Relapse studies

CRITICAL REVIEW OFCRITICAL REVIEW OF
LONG TERM RELAPSELONG TERM RELAPSE
STUDIESSTUDIES

 INTRODUCTION
 TERMINOLOGY OF POSTORTHODONTIC CHANGES
 RETENTION AND RELAPSE-DEFINITIONS
 DIFFERENT SCHOOLS OF THOUGHT FOR RELAPSE
 BASIC THEORMS FOR RELAPSE
 CAUSATIVE FACTORS FOR RELAPSE
 TREATMENT CHANGES IN DENTITION AND
STUDIES FOR ITS RELAPSE
 EXTRACTION VS NON-EXTRACTION TREATMENT
– RELAPSE STUDIES
 ANTERIOR OPEN BITE AND RELAPSE STUDIES
 ORTHOPEDIC TREATMENT AND RELAPSE
 FUNCTIONAL APPLIANCE TREATMENT AND
RELAPSE
 ORTHOGNATHIC SURGERY AND RELAPSE
STUDIES
 CONCLUSION

INTRODUCTIONINTRODUCTION
Relapse can be defined as a return toward the preexisting
(pretreatment) condition, and relapse of teeth after
orthodontic treatment has been a topic of persistent
interest throughout most of this century.
Angle stated that “The problem involved in retention is
so great as to test the utmost skill of the most competent
orthodontist, often being greater than the difficulties
being encountered in the treatment of the case up to this
point.”
Tweed stated that determining the anterior limits of the
denture was the key to stability.

Mershon stated that the final position of the teeth was like
“an argument with Mother Nature,” who always won.
Hawley said that he would “give half of his fee to anyone
who would be responsible for the retention of his results
when the active appliance was removed.”
Almost most of the conditions like mandibular anterior
crowding, arch length and width, arch form, deep bite,
anterior open bite, tooth rotations, and treatment approaches
like intrusion, arch expansion, extractions, functional
appliance therapy, orthopedic treatment and orthognathic
surgeries showed the tendency for relapse after treatment
over prolonged period of time.

A major objective of orthodontic treatment is to achieve
long-term stability of the occlusion. Most studies of
relapse have examined patients within 5 years of
orthodontic treatment; few studies of people treated a
decade or more in the past have been published.
Recently various authors studied relapse on a long-term
basis to assess the stability and outcome of orthodontic
treatment.

TERMINOLOGY OF POSTORTHODONTICTERMINOLOGY OF POSTORTHODONTIC
CHANGESCHANGES
PHYSIOLOGIC RECOVERY
Horowitz and Hixon (1969) explain physiologic
recovery as the change to the original physiologic state
after completing treatment.
DEVELOPMENTAL CHANGES
Developmental changes are those which occur
irrespective of whether orthodontic treatment was
implemented or not. These changes could easily be
overlooked when assessing posttreatment relapse.

GROWTH RECOVERY
Skeletal alterations or orthopedic metamorphosis can
be induced as part of phase 1 or early treatment in the
young patient when growth processes are still active.
Factors such as the genetic characteristics, the force of
gravity, and the skeletal pattern become reoperative and
express themselves again. Subsequently, growth
patterns will “recover” from the original treatment
changes and a second metamorphosis back to the
originally determined genetic pattern is seen to occur,
especially in the mandible. This type of change is not
relapse, but rather unfortunate growth changes.

POSTRETENTION SETTLING
Settling can be described as the establishment of a
desired position, the act of ceasing to move or “settling
down” and maintaining a correctly balanced position.
This term thus indicates the posttreatment changing
process versus a term such metaposition, which refers to
the meticulously planned changes after the removal of
the orthodontic appliances.
METAPOSITION
Metaposition denotes the desirable and expected
posttreatment changes that are anticipated (Ricketts,
1993). These changes are not relapse and must be part
of thet treatment itself.

RECIDIEF
The term “recidief” has been used to describe changes
that occur from the end of treatment back to the
original situation (Dermaut, 1974).
IMBRICATION
Imbrication is the term often used to describe incisor
irregularity or crowding whether seen before or after
treatment.

RELAPSE AND RETENTION - DEFINITIONSRELAPSE AND RETENTION - DEFINITIONS
RELAPSE
Robert Moyers states that relapse is the term applied to the
loss of any correction achieved by orthodontic treatment.
Horowitz and Hixon (1969) defined relapse in general as
‘changes in tooth position after orthodontic treatment’.
Riedel (1976) believed that the word ‘relapse’ was too harsh a
description of the changes that follow orthodontic treatment
and he preferred the term “posttreatment adjustment” for these
changes.

Enlow (1980) defined relapse as “ a histogenetic and
morphogenic response to some anatomical and
functional violation of an existing state of anatomic
and functional balance.” It is usually thought of as a
“rebound” movement in which teeth recoil back
somewhere close to their original positions once
retentive forces are moved.
The orthodontist must distinguish the rapid relapse
occurring during the period of remodeling of
periodontal structures, from the slow relapse which
responds to late changes occurring during the post-
retention period.

RETENTION
Moyers (1973) defined retention as “the holding of teeth
following orthodontic treatment in the treated position for the
period of time necessary for the maintenance of the result.”
Joondeph and Riedel (1985) explain retention as “the holding
of teeth in ideal aesthetic and functional positions.” Retention is
accomplished by a variety of mechanical appliances.
DIFFERENT SCHOOLS OF THOUGHT FOR RELAPSEDIFFERENT SCHOOLS OF THOUGHT FOR RELAPSE
THE OCCLUSION SCHOOL
Kingsley (1880) stated, “The occlusion of the teeth is the most
potent factor in determining the stability in a new position”.

THE APICAL BASE SCHOOL
In the middle 1920s a second school of thought formed around
the writings of Axel Lundstrom (1925), who suggested that
the apical base was one of the most important factors in the
correction of malocclusion and maintenance of a correct
occlusion. McCauley (1944) suggested that intercanine width
and intermolar width should be maintained as originally
presented to minimize retention problems. Strang (1958)
further enforced and substantiated this theory. Nance (1947)
noted, “Arch length may be permanently increased to a limited
extent.

THE MANDIBULAR INCISAL SCHOOL
Grieve (1944) and Tweed (1952) suggested that the
mandibular incisors must be kept upright and over basal
bone.
THE MUSCULATURE SCHOOL
Rogers (1922) introduced a consideration of the necessity
of establishing proper functional muscle balance.

BASIC THEORMS FOR RELAPSEBASIC THEORMS FOR RELAPSE
Riedel (1975) has discussed a number of popular
explanations of retention and relapse.
THEORM 1: Teeth that have been moved tend to return to
their former positions.
THEORM 2: Elimination of the cause of malocclusion will
prevent recurrence.
THEORM 3: Malocclusion should be overcorrected as a
safety factor.
THEORM 4: Proper occlusion is a potent factor in holding
teeth in their corrected positions.
THEORM 5: Bone and adjacent tissues must be allowed to
reorganize around newly positioned teeth.

THEORM 6: If lower incisors are placed upright over
basal bone, they are more likely to remain in good
alignment.
THEORM 7: Corrections carried out during periods of
growth are less likely to relapse.
THEORM 8: The farther teeth have been moved, the less
likelihood of relapse.
THEORM 9: Arch form, particularly in the mandibular
arch, cannot be permanently altered by appliance therapy.
An additional theorem added to Riedel’s theorem is,
THEOREM 10: Many treated malocclusions require
permanent retaining devices.

CAUSATIVE FACTORS FOR RELAPSECAUSATIVE FACTORS FOR RELAPSE
Many potential causative factors of relapse have been
discussed, accompanied by cause-and-effect conclusions for
clinical guidelines. These include,
1) Patient age
2) Length of retention
3) Mandibular rotation
4) Arch dimensions
5) Third molars
6) Tooth size
7) Apical base
8) Position of mandibular incisors
9) Oral habits, and the skill of the operator

Most of these causative factors may be related to,
a) Craniofacial growth
b) Dental development
c) Muscle function
CRANIOFACIAL GROWTH
 Bjork (1968) showed the high variability of normal
facial growth in one of his first studies describing the use
of metal implants in cephalometrics. Late growth changes
may be responsible for posttreatment relapse, especially
after correction of class III malocclusion.
 Growth and changes in muscles and surrounding soft
tissue structures are relatively well synchronized with the
growth of the skeletal framework.

 The craniofacial complex is regarded as a structure with
specific functions, classified as functional cranial
components, and consisting of a functional matrix and a
skeletal unit, which protects and supports this matrix. It has
been shown that parts of the functional matrix have a direct
influence on the bone during orthodontic treatment.
 Relapse of the overjet and overbite has been observed and
has been mainly due to changes in incisor inclination. The
tendency to relapse is slightly greater in class II division 2
cases than in class II division 1 cases.

 As the maxillary growth is completed on average 2 to 3
years before mandibular growth, dentoalveolar structures may
have difficulties in compensating for this discrepancy, which
may result in an increased overbite.
Bjork (1972) and Sakuda (1976) showed that the
dentoalveolar structures may be influenced by the facial
morphology.
 Permanent teeth in low angle cases should have a more
anteriorly directed path of eruption than in normal individuals,
which, together with a deep bite, might unfavourably
influence the stability in the lower anterior region.
 Mandibular incisor crowding is also believed to be related
to anterior (upward) rotation of the mandible.

DEVELOPMENT OF THE DENTITION
Continuous eruption of teeth→ The physiologic changes
of the dentition from early childhood into adolescence,
and from young adulthood into adulthood are gradual
process. A slight continuous eruption of teeth has been
observed even after the establishment of occlusion post
adolescence.
Arch length changes→ The arches reduce sagittally until
the age of 14 years and even later. Crowding of the lower
incisors quite commonly develops in modern man and
coincides with this decrease in arch length.

Tooth size→ The mesiodistal tooth size has been
discussed as a causative factor of the late crowding.
Begg (1954) analyzed interproximal attrition in old
Australian aborigines and concluded that teeth in modern
man are too large for the dental arches and hence become
crowded. Corrucini (1990) showed that small jaws rather
than large teeth underlie tooth-arch discrepancy.
Mandibular 3rd
molars→ Richardson (1989) stressed that
the third molar plays a passive role in the development of
late lower arch crowding.

Arch width changes→ Richardson (1995) showed that
increased lower arch crowding could be found in
association with both increased and decreased arch width,
depending on the direction of movement of the canines.
Decrease of the mandibular intercanine width is generally
considered to be associated with late lower crowding.
Because dental development continues at a slow persistent
rate from adolescence into adulthood, there is no definitive
method to distinguish between normal age-related events
and relapse after orthodontic treatment.

SOFT TISSUE MATRIX
The dentoalveolar changes are not only the result of the
influence of growth on tooth movements but also a function of
the soft tissue matrix surrounding the hard tissue structures. It
has been stressed that in the absence of muscular imbalance, a
well-established interdigitation may greatly assist in maintaining
the end result of tooth movement.
Establishing the most precise intercuspal relationship
between dental arches will not prevent relapse from occurring if
a strong adverse muscular pressure exists.
It is therefore important to stress that if a malocclusion, caused
or maintained by muscular or other soft tissue dysfunction, has
been morphologically corrected without any alteration in
muscular behaviour, a stable posttreatment result is unlikely.

TREATMENT TIME / PATIENT’S AGE
Corrections carried out during periods of growth and
eruption of teeth is considered to be less likely to
relapse.
According to Reitan (1967), there will be little or no
relapse following orthodontic movement of an erupting
tooth, because of its supporting tissues are in a stage
proliferation as a result of the eruption process.
New fibers will be formed as the root develops, and
these new fibers will assist in maintaining the new
tooth position.

PERIODONTAL FORCE AND RELAPSE
Southard and Tolley in AJO 1992 investigated the
interproximal force (IPF) at the mandibular first molar-
second premolar contact and determined that whether the
periodontium maintains the contacts of approximating
mandibular teeth in a continuous state of compression.
Results indicated that,
Contacts of approximating mandibular teeth are maintained
in a continuous state of compression. This compressive
force is generated by the supporting periodontium and acts
through the dental contact points, even when the dental
arches are apart. Further, this force is increased for a period
after chewing.

If inter proximal force (IPF) does exert an
influence on dental alignment, it probably
acts in conjunction with lip and cheek
forces to collapse the arch and is opposed
by tongue force, which tends to expand
the arch.
It follows that the influence of IPF should
be more evident in the anterior region of
the arch where the contact points are
narrower, the crowns more tapered, and
the expansive force from the tongue more
intermittent than in the posterior region of
the arch.

The existence of a continuous, compressive force
(IPF), originating in the periodontium and acting on
approximating teeth at their contact points, which is
increased after occlusal loading, may help to explain long-
term posttreatment crowding of the mandibular anterior
teeth, physiologic drifting of teeth, and maintenance of
posterior dental contacts after interproximal wear.

TREATMENT CHANGES IN DENTITION ANDTREATMENT CHANGES IN DENTITION AND
STUDIES FOR ITS RELAPSESTUDIES FOR ITS RELAPSE
LONG TERM STABILITY OF ORTHODONTIC
TREATMENT
Bishara (AJO 1963) examined the tendency for
overbite, overjet and intercanine width to return toward
the original condition. In a sample of 31 patients with
four bicuspid extractions and edgewise mechanics, he
studied the stability of treatment a minimum of six
months out of retention.

He found that,
 The percentage of overbite relapse was clearly
greater than that of overjet relapse.
 The maxillary intercanine width was more stable than
the mandibular intercanine width.
 He pointed out that this may be explained by the fact
that “whereas the mandible continues to grow
downward and forward, the maxilla is more stable” and
that “the lower dentition is confined within the
maxillary arch thereby assuming a smaller arch length
over time.”

Sadowsky and Sakols in AJO 1982 evaluated the long-term
stability of orthodontic treatment in a group of ninety-six
former patients who were treated between 12 and 35 years
previously with a full-banded edgewise appliance prior to
adulthood, with an average posttreatment time of 20 years.
Patients had Class I and Class II malocclusions only.
The Class I cases were almost equally divided between
extraction and nonextraction treatment approaches, while
almost twice as many of the Class II cases were treated with a
nonextraction approach as were treated with an extraction
approach.

They concluded that,
 It was apparent that many years after orthodontic treatment
a large number of cases (72 percent) exhibited dental
relationships that were outside an ideal range.
 In most cases, however, patients showed an improvement in
their occlusions over the long term.
 In contrast, the long-term result as compared to the original
malocclusion exhibited increased overbite in fourteen cases
(16 percent), increased mandibular anterior crowding in nine
cases (9 percent), and increased overjet in five cases (5
percent).
 It is suggested that orthodontists should be well aware of
long-term changes in dental relationships many years after
treatment and take these into account when advising patients
as to the potential benefits of orthodontic treatment.

Uhde et al (Angle 1983) examined the posttreatment
changes in 72 patients treated with edgewise mechanics,
of which 27 had extractions and 45 were treated by non-
extraction means.
Retention of the teeth was done with an upper Hawley
type appliance and a lower fixed lingual retainer.
The patients were from 12 to 35 years out of retention
when the study was performed.

The findings were that,
 Overbite and overjet tended to increase irrespective of
the initial malocclusion.
 The molar relationships shifted slightly toward Class II
with time, and the intercuspid width was in general unstable
in the lower arch and more stable in the upper arch.
 All groups showed some posttreatment crowding in the
lower arch, but less than the pretreatment.
 No difference was found in the amount of postretention
crowding between patients with extractions and those
without extractions.

Vaden and Harris in AJO 1997 quantified changes in tooth
relationships in a series of 36 patients who were treated with
premolar extractions and fixed conventional edgewise
appliances and evaluated at 6 years and again at 15 years after
treatment. They concluded that,
 The maxillary and mandibular arches became shorter and
narrower with age.
 More than half (58%) of the mandibular incisor irregularity
index correction was maintained. At the second recall
examination, 15 years after treatment, the mandibular incisor
irregularity index averaged 2.6-well within the range termed
"minimal irregularity" by Little.

 Most of the posttreatment mandibular incisor irregularity
in this sample was at the lateral incisor-canine contact area,
with the canine slipping anterior to the lateral incisor, giving
the arch a square appearance. This slippage at the lateral
incisor-canine contact area may have resulted from the
canine's return to the pretreatment intercanine width or from
the anterior component of force.
 Most (96%) of the maxillary incisor irregularity
correction was maintained. At the second recall, the
maxillary irregularity index was only 1.8.
 More than 90% of the patients in this study were better
off 15 years after treatment than they were before treatment.

Burleigh in AJO 1998 used a case-control study
design to test whether pretreatment malalignment in
terms of irregularity and spacing of the maxillary
anterior teeth and the quality of the orthodontic
alignment are of significance for postretention
relapse of alignment.
Sets of study models made before and after
orthodontic treatment, and long-term out of retention
of 745 patients were screened.

The results suggest that,
 Anatomic contact point displacement of the maxillary
anterior teeth and maxillary incisor rotation relative to the
dental arch, as well as interdental spacing before treatment,
are significant risk factors for postretention relapse of
alignment.
 The pattern of postretention contact point displacement
and interdental spacing may be random relative to the
pattern of initial tooth positions, whereas the pattern of
rotational displacement relative to the dental arch has a
strong tendency to repeat itself.

Al Yami et al in AJO 1999 studied the stability of
orthodontic treatment after 10 years postretention. Dental
casts of 1016 patients were evaluated for the long-term
treatment outcome using the Peer Assessment Rating (PAR)
index. The PAR index was measured at the pretreatment
stage, directly posttreatment, postretention, 2 years
postretention, 5 years postretention, and 10 years
postretention.

 The results indicate that 67% of the achieved orthodontic
treatment result was maintained 10 years postretention.
 About half of the total relapse (as measured with the PAR
index) takes place in the first 2 years after retention. All
occlusal traits relapsed gradually over time but remained
stable from 5 years postretention with the exception of the
lower anterior contact point displacement, which showed a
fast and continuous increase even exceeding the initial score.
 The results of this type of studies enable clinicians to
inform their patients about treatment limitations in order to
better meet their expectations.

ARCH LENGTH, ARCH WIDTH AND ARCH FORM
CHANGES
It is generally agreed that arch form and width should be
maintained during orthodontic treatment and in certain cases,
where arch development has occurred under adverse
environmental conditions, arch expansion as a treatment goal
may be tolerated.
Studies by Welch (1956), Amott (1962), Arnold (1963), and
Kahl-Nieke (BJO 1995) show the evidence that intercanine
and intermolar widths decrease during the postretention
period, especially if expanded during treatment. For this
reason, the maintenance of arch form rather than arch
development is generally recommended.

Shapiro (AJO 1974) studied the posttreatment stability of
patients with Class I and Class II malocclusions, treated with
and without extractions and found that Class II division 2
cases had a greater ability to maintain intercanine width
increases in the lower arch than Class II division 1 and Class I
cases. He further noted that the arch length reduction during
treatment in the Class II division 2 cases was less than in the
other types of malocclusions.
This statement, however, was based on a sample of six
patients and was not accepted by Little et al (AJO 1981) who
explained that intercanine and intermolar width will relapse if
expanded in Class II Division 2 cases as much as in other
Angle classifications.

DEEP BITE CORRECTION AND ITS RELAPSE
Correcting deep bite can be accomplished by true
intrusion of anterior teeth, extrusion of posterior teeth,
or a combination of intrusion and extrusion.
The results of most studies concerning the stability of
overbite correction indicate a decrease in overbite
during treatment followed by as increase in overbite
after appliance removal.

Simons (AJO 1973) found that patients with an initially
deep overbite had the deepest overbite 10 years
postretention and that protrusion of incisors was correlated
with overbite relapse but was not related to whether or not
extractions were performed. He believed that occlusal plane
changes during treatment tended to relapse to their original
angulation, and this correlated with deep bite relapse. He
concluded that mandibular growth, with a vertical
component, was correlated with overbite stability.

Most studies evaluating overbite stability are those in
which the overbite was corrected by molar extrusion.
Schudy (Angle 1968) stated that the lower incisors have a
very strong tendency to extrude in the posttreatment
period and should never be intruded unless unavoidable.
Creekmore (1967) and Zingeser (1964) also reported
that incisors should not be intruded except in rare
circumstances in which no vertical growth is occurring.
This is because molar extrusion to correct deep overbite in
patients with no vertical growth is difficult and unstable.

Dake and Sinclair (AJO 1989) studied the stability of
incisor intrusion as a method of correcting deep bite. They
studied incisor intrusion with the utility arch in 30 Class II
patients with an overbite of more than 50 percent. All of
these patients were treated without extraction while they
were still growing. They found that after treatment,
 Maxillary incisors uprighted and extruded about 2 mm
after being intruded an average of only 1.2 mm. Since all
measurements were made at the incisal edge, it is
questionable if true intrusion was achieved or just flaring
and molar extrusion.

 However, deep overbite was successfully treated in
these patients since molar extrusion and growth did
occur during and following treatment.
 Lower incisor intrusion during treatment was not
associated with posttreatment overbite relapse.
 They also noted overbite relapse of 20 percent
using reverse curve of Spee wire mechanics and
overbite relapse of 34 percent in then group treated
with utility arch mechanics.

MANDIBULAR ANTERIOR CROWDING - RELAPSEMANDIBULAR ANTERIOR CROWDING - RELAPSE
STUDIESSTUDIES
Fastlicht in AJO 1970 compared the degree of crowding of
the anterior teeth in cases, which were treated
orthodontically years before with those which were not
treated, in order to determine whether treatment had had an
influence through time on the crowding of the incisors, and
clarified the causes of mandibular crowding. Sample
consisted of two groups orthodontically treated and
untreated of 28 patients in each group.

The conclusions derived were,
 The crowding of the incisors was an anatomic-
physiologic phenomenon of adaptation observed in
orthodontically treated cases, as well as in untreated cases,
which resulted from the combination of several factors,
such as sex, anatomic predisposition dolichocephalic or
long-faced persons, tooth-size discrepancies, exaggerated
overbite, extrusion of the canines, reduction of the
intercanine width, age, muscle function, and, in some
cases, imperfect mechano-therapy.
 There was less crowding of the incisors in the treated
group. Thus, it is assumed that treatment has a favorable
influence over the stability of the dental arches.

 The larger the mesiodistal width of the incisors, the greater
the crowding will be, if there is a lack of proportion.
 Maxillary and mandibular incisors were larger in males.
 Crowding of the mandibular incisors was more noticeable
in males.
 The third molars were not related to crowding of the
incisors.
 Age was a positive but secondary factor in crowding of the
incisors.
 In general, the values and differences of the variables
between sexes turned out to be more regular and significant in
females.
 Positional changes of teeth were noted to be less in the
maxilla than in the mandible.

Little, Wallen in AJO 1981 evaluated the mandibular
anterior alignment, using serial long-term dental cast
records of cases treated by conventional edgewise
orthodontic means following removal of all four first
premolars. Sixty-five cases with complete records before
treatment, at the end of treatment, and a minimum of 10
years out of retention (at least 10 years after complete
removal of all retainer devices) were taken.

 Long-term alignment was variable and unpredictable.
 No descriptive characteristics, such as Angle class, length
of retention, age at the initiation of treatment, or sex, and no
measured variables, such as initial or end-of-active-treatment
alignment, overbite, overjet, arch width, or arch length, were
of value in predicting the long-term result.
 Arch dimensions of width and length typically decreased
after retention whereas crowding increased. This occurred in
spite of treatment maintenance of initial intercanine width,
treatment expansion, or constriction.
Success at maintaining satisfactory mandibular anterior
alignment is less than 30 percent, with nearly 20 percent of the
cases likely to show marked crowding many years after
removal of retainers.

Pretreatment, end of treatment, 10-year postretention, and 20-
year postretention records of 31 four premolar extraction
cases were assessed by Little, Riedel, and Årtun in AJO
1988 to evaluate stability and relapse of mandibular anterior
alignment. This study is a sequel to the previous study by
Little and Wallen in AJO 1981.The results showed that,
 Crowding continued to increase during the 10- to 20-
year postretention phase but to a lesser degree than from the
end of retention to 10 years postretention.
 Only 10% of the cases were judged to have clinically
acceptable mandibular alignment at the last stage of
diagnostic records.
Cases responded in a diverse unpredictable manner with no
apparent predictors of future success when considering
pretreatment records or the treated results.

Jon Årtun, Garol and Little in Angle 1996 evaluated
the long-term stability of mandibular anterior alignment
in a large group of Class II, Division 1, patients who
demonstrated successful occlusal results at the end of
active treatment. Sets of study models and cephalograms
of 33 males and 45 female patients made before, after
orthodontic treatment and long-term postretention (14
years out of retention) were examined. The results
demonstrated,
 An increase of incisor irregularity and a reduction
of intercanine width and arch length postretention.

 Long-term changes in incisor alignment are highly variable,
and chances of maintaining incisor alignment are less than
50%, despite successful occlusal results at the time of
appliance removal.
 Narrow pretreatment intercanine width and high
pretreatment incisor irregularity were significant predictors of
relapse. Treatment increase of intercanine width and
postretention decrease of intercanine width and arch length
were associated with relapse.
 These results may support a rationale for “semi-permanent”
retention of the mandibular anterior segment following
appliance removal.

Anwar Ali Shah in AJO 2003 reviewed the mandibular
incisor postretention stability outcomes in the setting of
different treatment techniques and different ages of
beginning orthodontic treatment. He reviewed
posttreatment studies by various authors and concluded
that,
 All the studies reviewed demonstrate all the inherent
problems of a retrospective study.
 Randomized controlled trials would be the best solution;
these are currently difficult due to problems with ethical
approval, difficulty of a long term follow-up, and drop out
of patients from the study.

 Unless a study can be designed in which both
groups, extraction and non-extraction, are equally
likely to make either decision, no valid conclusion can
be derived.
 Mandibular incisor relapse seems to be minimal
when palatal expansion is combined with a prolonged
retention period.
 In the future, it would be interesting to study
mandibular relapse in patients having palatal
expansion and also comparable retention periods as
patients having first premolar extractions.

ROLE OF MANDIBULAR 3ROLE OF MANDIBULAR 3RDRD
MOLARS INMOLARS IN
MANDIBULAR ANTERIOR CROWDINGMANDIBULAR ANTERIOR CROWDING
Richardson in AJO 1989 reviewed the evidence in support
of the theory that the presence of a third molar is one of the
causes of such crowding and found that,
 Late lower arch crowding in the untreated individuals
during the postadolescent period is caused by pressure from
the back of the arch and presence of a third molar is the
cause of late lower arch crowding. This does not preclude
the involvement of other causative factors.
 The cause of late crowding may differ from one subject to
another or there may be more than one factor contributing to
the development of late crowding in any one individual.

Studies Relating Third Molars to Crowding of the Dentition
Bergstrom and Jensen’s study (1961) was designed to
determine the extent to which third molars are responsible for
secondary tooth crowding. They concluded that the presence of a
third molar appeared to exert some influence on the development
of the dental arch but not to the extent that would justify either
the removal of the tooth germ, or the extraction of the third
molars, other than in exceptional instances.
In another study, Vego (Angle 1962) longitudinally examined 40
individuals with lower third molars present and 25 patients with
lower third molars congenitally absent. He concluded that the
erupting lower third molars can exert a force on the neighboring
teeth. He also indicated, that there are multiple factors involved
in the crowding of the arch.

Retrospective studies indicating a lack of correlation between
mandibular third molars and postretention crowding
Kaplan (AJO 1974) investigated whether mandibular third
molars have a significant influence on posttreatment changes
in the mandibular arch, specifically on anterior crowding
relapse. He concluded that the presence of third molars does
not produce a greater degree of lower anterior crowding or
rotational relapse after cessation of retention. According to
Kaplan, the theory that third molars exert pressure on the
teeth mesial to them could not be substantiated.

Ades et al, Joondeph and Little (AJO 1990) in their
cephalometric study, found no significant differences in
mandibular growth patterns between the various third
molar groups whether erupted, impacted or
congenitally missing, also with and without premolar
extractions. They concluded that there is no basis for
recommending prophylactic third molar extractions to
alleviate or prevent mandibular incisor crowding.

Bishara in AJO 1999 reviewed the various pertinent
studies that studied the role of third molars in lower
anterior crowding. He concluded that,
 The influence of the third molars on the alignment of
the anterior dentition may be controversial, but there is no
evidence to incriminate these teeth as being the only or
even the major etiologic factor in the posttreatment
changes in incisor alignment.
 The evidence suggests that the only relationship
between these two phenomena is that they occur at
approximately the same stage of development, i.e., in
adolescence and early adulthood. But this is not a cause
and effect relationship.
If extraction is indicated, third molars should be removed
in young adulthood rather than at an older age.

CURVE OF SPEE AND ITS RELAPSECURVE OF SPEE AND ITS RELAPSE
Kyle R. Shannon in AJO 2004 evaluated the
treatment of the curve of Spee and its stability after
treatment. The mean posttreatment period was 2 years
8 months, with a range of 2 years to 5 years 8 months.
There were 23 Class I, 21 Class II division 1, and 6
Class II division 2 patients out of whom 20 were
treated as extraction and 30 as non-extraction cases.
Results showed that,
 The mesiobuccal cusp of the first molar was most
commonly the deepest part of the curve followed
closely by the distobuccal cusps of the first molar and
the second premolar.

 Smaller mandibular plane angle, smaller FOP-MP angle,
mesially inclined first and second molars, deep overbite, and
increased overjet all correlated with deeper pretreatment
curve depth.
 The mesiobuccal cusp of the first molar relapsed 20% and
continued to be the deepest part of the curve.
 Patients with fixed retainers after treatment exhibited
significantly less relapse than those with removable
mandibular retainers.
 This study found no relationship between skeletal
measurements (FMA, ANB, PFH, LAFH) to curve of Spee
relapse. This is in contrast to findings by Givins (1970), who
found more relapse in patients with low mandibular plane
angles.

 No significant differences in curve of Spee relapse were
found between Class I, Class II division 1, or Class II
division 2 malocclusions and also between extraction and
non-extraction groups.
 Patients with more second molar uprighting during
treatment exhibited more curve relapse than those with less
molar uprighting.
 The more the curve of Spee was leveled with treatment,
the more it relapsed after treatment.

EXTRACTION VS NON-EXTRACTIONEXTRACTION VS NON-EXTRACTION
TREATMENT – RELAPSE STUDIESTREATMENT – RELAPSE STUDIES
The controversy regarding the role of extractions in
preventing relapse of orthodontic treatment still exists
after nearly a century of debate.
Kuftinec and Strom (AJO1975) examined 50 cases, 25
extraction and 25 non-extraction, four months or more
after discontinuing retention and found that lower incisor
relapse was greater in non-extraction cases.

Sandusky (1983) reported on postretention stability of 85
extraction cases treated by Tweed and Tweed Foundation
members. He reported less than 10 percent relapse of the
lower incisors using Little’s irregularity index. He found the
lower incisors tended to move forward postretention and the
occlusal plane-Frankfort horizontal plane-angle decreased.
Glenn in AJO 1987 studied 28 cases of non-extraction
treatment an average of eight years postretention. He found
that incisor irregularity increased slightly postretention. Lower
incisors were proclined during treatment and tended to remain
stable postretention. Class II malocclusions with large ANB
differences showed the most lower relapse postretention.

Little and Riedel in Angle 1990 evaluated 30 patients who had
undergone serial extraction of deciduous teeth plus first
premolars followed by comprehensive orthodontic treatment and
retention. Records were taken for the stages pre-extraction, start
of active treatment, end of active treatment, and a minimum of 10
years postretention. All cases were treated with standard
edgewise mechanics and were judged clinically satisfactory by
the end of active treatment.
Results showed that,
 Twenty-two of the 30 cases (73%) demonstrated clinically
unsatisfactory mandibular anterior alignment postretention.
 Intercanine width and arch length decreased in 29 of the 30
cases by the postretention stage.
 There was no difference between the serial extraction sample
and a matched sample extracted and treated after full eruption.

McReynolds, Little in Angle 1991 evaluated the
dental casts and cephalometric radiographs of 46
patients, treated with mandibular second premolar
extraction and edgewise orthodontic mechanotherapy,
for changes over a minimum 10-year postretention
period. The sample was divided into two groups: early
(mixed dentition) extraction of mandibular second
premolars and late (permanent dentition) extraction of
mandibular second premolars.

Results showed,
 No difference in long-term stability between the two
groups. Arch length and arch width decreased with time
and incisor irregularity increased throughout the
postretention period.
 No predictors or associations could be found to help the
clinician in determining the long-term prognosis in terms
of stability. The sample was regrouped according to the
postretention degree of incisor irregularity.
 Statistically significant differences in cephalometric
measurements were found between the minimally crowded
group and the moderately to severely crowded group.

Paquette, Beattie, and Johnston in AJO 1992 compared
the long-term effects of extraction and nonextraction
edgewise treatments in 63 patients with Class ll, Division 1
malocclusions. A lateral cephalogram, study models, and a
self-evaluation of the esthetic impact of treatment were
obtained from each of the 33 extraction and 30
nonextraction subjects. The average posttreatment interval
was 14.5 years. They concluded that,
 For the borderline patient, nonextraction treatment
produced a significantly more protrusive denture (about 2
mm), both at the end of treatment and at recall over a decade
later.

 Despite the significant between-treatment differences,
the majority of the subjects in both groups showed less
than 3.5 mm of lower anterior irregularity.
 In general, the pattern of relapse was unrelated to the
type of treatment or to the posttreatment position and
orientation of the denture and, instead, appears to
constitute a dentoalveolar compensation produced by the
differential growth of the jaws following treatment.
 Ultimately, both the overjet and molar corrections
were derived almost entirely from the differential growth
of the jaws, rather than tooth movement relative to basal
bone

Luppanapornlarp and Johnston in Angle 1993 assessed
the anatomical basis of the extraction/nonextraction
decision and performed a long-term comparison of
outcomes in “clear-cut” extraction and nonextraction
Class II patients. They concluded that,
 Premolar extraction reduces soft- and hardtissue
convexity by 2–3 mm, whereas nonextraction therapy has
little effect
 In general, posttreatment changes (including an
additional convexity reduction) are about the same in both
groups

 When growth is finished, clear-cut nonextraction
patients tend to have “flatter” profiles than do premolar-
extraction patients who present with ponderable
crowding and spacing
 Pre- and posttreatment tooth movements tend to be
related to the pattern of jaw-growth; some forms of
relapse, therefore, may be a dentoalveolar compensation
for residual posttreatment growth.
 In nonextraction treatment, the upper buccal
segments are commonly “distalized,” whereas they tend
to come forward if premolars have been extracted.

Elms, Buschang and Alexander in AJO 1996 evaluated the
long-term stability of Class II, Division 1 in 42 patients (34
females and 8 males) treated with nonextraction cervical face
bow therapy. Model analysis and cephalometric analysis were
performed. The results showed that,
 Mandibular intercanine width decreased 0.3 mm during the
postretention period; the remaining width measures increased
or remained stable.
 Arch length, which did not change during treatment,
decreased 1.0 mm after treatment.
 Both overjet (0.5 mm) and overbite (0.4 mm) showed small
increases after retention.
 Mandibular incisor irregularity was decreased 2.7 mm
during treatment and increased only 0.4 mm after treatment.

ANTERIOR OPEN BITE AND RELAPSE STUDIESANTERIOR OPEN BITE AND RELAPSE STUDIES
Anterior openbite malocclusion is considered one of the
most difficult problems to treat by any means. Proper
diagnosis, successful treatment, and long-term retention of
openbite malocclusion have been a constant subject of
discussion and research studies.
Lopez-Gavito and Wallen in AJO 1985 evaluated the
long-term response of the anterior open-bite malocclusion
in forty-one white subjects who had undergone orthodontic
treatment and were out of retention a minimum of 9 years 6
months. They concluded that,
 More than 35% of the treated open-bite patients
demonstrated a postretention open bite of 3 mm or more.

 There was a significant trend toward decreasing mandibular
arch dimensions with time, with the exception of the Irregularity
Index which increased. These dental changes were not
significantly different when the sample was divided into
postretention relapse and stable open-bite categories.
 Neither the magnitude of pretreatment open bite, the
mandibular plane angle, nor any other single parameter of
dentofacial form proved to be a reliable predictor of
posttreatment stability or relapse.
 With numerous exceptions, the subgroup demonstrating
relapse of the treated open bite showed the following
characteristics posttreatment across time:
 Less mandibular anterior dental height.
 Less upper anterior facial height.
 Greater lower anterior facial height.
 Less posterior facial height.

Huang and Justus in Angle 1990 studied the stability
of anterior open bite in 33 patients treated with crib
therapy. They concluded that,
 Patients who achieve a positive overbite with crib
therapy have a good chance of maintaining a positive
overbite after orthodontic treatment is completed and
is applicable for both growing and non-growing
patients.
 The reason for this increased stability may be due
to a modification of tongue position or posture

Kim et al in AJO 2000 evaluated the stability of
anterior openbite correction in 55 white patients
treated with multiloop edgewise archwire therapy. The
lateral cephalograms were analyzed for skeletal,
esthetic, and dentoalveolar changes. The results
suggest that,
 The openbite was corrected by retraction and
extrusion of the anterior teeth and the uprighting
movement of the posterior teeth.
 The upper and lower occlusal planes moved toward
each other.

 There were some significant changes in the skeletal
variables in the growing group. The anterior LFH,
anterior TFH, and posterior LFH increased. The palatal
plane moved downward anteriorly, and the gonial angle
decreased. There were not any significant changes in
skeletal variables for the nongrowing group. There was
retraction of the upper lip in both the growing and the
nongrowing groups.
The correction of openbite obtained by the MEAW
therapy was proven to be very stable.
The relapse in the overbite during the 2-year follow-up
period was 0.23 mm for the growing group and 0.35 mm
for the nongrowing group; these figures were not
significant.

Freitas et al in AJO 2004 evaluated the stability of extraction
therapy for the anterior open bite in the permanent dentition an
average of 8.35 years after retention.
Records were obtained for pretreatment, posttreatment,
postretention stages from 31 patients who had undergone
orthodontic treatment with fixed appliances. The results
suggested that,
 Eight patients (25.8%) showed a clinically significant
relapse of the open bite. Consequently, 74.2% of the patients
in the experimental group showed a clinically significant
stability of the anterior open bite correction in the long term.
 During posttreatment period counterclockwise rotation of
the mandible occurred and this might have contributed to the
stability of the overbite after treatment
 This study suggests that the extraction approach seems to
be more stable than non-extraction.

ORTHOPEDIC TREATMENT AND RELAPSE STUDIESORTHOPEDIC TREATMENT AND RELAPSE STUDIES
PALATAL EXPANSION AND ITS RELAPSE
Expansion through maxillary suture widening by rapid
maxillary expanders has been claimed to promote stability after
retention. Stability has been attributed to the skeletal
component of arch enlargement obtained by the expansion
appliance as opposed to dental expansion as a result of
edgewise appliance mechanotherapy.
Studies on immediate treatment effects of rapid palatal
expansion have reported increases in arch width as a result of
combined skeletal and dental expansion. Short-term follow-up
has indicated a rebound effect of the dental component, yet a
relative stability of the skeletal aspect of the expansion.

The implant studies by Krebs (1964) during a 7-year
observation period found a substantial reduction in dental
arch width after discontinuation of retention which
continued for as long as 4 to 5 years.
Skieller (1964) carried out scientific study where he inserted
metal implants into thirteen girls and seven boys, using an
expansion appliance. This was opened at the rate of 0.5 mm.
per week for 7 months and then maintained for 12 months.
He found that both the teeth and the vault widened and that
the vault continued to widen both during retention and
thereafter. The teeth, however, commenced to relapse at the
end of the expansion and continued to do so out of retention,
with the relapse amounting on average to about 25 percent
of the total opening.

Although he does not mention it, Skieller's, figures show that
the dental relapse was less for the patients under 9 years old
and noticeably higher for those over 12 years of age.
Stockfish (1969) found 50% of relapse within 3 to 5 years
after retention after rapid palatal expansion.
Linder-Aronson and Lindgren (1979) performed a 5-year
posttreatment study and noted that only 45% of the initially
achieved rapid palatal expansion was maintained. They also
found a residual expansion of 38% and 59% for intercanine
and intermolar widths, respectively, over a period of
observation.

Mew in AJO 1983 studied twenty-five patients (10 boys, 15
girls) who were consecutively treated with maxillary
expansion. The cases were overexpanded 2 to 4 mm. The
expansion was measured 2 or 3 months out of retention to
allow the overexpansion to settle. Measurements were made
again 2½ years out of retention. The net expansion had been
3.5 mm., and this had subsequently not relapsed.
Herold (BJO 1989) reported that the increase in intercanine
and intermolar widths observed during treatment with palatal
expansion was followed by relapse, with a residual increase
of 2.1 mm (62.5%) and 3.1 mm (56.4%), respectively.

Moussa et al, O’Reilly in AJO 1995 evaluated the
long-term changes of maxillary and mandibular dental
arch measurements in patients who were treated with
the soft tissue-borne palatal expander and edgewise
appliances and its stability.
The sample comprised of 165 dental casts randomly
selected from patients who had been out of retention for
8 to 10 years at a mean age of 30 years.

 Maxillary intercanine width and maxillary and mandibular
intermolar widths after retention closely approximated the
posttreatment dimensions and were larger than their
pretreatment dimensions.
 Mandibular intercanine width, arch length, and arch
perimeter after retention closely approximated pretreatment
dimensions.
 Incisor irregularity after retention was minimum for both
maxillary and mandibular arch.
 Treatment with the rapid palatal expander presented good
stability for upper intercanine width, upper and lower
intermolar widths and incisor irregularity.
 Lower intercanine, arch length, and perimeter presented
poor stability.

Jeffrey L. Berger in AJO 1998 examined and
compared the stability of orthopedic and surgically
assisted rapid palatal expansion over time. Orthopedic
expansion group consisted of 14 males and 10 females
with ages ranged from 6 years to 12 years and
Surgically assisted rapid palatal expansion group
consisted of 12 males and 16 females with ages
ranging from 13 years to 35 years. Dental models and
PA cephalograms were obtained immediately before
and after expansion, at removal of the expansion
device, and 1 year after removal of the appliance.

From the study he concluded that,
 Clinically, there is no difference in the stability of
surgically assisted rapid palatal expansion and
nonsurgical orthopedic expansion.
 The length of time after appliance removal was a
year or slightly longer. These patients were kept in
retention during the 1-year period thus demonstrating
the importance of retainers to control perioral forces
and maintain stability. Both the orthopedic and the
surgical groups showed stable results.

CHIN CUP THERAPY
Adolfo Ferro in AJO 2003 evaluated the long term
stability of skeletal Class III patients treated with splints,
Class III elastics, and chincup (SEC III) and investigated
the main determinants of relapse. Cephalometric data for
52 patients (22 men, 30 women) at pretreatment,
posttreatment, and 3 years after retention were studied.
The results showed that,
 The SEC III appliance achieved a long-term Class III
occlusal correction in a high percentage (88.5%) of
successfully treated patients. Thus, SEC III treatment is
reliable at least at the end of the facial growth, as defined
by age.

 At the end of the follow-up period (an average of 9
years), only 6 of the 52 patients had clinical relapse
(overjet ≤0)
 At the end of treatment, the best predictors of relapse
seem to be low Wits appraisal, ANB angle, and overbite,
and large SNB.
 Significantly greater decreases of the Wits appraisal
and increases of ramus length during the follow-up were
further associated with relapse.
 Relapse appears to be affected by increased growth of
the mandibular ramus and the ramus growth was
remarkable only in patients with reduced overbite, low
Wits appraisal and ANB angle, and high SNB angle.

FUNCTIONAL APPLIANCE TREATMENT ANDFUNCTIONAL APPLIANCE TREATMENT AND
RELAPSE STUDIESRELAPSE STUDIES
Pancherz in EJO 1981 did a short term follow-up study
after Herbst appliance treatment of Class II malocclusions.
He found that on a short-term follow-up basis, it is as if a
Class I dental arch relationship is maintained by a stable
cuspal interdigitation of the upper and lower teeth, while
relapse tends to occur in cases with unstable occlusal
conditions.

Pancherz and Hansen in EJO 1986 studied a group of
patients with malocclusions who were treated with the
Herbst appliance in the early permanent dentition 6 and
12 months after active treatment and found that
dentoalveolar and skeletal relapse was about 30% of the
accomplished treatment effect.
The relapse occurred primarily during the first 6 months
after treatment and resulted in the tendency toward
increased overjet.

Pancherz in AJO 1991 performed a long term
cephalometric investigation to analyze the nature of Class
II relapse after Herbst appliance treatment, comparing
stable and relapse cases at least 5 years after treatment. A
total of 118 patients with Class II, Division 1
malocclusions were treated with the Herbst appliance.
Lateral cephalograms taken before and immediately after
Herbst treatment, as well as 6 months and 5 to 10 years
after treatment, were analyzed.

The results revealed that,
 Relapse in the overjet and sagittal molar relationship
resulted mainly from posttreatment maxillary and mandibular
dental changes.
 In particular, the maxillary incisors and molars moved
significantly to a more anterior position in the relapse group
than in the stable group.
 The interrelation between maxillary and mandibular
posttreatment growth was favorable and did not contribute to
the occlusal relapse.
 It is hypothesized that the main causes of the Class II
relapse in patients treated with the Herbst appliance were a
persisting lip-tongue dysfunction habit and an unstable cuspal
interdigitation after treatment.

Wieslander in AJO 1993 investigated the long-term
effect of treatment with headgear-Herbst appliance in early
mixed dentition in children with severe Class II
malocclusions.
A group of children age 8 years 8 months was initially
treated for 5 months with a headgear-Herbst appliance
followed by a 3- to 5-year period of activator retention.
The patients were studied out of retention at the mean age
of 17 years 4 months and compared with an untreated
control group.

Positive findings of the study includes the following:
 A rapid improvement of the anteroposterior jaw
discrepancy because of 24-hour wear of the appliance for 5
months.
 A significant maxillary effect during active treatment
and retention resulting in a 2.3 mm posterior gain after
retention, which compensates for the mandibular relapse
tendency. It resulted in an average statistically and
clinically significant 2.9° reduction of the ANB angle and a
3.8 mm skeletal improvement of the sagittal jaw
relationship out of retention.

Negative findings include the following:
 A prolonged retention ranging over several years of
activator wear was necessary to minimize relapse after
Herbst treatment.
 A modest long-term effect on the mandible 8 years after
treatment. In many cases the long-term mandibular effect
was considerably larger and of clinical importance.
However, in other cases that cooperated poorly during
retention, it was less.
 A rather small increase in mandibular length. The
significant average 2.0 mm increase in the condylion-
gnathion distance observed after 5 months of Herbst
treatment was reduced to 1.2 mm after retention and was
not statistically significant.

Somchai Satravaha in AJO 1999 examined the skeletal
changes produced by Class III activator during the
treatment of patients with skeletal Class III malocclusions
and characterized the stability of these changes in the
years after treatment (6.6 ± 2.1 years after the end of
activator treatment). The results indicated that,
 During the treatment, the Class III activator produced a
statistically significant skeletal effect and this change
remained through the postactivator period.
 The gonial angle exhibited a compensatory decline
during the postactivator period.
 The skeletal profile was improved after the treatment
and was not lost during the posttreatment period despite
significant increase in maxillomandibular differential.

ORTHOGNATHIC SURGERY AND RELAPSEORTHOGNATHIC SURGERY AND RELAPSE
STUDIESSTUDIES
MAXILLARY SURGERIES AND ITS RELAPSE
Schuchardt (1959) first reported superior movement of
the maxilla, who used a two-stage approach and limited
his surgical procedure to the posterior maxilla. He
reported relapse problems that in retrospect probably
were caused primarily by incomplete mobilization of
the dentoalveolar segments at surgery.

Willmar (1974) undertook the first quantitative follow-up
study on LeFort I osteotomy with the use of surgically
placed metal markers. Although 106 patients were studied,
only three had ''idiopathic long face.'' These cases
demonstrated stability of markers and occlusion throughout
the 1-year observation period, with an ''insignificant" 10%
superior relapse occurring at the anterior marker.
Bell and McBride (1977) examined 41 patients with
vertical maxillary excess who underwent maxillary
superior repositioning by LeFort I osteotomy. They
evaluated their results clinically and noticed stability
without relapse in the cases examined.

Hartog (1982) evaluated skeletal stability and soft-tissue
changes after superior repositioning of the maxilla, and
reported that good stability was attained. The sample
included multiple segments and combined procedures
with only three one-piece osteotomies.
Washburn, Schendel, and Epker (1982) reported their
experiences with superior maxillary repositioning in a
group of 15 young patients and indicated that the
postsurgical jaw relationship was maintained even in
patients who experienced postsurgical growth.

Proffit, Phillips, and Turvey in AJO 1987 analyzed the
cephalometric data from 61 patients who had undergone
superior repositioning of the maxilla via LeFort I osteotomy
by means of the downfracture technique and evaluated the
stability of skeletal and dental landmarks at various time
intervals up to 1 year.
None of these patients had concurrent mandibular ramus or
body osteotomy except genioplasty and all had at least 2
mm intrusion at the maxillary incisor or molar.
The results indicated that,
 During the first 6 weeks postoperatively, the maxilla
showed a strong tendency to move farther upward in the
patients in whom it was not stable.
 The posterior maxilla was vertically stable in 90% of the
patients, the anterior maxilla in 80%.

 Horizontally, skeletal landmarks were stable in 80%,
but when changes occurred, there was a tendency for
the anterior maxilla to move back when it had been
advanced.
 After the first 6 weeks, the posterior maxilla was
stable vertically in all patients, but in 20% anterior
maxillary landmarks moved downward, opposite to the
direction of movement during fixation.
 In 11 of the 15 patients who demonstrated vertical
changes postsurgery, the movement from fixation
release to 1 year follow-up was opposite and
approximately equal to the initial change, so that the
net movement after 1 year was less than 2 mm.

 Only 6.5% (four patients) demonstrated 2 mm or
greater net vertical movement for any of the variables
studied 1 year after surgical treatment.
There was no indication that the amount of presurgical
orthodontic movement of incisors, the presence of
multiple segments at surgery, the age of the patient, the
presence or absence of genioplasty, or the presence or
absence of suspension wires was a risk factor for
instability.

MANDIBULAR SURGERIES AND ITS RELAPSE
Lake, McNeill, Little in AJO 1981 evaluated surgical
advancement of the mandible by retrospective
cephalometric and computer analysis for longitudinal
skeletal and dental changes an average of 3½ years after
surgery.
52 patients (19 males and 33 females) underwent
surgical advancement of the mandible by means of
bilateral sagittal osteotomy of the mandibular vertical
rami.

From the results, relationships between specific
parameters and skeletal relapse have been
demonstrated:
 Positional change of the proximal segment was
found to be the most important parameter in
determining stability or relapse of the advanced
mandible.
Anteroinferior condylar displacement and increase in
posterior facial height at the time of surgery or
immediately postoperatively were associated with
subsequent skeletal relapse of the distal mandibular
segment.

The magnitude of advancement was a primary factor
in mandibular stability. As the magnitude of
advancement increased, the net amount of relapse tended
to increase. The dynamic function and variability of the
mandible's musculoskeletal system and its periosteal
integument may play a dominant role in the nature of the
postsurgical response.
 Preoperative measurement of the mandibular plane
angle did not prove to be a reliable predictor of
subsequent mandibular relapse. However, patients with
high mandibular plane angles did undergo more relapse
than did patients with either normal or low angles.
 No significant relationship was found between
skeletal relapse and the age of the patient.

Huang and Ross in AJO 1982 evaluated the short-term
and long-term effects of surgical lengthening of the
retrognathic, growing mandible in children. Twenty-two
patients 12 boys and 10 girls underwent mandible-
lengthening procedures at the mean ages of 14.1 years
(boys) and 13.4 years (girls). The results indicated that,
 The response to this mandible-lengthening surgery in the
growing child varied with the amount of lengthening
performed but did not appear to vary with age (after 11
years), sex, etiology of the mandibular discrepancy,
mandibular plane angle, deep- or open-bite, or concomitant
surgical procedures.

 Lengthening of more than 11 mm. was usually
accompanied by extensive relapse, with major
remodeling of the condyle or posterior symphysis or
both.
 Lengthening of less than 9 mm. was followed by little
or no relapse.
 No further clinically significant growth of the
mandible occurred following mandible lengthening as
performed after the age of 11 years.
 The mandible returned to its preoperative growth
direction within 2 years after surgery.

Ellis and Carlson (J Oral Maxillofac Surg 1983)
performed an experimental investigation of mandibular
advancement in Macaca mulatta monkeys. The skeletal
stability two years after mandibular advancement surgery
with and without suprahyoid myotomy was evaluated. The
results demonstrated that,
 Mandibular advancement without suprahyoid myotomy
was associated with a statistically significant 13% relapse.
 There was no relapse after mandibular advancement with
suprahyoid myotomy.
 It was concluded that, the suprahyoid muscle complex
does play a significant role in relapse after mandibular
advancement.

Because of the fact that skeletal relapse after mandibular
advancement without myotomy occurred only during the
period of maxillomandibular fixation, that is, the first 6
weeks, it was hypothesized that,
(1) The surgical procedure caused a stretching of the
suprahyoid complex resulting in a posteriorly oriented
force on the distal bone segment, and
(2) This force was transitory in nature and became
diminished over time as the suprahyoid muscle complex
adapted to the initial stretch by permanently increasing in
length.

David Carlson in AJO 1987 performed an experimental
investigation as a sequal to the previous investigation by
Ellis and Carlson (J Oral Maxillofac Surg 1983).
They studied the short-term change and long-term (2
years postsurgery) adaptation of the suprahyoid muscle
complex after mandibular advancement surgery with and
without suprahyoid myotomy in 10 adult rhesus monkeys
(Macaca mulatta).

The results for the nonmyotomy group showed that,
(1) The suprahyoid complex was elongated approximately
two thirds the amount of mandibular lengthening,
(2) The major immediate adaptations within the suprahyoid
complex after the surgical procedure occurred at the
muscle-bone interface and the muscle-tendon interFace,
(3) The change in length at the muscle-tendon junction was
maintained throughout the 2-year follow-up period,
indicating that significant long-term adaptations took place
primarily at that location, and
(4) No significant short-term changes or long-term
adaptations were seen within the anterior digastric muscle
or the intermediate digastric tendon.

Within the myotomy group, it was found that (1) the
suprahyoid complex recoiled immediately after myotomy such
that the anterior belly of the digastric muscle became separated
from the advanced distal mandibular segment by more than
twice the amount of mandibular lengthening,
(2) The anterior digastric muscle remained essentially at this
posterior position throughout the 2-year follow-up period, and
(3) Though not significant, there was a trend for a decrease in
the length of the anterior digastric muscle belly.
On the basis of these results, it was concluded that both short-
term changes and long-term adaptations to lengthening of the
suprahyoid complex as a result of mandibular lengthening
occur primarily within the connective tissues comprising the
muscle-tendon and muscle-bone interfaces, not within the
muscle fibers themselves.

Komori in AJO 1987 evaluated the use of skeletal
fixation for skeletal stability during the period of
intermaxillary fixation following a modified sagittal
split ramus osteotomy for mandibular prognathism. A
combination of bilateral maxillary peralveolar wires and
circummandibular wires in the canine region was used
for the fixation.
A total of 17 Japanese patients as two groups- 10
patients with fixation and a control group without the
fixation were compared cephalometrically.

The results showed that,
 Statistically significant differences existed in the amount
and pattern of relapse; the fixation produced a significant effect
on retention of the corrected chin position.
 As a consequence, downward and backward rotation of the
distal fragment of the mandible and compensatory incisor
extrusion were notably controlled.
 However, upward shift of the posterior end of the distal
fragment occurred persistently even in the fixation group,
causing considerable intrusion of the posterior teeth in
comparison with the control group.
This seems to indicate that tension, probably exerted by the
pterygomasseteric sling, is important in postoperative skeletal
instability.

DOUBLE JAW SURGERIES AND ITS RELAPSE
Numerous theories have been advanced to explain the
reasons for relapse in these kinds of surgery:
(1) Stretching of the muscles of mastication and the
suprahyoid musculature (Poulton 1973, McNamara 1978)
(2) Condylar distraction during surgery (Epker 1978,
Schendel 1980, Worms 1980)
(3) Upward and forward rotation of the mandible (Poulton
1973, Epker 1978)
(4) Changes in rotational position between the proximal and
distal segments (Reitzik 1973, Lake 1981)

Numerous fixation techniques have also been advocated
to reduce postsurgical relapse. These have included,
(1) Upper- and lower-border wiring (Booth1981)
(2) Steinmann pins to stabilize the maxilla (Bennett
1985)
(3) Skeletal-wire fixation (Schendel 1980) and
(4) Rigid fixation (Champy 1978)
Early studies of mandibular advancement and maxillary
LeFort I osteotomy by Poulton (AJO 1971), Wilmar
(AJO 1974) revealed that mandibular relapse tended to
be greater than maxillary relapse.

Brammer (1980) studied the stability after bimaxillary
surgery to correct vertical maxillary excess and
mandibular deficiency.
He concluded that the stability of double jaw surgery
reported less mandibular relapse but more maxillary
relapse than for the same procedures performed
independently in one jaw at a time.

Satrom, Sinclair in AJO 1991 compared the stability of
rigid fixation with that of skeletal-wire fixation in a sample
of 35 patients who had undergone maxillary impaction and
simultaneous mandibular advancement.
The authors concluded that,
 The maxilla was relatively stable for both fixation
techniques, remaining within 1 mm of its postsurgical
position, both horizontally and vertically.
 Rigid fixation tended to improve maxillary stability,
primarily by limiting relapse to less than 2 mm.

 Mandibular length was significantly more stable in
the rigid-fixation sample.
 Rigid fixation produced significantly better control
of the angulation between the proximal and distal
segments. This rotational control appeared to be a
major factor in the increased overall stability of the
rigid-fixation sample.
The amount of relapse was correlated to the amount of
mandibular advancement in the wire-fixation sample
but not in the rigid-fixation sample.

CONCLUSIONCONCLUSION
Treatment goals are usually stated in cephalometric terms for
individual tooth positions with insufficient attention to
accommodating for skeletal variations. Nor are treatment
goals often phrased in terms of occlusal dynamics. Most
malocclusions are stable before therapy. If they are not at the
end of the treatment, it may be the fault of the dentist. All
treated malocclusions must eventually be returned from
control by appliances to control by the patient’s own
musculature.
Proper goals of treatment, careful mechanotherapy, precise
occlusal equilibration, and well-chosen retention procedures
play a role in achieving occlusal homeostasis.

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