Retention and relapse /certified fixed orthodontic courses by Indian dental academy

RETENTION

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INDIAN DENTAL ACADEMY
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RETENTION
The phase following active orthodontic
treatment aimed at stabilization of achieved
orthodontic correction or holding of the
teeth in ideal functional esthetic occlusion.
The holding of the teeth in ideal esthetic and
functional position

Angle summarized orthodontic retention as
follows:
"After malposed teeth have been moved into the
desired position they must be mechanically
supported until all the tissues involved in their
support and maintenance in their new positions
shall have become thoroughly modified, both in
structure and in function, to meet the new
requirements."

Orthodontics dates back to the very first century
when Roman writers Pliny and Galen, who were
the founder of experimental medicine, both
recommended filing of a tooth that projected
from trauma and other reasons.
Knowledge about stability of treatment was
finally put forth by Emerson C. Angell (1860), as
a byproduct of his palate-splitting procedure. He
mentioned the necessity to preserve or retain
space to until complete eruption and development
of the teeth in question.

Alfred Coleman (1865) wrote about restoration of various
conditions by muscular pressure— in other words, the first
allusion to relapse. More than a century later, clinicians
still refer to abnormal muscular pressure as a dominant
factor in the cause of relapse.
Brown-Mason (1872) (in England) described a retaining
plate for surgically rotated teeth. Thus, after more than 19
centuries of mechanical orthodontic intervention,
recognition of the possible instability of treatment
emerged, and thus the concept of a retaining appliance was
born.

One of the earliest retaining appliances was described by
James W. Smith (1881). It was a simple vulcanite plate
with a bar extending over the labial aspect of the
maxillary incisor teeth.
Jackson (1904) suggested that ''after they have been rotated
as far as desired, the soft tissue be separated from the neck
of the tooth and allowed to reunite in the new location,
depending on the cicatrix thus formed to prevent their
retrograde movement— in short fiberotomy.


Finally, Angle devised and described many
ingenious mechanical combinations of cemented
bands and spurs, the action of which were, to
quote his descriptive phrase, "to antagonize the
movement of teeth only in the direction of their
tendencies."
Also in his quest for the ultimate retainers, it is
interesting to note that Angle's intricate pin and
tube active treatment appliance was developed
primarily as a working retainer to achieve bodily
movement or uprighting of teeth that had been
tipped outward in expansion.

W. S. Bonwill's work (1887) described an ideal
morphologic arrangement of teeth and jaws based on his
study of more than 2000 skulls. He thoroughly informed
his patients of the limits of treatment and the necessity of
adequate retention. Also, Bonwill advised the
orthodontists to set fees high enough to "insure their own
interest and drive the parties concerned up to their
duties.“


 SCHOOL

OF THOUGHTS

The Occlusion School 1880 by Kingsley stated

that the occlusion of teeth is the most potent factor
in determining the stability of the new position.
The apical base school 1920
by Alex Lundstrom suggested that apical base is
the most important factor in the correction of
malocclusion and
maintenance of
correct
occlusion.

The mandibular incisor school by Grieve and Tweed in
1952 suggested that the mandibular incisors must be kept
upright and over the basal bone.
The musculature school 1922 suggested that the proper
functional muscle balance was necessary for maintenance
of stability


Basic theorems
Theorem 1: Teeth that have been moved tend to return to their
former positions. This tendency is due to musculature, apical base
transseptal fibers, bone morphology.
Theorem 2: Elimination of cause of malocclusion will prevent
recurrence. Habits such as thumb/finger sucking/lip biting are
easy to diagnose as being the cause of malocclusion and can be
easily negated to prevent recurrence.
The most causative factor as tongue posture can influence and
cause anterior/lateral open bite.Tongue posture can be due to
open bite secondary to mouth breathing/nasopharynx
obstruction which in turn can be due to anatomic blockage,
allergic disease or adenoid hyperplasia.Dentofacial changes due
to functional alternation appear to become more severe with age.

Theorem 3
Malocclusion should be overcorrected as a safety factor”
In Class II malocclusion it is in practice to get it into edge
to edge incisor relationship by overcoming muscle force
rather than by tooth movement only.
Over correction of deep bite is an accepted practice.
Over rotation to prevent relapse of rotation is not
successful as evidence suggests but, is possible by
supracrestal fiberotomy.

Theorem 4


“Proper occlusion is a potent factor to hold the teeth in that
position”
Overfunction or Pounding (exerting pressure) of the
mandibular canine by maxillary canine is very often blamed
for anterior teeth crowding.



However, evidence suggests tremendous wear , that the teeth
undergo indicates that they do not move in response to
regular grinding and tapping.



Studies indicate that mandibular arches are not stable in both
anterior tooth contact and open bite patients without canine
contact in centric position and functional excursion. Thus this
theory is doubtful.



This again does not mean that proper intercuspation or
interlocking of the canine is the most potent factor in retention.

Theorem 5
“Bone and adjacent tissues must be allowed time to
reorganize around newly positioned teeth”.
Histologic studies have shown that the bone and tissue
around the teeth, that have been moved, require
considerable amount of time before complete
remineralization occurs.
Some authors believe that retainers should be fixed and
others feel that the retainers should be only
inhibitory in nature with no the fixation to allow natural
functioning of teeth.

Theorem 6
“If the lower incisors are placed upright over the basal bone,
they are more likely to remain in good alignment”.
But no satisfactory method exists for anyone to specify the
beginning or end of basal bone.
In case of anterior teeth with buccal inclination; attempts to push
them lingually causes expansion or collapse in canine area.
If anterior teeth are already inclined lingually further pressure
to the lingual won’t cause collapse.
So if the clinician must make an error in in positioning of the
mandibular incisor, it is better to err in the lingual direction
rather than a labial inclination.

Theorem 7
“Corrections carried out during periods of growth are less likely
to relapse”.
Hence treatment should begin at the earliest possible age.
Correction of disto-occlusion and maintaining the corrected
position is difficult without extraction.
Advantages of early treatment
1. Prevents progressive irreversible tissue and bony changes.
2. Maximize use of growth and development.
3. Allows interception of malocclusion before excess dental and
morphological compensations.
4. Allows correction of skeletal malrelationships while sutures
are morphological immature and more amenable to alterations.

Theorem 8
“The further the teeth have moved the less the likelihood
of relapse”.
There is little evidence to support this and the opposite of
this statement may be true.


Theorem 9
“Arch form particularly the mandibular arch cannot be
permanently altered by appliance therapy”.
Therefore treatment should be directed towards
maintaining them.
Dallas McCanley have suggested that canine width and
the bimolar width are of such uncompromising nature that
they should be considered as fixed quantities and build
the arches around them.


Theorem 10
“Many malocclusion requires permanent
retaining device model”.


Biologic Basis for Orthodontic Relapse
According to Angle, orthodontic correction will
remain stable if the teeth are aligned into a normal
occlusion and provided with adequate retention.
Orthodontic relapse includes crowding or spacing of
teeth, return to increased overbite and overjet and
instability of class II and class III corrections.
Relapse is defined as “return towards pre-treatment
conditions”.

Tissue Response in Periodontium
If orthodontic tooth movement is not followed by
remodeling of supporting tissues, the tooth will tend to
relapse.
The periodontal ligament has the ability to invest its
fibrils in the alveolar bone and cementum during
deposition, thus acting as an anchorage zone for the
teeth.
The remodeling of the fibrous system on the tension side
is related to the direction of the pull on the tooth
resulting in the production of new fibers in that
direction.
Most of the relapse tendency is caused by the structures

Reiton has evaluated the degree of relapse following
tipping without retention and concluded that:
– Some amount of relapse occurs immediately after 2
hours of removing the appliance as the tooth begins
to upright within the PDL space.
– After 4 days, the tooth comes to a stand still due to
formation of the hyalinization area on the tension
side.
– After elimination of the hyalinised area, relapse
continues.
– Unlike PDL, the supra-crestal alveolar fibers are not
anchored in the bony wall and hence they cannot
be readily remodeled. Hence they have less chance
of being reorganized. Remodeling of the gingival

– These gingival fibers are slow to remodel after tooth
movement, as the main function of these fiber groups
is to protect the alveolar processes and maintain
tooth position and interproximal contact.
– The transseptal fiber stabilizes the teeth against
separating forces and may actually maintain the
contacts of adjacent teeth.
– Removal of proximal teeth contacts will allow the
transseptal fibers to contract and produce
approximation of adjacent teeth.
– Surgical pre-incision of supra alveolar structures
(fibrotomy) may prevent or reduce relapse.

– The fibrils connecting heavy frenulum attachments to
the alveolar processes need a very long period of
remodeling.
– Stress induced by orthodontic forces lead to increased
formation of “oxytalan”. Increased presence of oxytalan
in periodontium under stress situations is associated
with an increase in vascular activity, rather than an
attempt to support and strengthen the tooth position.
– Fiber bundles on the tension side tend to become
arranged according to the physiologic movement of the
tooth. During retention, new bone fills the space
between bone spicules. This arrangement and
calcification of new bone spicules results in a fairly
dense bone tissue, which will prevent relapse.

Retention is necessary for three reasons:
The gingival and periodontal tissues are affected by
orthodontic tooth movements and require time for
reorganization, when an active appliance is removed.
After treatment, the teeth are in unstable condition. So the
soft tissue pressures constantly produce relapse tendency.
Growth changes can alter orthodontic results.


Reorganization of Periodontal Tissues:
Orthodontic tooth movement requires widening of PDL
space and disruption of the collagen fiber bundles.
Restoration of the normal PDL architecture begins
once the teeth can respond individually to the forces
of mastication.
It requires 3-4 months period and the little amount of
mobility that is present at appliance removal
disappears.
Small but prolonged imbalances in tongue, lip-cheek
pressures or pressure from gingival fibers are resisted
by “active stabilization”.

The disruption of PDL due to orthodontic tooth
movement has little effect on stabilization on
occlusal forces, but it reduces or eliminates the
active stabilization.
This means that immediately after the orthodontic
appliances are removed, teeth will be unstable in
the face of occlusal and soft tissue pressures.




The gingival fiber networks must also remodel to
accommodate the new tooth positions. Both
collagenous and elastic fibers of the gingiva are very
slow at reorganization.



Collagen fibers requires 4-6 months to reorganize but
the elastic supracrestal fibers are extremely slow at
reorganization and are capable of exerting forces
capable of displacing teeth one year after removal of
appliance.



Patients with severe rotations, sectioning the
supracrestal fibers around the severely malposed or
rotated teeth (just before the time of appliance
removal) is a recommended procedure, as it reduces

Principles of Retention:
Teeth will tend to move back in the direction form which
they came due to the elastic recoil of gingival fibers and
due to the unbalanced tongue lip forces.
Teeth require full time retention for first 3 to 4 months.
To promote reorganization of the PDL the teeth should be
free to flex individually during mastication as the alveolar
bone bends in response to heavy occlusal loads..

Due to the slow response of the gingival fibers,
retention is continued for 12 months and can be
reduced to part time wear after the first 3-4 months.
In adult patients who are not growing, permanent
retention may be required because of lip, cheeks and
tongue pressures that are too large to balance out.
Patients who are growing, usually need retention until
growth has reduced to the low levels that characterize
adult life.

Occlusal Changes Related To Growth:
Skeletal problems tend to recur in all three planes of
space, if growth continues.
As the transverse growth is completed first, it causes less
of a problem clinically than changes from late anteroposterior and vertical growth.
Skeletal growth tends to recur as in most of the patients
the original growth pattern continues as long as they are
growing.



Orthodontic treatment is done mostly in early
permanent dentition, goes on for 18-30 months;
meaning that active growth treatment will conclude
by the age of 14-15 years.



Very slow growth continues throughout adult life
and the same pattern that led to malocclusion in the
first place can contribute to deterioration in occlusal
relationship, many years after treatment.


Factors affecting retention

1. Forces from PDL and gingiva
2. Forces from Soft Tissue
a) Lower labial segment
b) Arch width/Bicanine/Bimolar
c) Arch length
d) Overjet depends on lip position /size
3. Occlusal factors aid stability
a) Correction or Class II to Class I
b) Multi directional chewing pattern
c) Post treatment facial growth and development.
4. Axial Inclinations: The further orthodontist have retracted
mandibular incisor the further they have to retract maxillary
incisor. Tipping it to upright results in deep bite.

Conditions requiring retention
1) No Retention Required
i) Corrected cross bites
Anterior
Posterior
ii) Dentition treatment by serial extractions
iii) Correction achieved by retardation of maxillary
growth once the patient has passed through
growth period.
iv) Maxillary and mandibular teeth whose separated
to allow for eruption of teeth previously blocked.

2) Limited Retention

Class I non extraction cases with protrusion of incisors.
Class I or class II extraction case, particularly in maxillary
arch until lip and tongue pressure becomes normal.
Retainers/Headgears can be used
Corrected deep bite.
Overbite correction achieved as the result of bite opening
Severe occlusal plane tipping
Mild to moderate correction of rotated teeth-Gingivectomy
Ectopic eruption/presence of supernumerary teeth these
tooth have tendency to intrude themselves when released
Excessive spacing between maxillary incisors
Class II division II because of increase in intercanine width

3) Permanent/Semi-permanent Retention


Cases in which mandibular arch was
expanded cases of generalized spacing
instances of severe rotations diastema.


Retention for Class II Correction:

Relapse is usually due to the forward movement of
maxillary teeth and backward movement in the lower
arch, and the differential growth of the maxilla in
relation to the mandible.
Tooth movement is caused by local periodontal and
gingival factors and it can be an important short term
problem. Whereas the differential jaw growth is a
more of a long term problem as it alters jaw position
and therefore it contributes to repositioning of the
teeth.
Overcorrection, during finishing procedure, controls
tooth movement that would lead to class II relapse.
Even with good retention period, 1-2 mm of anterowww.indinadentalacademy.com
posterior change caused by adjustment in tooth

Class II elastics tend to move the lower incisors forward
during class II correction.
– Lip pressure will try to push these incisors upright
leading to crowding and return of overbite and overjet.
– If more than 2 mm of forward positioning of the lower
incisors has been achieved during treatment,
permanent retention is required.
Long term relapse usually occurs due to differential jaw
growth. After active treatment is completed, more of
forward growth of maxilla is likely to occur than the
mandibular growth.
If maxillary growth is restrained by either extraoral force or
functional appliance, some amount of post-treatment
rebound may occur.
This relapse tendency can be controlled with a head gear
to upper molar on a reduced basis, in conjunction with a
retainer to hold the tooth in alignment.

The other method is to use a functional appliance to
hold the tooth position and occlusal relationship.
For patients with less severe problems, in whom
continued growth may or may not cause problems of
relapse, conventional maxillary and mandibular
retainers can be given.
A functional appliance can be worn at night if relapse
begins to appear.
Severe skeletal problem: 12-24 months of retention.
The more the severe initial class II; and the younger
the patient during active treatment, the more likely that
either headgear or functional appliance will be needed
as retainer.

Retention after Class III Correction:
 Relapse

due to mandibular growth is most likely to occur
and this stage of growth is difficult to control; not even
with a chin cap.
 A chin cap tends to rotate the mandible downwards,
causing growth to be expressed more vertically and less
horizontally.
 If facial height is normal or excessive after orthodontic
treatment; and relapse occurs due to mandibular growth,
the surgical correction after the completion of growth is
the only option.
 In mild class III, a functional appliance or a positioner is
sufficient to maintain occlusal relationship during posttreatment growth.

Retention after Deep Bite Correction:
 Retention

is accomplished using a removable upper
retainer with an anterior bite plate so that the lower
incisors will contact, if the bite begins to deepen.
This retainer does not separate the posterior teeth.

 This

bite plate is continued as the vertical growth
continues into the late teens.

 Worn
 Bite

for several years after fixed treatment.

depth can be maintained by wearing the
retainer only at night after stability has been
achieved.

Retention after Open Bite Correction:

 Retention

by a combination of depression of incisors and
elongation of molars.
 Active habits --- intrusive forces on incisors --- altered
posture of the jaws --- supraeruption of molars.
 Relapse

of open bite is always due to elongation of the
posterior teeth.

 Control

of openbite relapse --- high pull head gear to the
upper molars with a standard removable retainer
OR
 An appliance with bite blocks between the posterior teeth,
which stretches the patient’s soft tissues to provide force
opposing eruption.

Retention of Lower Incisor Alignment:
Skeletal growth has the potential for altering the
position of the teeth.
If the mandible grows downwards and forwards, the
lower teeth get pushed into the lower lip which tipping
them distally. For this reason, growth in normal or
class III patients is usually associated with lower
incisor crowding.
A retainer in lower incisor region is adequate to prevent
crowding until growth has declined.
Orthodontic retention should be continued till the third
molars have erupted or have been removed.
Full time wear for first 3-4 months. followed by night time
wear and then gradually wearing them off.

Part time retention: 12 months.
In non-growing patients retention is continued till
remodeling of the gingival fibers occurs; but if
significant amount of growth is remaining, part
time retention is only needed until completion of
growth.
All cases treated in early permanent dentition require
retention of anterior alignment till the late teens.
If permanent retention is needed, fixed retainer can
be used for intra-arch relation.


Removable Appliances:
Hawley Retainer:
 Designed in 1920 as an
active removable appliance.
 Incorporates clasps on molar teeth and an outer
labial bow with adjustment loops spanning from
canine to canine.
 Earlier fully banded retainers were used, hence
after debanding some amount of
space was always remaining.
Hence, Hawley appliance
was used as an appliance
for closing band spaces.

In first premolar extraction cases, the standard
design of Hawley retainer cannot be used as
its labial bow extends across the first
premolar extraction space, tendency to
wedge it open.

Modification
 The bow can be soldered to the buccal segment of the
Adam’s clasps or


 Labial

bow is wrapped around the entire arch
using circumferential clasps on second molars
for retention

Circumferential clasp on the last molars or lingual
extension clasps can be used instead of the
Adam’s clasp, if the occlusion is tight.


 The

palatal coverage of any removable retainer
can be used for the addition of bite plane
lingual to the upper incisors to correct bite
depth.
 The lower retainer is somewhat fragile and may
be difficult to insert because of undercuts in the
premolar and molar region.


Positioner
 Excellent finishing device
 Uncomfortable for patient
 Sleep well tolerated
 They do not retain
rotations well
 Overbite tends to
increase while
the positioner
being worn.


Drawbacks: Tooth Positioners:
The pattern of wear of positioner does not match the
pattern usually desired for retainers.
• Difficult to wear full time.
• Positioners do not retain incisor irregularities
and rotations as well as standard retainers.
The reason being that the retainers require full
time wear initially, and positioners are worn
only for about 4 hours.
Advantage Tooth Positioners:
Maintains occlusal relationships and intra-arch tooth
positions.
For a patient with class III relapse tendency, a
positioner made with jaws related somewhat
downwards and backwards may be useful.

Fixed Retainers:
Indications:
 Maintenance of lower incisor position during growth:
Even a small amount of growth between the age 16 and
20 can cause re-crowding. Relapse is always
accompanied by lingual tipping of the central and lateral
incisors.
 A fixed lingual canine to canine retainer can be
fabricated with bands on the canines or can be bonded
to the lingual surface.


A

fixed lingual bar attached only to the canines and
resting against the flat lingual surfaces of the lower
incisors above the cingulum. This prevents the
canines and incisors from moving lingually an
defective in maintaining corrections of rotations.

Disadvantage:
 Creating band space can be a problem unless bands
are used during treatment.
 Labial part of the band tends to trap plaque leading to
decalcification.

 It

is attached only to the canines, resting passively
against the central and lateral incisors.

 It

is also possible to bond a fixed lingual retainer to
one or more of incisor teeth. Indicated in severely
rotated teeth.

 If

the span of retainer wire is bonded on an
intermediate tooth or teeth, a more flexible wire
should be used. E.g. Braided SS arch wire.


Diastema Maintenance:
 This is another indication for fixed permanent
retention, especially if the diastema between the
maxillary central incisors has been closed.
 Even if frenectomy is done, there is tendency for the
incisors to open up.
 A bonded section of flexible wire can be used,
contoured in such a way that it lies near the cingulum
to keep it away from the occlusal contact.
 Objective of the
retainer is to hold
the teeth together
while allowing
them some mobility
to move independently
during function.

Maintenance Of Pontic Space:
 A fixed retainer is the last choice to maintain a
space where bridge pontic will be eventually
placed.
 A heavy intra-coronal wire bonded in a shallow
preparation in the future abutment should be
used. Longer the span --- heavier the wire.


Maintenance of Extraction Space:
 A fixed retainer is more reliable and better
tolerated than a full time removable retainer.
Spaces reopen unless the retainer is worn
constantly.
 It is always better in adults to bond the fixed
retainer on the facial surface of the posterior teeth
when spaces have been closed.
 Disadvantage: Difficult to maintain hygiene.


Active Retainers:
 “Active retainers” is a misnomer as a device cannot
be actively moving the teeth and serve as a retainer
at the same time.
 Relapse

or growth change may require minor tooth
movements to be carried out during retention period.
This is usually done with a removable appliance that
continues to act as a retainer after it has repositioned
the teeth. E.g. Hawley retainer.


Essix Retainers: Jan 1997 JCO,

JOHN J. SHERIDAN, MCMINN,

Orthodontists' concept of retention is moving toward the idea
that teeth will move unless retained indefinitely.
The cornerstone of Essix permanent retention is the complete
delegation of responsibility to the patient.
Essix .75mm (.030") thermoplastic copolyester is mandatory for
the fabrication of Essix retainers. Thinner, 0.5mm material is too
flimsy, while thicker, l mm material lacks flexibility.
Copolyester, unlike polycarbonates, does not require heat
treatment before thermoforming. It is much stronger, clearer, and
resistant to abrasion than acrylic sheet, and thus produces thinner
yet www.indinadentalacademy.com
sturdier appliances.

They are a thinner, but
stronger, cuspid-to-cuspid
version of the full-arch,
vacuum-formed devices.

Advantages include:

The ability to supervise
without office visits.
Absolute stability of the
anterior teeth.
Durability and ease of cleaning.
Low cost and ease of fabrication.
Minimal bulk and thickness (.015").
The brilliant appearance of the teeth is caused by light
reflection.

Permanent Lingual Bonded Retainer
JEREMY D. ORCHIN, DDS JCO 1990 Apr.

Lingual Bonded Retainer Kit includes a specially formulated
Fiberthread (Kevlar) and light-cured composite resin .
Fiberthread has four times the strength of stainless steel of
equal dimensions, allowing the use of thread about .010 " in
diameter.
It is soft and flexible prior to bonding, which permits easy and
rapid adaptation to any lingual configuration. The light-cured
composite is designed with the proper consistency to integrate
with the Fiberthread and provide a strong bond to the prepared
enamel surface

Patients are impressed with its comfort, ease of maintenance,
and appearance.
Because the retainer can be placed before removal of all
labial brackets, the anterior brackets can be debonded and
retention begun during posterior space closure or finishing.
The thinness of the material also allows its use, in most cases,
as a fixed retainer palatal to the upper incisors

Bonded Maxillary Custom Lingual Retainer - FRANK W.
KRAUSE, DDS, JCO 1997 Volume 1984 Oct
The bonded maxillary custom lingual retainer (MCLR) was
designed for alignment and rotational control during retention
of maxillary anterior teeth and to help overcome two other
major problems associated with bonded lingual retention in the
maxillary arch:
1. Tedious and time-consuming.
2. Occlusal stress exerted against maxillary lingual retainers,
through direct occlusal contact or biting forces that tend to
break bonds.

The maxillary custom lingual retainer is constructed of
lingual bonding bases joined by a rectangular .018" ´ .022"
soft steel wire. The triangular shape and slightly rounded
sides and corners of these bases conform well to the lingual
anatomy of the incisors.


Removable Plastic Herbst Retainer RAYMOND P.
HOWE, JCO, 1987 Aug
The design of the RPH retainer is similar to that of the
Removable Plastic Herbst treatment appliance. Upper and
lower plastic splints are fabricated over a supporting wire
framework and connected by the Herbst mechanism .
The principal difference between the retainer and the
treatment appliance is that the retainer has full occlusal
coverage on all teeth, including the upper incisors. This
maintains tooth positions and prevents passive eruption.


Advantages:
Retreatment Appliance
Post-Surgical Retainer
Aid for Obstructive Sleep Apnea
Anterior Repositioning Splint


Third Molars and Orthodontic Diagnosis
ROBERT J. SCHULHOF JCO on 1976 Apr(272 - 281):
According to Bjork, approximately 45% of the population will
have impacted lower third molars.
The eruption of third molars is blamed for relapse in many
cases. Extraction of bicuspids has been justified as creation of
space for the erupting third molars. Temporomandibular joint
problems have been reported to occur both from malposition
of third molars and from their absence.
Can Erupting Third Molars Cause Crowding?
This has been a subject of considerable controversy in
orthodontics. Some investigators say yes, others say no.
Dr. Leroy Vego determined that arch perimeter loss was, on
average, .8mm greater in cases with third molars than in cases
with congenitally missing third molars, and this was shown to
be statistically significant.

Vego's work showed that the probability of a loss of more than
3mm was approximately 8% in cases without third molars, but
33% (more than four times as likely) in cases with erupting
third molars.
Hence, from this work it can be concluded that, whereas the
third molars are not always the reason for teenage mandibular
crowding, they are a significant contributor in a great number
of cases.


Other researchers have reported "no significant differences"
between cases with and without third molars.
Kaplan concluded: "These data indicate that the third molars
does not appear to produce a greater degree of lower anterior
crowding and rotational relapse after the cessation of retention
The theory that third molars exert pressure on the teeth mesial
to them could not be substantiated in this study."
A closer look at the details of Kaplan's work shows, however,
that the group with erupting third molars had an average of
1mm more crowding than the group with third molar agenesis,
almost precisely the same result as Vego obtained.

A long-term prospective evaluation of the circumferential
supracrestal fiberotomy in alleviating orthodontic relapse AJODO 1988 May - Edwards
There are two soft-tissue periodontal entities that may influence
the stability of the teeth following orthodontic movement: the
supra-alveolar group of fibers and the principal fibers of the
periodontal ligament.
The method by which these soft tissues might apply a force
capable of moving teeth is not clear since these tissues are
composed primarily of non-elastic collagenous fibers.

In any case the potential for relapse forces in the fibers of the
periodontal ligament and transseptal groups most adjacent to
the alveolar crest is certainly minimal because these tissues
have been shown to possess a dynamic remodeling mechanism
that is quite efficient.
How does a tissue that is essentially composed of inelastic,
non-contractile tissue apply a force? As yet the answer is
unknown.
One possibility may involve that the length of collagen fiber
can be altered by adjusting the ion concentration of its
surrounding medium; thus, a mechanism is proposed by which
the contractile collagen could "recoil" following orthodontic
tooth movement.

Another histologic explanation of relapse force may relate to
the elastic-like oxytalan fibers that apparently increase in
concentration in the supracrestal tissues during the rotational
movement of teeth.
However, although these oxytalan fibers possess some staining
properties similar to elastic fibers, there is no direct evidence
that they are physiologically similar to elastic fibers.
Fullmer, Sheetz, and Narkates cautioned that oxytalan could
actually represent altered collagen fibers.
In summary, there is no substantial evidence at the present
time to explain the mechanism by which the gingival soft
tissues may apply a force capable of moving the teeth.

Edwards reported on a simple surgical technique to
alleviate the influence that the supracrestal
periodontal fibers presumably have on rotational
relapse. He has termed the procedure a
circumferential supracrestal fiberotomy (CSF)
procedure.
Basically, this technique consists of inserting a
surgical blade into the gingival sulcus and
severing the epithelial attachment surrounding
the involved teeth. The blade also transects the
transseptal fibers by interdentally entering the
periodontal ligament space. Although the
transseptal groups adjacent to the alveolar crest,
as well as the principal fibers of the periodontal
ligament, do show relatively rapid reorganization
following tooth rotation and thus are presumably
not of importance in the relapse mechanism, No
surgical dressings are indicated and clinical
healing usually is complete in 7 to 10 days.

The CSF procedure is not recommended during active
movement of the teeth or in cases with gingival
inflammation. Although the most obvious condition
for the use of the supracrestal fiberotomies is that of
the rotated tooth, the procedure has also been
recommended following labiolingual orthodontic
tooth movement.


The logic of modern retention procedures Henry
Kaplan AJO-DO 1988 Apr (325-340):
Hellman's (1936)7 statement that ''We are almost in
complete ignorance of the factors which pertain to
retention for the individual patient.“
Reitan's (1959, 1966, 1967) microscopic studies of
postretention treatment changes excited the
orthodontic community worldwide. He
demonstrated in animal studies that the
supracrestal gingival fibers (collagenous) appear
histologically taut and directionally deviated after
tooth rotation, and that this condition did not lessen
even after years of retention.

Williams (1985),188 in addition to stripping, added five other
treatment "keys," which he said will eliminate the need for
lower retainers, but he showed a 2-year follow-up of one
case.
These approaches and that of Peck and Peck's (1972)61
reproximation studies are seemingly based upon the
theoretical concept of polished broad contact areas
described by Begg in Stone Age men.
Begg made the deduction that it was the primitive rough
diet of the Australian aborigines that was responsible for
well-aligned teeth. On the other hand, it was believed that
failure to achieve polished broad contact areas during and
following orthodontic treatment of modern civilized man
with a lack of comparable attrition would require a
technique for realignment and stripping of crowded lower
incisors to prevent or correct relapse.

Muchnic informed his patients:
In most cases the retention period was planned
with expected growth and maturation in mind,
because the forces which work so efficiently in
treatment to inhibit growth in one area while
allowing growth to continue in another should
not necessarily be discontinued because the
bands have been removed and the teeth are in
proper occlusion.
He has gone to the extent of informing the patient
that there is 33% chance of relapse not
occurring in every case i.e one in every three
case will not relapse.

 Evidence

of instability is often first noted by
progressive crowding of mandibular incisors
following removal of retaining devices. Whatever
may be the of causes of relapse, mandibular
irregularity is the precursor of maxillary crowding,
deepening of the overbite, and generalized
deterioration of the treated case."
 Second, the popular conceptions of greater
stability of a case post-retention, such as
maintaining canine and molar width, were usually
upheld, but in some cases it did not ensure stability
because mandibular incisor relapse occurred even
when intra-canine width was not violated in
treatment

 Third,

how does the orthodontist reconcile the
statements that arch length could almost never be
increased and as a rule decreased postretention
with the finding of another study that "Premolar
width expansion in non extraction treatment has
only slight tendency to decrease post retention"?
The latter would seem to lead to anterior crowding.
 Fourth,

serial extraction procedures followed by full
orthodontic treatment showed more stability, but
some incisor relapse was still reported for these
cases in post-retention studies even though early
rotations had been performed and held during a
growth period.

 What

then are the conclusions of this article that are
of significance to the orthodontist in addressing the
patient's recurring question about the need and
duration of retention?
 It is suggested that the clinician simply tell the
patient in understandable language what is and
what is not known about the "state of the art" of
retention that is applicable to the individual, whose
facial- dental objectives of treatment have been
satisfactorily achieved.


1There are very few cases requiring minimum or no
retaining appliances and these would include:
a. Blocked out canines in Class I extraction cases with
no crowding
b. Class I anterior and/or posterior crossbites with very
steep cusps and no anterior crowding
c. Class II cases slightly over-treated with sufficient arch
length indicated by mandibular anterior spacing and
absolutely no mandibular incisor rotations
2. Routine cases, extraction or nonextraction, should have
retaining appliances— fixed or removable.
a. At least until the destiny of the third molar teeth is
determined [or]
b. Until the growth process has slowed in late teens and
early twenties [and]
c. Afterward at the option of the patient

3. Cases that will need indefinite retention
a. Class II, Division 2 Angle deep bite cases
b. Arch expansion treatment for esthetic demands
c. Patients with uncontrolled muscular or tongue habits
4. Cases that require operative procedures with
indefinite retention
a. Treatment limitations such as tooth size
discrepancies may result in increased overbite or
super Class I.
b. larger mandibular teeth will result in end-to-end
incisor relationships, maxillary spacing, or buccal endon occlusion.
c. Stripping or reproximation of oversized teeth and
esthetic bonding of malshaped or undersized teeth
may help resolve this problem.
d. A vertical incisal www.indinadentalacademy.com
relationship, which cannot be

5. Cases requiring special construction and/or renewal
of removable retaining appliances or acrylic on the
labial bows
a. Posttreatment adolescent palatal changes
b. Late mandibular growth spurt139 and Tweed type C
growers
c. To maintain torque and overbite correction
6. The orthodontist can never be completely certain that
the individual case will be in the 33% that will not
relapse, even if only mildly.
7. The patient should be apprised of the expected
changes of the maturing dentition, especially of
mandibular and maxillary crowding

Finally, in this era of informed patient consent, what
then, in the opinion of the author, is the logical
answer to the question of when the orthodontist
has the-sole option of prescribing very limited
retention or no retention? The answer is only
when there is absolute certainty that there will be
no relapse.


Summary:
Occlusion is a result of developmental processes in which the
main events are facial growth, dental development, and
function. These genetically and environmentally conditioned
processes continue to change throughout life, showing
significant individual variation.
The dynamics of facial development with variations in
maxillary and mandibular growth, together with dento-alveolar
development need to be better understood before orthodontist
can expect to achieve more stable treatment results.
Although appliances and mechanics used for correction of
malocclusion have improved in recent decades, the
identification of the etiologic factors that cause relapse has
proven elusive.

To conclude:
Quote Norman Kingsley (1908), "Father of Orthodontia," in his
last published article, had these prophetic words to say about
retention
“It is not so difficult to straighten crooked teeth, to get the
dental system into a position acceptable to your patients and
yourself, but to hold it there until it becomes permanently
settled, is a much more serious problem. It is the one important
consideration in all your prognosis, and the success of
orthodontia as a science and as art lies in the [retainer].... Do
not discharge the case or abandon retainers until there is a
reasonable expectation of permanence. You may rightfully ask
of that experience, how long will that be? Your patient will
pester you with the same query. Out of the same observation
and experience I can only answer, I am agnostic, I don't know,
in each and every individual case I do not know.

Thank you

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