Ld retention and relapse

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Retention and relapse in orthodontics

Introduct

ion

The problem of retention and relapse was born with the science of Orthodontics

and continues to persistently plague Orthodontic researchers and clinicians. Most authors of

Orthodontic textbooks, from ngle to the present!day writers, ha"e included the chapters on

retention and relapse in their publications. #n spite of all the ad"ances in the acti"e treatment

procedures, "ery few practitioners underrate the significance of retention. $e are yet pu%%led

how to sol"e the problem&

$ith the establishment of concept of normal occlusion and the classification schemethat incorporated the line, by the early '())*s orthodontics was no longer +ust the alignment

of irregular teeth, instead it had e"ol"ed into the treatment of malocclusion. ince precisely

defined relationships re-uire a full complement of teeth in both arches, maintaining an intact

dentition becomes an important goal of orthodontic treatment. ngle and his followers

strongly opposed extraction for orthodontic purposes. Treatment goal during this period was

#deal Occlusion.'

$ith the entry into 'stcentury, the goals ha"e somewhat appeared to change. The

goal of Modern Orthodontics is creation of best balance among occlusal relations, dental and

facial esthetics, stability of the results and its long term maintenance and restoration of

dentition /T$0012'. ims of orthodontic treatment ha"e been summari%ed by 3ackson as

3ackson*s triad. The three main ob+ecti"es are4

/a2 5unctional efficacy

/b2 tructural balance

/c2 0sthetic harmony

Retention is that part of orthodontic treatment during which a passi"e appliance is

used to maintain orthodontic correction of dental and skeletal structures and thereby

counteract relapse or the tendency for return of characteristics to original malocclusion.

Retention was defined by Moyers6as the holding of teeth followed by orthodontic treatment

in the treated position for the period of time necessary for the maintenance of the results.

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Riedel7 defined retention as the holding of teeth in ideal esthetic and functional

position.

Relapse may be defined as return of the corrected malocclusion towards the original

condition.

Moyers6defined relapse as loss of any correction achie"ed by orthodontic treatment.

The retention period has e"en been called econdary orthodontic treatment. 8lthough it

has been stated that correct diagnosis and planning of treatment, followed by a careful

stabili%ation of the final result, would minimi%e the importance of retention, relapse

tendencies still exist in a fairly high percentage of cases treated. 0"en if these precautions are

taken, howe"er, relapse after tooth mo"ement still remains a complex problem, with a

"arying number of factors in"ol"ed.

Orthodontists ha"e been concerned by relapse process for decades. e"eral studies

ha"e been carried out to determine the changes taking place se"eral years after orthodontic

treatment and the influencing factors. 5actors including growth, periodontium, age, third

molars, tooth dimensions etc ha"e been held responsible for post treatment relapse. e"eral

procedures ha"e been de"ised to ensure stability and pre"ent or at least a"oid post treatment

changes so as to reduce relapse. To achie"e this purpose, a proper understanding of the

changes occurring, "arious factors affecting relapse and retention procedures is important.

Thus our Orthodontic forefathers faced the problems of retention and the continued

trend, which owes to the biological and mechanical limitations, demands e"ery Orthodontic

student to go through the state of art of this perineal problem Retention and Relapse which

also is the purpose of this library dissertation.


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Historical background 9

look back at the origins of orthodontics (Weinberger)has shown that the necessity

of retention was not mentioned until about '( centuries after the first treatment modality was

described and would pro"ide a clue to establishing the priority of the esthetic needs of the

prospecti"e orthodontic patient. s Weinbergerstates, lthough orthodontics had its origins

in medicine, it had its beginnings in aesthetics. :ikewise, the modern well!trained clinical

orthodontist has recogni%ed that the most desirable facial!dental esthetics may be +ust as

important as excellent posterior occlusion and good function!possibly more so from the

standpoint of the patient*s needs. ;owe"er, there appears to be as much contro"ersy o"er thepresent treatment methods of achie"ing facial!dental ob+ecti"es as there was in the Case,

Dewey, Cryerextraction!nonextraction contro"ersy in '('', which still persists three fourths

of a century later in the writings of Tweed, Ricketts, Begg, Ten Hoeve, and Williamson.

dditional insight into the retention problem may be gained and our present day

limitations in achie"ing predictable stability appreciated when we learn about the anti-uity of

some of our still current modes of orthodontic treatment. #n the beginning, says Weinberger,

people sought relief because of the disfigurement of the crooked and irregular placed teeth9). #n that year4merson C. $ngell (+%*),as a byproduct

of his palate!splitting procedure, mentions the necessity to preser"e or retain space. ngell

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described his method of employing a +ackscrew for?rapid opening of the maxillary median

suture or to enlarge the face in the maxillary dental arches, in order to establish occlusion

without extraction of teeth?The time for this expansion need not exceed two weeks, after

which it is only necessary to preser"e or retain the space until complete eruption and

de"elopment of teeth in -uestion.

Only 8 years later in 0ngland,$l#red Coleman (+%') wrote about restoration of the

former condition by muscular pressure!in other words, the first illusion to relapse. More than

a century later, clinicians still refer to abnormal muscular pressure as a dominant factor in the

cause of relapse. #n the following year, C.$. 5arvin (+%%)described the physiologic reasons

for retention. #ndeed, he went a step further in his writing and emphasi%ed the necessity of

the preser"ation of correct facial expression or aesthetics as one of the ob+ecti"es of

orthodontic treatment. @ot long after, Brown5ason (+-&) (in 4ngland) described a

retaining plate for surgically rotated teeth. Thus, after more than '( centuries of some kind of

mechanical orthodontic inter"ention, recognition of the possible instability of treatment

emerged and the concept of a retaining appliance was born.

One of the earliest retaining appliances in the Anited tates was described by6ames

W. 2mit/ (++) before the ;ar"ard Odontological ociety in Boston. #t was a simple

"ulcanite plate with a bar extending o"er the labial aspect of the maxillary incisor teeth. #n

'>>6,H.C. 7"inbeydescribed a slightly more sophisticated maxillary retaining plate that had

strips of metal extending from the "ulcanite plate o"er the anterior teeth.

6ackson (+*3)mentioned the importance of retention and designed many retaining

de"ices!some permanent when necessary. lso, to pre"ent the tendency of the teeth to change

their positions after the remo"al of the retainer, he suggested that after they ha"e 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 upon the cicatrix thus formed to pre"ent their

retrograde mo"ement!in short fiberotomy.

$nglestated that obtaining normal occlusion /with steep cusp height2 during the

eruption period would decrease retention time, but added that when habits are not o"ercome

and the rotations and disturbance to the fibers of the periodontal membrane are "ery marked,

he described cutting gingi"al fibers to counteract this in his sixth edition publication /'())2.

;e warned that most appliances were remo"ed too soon before teeth were thoroughly

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established in occlusion, and he ad"ised, #n doubtful cases, wearing delicate and efficient

appliances indefinitely may be far less ob+ectionable than a malocclusion.

5inally $ngle de"ised and described many ingenious mechanical combinations of

cemented bands and spurs, the action of which were, to -uote his uni-uely descripti"e phase,

to antagoni%e the mo"ement of teeth only on the direction of their tendencies. lso in his

-uest for the ultimate retainers, it is interesting to note that ngle*s intricate pin and tube

acti"e treatment appliance was de"eloped primarily as a working retainer to achie"e bodily

mo"ement or uprighting of teeth that had been tipped outward in expansion.

#n his article, Crinciples of Retention, Case listed the following principles4 Cost

treatment influence of surrounding tissues would return to their former irregular position

after retention primarily because of the more important factor of hereditary< stretched and

bent fiber structures would be brought to e-uilibrium in their changed positions by the

physiologic process of nature< retention should be of ade-uate force to antagoni%e reacti"e

tendencies for relapse and held, often indefinitely by a fixed appliance, unless teeth are

brought to positions of what he called positi"e self!fixation by occlusion< o"er correction

and slower mo"ement of teeth< use of inconspicuous fixed retainer, incorporation of strong

intermaxillary and "ertical elastics with chin cups to o"ercome the reacti"e or relapsing

forces of the corrected mesial or distal occlusion as well as open or closed bites< for retaining

diastemata of both the maxillary and mandibular anterior teeth, gold staples were cemented

into drilled preparations in all lingual cingula, which remained in place for more than )

years.

hundred years ago,Bonwilldescribed an ideal morphologic arrangement of teeth

and +aws based on his study of more than ))) skulls. ;e placed study models in anatomic

articulators, used wax set!ups of plaster teeth for extraction decisions< and thoroughly

informed his patients on the limits of treatment and the necessity of ade-uate retention.

8ormal 9ingsley (+*),who is referred to as the 5ather of Orthodontia, in a letter

/his last published article2 to the alumni of the ngle chool of Orthodontia written 8) years

after his first article appeared, had these prophetic words to say about retention.

#t 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

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settled, is a much more serious problem. #t is the one important consideration in all your

prognosis, and the success of orthodontia as a science and as art lies in the DretainerE?

errar (+1+++1),also referred to as one of the fathers of orthodontics!that is,

scientific orthodontics!the man who introduced the term intermittent force and wrote,

according to Weinberger, the greatest text on orthodontia in his experience, said /about

retention2 that when the teeth are fully regulated they should be retained in position for a

year, perhaps longer.

#n summary, in the little more than one half century following ngell*s use of a

retaining plate in his palate!splitting techni-ue, there was general adherence to the necessity

of retention and e"en a similarity of appliances, but the knowledge gained was based solely

on the clinical experience and obser"ation of the aforementioned pioneer orthodontic

masters.

The next -uarter century witnessed the much needed addition of a more scientific

dimension to the retention literature as the clinical reports of the duration of a "ariety of

retaining appliances and the obser"ations and opinions ad"ocated by /'2 the following

orthodontic inno"ators and clinical scholars4 Hawley (++), Ha/n (+33), :"ndstrom

(+&), Hellman (+1%), 5ers/on (+1%), 5arc"s (+1), 5cCa"ley (+33), Tweed (+'3),

and !rieves (+33); /2 experimentally trained research!oriented orthodontists, 2kogborg

(+&) and


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likened the final positioning of teeth to an argument in which mother nature always had the

last word.

Ha/n (+33),dismayed by the apparent lack of will of the ma+ority of the profession

to study the retention problem ade-uately, obser"ed that retention in orthodontics is like a

neglected Fstep child*.

#n another "iew, 5cCa"ley (+33) a prophet before his time, proclaimed the

importance of canine position and referred to the canine rise as a protecti"e mechanism for

maintaining arch stability.

Goncurrent with the abo"e!mentioned work of clinical scholars, sgeneric statement that #f regular growth of any

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part of the body is interfered with by any cause, related parts tend towards compensation.

Thus,isc/erbelie"ed that a compensatory ad+ustment of facial growth would occur after

orthodontics since there has been an interference in the unfolding of the face. ;e continues4

Iery often the orthodontic forces are but an interlude in the continuous de"elopment of the

face, and pre!treatment and post!treatment stability is a result of an e-uilibrium between the

component parts of the dental! facial complex and in the random and dynamic changes

occurring post! treatment, the denture must be protected or retained during the acti"e period

of facial!dental growth changes or at least until cessation of ma+or growth changes.

2c/wart@ reiterated this theme and described internal oppositional forces or

electric effect that was beyond the control of the orthodontist. 1uring the posttreatment

period, 2c/wart@said #nternal and external forces playing on the denture lead to %ero and

stability. #t is only a momentary static situation, because growth and change is occurring and

the e-uilibrium that results must somehow anticipate and include both growth and change to

insure stability.

#n direct contrast, !eorge !rieves (+33) belie"ed that the cause of most

malocclusions was the forward translations of teeth /in agreement with a similar proposal in

the earlier work of6. 2imms Wallace, +&-2 and that when teeth ha"e been placed backward

and upright o"er basal bone they would be stable and hence ha"e no need for retention.

lthough Tweedad"ocated placing teeth back and upright o"er basal bone, he prescribed 8

years retention in most cases and e"en longer periods when needed.

!eorge $nderson>s (+3&)obser"ations led him to the conclusion that nothing was

stationary in the human masticatory field.

There has been stability worthy of the name in the de"eloping masticatory field or in

the fully erupted denture, and that retention was not a minor but a "ery serious matter and a

basic part of orthodontic therapy.

1uring this same period, the application of facial, +aw and body muscular exercises

/myofunctional therapy2 with fixed appliances for successful treatment and retention was

brought forth in a series of publications from '(68 to '(8' by$l#red P. Rogers (+'+).

#n contrast, Dallas 5cCa"ley (+33)placed great emphasis on maintaining canine

position, arch form, and width as related to functional +aw mo"ements to achie"e

posttreatment stability.

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2tedman (+%+, +%-), in a comprehensi"e approach to retention, referred to an

enlarged pharyngeal space, emotionally initiated mentalis or mimetic muscle hypertension,

and anterior component of force of mandibular third molars because of insufficient growth as

factors in bringing about undesirable posttreatment changes or relapse.

2tedmanad"ocated the use of specially constructed, fixed and remo"able retainers

and he may ha"e implied their long!range use when it was not the case in his theoretical

statement4

:asting occlusal changes occur only in these particular patients whose internal forces

ha"e changed in such a manner during treatment and retention as to support those particular

teeth in the newly ac-uired positions, with new functional and emotional habits.

Riedel>s (+%*)comprehensi"e re"iew of retention was a forerunner of his subse-uent

')!year post!retention relapse studies and those of his graduate students at the Ani"ersity of

$ashington in eattle. These and the multitude of postretention relapse studies by others

report their extensi"eness, unpredictability, and se"erity, and are the grim realities facing the

orthodontic clinician.

#n essence, these relapse tendencies were graphically described by !raber (+%%)and

by9ing (+-3).

Iery often the characteristics of the malocclusions by which we determine

classification seem to reoccur in an alarming degree post!retention. Relapses of crowding,

rotations, mesio!distal relations, o"erbite, o"er+et and arch width and form reappear

subse-uent to retention. There is no assurance that relapse will not happen e"en when surgery

is combined with orthodontic treatment.

9ingdescribes the characteristics of post!retention relapse as an o"erall slipping

back or dental changes, "ery much in agreement with !raber.

#n specific postretention relapse studies, attention has been focused on the stability or

relapse of canines and molar width, mandibular arch form, mandibular incisor crowding,

rotations, o"erbite and o"er+et, and the presence or absence of mandibular third molars. #n all

these studies, extraction or nonextraction, there appears to be sufficient unpredictability of

which cases will or will not relapse for all but a minority of treatment procedures.

The relapse tendencies reported in the abo"e!mentioned studies ha"e occurred with

treatment using what has been considered to be con"entional orthodontic forces. #t is

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important to know whether there is a difference in the effect of the orthopedic palate!splitting

forces reintroduced clinically byDeric/sweiler (+'%)and continued by9ork/a"s (+%*)in

=ermany. oon after !raber and Haas reported clinical /extraoral and palate! splitting2

studies, and Mc@amara reported experimental studies. 0xperimental and clinical reports on

the effect of high!pull orthopedic forces byWatson (+-&), T/om=son (+-3), 4lder and

T"erge (+-3), Cleal (+-3), and Wislander (+-3)differ on the extent of skeletal stability,

but show high agreement to the effect that dental instability or relapse, especially mandibular

incisor changes following orthopedic forces, is consistent with the continuing changes that

occur in con"entional force treatment.

There is a recent trend of orthodontists in the Anited tates to report the use of

acti"ators andJor functional appliances, alone or as a preliminary to a secondary period of

treatment, using a multibracketed fixed appliance. long with this trend, there is also the

belief that the results will be more stable.

Reitan>s (+', +%%, +%-)microscopic studies of postretention treatment changes

excited the orthodontic community worldwide. ;e demonstrated in animal studies that the

supracrestal gingi"al fibers /collagenous2 appear histologically taut and directionally

de"iated after tooth rotation, and that this condition did not lessen e"en after years of

retention.

#n response to Reitan>swork, many surgical approaches with experimental animals

and human sub+ects to control or lessen rotational relapse in orthodontic treatment ha"e been

reported in the literature.

9ole (+')remo"ed the buccal and lingual cortical plates on human patients before

initiating orthodontic mo"ement, somewhat reminiscent of the septotomy of Talbot (+%)

and 2kogsborg (+&-). T/om=son (+') /repeated by Boese in '(9(2 remo"ed all the

attached gingi"al tissue on experimental animals, lea"ing only the mucosa surrounding

rotated teeth.

4dward>s (+-*) clinical orthodontic study was based on Ba"er>s (+%1) thesis

describing mesial and distal incisions of transseptal fibers of rotated teeth in experimental

animals and4dward>s own similar animal study /'(9>2.

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Parker (+-&),in a clinical study of transseptal fibers, states4 Rotational relapse is a

normal, predictable, physiological response to abnormal forces ? The paralleling of tooth

roots, discriminate transection of free gingi"al fibers and ade-uate retention time are "ery

important and useful ad+uncts to stability in treated orthodontic cases.

$ith the growing e"idence that the presence of intact transseptal fibers was the ma+or

"illain in rotational relapse,9a=lan (+-%) undertook a natural sur"ey of '))) orthodontists

to determine the extent of circumferential supracrestal fiberotomy as an ad+unct to retention

procedures. ;e concluded4

$hile it appears that this surgical techni-ue is not widely prescribed, it seems

reasonably problem free and its use will probably be increasing in the future. D;e cautions,E

There are as yet no follow!up studies of the efficacy of this treatment procedure.

5inally, 2c/acter and Bernick>s (+-3) conclusion, in an experimental study on

nonhuman primates that their study did not answer the problem of why certain rotations do

not occur e"en after surgical transection of the fibers must be pertinent to all

aforementioned fiberotomy studies.

lmost in lieu of retention or in retreatment, there ha"e been studies of stripping

either to pre"ent rerotation of the mandibular incisor or to correct the relapse of the

mandibular incisors, followed with or without retaining appliances. Kelston (+%)presented

a techni-ue for realignment with wires and ligatures after stripping of crowded lower incisor

teeth. Paskow (+-*) reported self!alignment following interproximal stripping of lower

incisors and was indefinite about retainers.Boesereported a combined procedure of stripping

and circumferential supracrestal fiberotomy with no lower retainer placed. #n his 7!( years

follow L up, he noted that the lower incisor segment did mo"e, but mo"ed in a unit rather

than each tooth indi"idually. ;e concluded4

G5 and reproximation is not a guarantee for permanent ideal lower anterior tooth

alignment, but was percei"ed as a useful process, which appears to work within a framework

of natural changes that ine"itably will occur.

Williams (+'),in addition to stripping, added fi"e other treatment keys, which he said

will eliminate the need for lower retainers, but he showed a !year follow!up of one case.

These approaches and that ofPeck and Peck>s (+-&) reproximation studies are seemingly

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based upon the theoretical concept of polished broad contact areas described by Begg in

tone ge men. Begg made the deduction that it was the primiti"e rough diet of the

ustralian aborigines that was responsible for well!aligned teeth. On the other hand, it was

belie"ed that failure to achie"e polished broad contact areas during and following orthodontic

treatment of modern ci"ili%ed man with a lack of comparable attrition would re-uire a

techni-ue for realignment and stripping of crowded lower incisors to pre"ent or correct

relapse.

Waldron (+3&) designed his retaining appliances on the basis of the rationale of


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anterior hooks using latex elastics and a bite!plate, which would permit the maxillary incisor

teeth to tip slightly labially.

Tweedreferred to a retrospecti"e study /8 years posttreatment2 on retention that he

had conducted on a follow!up group of his own patients consisting of ')) extraction and '))

nonextraction cases. ;e said that in general while many patients /had2 lo"ely faces teeth,

in others, the picture DwasE the opposite and that the extraction cases seemed to be nicer

than nonextraction cases many years after treatment.

Tweedacknowledged that in his opinion abnormal muscle function was a ma+or

factor in relapse e"en though he did not know how much one could change muscle function

as a result of orthodontic procedure. @e"ertheless, he said he would try to o"ercome the

per"erse muscle and tongue habits.

2and"sky (+3)reported a postretention relapse study /')!year a"erage2 of >8 Tweed

treated cases!78 by Tweedhimself and 7) by Tweed #o"ndation members.The mandibular

incisor relapse was shown to be -uite small less than ')N using the :ittle index!but other

changes occurred, namely, forward mo"ement of lower incisors and change of occlusal

plane.

t the same time,:ittle (+3)reported on a ')!year postretention relapse study of

78) cumulati"e cases from the Ani"ersity of $ashington group at eattle, led by Riedel.

:ittle showed that 99N of these cases exhibited mandibular incisor relapse with no statistical

support of predictability of which cases would relapse and which would remain stable.

Philosophies or schools of thought of retention

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5or many years clinicians did not agree about the need for retention. O"er the years,

different philosophies or schools of thought ha"e de"eloped in regard to the retention and our

present!day concepts generally combine se"eral of these.H

1) The occlusion school:

9ingsley (+*) stated, The occlusion of the teeth is the most potent factor in

determining the stability in a new position. Many early writers considered that proper

occlusion was of primary importance in retention and has been repeatedly stressed in the

literature (Reitan, 2c/"dy, 9a/l 8ieke). $nglebelie"ed that permanency of treatment result

could be ensured by creating a normal occlusion with a full complement of teeth, pro"ided

there was ade-uate retention and "igorous masticatory function.

2) The apical base school:

#n the middle '()*s a second school of thought formed around the writings of $0el

:"ndstrom,who suggested that the apical base was one of the most important factors in the

correction of malocclusion and maintenance of a correct occlusion. ;is clinical studies on

apical base did much to counteract the dominance of the expansionists led by $ngle. ;e

stated that occlusal function alone could not control the form and amount of apical base

rather the apical base is in largely capable of affecting the dental occlusion.Dallas 5cCa"ley

(+33)placed great emphasis on maintaining canine position, arch form and width as related

to functional +aw mo"ements to achie"e post treatment stability. ;e suggested that

intercanine width intermolar width should be maintained as originally presented to

minimi%e retention problems. 2trangfurther enforced and substantiated this theory. 8ance

(+3-) noted that, arch length may be permanently increased to a limited extent. This

school of thought suggested that mandibular intercanine width and intermolar width

dimensions show a strong tendency to relapse and should be considered in"iolate.

3) The mandibular incisor school:

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!eorge !rieves (+33) stated that cause of most malocclusions was the forward

translation of teeth and that when teeth ha"e been placed backward and upright o"er basal

bone they would be stable and hence ha"e no need for retention. Tweed (+33,+'&) also

suggested that the mandibular incisors must be kept upright and o"er the basal bone.

4) The musculature school:

$l#red P. Rogers (+&&) introduced a consideration of the necessity of establishing

proper functional muscle balance. Other corroborated this theory. 2trang (+'%) stated as

follows!The width as measured occurs from one canine to another in the mandibular

denture, is an accurate index to the muscular balance inherent to the indi"idual and dictates

the limits of the denture expansion in this area of treatment. d"erse J abnormal muscle

acti"ity has been "ariously proposed by many authors including Coleman, $ngle, Case,

2trange, Tweed, 2tedman andRogersas, if not the cause, then atleast a ma+or contributing

factor of relapse.

Orthodontists ha"e come to reali%e that retention is not separate from orthodontic

treatment but that it is part of treatment itself and must be included in treatment planning.

tability has become a primary ob+ecti"e in orthodontic treatment, for without it

either ideal function or ideal esthetics, or both, may be lost. Retention depends on what is

accomplished during treatment. Gare must be exercised to establish a proper occlusion within

the bounds of normal muscle balance and with careful regard to the apical base or bases

a"ailable and the relationships of these bases to one another.

Basic theorems of retentionH, >

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Theorem 1: Teeth that hae been moed tend to return to their former positions!

There is little agreement as to the reason for this tendency< suggested influences

include musculature, apical base, transseptal fibers, and bone morphology. $hate"er the

reason, there seems to be general agreement that teeth should be held in their corrected

positions for some time after changes are made in their positions. Only a few orthodontists

ha"e suggested that retention is routinely unnecessary. The -uestion of why teeth ha"e a

tendency to return to their former positions has, to this date, no real answer.

Theorem 2: "limination of the cause of malocclusion #ill preent recurrence!

Antil more is known about the causati"e factors that are related to particular types of

malocclusion, little can be done about their elimination. Therefore, a proper diagnosis based

on determining the cause of the malocclusion is in"aluable.

$hen ob"ious habits such as thumb or finger sucking or lip biting or tongue thrusting

are the causes of malocclusion, little difficulty is presented in diagnosis of the determining

cause. Anfortunately many of our malocclusions appear with apparently unknown origins or

at least origins about which we can do little. Gertainly heredity plays a most important part in

determining the presence of many malocclusions. #t is important, howe"er, in regard to

retention, that the causati"e factors for a gi"en malocclusion be pre"ented for recurring.

Theorem 3: $alocclusion should be oercorrected as a safet% factor!

Therefore, it is well to o"ercorrect the "arious malpositions and malrelations of teeth

and +aws. #t is common practice on the part of many orthodontists to o"ercorrect class ##

malocclusions into an edge!to!edge incisor relationship. Orthodontists must be aware,

howe"er, that these o"ercorrections may be the result of o"ercoming muscular balance rather

than absolute tooth mo"ement. The unrestricted use of class ## elastics sometimes produces a

mesial displacement of the mandible, which is almost impossible to detect until elastics ha"e

been discontinued long enough to allow normal mandibular posture.

The same phenomenon may be seen in the use of class ### elastic forces. The use of

elastics must be likened to the use of traction forces in orthopedic surgery, in which muscular

forces are o"ercome by constant pull. ;owe"er, absolute o"ercorrection is possible and has

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been demonstrated in many instances. O"ercorrection of deep o"erbite is an accepted

procedure in many practices.

Gertainly, satisfactory maintenance of o"erbite correction depends on the

establishment of satisfactory correction during treatment.

One of the most irritating types of relapse is the tendency for a pre"iously rotated

tooth to rotate towards its former position. :ittle e"idence is a"ailable to show that

o"errotation has been carried out and there is e"en less e"idence to indicate that such

o"errotation is successful in pre"enting the return to the former position.

Theorem 4: Proper occlusion is a potent factor in holding teeth in their corrected

positions!

n orthodontist should attempt to produce the best possible occlusion of the teeth.

The influence of occlusion is a factor in retention which has often been mentioned and

certainly the best possible occlusion is a factor in the retention of corrected malocclusions.

$hether or not it is the most important factor is certainly debatable. #n too many instances

we ha"e seen teeth, e"en with high cusps, locked into normal occlusion that will still tend to

return to their former positions. #t is e"ident that many orthodontists consider the denture

from a static "iewpoint, i.e., with the teeth in occlusion. The functional relationships of teeth

are certainly important factors in retention and this has been recently emphasi%ed by

numerous authors directing our efforts toward proper occlusal e-uilibration. 5rom the

standpoint of reducing the potential of irritations to the periodontium, an excellent functional

occlusion is certainly to be desired.

Orthodontists often blame o"erfunction or pounding of the mandibular canines by the

maxillary canines as a cause of relapse in the mandibular anterior area. The e"eryday

e"idence presented by the tremendous wear that may teeth undergo would indicate that they

do not mo"e in response to repeated grinding and tapping until the bone has either been so

thoroughly destroyed that it allows their migration, or until fibrous tissue builds up to a

degree where it actually mo"es the teeth and function on these teeth is actually not possible.

Gertainly instances of mandibular anterior irregularity or collapse are common, in which

canines either ha"e not yet erupted or are not actually in occlusion. @o doubt, we can say that

a perfectly normal denture functions best.

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Theorem &: Bone and ad'acent tissues must be allo#ed to reorgani(e around ne#l%

positioned teeth!

ome type of retaining appliance should be used either fixed and rigid or an appliance

that is inhibitory in nature and not dependant on the teeth for some length of time.

;istological e"idence indicates that both bone and tissue around teeth which ha"e been

mo"ed by orthodontic appliances are altered and that considerable time must elapse before

complete reorgani%ation occurs. ome authors ha"e indicated that retainers should be fixed

and rigid such as$ngle, who suggested = wire, band and spur type attachments, bands

soldered together etc. Others ha"e indicated that retainers should only be inhibitory and ha"e

no positi"e fixation to allow for the natural functioning of teeth. #t has been suggested that

the mandibular lingual arch admirably suits this description.


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perpendicular to the mandibular plane, or a plus or minus 8 from mandibular plane, or a

relation to occlusal plane, or 5rankfort hori%ontal plane. s to what is basal bone, there is no

experimental e"idence to indicate that anyone can specify that where this bone begins or

ends, and there seems to be no satisfactory method of measuring it.

#t has sometimes been assumed that teeth that are upright are also o"er basal bone.

;owe"er, in certain cases the roots of mandibular incisors ha"e been mo"ed labially to a

considerable degree in the process of uprighting these teeth. #t is significant that many

malocclusions present with mandibular incisors upright and o"er basal bone, and yet these

teeth are both crowded and rotated. ;ence the teeth that supposedly ha"e the attributes of

stability can actually be in a state of malocclusion.

5rom a purely mechanical standpoint a certain amount of "irtue exists in inclining the

mandibular incisors slightly to the lingual. Those who ha"e set mandibular anterior teeth

during fabrication of a diagnostic set up ha"e noted that if the teeth are aligned with a labial

inclination, attempts to push them lingually results in expansion in the canine area or collapse

of the teeth. On the other hand, if the anterior teeth are inclined lingually, further pressure to

the lingual does not cause collapse, and tipping to the labial only creates spacing. ;ence, if

we are to make any errors in positioning our mandibular incisor teeth, it is probably well to

err in the direction of a lingual rather than a labial inclination.

#f the patient is growing, the mandibular anterior segment may exhibit a physiologic

migration in relation to the mandibular body in a distal direction that is apart from the

orthodontic treatment. Mandibular arch form plays a more important role in stable

mandibular tooth alignment than does the relati"e antero!posterior relationship of mandibular

denture to base.

Theorem +: ,orrections carried out during periods of gro#th are less likel% to relapse!

Therefore orthodontic treatment should be instituted at the earliest possible age.

There seems to be little possible e"idence to substantiate this statement< howe"er, it has a

good deal in its fa"or from a logical standpoint if orthodontists are in any way able to

influence the growth and de"elopment of the maxilla andJor the mandible. #t is certainly

logical to presume that the growth of maxilla or mandible can only be influenced while the

indi"idual is growing and that once growth has been completed this potential is no longer

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a"ailable. $hen treatment depends on a retardation or change of direction of growth,

treatment must be instituted early during periods of acti"e growth.

0arly diagnosis and treatment planning appear to afford certain ad"antages in long!

term stability. #nstitution of early treatment can pre"ent progressi"e, irre"ersible tissue or

bony changes, maximi%e the use of growth and de"elopment with concomitant tooth

eruption, allow interception of the malocclusion before excessi"e dental and morphologic

compensations, and allow correction of skeletal malrelationships while structures are

morphologically immature and more amenable to alteration.

Much has been said about the change in muscular balance established by changing

the positions of teeth, which in turn will promote rather than retard normal growth. $hether

malrelations in muscle balance ha"e as much influence on growth and de"elopment as has

been supposed is "ery difficult to say. Ghanges in muscle balance in a normal direction allow

for more normal de"elopment of the dentition< in relation to retention, normal muscle balance

should allow for normal arch alignment.

$e can say here, howe"er, that where treatment depends on retardation or change in

direction of growth such as is effected in headgear therapy, treatment must be instituted

during a period of growth.

Theorem -: The further teeth hae been moed* the less likelihood of relapse!

Thus, cases in which it has been necessary to mo"e teeth a great distance are in need

of lesser retenti"e attention or it is desirable to mo"e teeth farther in the process of

orthodontic treatment.

#t is possible that positioning far from the original en"ironment will produce

e-uilibrium states permitting more satisfactory occlusions, but the wisdom of this rule has

not yet been put to the test. 5or e.g.4 in bimaxillary protrusions produced during orthodontic

treatment ha"e not shown a tendency to relapse inspite of the fact that there is a pronounced

labial axial inclination of both maxillary and mandibular incisor teeth. #t might well be that in

some of these cases the teeth are mo"ed far enough to be outside of the influence of labial

musculature, actually there is little real e"idence to support the statement that the farther

teeth ha"e been mo"ed the less relapse tendency they will ha"e. #n fact, the opposite may be

true. #t may be more desirable through guidance of eruption and early interception of skeletal

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dysplasias to minimi%e the need for future extensi"e tooth mo"ement with the resultant

influence on the functional en"ironment and such local factors as supracrestal fibers.

Theorem .: /rch form* particularl% in the mandibular arch* cannot be permanentl%

altered b% appliance therap%!

Therefore, treatment should be aimed at maintaining, in most instances, the arch form

presented by the original malocclusion as much as possible.

The e"idence brought to the author*s attention by8ance that attempts to alter arch

form in the human dentition generally met with failure has been accepted realistically by

most orthodontist. tudies of treated orthodontic cases out of retention ha"e lent credence to

this type of thinking. #n '(77, 5cCa"ley made the following statement4 ince these two

mandibular dimensions, molar width and canine width are of such an uncompromising

nature, one might establish them as fixed -uantities and build the arches around them.

2trangsaid essentially the same thing in '(794 # am firmly con"inced that axiom of the

mandibular canine width may be stated as follows4 The width as measured across from one

canine to the other in mandibular denture is an accurate index to the muscular balance

inherent to the indi"idual and dictates the limits of denture expansion in this area of

treatment.

e"eral instances of three or more millimeters of expansion of intercanine width were

found, but in these instances mandibular canines had been considerably constricted and were

blocked lingually to the general outline form in the mandibular arch. Gertainly there are

exceptions to the rule of in"iolability of mandibular arch form and intercanine width, but we

cannot expect all our patients to be exceptions. 0xtraction of two mandibular incisors

sometimes satisfies the re-uirements of the arch form without intercanine expansion /with

remo"al of two maxillary bicuspids2.

Of these theorems the following seem to be the most important4

'2 Teeth do tend to mo"e back toward their former position62 '(coined a phrase Gountdown to Retention, which he ga"e

to describe the time when retention should begin. The countdown begins when the patient*s

teeth ha"e been properly positioned L Gentric relation achie"ed, roots at extraction sites

parallel, mandibular canine width not expanded, proper buccal and labial tor-ue, normal

o"erbiteJo"er+et relationships, and Glass # relationships.

ny retention procedure before beginning should fulfill the following criteria4

1) ,orrection and oercorrection of the /P 'a# relationship:

Gonsiderations of anteroposterior skeletal and dental corrections are "ery essential

part of any appliance systems.

O"ercorrection of the Glass ## case is the greatest challenge in this area. #f corrected

only to the desired end position, many Glass ## cases will show a relapse of o"er+et and a

deepening of the bite. These patients benefit from o"ercorrection to an edge!to!edge position

and maintenance of that position with nighttime Glass ## elastics for 9 to > weeks, followed

by setting into an ideal Glass # relationship.)

2) "stablishing correct tip of the upper and lo#er anterior teeth:

#t is necessary to establish correct tip of the upper and lower anterior teeth at the end

of the treatment by mode of any appliance system. 5or all teeth, the gingi"al portion of long

axis of each crown should be distal to the occlusal portion of the long axis of each crown.)

3) "stablishing correct torue of the upper and lo#er anterior teeth:

#t is often necessary to ad+ust the tor-ue in the upper and lower anterior segments at

"arious stages of treatment.

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A. Moderate-to-severe Class II case before treatment. B. After overjet reduction, torque

has been lost in upper anterior segment and lower incisors are angulated forward. C.

Additional torque needed in archwires to recover correct incisor angulation.

The most common example is during o"er+et correction of the moderate!to!se"ere

Glass ## cases, when the tor-ue is fre-uently lost in the upper anterior segment while the

lower incisors are angulated forward. #n this situation, it may be necessary to compensate by

adding lingual root tor-ue to the upper anterior teeth and labial root tor-ue to the lower

anteriors.)

4) ,oordinating arch #idths and archform:

Gareful coordination of archwires from the beginning of treatment through the

rectangular wire phase will pre"ent unwanted and troublesome crossbites from de"eloping. #f

the patient*s archwidths are not properly coordinated at the start of treatment, this can be

compensated for by narrowing or widening the appropriate archwires from the earliest stages

of treatment.)

A. Cross-elastics in cuspid areas used to

compensate for asmmetrical upper

archform !smmetrical arch indicated b dashed line". B.

Modi#ed upper

archform !dotted line"$ archwire canted in direction opposite

to asmmetr.

&) "stablishing correct posterior cro#n torue:

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Gorrect posterior crown tor-ue is essential to pre"ent posterior interferences from

de"eloping and to allow the seating of centric cusps. The tor-ue built into pread+usted

posterior brackets usually eliminates the need for wire bending.)

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) "stablishing marginal ridge relationships and contact points:

Marginal ridges of ad+acent teeth should be at the same le"el or within ).8 mm of the

same le"el. Radiographically, the cementoenamel +unctions should be at the same relati"e

height, resulting in a flat bone le"el between ad+acent teeth.

Croper marginal ridge relationships in the finishing stage are primarily a function of bracket

height. $ith the standard edgewise appliance, the most common method of determining

bracket height in"ol"ed is by placing the brackets a specified distance from the incisal or

occlusal surfaces of the teeth. The brackets were thus located relati"ely more incisally or

occlusally on large teeth than on small teeth, which could result in tor-ue or in!out errors.

A. Brac%ets placed &mm above incisal edges,

according to standard edgewise technique. 'ith (mm

central incisor !left", brac%et is )* percent of distance

up crown surface. 'ith +*mm central incisor !right",

brac%et is * percent of distance up crown surface. B.

ame teeth with brac%ets positioned in center of

clinical crowns, according to Andrews.

more reliable guideline is the center of the clinical crown, as described by ndrews,

which pro"ides a consistent bracket position regardless of tooth si%e.

#ncorrect bracket height becomes apparent early in the le"eling and aligning stage of

treatment. ;ence, it is effecti"e to reposition brackets as early as possible, so that time is not

wasted stepping archwires or repositioning brackets during the finishing stage. )

A. pper central incisor with incorrect brac%et height and

compensating step

in ./+0 archwire. B. Brac%et repositioned at ne1t

appointment, with ./+)0 archwire.

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+) ,orrection of midline discrepancies:

Most minor midline discrepancies of 6 mm or less can be corrected with rectangular

wires in the finishing stage, whereas greater discrepancies re-uire attention earlier in

treatment. There are fi"e methods of elastic wear for specific situations4

/2 single class ## elastic on one side and a double class ## elastic on the other, for cases

with a bilateral class ## component.

/B2 single class ## elastic on one side only, when the o"er+et results in a slight class ##

relationship on that side and the opposite side is in a class # position.

/G2 Glass ### elastics on one side and class ## elastics on the other, for cases with the

corresponding dental relationships.

Methods of elastic wear to correct minor midline

discrepancies during #nishing stage. A. Case with

bilateral Class II component$ double Class II elastics on

right side, single Class II elastic on left. B. Case with

Class II molar relationship on right side and Class I on

left$ single Class II elastic on right side. C. Case with

Class II molar relationship on right side and Class III on

left$ corresponding interma1illar elastics.

/12 single class ### elastic on one side only, when that side is in a class ### position and

the opposite side has a class # dental relationship.

/02 n anterior cross!elastic, when the discrepancy occurs primarily in the anterior

segments.

2. Case with Class I dental relationship on

right side and Class III on left$ single Class III

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elastic on left side. 3. Case with discrepanc primaril in anterior segment$ anterior

cross-elastic.

symmetrical elastics should be used for a minimum period of time, and only with

rectangular archwires, because of their tendency to cant the occlusal plane. The archwires

should be tied back while these elastics are worn so that the wires do not slide around the

arch, causing unwanted space opening and distortion of the archform.)

-) "stablishing the interdigitation of teeth:

Maximum intercuspation should be established between the buccal cusps of the

mandibular posterior teeth and the lingual cusps of the maxillary posterior teeth. 0ach

functional cusp should be in contact with the opposing arch.

$hen the rectangular wires ha"e been placed for a long period, the teeth are often

unable to settle into an ideally finished position. #t is helpful to allow each case to settle

before debonding by using a lower .)'7 round archwire and an upper .)'7 round sectional

wire from lateral incisor to lateral incisor. This is accompanied by "ertical triangular elastics.

4ertical triangular elastics used in settling phase before debonding.

#f the teeth ha"e settled properly after two to four weeks, then the patient can be

scheduled for debonding. #f the teeth are not properly positioned, the patient can return to

hea"ier archwires for additional finishing.

The retainers will fit more properly after settling than if they immediately follow

rectangular wires.)

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.) ,hecking cephalometric ob'ecties:

Crogress headfilms should be taken about halfway through treatment to allow time for

reassessment of anchorage and possible changes in the di"ision of treatment time. Taking a

headfilm in the end of treatment may be important for the orthodontist*s education and for

e"aluating the success or failure of treatment, but it pro"ides no practical ad"antage to the

patient.

#mportant factors to e"aluate with progress and final cephalometric x!rays include the

anteroposterior position of the incisors, the incisor angulations, changes in the occlusal plane,

the degree to which "ertical de"elopment has occurred or been restricted, and the success of

the correction of hori%ontal and skeletal components of the case. uperimposition of the

progress and final x!rays on the pretreatment x!ray will help determine the orthodontic

changes that ha"e occurred.)

18) ,hecking the parallelism of the roots:

=enerally, the roots of the maxillary and mandibular teeth should be parallel to each

other and perpendicular to the occlusal plane, as "iewed in the panaromic radiograph. ;ence,

a panaromic x!ray should be taken before debanding to e"aluate root parallelism. #f roots are

properly angulated, sufficient bone will be present between ad+acent roots, an important

consideration in periodontal health. #f crown!root angulation is beyond normal standards,

bracket repositioning or archwire bending may be re-uired to modify the root positions.)

11) $aintaining the closure of all spaces:

ll spaces within the dental arches should be closed. #t is important that space closure

be maintained, particularly in extraction cases, by using passi"e tiebacks in the finishing

stage.

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Maintenance of lower arch space closure with passive wire tiebac% between molar

brac%et and soldered archwire hoo%.

Otherwise, spaces fre-uently open during finishing and must be reclosed. Open

spaces not only are unaesthetic, but also may lead to food impaction.)

12) "aluating facial and profile esthetics:

0sthetic e"aluation is an ongoing process during all stages of orthodontic treatment.

pro+ection of esthetic goals should be made as part of the treatment plan. The facial and

profile esthetics can then be monitored clinically, as well as with progress and final

cephalometric x!rays.)

13) ,hecking for T$9 d%sfunctions such as clicking and locking:

TM3 dysfunction is a broad sub+ect and the following are some of the recommendations

gi"en which a clinician should take into account4

/i2 1ocument any e"idence of TM3 dysfunction prior to treatment, and inform the

patient that such symptoms exist.

/ii2 Monitor the patient for symptoms of TM3 dysfunction during treatment. #f

problems are managed before the de"elopment of true internal derangement, then

+oint function can often be re!established without permanent damage with the help

of a short phase of splint and physical therapy, concurrent with the orthodontic

treatment, until the symptoms are eliminated. ;eadgears and elastic forces should

be stopped while managing the TM3 problems.

/iii2 Monitor the patient for symptoms of TM3 dysfunction during retention. Taking

tomographic x!rays before treatment, as well as to 6 months before debonding,

is helpful in detecting irregularities within the +oint and in e"aluating the clinical

position of the condyle.

A. 5atient showing anterior

s%id with corresponding

anterior condlar position.

6eadgear or Class II

mechanics should be

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continued to eliminate anterior s%id and allow condle to seat in fossa. B. 5atient

showing signi#cantl posterior condlar position with no evidence of anterior s%id. light

amount of anterior s%id should be provided b ceasing headgear or Class II

3lastics, or using Class III elastics, to achieve more centered position

The orthodontic patients generally benefit from the establishment of a seated and

reasonably concentric condylar position. forward or retruded condyle can often be

corrected during the finishing stage, in con+unction with minor changes in antero!posterior

and "ertical +aw position.)

14) ,hecking functional moements:

Before debonding, the patient should be checked for interferences during protrusi"e

mo"ements and lateral excursions. #t is important that the lower eight most anterior teeth

make contact with the upper six most anterior teeth during protrusi"e mo"ements. This

normally re-uires a slight widening of the archform in the bicuspid area, so that the mesial of

the lower bicuspids contacts the distal of the upper cuspids.

#n lateral excursions, the patient should experience cuspid rise with slight anterior

contact and disclusion of posterior teeth on both the working and balancing sides. econd

molars should normally be banded to pre"ent interferences in this critical area during lateral

excursions.)

1&) etermining if all habits hae been corrected:

;abits such as tongue thrusting will usually ha"e been corrected before the finishing

stage is reached, because as the patient grows, airway si%e increases and the tongue can

assume a more posterior position. lso, as the dental en"ironment that that supported the

habit is impro"ed orthodontically, the tongue and lip musculature adapt to the impro"ed

en"ironment and normal function begins to occur.)

1) ,orrection of rotations and oercorrection #here needed:

Most rotations will ha"e been eliminated before the finishing stage, particularly if

force le"els are kept low. ny remaining rotations can be corrected during finishing by one of

three methods4

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/i2 Rubber rotation wedges under the rectangular archwire.

/ii2 teiner rotation wedges L these are useful because they can be placed after the

archwire is in position.

/iii2 :ingual elastics L most effecti"e method.

These rotations should be slightly o"ercorrected during finishing to minimi%e relapse,

particularly in extraction cases.)

1+) "stablishing a relatiel% flat plane of occlusion:

Reasons for completing cases to a relati"ely flat occlusal plane to a slight arc in the

second molar region, according to ndrews, include the proper fit of the upper dentition

against the lower dentition. $hen a cur"e of spee is left in the lower arch, for example, there

is a tendency towards increased o"er+et, since the lower teeth occupy less room than the

opposing upper teeth. 1eep bite cases also benefit from o"ercorrection of the cur"e of spee,

because most deep bites tend to relapse.

#f the occlusal planes are not le"eled before finishing and detailing, the archwires will

not slide easily through the bracket slots during space closure with sliding mechanics.)

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uration of retention

;ow long should the orthodontist continue retention& The answer to this -uestion

"aries from not at all to fore"er. The answer also depends on the type of case treated, the ageof the patient, what the parent and the patient expect of the orthodontic treatment, all of the

limitations inherent in the case, and finally, what the orthodontist himself expects of his

treatment. #n the a"erage adolescent, when considerable growth and remodeling of the bony

en"ironment can be expected, it is reasonable to expect that retention should logically be

continued until the effect of these changes has slowed down. =enerally, this occurs at the

time the third molars erupt< hence it has been a rule for many to continue retention until these

teeth ha"e erupted or ha"e been remo"ed.'

o, to conclude some form of retention will probably be maintained until e"idence of

completion of growth is forthcoming, and consideration should be gi"en to the use of

retainers on and as needed basis indefinitely to ensure maintenance of tooth relationships. #t

should be4'

0ssentially full!time for the first 6 to 7 months, except that the retainers not only can

but should be remo"ed while eating /unless periodontal bone loss or other special

circumstances re-uire permanent splinting2.

Gontinued on a part!time basis for at least ' months, to allow time for remodeling of

gingi"al tissues.

#f significant growth remains, continued part!time until completion of growth.

5or practical purposes this means that nearly all patients treated in the early

permanent dentition will re-uire retention of incisor alignment until the late teens, and in

those with skeletal disproportions initially, part!time use of a functional appliance or

extraoral force probably will be needed.

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Ph%siologic recoer% or relapse

5or a successful result to an orthodontic experience, retention must be anticipated and

planned as a "ery important part of treatment of the dentition rather than as an apatheticallyundertaken aftermath or necessary e"il to the patient and orthodontist alike, which would

otherwise lead to a relapse process.

#n orthodontics it is important to differentiate between relapse and normal

de"elopmental changes in order to resol"e our responsibilities during retention.

Relapse is a return of detrimental features of the original malocclusion< while

de"elopmental changes refer to the indi"idual*s maturation process. To make this distinction,

we should ha"e a general understanding of growth, de"elopment, maturation to old age,

response to treatment techni-ues, and those factors necessary for an impro"ed or healthier

dentofacial en"ironment.

;orowit% and ;ixson', suggested that the term relapse should be replaced by the

term physiologic reco"ery as the dentition continuously changes throughout life. Biologically

these changes represent a reco"ery and rebound of indi"idual dental de"elopment pattern.

=rowth and remodeling are =erman factors of physiologic ad+ustments after acti"e

treatment< this remodeling ne"er stops, but the balance between apposition and resorption

change with ageing. #n addition to physiologic reco"ery, normal growth changes must be

included as contributing to continuous adaptation process that sustains the long!term stability

of dental apparatus.

malocclusion represents nature*s best effort to approach balance under the handicap

of asymmetric parts and disharmony. #t is as stable as the existing balance between muscle

and bone but can change until growth and maturation, +ust as in normal occlusion.

To establish an esthetically harmonious, functionally efficient and structurally balanced

dental arches in the area of functional tolerance "arious cardinal points like establishment of

proper static functional occlusion, archform and intercanine width maintenance, lower

incisors positioning, proper understanding of growth and de"elopment etc are "ery important.

Iiolation of the law of optimality is likely to re+ect the alteration imposed on an existing

orofacial en"ironment leading to relapse.

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,auses of orthodontic relapse

The complexity of the dento!maxillofacial organ, the marked changes that ha"e taken

place in its en"ironment since the time it e"ol"ed to its present form, and many otherinfluences L some of them understood and others not understood L contribute to instability of

the end results of acti"e orthodontic appliance therapy.

mong the goals of orthodontic treatment beyond facial and dental aesthetics,

function, and the health and longe"ity of the dentition is the achie"ement of stable or

relati"ely stable results. The reality of our present knowledge is that no form of treatment

guarantees absolute stability, nor does a well!treated case treated by the highest standards by

itself assure stability.

tability is not an absolute, and what one tries to do for a patient is to obtain

acceptable stability. The concept of acceptable stability is not an alibi for treatment but

recognition of biological limitations. The success of our treatment should be measured based

upon some type of ratio between the magnitude of patient impro"ement and the relapse.

uccess index')P Magnitude of #mpro"ement

Magnitude of Relapse

5ear of relapse is "ery real to most orthodontists and some are affected to a degree

that causes them to institute retention ad infinitum to all treated cases without regard to

indi"idual conditions.

$hy do successfully treated malocclusions fail& The sub+ect of failure is as "ast as

the field of orthodontics itself. #n fact, e"ery time we as orthodontist undertake to treat a

malocclusion we assume that the odds fa"or success but the possibility of failure, if not total,

exists in some degree.6

,auses of relapse:

The tendency of the teeth to undergo change of position immediately upon the

remo"al of the orthodontic appliances can be attributed to "arious factors like bone changes,

periodontal ligament tension, general metabolism, endocrine dysfunction, functional

adaptation of occlusion, inherent growth, tooth!si%e discrepancies, axial inclinations, soft

tissue maturation, connecti"e tissue changes and interference with the tra+ectorial forces

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established in function. $hen the aforementioned factors react fa"orably, the changes on

completion of treatment actually may help as time elapses to produce better esthetic tooth

arrangement and occlusion.

1);ate mandibular gro#th:

:ate mandibular growth may result in increased pressure at the front of the mouth.

Typically, the mandible grows and displaces forward at a faster rate than the maxilla

/measured to occlusal plane2 and the lower basal bone more than al"eolar bone. Tooth

compensations include the tendency of the lower incisors to mo"e lingually. #f the

mandibular incisors are not free to mo"e forward because of the restraining influence of the

upper arch, it is likely that they will become retroclined and, could be a contributing factor to

crowding in the lower anterior region. ;owe"er, no direct relationship between the increase

in crowding and the change in incisor inclination or position has been demonstrated.

:undstrom7examined 8 pairs of twins between the ages of ' and '8 years and 6 and 9

years. ;e found no relationship between anterior growth of gnathion and increased crowding,

or between changes in lower incisor inclination and increased crowding.

Richardson7measured changes in lower incisor inclination and position of the incisal

edge relati"e to the maxillary plane in 8' sub+ects with intact lower arches. Between the ages

of '6 and '> years, the a"erage change was proclination of +ust o"er ' with forward

mo"ement of '.) mm. #ncisor inclination was measured on the most procumbent lower

incisor. s contacts slip to permit imbrication, one or more incisors may procline as the

others retrocline in response to increased lingually directed force. This may mask any

relationship between increased crowding and incisor angulation.

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remains stable in most cases, increase in labial segment crowding is often associated with

dentoal"eolar adaptation. Mesial drift of buccal teeth contributes to the de"elopment of labial

segment crowding. Many causes of mesial drift ha"e been postulated, including the anterior

component of force, tensions in the supra!al"eolar connecti"e tissues and impactions of third

molars.8

@anda and @anda9 found that the pubertal growth spurt for patients with skeletal

deep bite occurs on a"erage '.8 to years later than is the case for open bite cases. 5or this

reason, a longer retention period for the skeletal deep bite patients is ad"ocated to counteract

the continuing effect of dentofacial growth after the completion of orthodontic treatment.

4) $andibular incisor dimensions5 Tooth structure:

Growding is slightly more common in persons whose teeth ha"e large mesiodistal

dimensions than in those with smaller teeth. mall but statistically significant correlations

between crowding and tooth width ha"e been found by some. Others found nonsignificant

correlations between these "ariables.

@o direct relationship has been established between an increase in lower arch

crowding and tooth structure. #t might be argued that teeth with large labiolingual dimensions

and broader contacts would be more stable and less likely to slip under pressure or tension.

The notation that mandibular incisor dimensions were correlated with lower incisor

crowding was reintroduced by Ceck and Ceck9, H after a study of 78 untreated normal

occlusions. They concluded that the ratio of mesiodistal /M12 to faciolingual /5:2

dimensions of lower incisors was an important factor in producing well!aligned mandibular

incisors. ;ence, they ad"ocated reduction of mandibular incisors to a gi"en faciolingualJ

mesiodistal ratio to increase stability. Ceck and Ceck*s work, howe"er, was critici%ed for the

following reasons. Their recommendations were based on a study in"ol"ing untreated rather

than treated cases. Qoung patients with ideal lower incisor alignment were used in the study.

#t is possible that these cases would show crowding if followed long term.

To e"aluate whether the Ceck and Ceck ratio had long!term "alue, =illmore and

:ittle9, H studied '67 treated and control cases a minimum of ') years presentation. They

showed a weak association between long!term irregularity and either incisor width or the

faciolingualJmesiodistal ratio. :ess than 9N of crowding can be explained by this ratio. #n

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addition, the actual mean difference in incisor widths between crowded and uncrowded cases

was only ).8 mm.

mith et al.7found nonsignificant correlations between crowding and labiolingual

incisor width in ')) untreated orthodontic sub+ects and ')) untreated adults, and low

significant correlations between crowding and mesiodistalJlabiolingual incisor ratio.

Cunky et al.7found nonsignificant correlations between labiolingual lower incisor

dimensions, or their labiolingualJ mesiodistal ratio and lower arch alignment in HH treated

cases or >9 untreated adult malocclusions.

=len et al.7could find no relationship between mesiodistalJlabiolingual ratio and

incisor irregularity in > nonextraction orthodontically treated cases, either before treatment

or 6 years after!retention.

0"idence from these studies suggests that tooth structure plays only a minor role /if

any2 in the etiology of late mandibular incisor crowding.

Boese>, ( introduced a concept of lower incisor reproximation to pro"ide broader

contact points and increase the a"ailable arch space in the mandibular anterior region. ;e did

a retrospecti"e study that in"ol"ed continued inter"ention during the retention period, e"en in

the presence of minor relapse. ;ence, we are unable to compare the results of this study with

results from other retention studies.

&) =cclusal factors:

The attachment apparatus of all teeth is an effecti"e hydrodynamic damping system,

like an automobile shock absorber, and is well!designed to withstand occlusal forces. #f teeth

did reposition themsel"es in response to occlusal forces, it would not be necessary for

dentists to be so careful with occlusal relationships. The teeth would make minor corrections

for themsel"es. This does happen +ust after the completion of orthodontic treatment, when the

teeth are hypermobile and the attachment apparatus is reorgani%ing. lterations in functional

occlusion may produce a different pattern of masticatory forces or an occlusion with

premature contacts. The importance of functional and stable occlusion posttreatment is

repeatedly stressed in the literature.

Brodie7suggested that with each stroke of mastication, the upper incisors recei"e a

separating impulse, whereas the lowers tend to come into closer contact. This implies

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retroclination of lower incisors. The principle may also be applied to indi"idual teeth coming

into premature contact, being displaced by the force of occlusion, and allowing ad+acent teeth

to mo"e toward each other, thus creating a crowded situation. Ganine guidance in lateral

excursion may cause a lingually directed force on lower canines, with a reduction of inter!

canine width.

On the other hand, Croffit7pointed out that the supporting structures of the teeth are

designed to withstand hea"y, short acting, forces, such as those of occlusion. @e"ertheless, it

seems possible that these forces, in combination with other factors, may contribute to tooth

mo"ement and crowding. Carafunctional acti"ity could exacerbate this phenomenon.

Occlusal relations may be altered by orthodontic treatment of the upper arch. 1ifferent types

of upper arch treatment may ha"e differing effects on the lower arch.

:ombardi7 suggested that there may be a relationship between o"ercorrection of

maxillary canines and mandibular incisor crowding.

Occlusal changes may also be caused by restorations, tooth loss with drifting, or the

de"elopment of grinding habits.

de-uate interincisal contact angle may pre"ent o"erbite relapse and good posterior

intercuspation pre"ents relapse of both crossbite and anteroposterior correction. :ess relapse

of mesiodistal mo"ement occurs in the absence of occlusal stress.

) Influence of the elements of the original malocclusion:

The most basic cause of relapse to occur is the persistence of the elements of original

malocclusion or the etiology. #f the underlying etiology is not remo"ed, the treatment is

destined to relapse. #t is mandatory for all clinicians to first diagnose a case properly, and

plan the treatment and retention initially itself, keeping the etiology in mind. The remo"al of

the etiologic factor before finishing is mandatory.

O"erbite increase postretention is related to the amount reduced during treatment,

although generally 6)N to 8)N of the correction is retained. #t is suggested that o"erbite

relapse tends to occur in the first years posttreatment and maintenance of the intercanine

width is thought to increase stability. #n the anterior open bite correction e"aluated in 7'

patients, 7)N showed marked relapse and the other 9)N showed stability of the result. The

relapse subgroup showed a greater increase in lower anterior face height during the

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postretention period than did the stable group, but no posttreatment "ariable could be used to

predict posttreatment relapse or stability.

Most studies do not support a greater relapse in class ## di"ision ' cases when

compared with other malocclusion groups, howe"er, a slight change in o"er+et toward

pretreatment "alues was demonstrated in all malocclusion groups. :abially inclined incisors

pretreatment tend to be associated with less long!term crowding. #t is postulated that the

weaker labial muscular forces do not induce lingual mo"ement of the dentition and

subse-uent arch length shortening.

$hen teeth are aligned by orthodontic treatment, there is a documented tendency for

a return toward the original pattern of malocclusion. 5or this reason, rotational o"ercorrection

has been ad"ocated. :ittle et al., howe"er, note that there are many exceptions to this rule

with greater than 8)N of the rotations or displacements relapsing in an opposite direction. 9

Adhe et al.'7formed a multiple regression analysis of o"er+et, o"erbite, intercanine

width, and intermolar width changes. They re"ealed that 7'N of late lower incisor crowding

could be explained by these "ariables. The relati"e contribution by these "ariables "aries

between indi"iduals with a similar degree of irregularity.

+) /lteration of arch form:

#t is generally agreed that arch form and width should be maintained during

orthodontic treatment.H, 9 #n certain cases, where arch de"elopment has occurred under

ad"erse en"ironmental conditions, arch expansion as a treatment goal may be tolerated.

There is e"idence to show that intercanine and intermolar width decreases during the

postretention period, especially if expanded during treatment /mott, rnold, $elch, and

others2. 5or this reason, the maintenance of arch form rather than arch de"elopment is

generally recommended. 0xpansion is thought to be better tolerated in class ## di"ision

cases that show a significantly greater ability to maintain intercanine expansion than class #

and class ## di"ision ' cases. This statement, howe"er, was based on a sample of 9 patients

and was not accepted by :ittle et al6)who maintained that intercanine and intermolar width

will relapse if expanded in class ## di"ision cases as much as in other ngle classifications.

nother exception to the maintenance of arch width may be found in cases of

mandibular expansion concurrent with rapid palatal expansion. ;aas6'and andstrom et al.6

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found that maintenance of 6 to 7 mm intercanine width and up to 9 mm intermolar width was

possible when expansion was carried out concurrently with maxillary apical base expansion.

These two studies, howe"er, are -uite misleading. ;aas study was based on ') cases and

primary canines were present in the initial records for two of these. ;ence, one cannot

extrapolate on the amount of canine expansion achie"ed, when in )N of this small sample,

the permanent canines were not present at the time of the original records. andstrom*s

statement that mandibular incisor stability is increased when the mandibular intercanine

width is expanded in con+unction with maxillary expansion is based on a sample of 'H

patients only years postretention.

Moussa et al.66reported on a sample of 88 patients who had undergone rapid palatal

expansion in con+unction with edgewise mechanotherapy a minimum of > years

postretention. Their results showed good stability for upper intercanine and upper and lower

intermolar widths. tability of the mandibular intercanine width, howe"er, was poor with the

posttreatment position closely approximating the pretreatment dimension.

1e :a Gru% et al.67 carried out a ')!year postretention study on >H patients to

determine the long!term stability of orthodontically induced changes in maxillary and

mandibular arch form. The results showed that although there was considerable indi"idual

"ariability, arch form tended to return toward the pretreatment shape. They concluded that the

patient*s pretreatment arch form appeared to be the best guide to future stability.

-) Periodontal forces:

#n series of experiments on monkeys, Cicton and Moss 7and Cicton7demonstrated

that the teeth are +oined together by a system of transeptal fibers under tension.

Croffit7claimed that a slight imbalance of force between the tongue on one side and

the lips and cheeks on the other is normally present. ;e suggested that the teeth are stabili%ed

against this slight imbalance by forces produced in the periodontal membrane by acti"e

metabolism.

outhard et al.7demonstrated the presence of a continuous periodontal force on the

mandibular dentition, acting to maintain proximal contacts in a state of compression. This

force was increased after occlusal loading. They found significant correlations between

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interproximal force and mandibular anterior malalignment. They concluded that periodontal

forces could contribute to the de"elopment of late lower arch crowding.

.) Periodontal and gingial tissues:

Orthodontic tooth mo"ement to correct tooth rotations is proposed to result in

stretching of the collagen fibers. These stretched fibers /transeptalJcollagen2 ha"e been

implicated in rotational relapse by pulling the teeth back toward their pretreatment position.68,

69

Brain and 0dwards9ad"ocated gingi"al fiber surgery /Gircumferential upracrestal

5iberotomy2 to allow for the release of soft tissue tension and reattachment of the fibers in a

passi"e orientation after orthodontic tooth rotation.

The theory of stretched collagen fibers as the cause of rotational relapse has recently

been -uestioned by Redlich et al.6Hwho analy%ed gingi"al tissue samples obtained from

rotated incisors in dog. They found that the rotational forces caused significant changes in the

integrity and spatial arrangement of the gingi"al tissues, changes that are inconsistent with

stretching. fter fiberotomy, reorgani%ation of the fibers similar to the control group was

e"ident. They concluded that the rotational relapse may actually originate in the elastic

properties of the whole gingi"al tissue rather than stretching of the gingi"al fibers as

pre"iously belie"ed.

18) >oft tissue maturation:

#t is generally accepted that dentoal"eolar structures are responsi"e to soft tissue

pressures and adapt to a position of balance between the muscles of the lips, cheeks and

tongue.

5rankel and :offler7showed that the reduction in mandibular arch length found in an

untreated control group was pre"ented in sub+ects treated with the functional regulator /5R2

appliance. They claimed that the "estibular shields of the functional regulator appliance

fa"orably influence the saggital de"elopment of the mandibular dental arch by eliminating

the restraining forces of the external muscular en"ironment.

$oodside et al.7and :inder!ronson and $oodside7showed that the lower incisors

of children who were mouth breathers were more retroclined and crowded compared with

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controls, and proclined after adenoidectomy and a changed mode of breathing that altered the

muscular en"ironment.

These studies show that lower arch alignment can impro"e after the remo"al of

ad"erse muscular forces and, although no direct relationship has been found between changes

in soft tissue forces and increased lower arch crowding, it is likely that such changes may

ad"ersely affect arrangement of the teeth.

:ate mandibular growth changes may bring the lower incisors into a different soft

tissue en"ironment.

ubtently and akuda7compared 8 patients who were orthodontically treated and

de"eloped late lower incisor crowding with 8 patients who did not. They found a strong

tendency to maintain the original intercanine width in all cases. The crowded cases had a

narrower intercanine width before treatment, which returned to its original dimension after

treatment expansion. They surmised that the lip musculature did not permit the necessary

intercanine expansion to maintain incisor alignment. They claimed as the mandible increases

in si%e, the lips exert greater pressure than the tongue, creating a lingually directed force that,

counteracted the mesial forces, causes incisor crowding.

Bench7 studied growth of the cer"ical "ertebrae, hyoid bone, and tongue in relation to

the facial skeleton and denture. ;e found that the hyoid bone and tongue descend with age,

relati"e to surrounding structures, and continue to do so after facial growth slows down. ;e

claimed that this was particularly true in persons with long faces and with lack of forward

growth and suggested that it could explain the de"elopment of late lower arch crowding.

Gohen and Iig7studied tongue growth on serial cephalograms of 8) sub+ects from

ages 7 to ) years. They found that tongue si%e relati"e to the intermaxillary space increased

with age. This might imply more forward pressure on lower teeth. They pointed out that the

descent of the tongue, as it grows, may compensate for any possible increase in forward

pressure because of larger tongue si%e.

Iig and Gohen7examined lip growth on the same sample and found that it continued

up to '( years and exceeded growth of anterior lower face height.

#n a longitudinal study of

Documents

Ld retention and relapse