and 0.7 mm in the
Jasper Jumper group, while the control group did not
experience change. The occlusal plane relative to SellaNasion rotated clockwise approximately 2 degrees in each of
the treated groups, but did not change in the control
group.
These authors theorized that mandibular growth is
stimulated with both the Forsus™ NFS and the Jasper Jumper.
Henig and Göz reported the effects of the Forsus™ NFS
on 13 growing Class II subjects.44 No control or comparison
groups were used.
The subjects’ ages ranged from 12.5
years to 17 years with an average of 14.2 years.
36
The
Forsus™ NFS appliance was in place for four months in each
subject. Cephalometric radiographs were taken at the times
of insertion and removal of the Forsus™ NFS appliances.
In
this study the SNB increased 0.5 degrees and the occlusal
plane rotated clockwise 4.2 degrees.
The upper incisors
were retroclined 5.3 degrees which contributed to the 1.4
mm distal movement of the upper incisor.
The lower
incisors were proclined 9.6 degrees, which contributed the
3.3 mm of lower incisor mesial movement observed.
Pogonion
was repositioned 1.2 mm forward after Forsus™ NFS
treatment.
The upper molars moved distally 0.8 mm and the
lower molars moved mesially 3.1 mm.
No other statistically
significant treatment changes were reported.
The
investigators noted widening of both arches based on
analyses of the dental casts.
Additionally, questionnaires
were given to all patients in order to determine the
problems that the appliance may pose.
The most common
problem noted was jaw restriction in yawning.
Other
problems included limited mouth opening, pain on the inside
of the cheeks, difficulty in cleaning the teeth, and change
in appearance. The Forsus™ FRD attempts to resolve opening
restrictions by introducing a telescoping mechanism.
Additionally, the Forsus™ FRD does not require the removal
of brackets, unlike the Forsus™ NFS.
37
Comparing Class II Elastics with Fixed Inter-Arch
Appliances
Only one study has compared the effects of Class II
correction obtained with elastics to those obtained with
fixed inter-arch appliances.
This is significant, as these
appliances have the potential to be compliance-free
alternatives in instances where a level of patient
compliance required for successful treatment is not
reached. Although these appliances may achieve a successful
result en lieu of Class II elastics, the skeletal and
dental changes that they produce may be significantly
different from elastics.
It is important that these
potential differences be identified and understood, so that
an appropriate decision can be made in evaluating
appliances.
Nelson et al. compared non-extraction, Class II
patients who had Begg treatment, which includes long-term
elastic wear, with patients who had undergone Herbst
treatment.12
The samples were matched based on age,
malocclusion, and somatic maturation (as assessed by
analyzing the distance curve of the standing height).
The
anterior lower facial height increased more in the Begg
group (4.2 mm) than in the Herbst group (3.2 mm). In the
Begg group, the mandibular plane angle increased 1.3
38
degrees; this angle remained unchanged in the Herbst group.
In the Begg group, the maxilla moved forward 1 mm more than
in the Herbst group, while the mandible moved forward 1 mm
more in the Herbst group. The maxillo-mandibular skeletal
improvements were approximately 2.0 mm greater in the
Herbst group than in the Begg group. The overjet reduction
was 2.1 mm larger in the Begg group, mostly due to dental
movements. While the molar corrections were similar in both
groups the skeletal improvement was 10% in the Begg group,
compared with 66% in the Herbst group.
Comparing the effects of various non-compliance
appliances is difficult due to the variation in research
protocols.
There is no set protocol for patient age,
duration of appliance placement, or anchorage preparation
for experimental groups.
Additionally, the use of
different cephalometric evaluations, reference landmarks,
and superimposition techniques to measure changes has
further confounded the data.
This has led to reports that
appear to present conflicting data.
Summary and Statement of Thesis
The Forsus FRD has the potential to be a viable
alternative for Class II correction in a non-compliant
patient.
In order to replace Class II elastics, the FRD
39
should provide similar or improved dental and skeletal
effects.
A complete investigation into the effects of this
device is appropriate and necessary in order to evaluate
the viability of the FRD as a compliance-free option to
replace Class II elastics.
Only one study comparing the
effects of Class II elastics to the effects of a
compliance-free appliance has been published.
If
compliance-free appliances are to be used as a substitute
in non-compliant patients, more investigation is warranted
into the similarities and differences in treatment results
with these appliances.
The purpose of this investigation is to describe the
sagittal and vertical effects that the Forsus Fatigue
Resistant Device produces on the maxillary and mandibular
dentition, as well as its effects on the maxillary and
mandibular apical bases.
These changes will be compared to
the changes produced by Class II elastics in a similar
sample of patients.
The effects of this device have yet to
be evaluated in the literature.
Complete evaluations of
new devices and techniques must be carried out in order to
provide the practitioner with the data necessary to make
informed decisions in treating their patients.
Not every
patient is capable of or willing to provide the compliance
necessary for Class II elastics.
40
In these instances
compliance-free appliances, such as the Forsus FRD, may be
an appropriate option.
By understanding the similarities
and/or differences produced by these two methods of Class
II treatment, a decision based on objective evidence can be
made regarding use of compliance-free appliances as
suitable substitutes in non-compliant patients.
41
Table 2.1: Summary of the inter-maxillary non-compliance
appliances
Appliance Name
Indications
Design
Herbst
•
Bilateral
telescoping
mechanism advancing
the mandible into
new position
•
•
•
Jasper JumperTM
•
•
•
•
•
•
MARA
•
•
•
Saif Springs
•
Eureka SpringTM
•
Forsus FRDTM
Dental Class II
malocclusion
Lower incisor
advancement Skeletal
Class II mandibular
deficiency
Upper molar
distalization
Dental Class II
malocclusion.
Lower incisor
advancement
Upper molar
distalization
Open Bites
Vertical Growers
Minimal vestibular
space
Dental Class II
malocclusion
Upper molar
distalization
Lower incisor
advancement
Class II traction
Dental Class II
malocclusion
• Upper molar
distalization
• Lower incisor
advancement
N/A
42
Inter-maxillary
springs in
compression
Bilateral
fitted to
stainless
crowns to
mandible
cams
molar
steel
advance
Class II coil
springs in tension
Telescopic rods with
integral light force
compression springs
Intermaxillary
Nitinol spring
providing reciprocal
push forces distally
against upper molar
and mesially against
lower canine or
premolar
Table 2.2: Summary of maxillary dental effects of interarch appliances.
Appliance
Method of measurement
Max 6
vertical
Max 6
sagittal
Angular:
Measurement of preand post- treatment
cephs
Linear:
Cartesian coordinate
system (see figure 2)
Angular:
measurement of preand post-treatment
cephs
Linear:
Bjork Analysis
(See figure 3)
3.0mm
0mm
Max 1
vert.
3.69mm
Max 1
sag.
1.4º
N/A
N/A
N/A
N/A
Angular and linear
measurements based on
pre- and post- treatment
cephs using various
skeletal landmarks as
reference points
0.2mm
-1.5mm
N/A
0.1º
Vertical and sagittal
measurements using
McNamara technique
(See figure 4)
0.1mm
-1.1mm
N/A
N/A
Cranial base
superimposition to
determine skeletal
changes, regional
superimposition to
assess dental changes
-1mm
-4.3mm
2.5mm
-4.7mm
Angular:
measurement of pre- and
post-treatment cephs
Linear:
Bjork Analysis
(See figure 3)
N/A
-1.4mm
N/A
-2.4mm
Angular:
measurement of pre- and
post-treatment cephs
Linear:
Bjork Analysis
(See figure 3)
0.6mm
0.9mm
0.6mm
-1.6mm
Angular and linear
measurements based on
pre- and post- treatment
cephs using various
skeletal landmarks as
reference points
-1.0mm
-2.0mm
1.0mm
-6.0º
/Author
Class II
Elastics
Ellen et
al.
(1998)
Class II
Elastics
Nelson et
al.
(1999)
Herbst
Valant and
Sinclair
(1989)
MARA
PangrazioKulbersh et
al. (2003)
Jasper
Jumper
Cope, et
al. (1994)
Jasper
Jumper
Weiland and
Bantleon
(1999)
Jasper
Jumper
Stucki and
Ingerval
(1998)
Jasper
Jumper
Covell et
al. (1999)
43
Table 2.3: Summary of mandibular dental effects of interarch appliances.
Appliance
Method of measurement
Mand 6
vertical
Mand 6
sagittal
Mand 1
vert.
Mand 1
sagit.
Angular:
Measurement of pre- and
post- treatment cephs
Linear:
Cartesian coordinate
system (see figure 2)
4.04mm
4.08mm
7.29mm
7.9º
Angular:
measurement of preand post-treatment
cephs
Linear:
Bjork Analysis
(See figure 3)
N/A
2mm
N/A
1.4mm
Angular and linear
measurements based on
pre- and post- treatment
cephs using various
skeletal landmarks as
reference points
1mm
1.6mm
N/A
2.4º
Vertical and sagittal
measurements using
McNamara technique
(See figure 4)
1.3mm
1.1mm
0.5mm
3.9º
Cranial base
superimposition to
determine skeletal
changes, regional
superimposition to
assess dental changes
Angular:
measurement of pre- and
post-treatment cephs
Linear:
Bjork Analysis
(See figure 3)
1.52mm
3.8mm
-1.7mm
4.4mm
N/A
1.6mm
N/A
0.8mm
Angular:
measurement of pre- and
post-treatment cephs
Linear:
Bjork Analysis
(See figure 3)
0.7mm
2.6mm
N/A
6.4º
Angular and linear
measurements based on
pre- and post- treatment
cephs using various
skeletal landmarks as
reference points
0.9mm
2.8mm
-1.0mm
5.3º
/Author
Class II
Elastics
Ellen, et
al.
(1998)
Class II
Elastics
Nelson, et
al.
(1999)
Herbst
Valant and
Sinclair
(1989)
MARA
PangrazioKulbersh et
al. (2003)
Jasper
Jumper
Cope, et
al. (1994)
Jasper
Jumper
Weiland and
Bantleon
(1999)
Jasper
Jumper
Stucki and
Ingerval
(1998)
Jasper
Jumper
Covell et
al. (1999)
44
Table 2.4: Summary of skeletal effects of inter-arch
appliances.
Appliance
/Author
Class II
Elastics
Ellen, et
al.
(1998)
Class II
Elastics
Nelson, et
al.
(1999)
Herbst
Valant and
Sinclair
(1989)
MARA
PangrazioKulbersh et
al. (2003)
Jasper
Jumper
Cope, et
al. (1994)
Jasper
Jumper
Weiland and
Bantleon
(1999)
Jasper
Jumper
Stucki and
Ingerval
(1998)
Jasper
Jumper
Covell et
al. (1999)
Method of
measurement
A
Point
B
Point
Mandib
Length
Occl
Plane
Lower
Face
Height
Angular:
Measurement of preand post- treatment
cephs
Linear:
Cartesian coordinate
system (see figure 2)
Angular:
measurement of preand post-treatment
cephs
Linear:
Bjork Analysis
(See figure 3)
-1.7°
-0.1°
1.7mm
0.8°
6.2mm
-1.0°
-0.4°
2.1mm
N/A
5.0mm
Angular and linear
measurements based on
pre- and posttreatment cephs using
various skeletal
reference points
-0.7°
1.3mm
3.3mm
N/A
4.2mm
Vertical and
sagittal
measurements using
McNamara technique
(See figure 4)
-0.4°
1.1°
4.5mm
0.4°
2.5mm
Cranial base
superimposition to
determine skeletal
changes, regional
superimposition to
assess dental changes
Angular:
measurement of preand post-treatment
cephs
Linear:
Bjork Analysis
(See figure 3)
Angular:
measurement of preand post-treatment
cephs
Linear:
Bjork Analysis
(See figure 3)
Angular and linear
measurements based on
pre- and posttreatment cephs using
various skeletal
landmarks as
reference points
-0.6°
-0.4°
0mm
N/A
N/A
-0.8°
1.2°
1.6mm
N/A
N/A
-0.6°
0.8°
1.6mm
N/A
-1.1mm
0.8°
0.3°
0.6
2.4º
-0.2mm
45
References
1. Stedman TL. Stedman's medical dictionary. 27th ed. New
York: Lippincott, Williams, & Wilkins; 1999.
2. Proffit WR, Fields HW, Jr., Moray LJ. Prevalence of
malocclusion and orthodontic treatment need in the United
States: estimates from the NHANES III survey. Int J Adult
Orthodon Orthognath Surg 1998;13:97-106.
3. Kelly JE, Harvey CR. An assessment of the occlusion of
the teeth of youths 12-17 years. Vital Health Stat 11
1977:1-65.
4. Angle EH. Treatment of malocclusion of the teeth. 7th
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5. Horowitz HS. A study of occlusal relations in 10-12 year
old Caucasian and Negro school children--summary report.
Int Dent J 1970;20:593-605.
6. Milacic M, Markovic M. A comparative occlusal and
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relationships. Br J Orthod 1983;10:53-54.
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Pract Dent Rec 1969;20:113-120.
8. McNamara JA, Jr. Components of class II malocclusion in
children 8-10 years of age. Angle Orthod 1981;51:177-202.
9. Buschang PH, Martins J. Childhood and adolescent changes
of skeletal relationships. Angle Orthod 1998;68:199-206;
discussion 207-198.
10. Ellen EK, Schneider BJ, Sellke T. A comparative study
of anchorage in bioprogressive versus standard edgewise
treatment in Class II correction with intermaxillary
46
elastic force. Am J Orthod Dentofacial Orthop 1998;114:430436.
11. Nelson B, Hansen K, Hagg U. Overjet reduction and molar
correction in fixed appliance treatment of class II,
division 1, malocclusions: sagittal and vertical
components. Am J Orthod Dentofacial Orthop 1999;115:13-23.
12. Nelson B, Hansen K, Hagg U. Class II correction in
patients treated with class II elastics and with fixed
functional appliances: a comparative study. Am J Orthod
Dentofacial Orthop 2000;118:142-149.
13. Gianelly AA, Arena SA, Bernstein L. A comparison of
Class II treatment changes noted with the light wire,
edgewise, and Frankel appliances. Am J Orthod 1984;86:269276.
14. Tovstein BC. Behavior of the occlusal plane and related
structures in treatment of Class II malocclusions. Angle
Orthod 1955;25:189-198.
15. Hanes RA. Bony profile changes resulting from cervical
traction compared with those resulting from intermaxillary
elastics. Am J Orthod 1959;45:353-364.
16. Bien SM. Analysis of the components of force used to
effect distal movement of teeth. Am J Orthod 1951;37:508521.
17. Zingeser M. Vertical response to Class II division 1
therapy. Angle Orthod 1964;34:58-64.
18. Adams CD, Meikle MC, Norwick KW, Turpin DL. Dentofacial
remodelling produced by intermaxillary forces in Macaca
mulatta. Arch Oral Biol 1972;17:1519-1535.
19. Remmer KR, Mamandras AH, Hunter WS, Way DC.
Cephalometric changes associated with treatment using the
47
activator, the Frankel appliance, and the fixed appliance.
Am J Orthod 1985;88:363-372.
20. Kanter F. Mandibular anchorage and extraoral force. Am
J Orthod 1956;42:194-207.
21. Meikle MC. The dentomaxillary complex and overjet
correction in Class II, division 1 malocclusion: objectives
of skeletal and alveolar remodeling. Am J Orthod
1980;77:184-197.
22. Beckwith FR, Ackerman RJ, Jr., Cobb CM, Tira DE. An
evaluation of factors affecting duration of orthodontic
treatment. Am J Orthod Dentofacial Orthop 1999;115:439-447.
23. Shia GJ. Treatment overruns. J Clin Orthod 1986;20:602604.
24. Skidmore KJ, Brook KJ, Thomson WM, Harding WJ. Factors
influencing treatment time in orthodontic patients. Am J
Orthod Dentofacial Orthop 2006;129:230-238.
25. Egolf RJ, BeGole EA, Upshaw HS. Factors associated with
orthodontic patient compliance with intraoral elastic and
headgear wear. Am J Orthod Dentofacial Orthop 1990;97:336348.
26. Brandao M, Pinho HS, Urias D. Clinical and quantitative
assessment of headgear compliance: a pilot study. Am J
Orthod Dentofacial Orthop 2006;129:239-244.
27. El-Mangoury NH. Orthodontic cooperation. Am J Orthod
1981;80:604-622.
28. Herbst E. Dreissigjahrige erfahrungen mit dem
retentionsscharnier. Zahnartzl Rundschau 1934;43:1515-1524.
29. Pancherz H. Treatment of class II malocclusions by
jumping the bite with the Herbst appliance. A cephalometric
investigation. Am J Orthod 1979;76:423-442.
48
30. Pancherz H. The effects, limitations, and long-term
dentofacial adaptations to treatment with the Herbst
appliance. Semin Orthod 1997;3:232-243.
31. Valant JR, Sinclair PM. Treatment effects of the Herbst
appliance. Am J Orthod Dentofacial Orthop 1989;95:138-147.
32. Coelho Fliho CM. Mandibular protraction appliances for
Class II treatment. J Clin Orthod 1995;29:319-336.
33. Coelho Fliho CM. Mandibular protraction appliance IV. J
Clin Orthod 2001;35:18-24.
34. Pangrazio-Kulbersh V, Berger JL, Chermak
R, Simon ES, Haerian A. Treatment effects of
anterior repositioning appliance on patients
malocclusion. Am J Orthod Dentofacial Orthop
295.
DS, Kaczynski
the mandibular
with Class II
2003;123:286-
35. McSherry PF, Bradley H. Class II correction-reducing
patient compliance: a review of the available techniques. J
Orthod 2000;27:219-225.
36. Cope JB, Buschang, P.H., Cope, D.D., Parker, J.,
Blackwood 3rd, H.O. Quantitative evaluation of craniofacial
changes with Jasper Jumper therapy. Angle Orthod
1994;64:113-122.
37. 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.
38. Stucki N, Ingervall B. The use of the Jasper Jumper for
the correction of Class II malocclusion in the young
permanent dentition. Eur J Orthod 1998;20:271-281.
39. Covell Jr DA, Trammell, D.W., Boero, R.P., West, R. . A
cephalometric study of Class II, division1 malocclusions
49
treated with the Jasper Jumper appliance. Angle Orthod
1999;69:311-320.
40. DeVincenzo J. The Eureka Spring: a new interarch force
delivery system. J Clin Orthod 1997;31:454-467.
41. Stromeyer EL, Caruso JM, DeVincenzo JP. A cephalometric
study of the Class II correction effects of the Eureka
Spring. Angle Orthod 2002;72:203-210.
42. 3M-Unitek. Forsus Fatigue Resistant Device with direct
push rod; 2002.
43. Karacay S, Akin E, Olmez H, Gurton AU, Sagdic D. Forsus
Nitinol Flat Spring and Jasper Jumper corrections of Class
II division 1 malocclusions. Angle Orthod 2006;76:666-672.
44. Heinig N, Goz G. Clinical application and effects of
the Forsus spring. A study of a new Herbst hybrid. J Orofac
Orthop 2001;62:436-450.
50
Chapter III: Journal Article
Abstract
Introduction: The Forsus™ Fatigue Resistant Device
(FRD) was tested as a compliance-free alternative to Class
II elastics.
Methods: A sample of 34 (14 females, 20
males) consecutively treated non-extraction FRD patients
ages 9 years, 0 months to 17 years, 0 months were matched
with a sample of 34 (14 females, 20 males) consecutively
treated non-extraction Class II elastics patients ages 9
years, 0 months to 17 years, 0 months based on four pretreatment variables (ANB, L1-GoMe, SN-GoMe, and treatment
duration).
Pre- and post-treatment cephalometric
radiographs were traced and analyzed using the pitchfork
analysis and a vertical cephalometric analysis. T-tests
were used to evaluate differences between groups.
Results:
No statistically significant differences were found in the
treatment changes between the groups.
There was a general
trend for mesial movement of the maxilla, mandible, and
dentition during treatment for both groups.
The mandibular
skeletal advancement and dental movements were greater than
51
those in the maxilla, which accounted for the Class II
correction.
groups.
Lower incisor proclination was seen in both
Vertically, both the maxillary and mandibular
molars exhibited eruption during treatment in both groups,
while lower incisor proclined with the incisal edge moving
closer to the lower border of the mandible.
Conclusions:
The Forsus™ FRD is an acceptable substitute for Class II
elastics for patients who appear to be non-compliant.
Greater forward displacement of the mandible compared to
the maxilla was the predominant factor in successfully
treated Class II patients with both Class II elastics and
the Forsus™ FRD appliance.
Introduction
Class II malocclusion presents a major and frequent
challenge to orthodontists.
According to NHANES III,
Class II malocclusion (based on overjet measurements
greater than 4 mm) is present in approximately 11% of the
US population and comprises approximately one-fifth of all
malocclusions.1
Data collected from 1966 to 1970 by the
52
United States National Health Survey, showed a similar
prevalence of Class II relationship. Numerous orthodontic
techniques and appliances aimed at producing a predictable
resolution of Class II malocclusions have been
introduced,including fixed or removable intra-arch
appliances, fixed or removable inter-arch appliances,
selective extraction patterns, and surgical repositioning
of one or both jaws.
Class II intermaxillary elastics are a typical interarch method used for correction.
The effects of Class II
elastics include mesial movement of the mandibular molars,
mesial movement and tipping of the mandibular incisors,
distal movement and tipping of the maxillary incisors,
extrusion of the mandibular molars and maxillary incisors,
and clockwise rotation of the mandibular plane and the
occlusal plane.2-7
Intermaxillary elastics rely heavily on patient
compliance for their effectiveness.
Compliance in
orthodontics is variable and difficult to predict.8 Poor
cooperation can lead to poor treatment results and/or
increased treatment time.9,10
Therefore, a number of
compliance-free inter-arch appliances have been developed.
Fixed inter-arch appliances typically demonstrate mesial
movement of the mandibular molars and mesial movement at
53
tipping of the mandibular incisors.
Reports on other
effects vary, particularly those pertaining to mandibular
growth.11-20
Only one study has compared the effects of
Class II correction obtained with elastics to those
obtained with fixed inter-arch (Herbst) appliances.4
It
showed that anterior lower facial height and the mandibular
plane angle increased more in the elastics group than in
the Herbst group.
While molar corrections were similar,
the skeletal improvement was 10% in the elastics group,
compared with 66% in the Herbst group.
It is significant that little attention has been paid
to the effects of Class II elastics compared to noncompliance appliances, because these appliances have the
potential to be compliance-free alternatives in instances
where the level of patient compliance required for
successful treatment has not been reached. Although fixed
inter-arch appliances may achieve a successful result en
lieu of Class II elastics, the skeletal and dental changes
that they produce may be significantly different from
elastics.
It is important that the potential differences
be identified and understood, so that an appropriate
decision can be made in evaluating appliances.
The present study was designed to evaluate the effects
of the Forsus™ Fatigue Resistant Device (FRD).
54
The Forsus™
FRD is a three-piece, telescoping system that incorporates
a super-elastic nickel-titanium coil spring. The FRD can be
assembled chair-side in a relatively short amount of time
because the device consists of only three parts, it is
completely compatible with complete fixed orthodontic
appliances, and it can be fabricated and incorporated into
the orthodontist’s pre-existing appliance.
The FRD
attaches at the maxillary first molar and on the mandibular
archwire, distal to either the canine or first premolar
bracket.
As the coil is compressed, opposing forces are
transmitted to the sites of attachment.
The properties of
the spring, theoretically, allow it to maintain a
continuous force without the possibility of fatigue.
Our
purpose was to determine the skeletal and dental effects
produced during Class II correction with the Forsus™ FRD
compared to the effects of Class II elastics.
Class II
elastics were chosen as the comparison group because it
represents a typical compliance-reliant method of Class II
correction.
Materials and Methods
Sample
A pre-treatment sample (T1) of 98 consecutively
treated patients (41 Forsus™ FRD and 57 Class II elastics)
55
was selected from the offices of two private practice
orthodontists (74 records from practice A and 24 records
from practice B).
•
The criteria for patient selection were:
Pre-treatment occlusion of at least end-on Class II
malocclusion
•
Treatment completed without any permanent teeth
extracted (excluding third molars)
•
Class I post-treatment occlusion
•
Starting age between of 9.0 years and 17.0 years
•
Good quality pre- and post-treatment cephalometric
radiographs
Patients were rejected if any appliances other than Forsus™
FRD or Class II elastics were used to correct the Class II
malocclusion.
Most previous reports of fixed inter-arch appliances
measured changes at the removal of the appliances, rather
than at the end of comprehensive treatment.
The present
study was designed to measure and describe the posttreatment differences between groups that were matched at
the start of treatment, but used different appliances to
correct the molar relationship.
Except for the method of
Class II correction employed, the treatments of the groups
were similar, consisting of full, fixed orthodontic
56
appliances.
By limiting the sample to two practitioners,
variation in treatment technique was minimized.
Class II
elastics were initially prescribed in the treatment of the
patients in the Forsus™ sample and may have been worn after
Forsus™ removal in order to maintain the occlusal
relationship.
In this respect, the patients in Forsus™
sample should be considered Forsus™ FRD/Class II elastics
patients.
Regardless, the Forsus™ appliance was the
appliance that was ultimately prescribed for Class II
correction in this group.
A dispersion analysis based on ANB, L1-GoMe, and
SN-GoMe angles, as well as treatment duration was performed
in order to ensure comparability across samples.
Outlying
subjects were removed to match the samples based on
starting skeletal relationships.
The final sample
consisted of 34 subjects per group (Table 3.1).
The post-
treatment (T2) records were processed after the outlying
subjects had been removed.
Data Collection
The pre- and post-treatment cephalometric radiographs
were hand-traced on acetate paper and 15 landmarks were
identified (Table 3.2).
In order to describe the skeletal
57
and dental sagittal treatment changes that occurred, the
radiographs were analyzed using the pitchfork analysis
(PFA).21
The PFA accounts for and summarizes sagittal
mandibular and maxillary molar movements, sagittal
maxillary and mandibular advancement relative to the
cranial base, and the contributions of all of these
movements in correcting the molar relationship (Figure
3.1).
Distal maxillary skeletal and dental movements and
mesial mandibular skeletal and dental movements, which aid
in Class II correction, were assigned positive values.
Movements that worsen Class II relations were assigned
negative values.
Incisor movements that affect overjet
were also measured and summarized.
All measurements are
made at the level of the occlusal plane.
In this instance,
the functional occlusal plane (FOP) was drawn through the
occlusal contact points of the molars and premolars.
Because the Forsus™ and Class II elastics were
expected to produce vertical and angular changes of the
dentition not described by the PFA, the following
measurements were also included:
1. mandibular incisor (L1) angulation in relation to
the mandibular plane (Go-Me)
2. maxillary incisor (U1) angulation to the SellaNasion line (SN)
58
3. maxillary molar (U6) mesial contact point vertical
distance perpendicular to Anterior Nasal SpinePosterior Nasal Spine (ANS-PNS)
4. mandibular molar (L6) mesial contact point
vertical distance perpendicular to Gonion-Menton
(GoMe)
5. maxillary incisor (U1 incisal edge vertical
distance perpendicular to ANS-PNS
6. mandibular incisor (L1) incisal edge vertical
distance perpendicular to Gonion-Menton (Go-Me)
7. functional occlusal plane (FOP) to Sella-Nasion
(SN)
Statistical Methods
Statistical analysis was preformed using SPSS
version 14.0 (SPSS Incorporated, Chicago, IL).
The
skewness and kurtosis statistics indicated normal
distributions.
Independent t-tests were used to evaluate
group differences.
Mean and standard deviation were used
to describe central tendencies and dispersion.
To insure intra-examiner reliability, nine
radiographs were randomly selected, re-traced, and angles
and distances were re-measured.
Cronbach’s Alpha test for
reliability showed that intraclass correlation was 0.987.
59
Results
Cephalometric Comparison
Pre-Treatment
No significant (p< .05) pre-treatment (T1) differences
existed between the two treatment groups for the variables
used for matching (ANB, L1-GoMe, SN-GoMe, and treatment
duration, Table 3.3).
The pre-treatment ANB was
0.7 degrees greater in the Forsus™ group.
L1-GoMe,
SN-GoMe, and treatment duration were closely matched.
A
statistically significant difference did exist between the
groups at T1 for U1-SN.
The elastics group had a higher
U1-SN angulation than the Forsus™ group (103.1 degrees and
98.3 degrees, respectively).
Post-Treatment
Statistically significant (p< .05) differences were
found post-treatment (T2) between the groups for L1-GoMe
vertical distance and OP-SN angle (Table 3.5).
The other
differences between the groups were not statistically
significant (p< .05).
U1-ANS-PNS, U6-ANS-PNS, and L6-GoMe
vertical distances were similar in both groups.
60
Treatment Changes Measured By Pitchfork
The pitchfork analysis showed that the maxilla moved
mesially 1.5 mm and the mandible moved mesially 3.8 mm in
the elastics group; the average apical base change was 2.3
mm (Table 3.4, Figure 3.2).
The maxillary molar moved
mesially 0.6 mm and the mandibular molar moved mesially 0.7
mm.
Total molar change (maxillary molar + mandibular molar
+ apical base change) was 2.4 mm.
The upper incisor moved
mesially 0.3 mm and the lower incisor moved mesially 0.8
mm.
Total incisor change (upper incisor + lower incisor +
apical base change) was 2.8 mm.
All changes were
statistically significant (p<.05), except for maxillary
incisor movement.
In the Forsus™ group, the pitchfork analysis showed
that the maxilla moved mesially 1.7 mm and the mandible
moved mesially 4.4 mm; the average apical base change was
2.6 mm.
The maxillary molar moved mesially 1.2 mm and the
mandibular molar moved mesially 1.8 mm.
Total molar change
(maxillary molar + mandibular molar + apical base change)
was 3.2 mm.
The upper incisor moved mesially 0.7 mm and
the lower incisor moved mesially 1.2 mm.
Total incisor
change (upper incisor + lower incisor + apical base change)
61
was 3.2 mm.
All changes were statistically significant
(p<.05), except for maxillary incisor movement.
The pitchfork analysis showed differences between the
groups for lower molar movements and total molar
corrections during treatment (Figure 3.2).
The 1.1 mm more
mesial movement and the 0.8 mm greater molar correction in
the Forsus™ group were statistically significant (p< .05
and p< .01, respectively).
During treatment, the mandible
and maxilla moved mesially, with the mandible moving a
greater amount than the maxilla in both groups.
Upper
molars and upper and lower incisors were moved mesially in
similar amounts in both groups.
Overjet was improved in
both groups.
Vertical and Angular Treatment Changes
The vertical and angular treatment changes showed no
statistically significant (p< .05) group differences. For
both groups, the U1-SN and L1-GoMe angulations increased,
the upper incisor tip moved further, vertically, from
ANS-PNS and the lower incisor tip moved closer to GoMe.
The upper and lower molars increased their vertical
distances from ANS-PNS and GoMe, respectively. The occlusal
plane rotated clockwise in both groups.
62
Discussion
The molar relationships of patients treated with
elastics were corrected primarily due to mandibular growth
changes.
Anterior mandibular displacement and mesial
mandibular molar movements accounted for approximately 158%
and 29% of the correction, respectively. Treatment changes
in the maxilla worked against the molar correction, with
anterior maxillary skeletal and dental movements limiting
the correction by approximately 63% and 25%, respectively.
Similar amounts of mandibular and maxillary advancements
have been previously reported for Class II elastic
treatments.22-24
Mesial movements of the maxilla, which
works against Class II correction, is a common finding in
elastics patients, even with the use of headgear.23,24
Non-
extraction Class II patients treated with standard edgewise
appliances, Class II elastics, and headgears show
mandibular displacements and dental movements accounting
for approximately 66% and 22% of the Class II correction,
and distal maxillary molar movement contributed another
29%; anterior maxillary skeletal movements limits the
correction by approximately 20%.23
The use of a
prescription appliance without headgear could account for
the maxillary molar anchorage loss seen in this study.
63
Molar anchorage is enhanced with headgear or Begg anchor
bends, both of which produce distal crown movement of the
maxillary molars.23,25
Anchorage loss in patients treated
with prescription appliances is approximately 1 mm greater
than with standard edgewise treatment.26
Because total
molar correction was less than previously reported with the
PFA, suggesting a less severe initial Class II
relationship, greater maxillary molar anchorage loss could
be tolerated while achieving satisfactory occlusal
results.23,25
Nelson et al. showed similar amounts of molar
correction in patients successfully treated with Class II
elastics and the Begg appliance.24
The vertical relationships of the teeth and
occlusal plane in the elastics patients indicate treatment
modifications of normal growth.
Maxillary and mandibular
molars, as well as maxillary incisors, experienced eruption
during treatment, as previously reported for elastics
treatment.2,27,28
Untreated controls show similar amounts of
maxillary molar eruption over a comparable time span, but
less mandibular molar eruption.16
This suggests that Class
II elastics may have contributed to additional mandibular
molar eruption during treatment. The OP-SN decreased
(rotated counterclockwise) 1.0 degrees, which was contrary
to the clockwise rotation previously reported for elastics,
64
but the differences are relatively small.2
Counterclockwise
rotation of the occlusal plane is normally observed in
untreated patients during adolescence and may have
counteracted the clockwise rotational tendency that
mandibular molar and maxillary incisor eruption would be
expected to affect.16
Differences could also be attributed
to the use of the functional occlusal plane was in this
study, rather than the Down’s occlusal plane or Pancherz’s
occlusal line, which are commonly used.2,14,15,18,20
The
functional occlusal plane, which is drawn through the
occlusal contact points of the first molars and premolars,
is less likely to rotate clockwise as upper incisors
extrude and lower incisors procline than planes which use
the incisors for reference.
As in the elastics group, molar correction for the
patients treated with the Forsus™ FRD appliance was
predominately due to mesial mandibular skeletal and dental
movements.
Anterior mandibular displacement and mesial
mandibular molar movement accounted for approximately 138%
and 56% of Class II correction, respectively. Treatment
changes with the Forsus™ also worked against molar
correction, as mesial skeletal and molar movements limited
correction by 91%.
DeVincenzo,13 who quantified the
skeletal and dental contributions to Class II correction
65
with the Eureka Spring, showed distal movement of the
maxilla (contributing 11%) and maxillary molars
(contributin 33%); mesial mandibular molar movements
contributing an additional 60%, and; relative posterior
movement of the mandible limiting molar correction by 4%.
However, DeVincenzo used the pterygoid vertical reference
line to calculate dental and skeletal changes.
The
functional occlusal plane, which was used as a reference in
this study, tends to show relatively greater skeletal
contributions in Class II correction.29
Karacay et al.30
reported no maxillary movement, approximately 1 mm of
anterior mandibular displacement, and equal amounts of
distal maxillary molar and mesial mandibular molar
movements in patients treated with the Forsus™ Nitinol Flat
Spring (NFS).
Other authors have also reported distal
movement of maxillary molars with the Forsus™ NFS and
similar appliances.11,16,20,30,31
The studies showing the
greatest distal effect on the maxillary molars measured the
effects immediately after inter-arch appliance
removal.11,18,20
Mesial movement with growth and anchorage
loss due to additional orthodontic treatment may mask or
negate these distal movements.
Stucki and Ingerval18 showed
that mesial maxillary molar movement occurred during the
observation period following removal of the Jasper Jumper.
66
Evaluation of patients treated with the Forsus™ FRD
appliance in this study was made after completion of
orthodontic treatment.
After Class I molar occlusion is
achieved and appliances are removed, it would be expected
that the maxillary molars would move mesially to keep pace
with the mandibular molars.
Fewer significant vertical changes were seen in the
Forsus™ group than the elastics group.
The maxillary and
mandibular molars both experienced eruption, but no
significant changes were seen for the upper incisors or
occlusal plane.
Similar amounts of mandibular molar
extrusion have been reported in Forsus™ NFS patients and
Jasper Jumper patients.11,12,18,30
Forsus™ NFS, Jasper Jumper,
and Eureka Spring reports show intrusion of the maxillary
molars.11-13,18,30
However, these reports again measured molar
position immediately after appliance removal, rather than
after treatment was finished.
Stuki and Ingerval18 showed
that, after Jasper Jumpers were removed, eruption of the
maxillary molars followed the intrusion that occurred
during treatment.
The present study measured changes after
orthodontic treatment was completed, and if intrusion was
achieved with Forsus™ treatment, it is followed by
eruption, which occurs with normal growth.
67
Comparison of the overall effects in the Forsus™ and
elastics groups reveals a relatively greater mesial
movement of the dentition, the maxilla, and the mandible in
the Forsus™ group.
Since a Class I molar relationship was
the final result in both groups, the Forsus™ group may have
started with a greater molar discrepancy.
The change in
L1-GoMe angulation was 2.5 degrees greater in the Forsus™
group than in the elastics group, but this difference was
also not statistically significant.
As the lower incisor
tip proclines, the vertical distance from incisal tip to
mandibular border would be expected to decrease in
proportion to its proclination.
Both groups studied
experienced decreases in the vertical distance from the
incisal tip of the lower incisors to the mandibular plane
during treatment.
The lower incisor proclined more and the
vertical distance from incisal tip to mandibular border
(L1-GoMe) decreased more in the Forsus™ group.
While group differences were evident for extrusion of
maxillary dentition as well as maxillary and mandibular
incisor proclination, the differences were not
statistically significant.
This was due to the amount of
variation in treatment changes seen within the groups.
Large variation in treatment changes is a common finding in
treated Class II patients.2,11-13,16,19,30
68
The variation is
likely due to the movements required to correct the
different types of dental compensations typically seen in
Class II patients.
Greater severity of the malocclusion
will require more extreme dental compensations.
Although care was taken to keep both groups closely
matched at the start of treatment, there were some
differences between the groups at T1.
The maxillary
incisor angulations were statistically different at the
start of treatment, with the Forsus™ group being more
upright (98.9 degrees compared to 103.1 degrees in the
elastics group).
At the end of treatment there were no
differences in upper incisor angulations between the
groups.
Cephalometric analysis showed that U1-SN
proclination was greater in the Forsus™ group, which is in
agreement with the pitchfork analysis showing a greater
tendency for mesial movement of the incisors in the Forsus™
group.
Conclusions
1) The Forsus™ FRD is an acceptable substitute for
Class II elastics for patients who appear to be noncompliant.
69
2) Greater forward displacement of the mandible
compared to the maxilla was the predominant factor in
successfully treated Class II patients with both Class II
elastics and the Forsus™ FRD appliance.
Acknowledgements
The authors wish to acknowledge Dr. Kevin Walde and
Dr. William Vogt for generously providing the records for
this study and Dr. Heidi Israel and Dr. Lysle E. Johnston,
Jr for their assistance during this project.
References
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cephalometric study of Class II, division1 malocclusions
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treated with the Jasper Jumper appliance. Angle Orthod
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delivery system. J Clin Orthod 1997;31:454-467.
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jumping the bite with the Herbst appliance. A cephalometric
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appliance. Semin Orthod 1997;3:232-243.
16. Pangrazio-Kulbersh V, Berger JL, Chermak
R, Simon ES, Haerian A. Treatment effects of
anterior repositioning appliance on patients
malocclusion. Am J Orthod Dentofacial Orthop
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DS, Kaczynski
the mandibular
with Class II
2003;123:286-
17. Stromeyer EL, Caruso JM, DeVincenzo JP. A cephalometric
study of the Class II correction effects of the Eureka
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18. Stucki N, Ingervall B. The use of the Jasper Jumper for
the correction of Class II malocclusion in the young
permanent dentition. Eur J Orthod 1998;20:271-281.
19. Valant JR, Sinclair PM. Treatment effects of the Herbst
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22. Egolf RJ, BeGole EA, Upshaw HS. Factors associated with
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28. Zingeser M. Vertical response to Class II division 1
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29. Mannchen R. A critical evaluation of the pitchfork
analysis. Eur J Orthod 2001;23:1-14.
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Nitinol Flat Spring and Jasper Jumper corrections of Class
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73
Figures
74
Distal
Mesial
Max + Mand = ABCH
ABCH + U6 + L6 = 6/6
ABCH + U1+ L1 = 1/1
Figure 3.1: Diagram of pitchfork analysis (modified from
Johnston)
Maxilla, mandible, molar, and incisor changes are all
represented. Mesial movements of the mandible and
mandibular dentition or distal movements of the maxilla and
maxillary dentition aid in Class I and overjet correction
and are assigned positive values. Mesial movements of the
maxilla and maxillary dentition or distal movements of the
mandible and mandibular dentition make Class II
malocclusion and overjet more severe and are assigned
negative values. The amount of mesial or distal movement
of the mandible in relation to the maxilla is summarized as
apical base change (ABCH). Correction of molar
relationship and overjet are summarized based on skeletal
(ABCH) and dental contributions.
B
A
75
C
Figure 3.2: Pitchfork summaries of treatment changes
Positive signs indicate movements in a direction which aids
Class I correction (distal movements in the maxilla/mesial
movements in the mandible). Negative signs indicate
movements which make Class II occlusion more severe (mesial
movements in the maxilla/distal movements in the maxilla).
A) Treatment changes in elastics group
B) Treatment changes in Forsus™ group
C) Summary of differences between groups
(Forsus™ - elastics)
76
Table 3.1 Sample Description
Males
Females
Class II
elastics
Forsus™
20
14
Average Start
Age
12.2
20
14
12.6
Tables
77
Group
Table 3.2: Summary of Cephalometric Landmarks and Definitions
LANDMARK
Abbrev
DEFINITION
A point
A
The deepest point on the premaxilla
below ANS
The tip of the anterior nasal spine
Anterior
Nasal
Spine
SE point
ANS
SE
B Point
B
D point
D
Upper 6
U6
The mesial contact point of the
maxillary first molar
Lower 6
L6
The mesial contact point of the
mandibular first molar
Lower
Incisor
L1
The tip of the incisal edge of the
mandibular central incisor
Upper
Incisor
U1
The tip of the incisal edge of the
maxillary central incisor
Posterior
Nasal
Spine
Sella
PNS
The most posterior point on the bony
hard palate
S
The center of the pituitary fossa
Nasion
N
The most anterior point of the
frontonasal suture
Gonion
Go
Menton
Me
Functional
Occlusal
Plane
FOP
The most anterior and inferior point
at the angle of the mandible
The most inferior point of the
mandibular symphysis
Plane drawn through the occlusal
contact points of the molars and
premolars
The intersection of the averaged
greater wings and planum of the
sphenoid
The deepest part of the anterior
mandible
The center of the cross-section of
the mandibular symphysis
78
Table 3.3: Pre-treatment comparison of elastics and Forsus™ groups for matched variables.
Elastics Sample Forsus™ Sample
Value
Units
x
SD
x
SD
Sig
79
ANB
deg
4.6
1.7
5.3
1.5
.10
L1-GoMe
deg
95.7
6.3
93.8
7.2
.25
SN-GoMe
deg
32.4
5.1
33.1
5.2
.52
Treatment
Duration
years
2.4
0.9
2.7
0.9
.12
Table 3.4: Pitchfork analysis comparison of treatment changes in elastics and Forsus™
groups.
Positive signs indicate movements in a direction which aids Class II correction
(distal movements in the maxilla/mesial movements in the mandible), negative signs
indicate movements which make Class II occlusion more severe (mesial movements in the
maxilla/distal movements in the maxilla).
_ Elastics Group_
__Forsus™ Group_
80
Variable
Units
mean
SD
mean
SD
Max
mm
-1.5**
1.3
-1.7**
1.1
.47
Mand
mm
3.8**
2.5
4.4**
2.2
.33
ABCH
mm
2.3**
1.7
2.6**
1.8
.44
U6
mm
-0.6**
1.1
-1.2**
1.5
.06
L6
mm
0.7**
1.3
1.8**
1.5
< .00
U6/L6
mm
2.4**
1.2
3.2**
1.7
.03
U1
mm
2.0
.50
L1
mm
-0.3
2.6
-0.7
Sig
2.0
1.2**
2.2
.42
0.8*
U1/L1
mm
2.8**
2.2
3.2**
1.9
.47
Bold values indicate statistical significance between groups (p < .05)
* denotes changes are significant at p< .05
** denotes changes are significant at p< .01
Table 3.5: Comparison of pre and post-treatment variables and treatment changes in
elastics and Forsus™ groups.
____Pre-Treatment
_
Elastics
Forsus™
Var
units mean
SD
___Post-Treatment__ _
Elastics Forsus™
mean
SD
Sig mean
SD
103.1 7.9
98.3
8.5
.01 103.7 5.8
mean
SD
Treatment Changes _
Elastics
Forsus™
Sig mean
SD
mean
SD
Sig
81
7.3 .28
0.6
9.3
3.7*
8.9
.16
3.5 .80
1.2**
2.1
0.5
2.3
.24
2.5 .41
2.0**
2.0
1.5**
1.7
.20
.48
99.7 5.9 100.9 8.2 .49
3.8**
5.5
6.3**
7.0
.11
7.4
.41
77.4 6.0
74.0 7.9 .04 -3.7**
5.4 -5.9**
6.4
.14
25.2
2.8
.16
29.3 2.6
28.5 3.1 .28
1.9
2.0
.86
19.2
4.1
.16
16.9 4.0
19.0 4.1 .03 -1.0
3.3
.34
U1-SN
deg
U1ANSPNS
mm
25.9 2.8
26.6
2.8
.21
27.0 3.1
U6ANSPNS
mm
18.3 2.2
18.4
2.3
.87
20.3 2.4
L1-GoMe
deg
95.8 6.2
94.6
8.0
L1-GoMe
mm
81.1 6.3
79.8
L6-GoMe
mm
26.1 2.0
OP-SN
deg
17.9 3.8
102.0
27.2
19.9
3.2**
3.3**
3.2 -0.2
Bold values indicate statistical significance between groups (p < .05)
* denotes changes are significant at p< .05
** denotes changes are significant at p< .01
Vita Auctoris
Graham Christopher Jones was born on November 6, 1977
in Los Angeles, California.
In 1987 he and his family
moved to Costa Rica, where they served as missionaries for
one year.
In 1991 he and his family moved to Des Moines,
WA and he attended Seattle Christian School.
He attended
Highline College in MidWay, WA from 1995-1996, Simpson
College in Redding, CA from 1996-1999, Shasta College in
Redding, CA from 1997-1999, and San Francisco State
University in San Francisco, CA from 1999-2000.
He
received his B.A. degree in Liberal Studies from Simpson
College in 1999.
Graham was a member of the men’s baseball
and basketball teams at Simpson College and has spent time
in Guatemala and the Philippines as part of an evangelical
basketball team.
In January 2000 he married Erika June
Dilley in Palmer, AK.
He entered dental school at the
University of California at San Francisco (UCSF) in 2000.
In 2004 he received his D.D.S. from UCSF.
Following
graduation from dental school, he began his studies at
Saint Louis University, in pursuit of a Master’s Degree
from the Orthodontics program.
Upon graduation in January
2007, he, his wife, Erika, and their son, Justus, will
relocate to the state of Washington where he will begin his
career as an orthodontist.
82