Retention

RetentionPresented by:

Shareef M.T. Shanableh2nd Year Orthodontic Resident

After malposed teeth have been moved into the desired position they must be mechanically supported until all tissues involved in their support and maintenance of their new positions shall have become thoroughly modified, both in structure and in function, to meet the new requirements ANGLE 1907

Edward H Angle2

Lectures Outline: Definitions.Causes of Relapse.Schools of Retention.Rationale of Retention.Types of Retention.Duration of Retention.

Definition

Moyers 1973 defined orthodontic Retention as :

The holding of teeth in the treated position, following orthodontic treatment, for the period of time necessary for the maintenance of the result.

Robert Edison Moyers4

Joondeph and Riedel 1985 explained Retention as:

The holding of teeth in ideal aesthetic and functional positions.

Dr. Donald R. Joondeph 5

Relapse

Defined by BSI 1993 as : The return, following correction, of the original features of malocclusion

Moyers The loss of any correction achieved by orthodontic treatment.

Updated definition

Unfavorable change (s) from the final tooth position at the end of orthodontic treatment.

British Standard Institution 6

Shareef Shanableh (SS) - British standard institutionReasons of RelapsePeriodontal or Physiological recovery Due to Elastic Recoil of the periodontal tissues (principal fibers of PDL,collagenous fibers of the gingiva supraelastic fibers, and alveolar bone). Hixon 1969

Pressure from the Surrounding Orofacial Tissues When neutral equilibrium zone disturbed or due to Soft tissue Maturation with Aging.Proffit 1978

3. Unfavorable Growth or growth changes. Growth relapse

4. Pressure from Occlusion.Proffit 1978

Reasons of Relapse5. Continuous Habits.6. Iatrogenic cause of relapse True relapse, Due to poor outcomes. For example: Changing Intercanine Width. Felton et al 1987 Since the teeth are placed in purely evidence based unstable position.

7. Idiopathic cause of relapse. For example: Relapse after treating a high angle Class II malocclusion due to idiopathic condylar resorption.

8. Combination.

Normal intercanine width Upper: males 35 females: 33 Lower: males 26 females: 258

Relapse Risk Factors

11Relapse risk factors Class 3 growing w family history or unfavorable growth10

Incisor retraction (if the pt has tongue thrust)11

Different Schools of Thought of retentionThe Occlusal School

Kingsley 1880 stated,

The occlusion of teeth is the most potent factor in determining the stability in a new position.

Different schools of thought of retention

The Apical Base schoolIn the middle 1920s a 2nd school of thought formed around the writings of Axel Lundstorm 1925, who suggested that the apical base was one of the most important factors in the correction of malocclusion and maintenance of a correct occlusion.

McCgauley 1944 suggested that intercanine width and intermolar width should be maintained as originally presented to minimize retention problems.

Strang 1958 further enforced and substantiated this theory. Nance 1947 noted, Arch length may be permanently increased only to a limited extent.

Different Schools of Thought of RetentionThe Mandibular Incisal school:

Grieve 1944 and Tweed 1952 suggested that the mandibular incisors must kept upright and over basal bone.

The Musculature school:

Rogers 1922 introduced a consideration of the necessity of establishing proper functional muscle balance.

Rationale of Retention

Retian 1967 mentioned that one of the main rationales behind retention is to:

Allow reorganization of the gingival and periodontal tissues affected by orthodontic tooth movement resist physiological relapse. His study showed that: The principal fibers of PDL takes 3 - 4 months to reorganize. The collagenous fibers of the gingiva take 4 - 6 months. The elastic fibers of the gingiva supracrestal takes 232 days. The alveolar bone takes one year.

Masticatory stimulation of PDL promote reorganization so that advise removing the retainer appliances during meal and avoid use of rigid retainer15

Rationale of RetentionTo prevent unwanted movement resulting from growth changes resist growth relapse.

To prevent relapse tendency of teeth that have been moved to an inhertintly unstable position resist true relapse and soft tissue maturation changes.

4. To permit neuromuscular adaptation to the corrected tooth position16

Basic Theorems for RetentionRichard And Riedel 1960 Has discussed a number of possible explanations of Retention and Relapse

Theorem 1:Teeth that have been moved tend to return to their former positions.

Theorem 2:Elimination of the cause of malocclusion will prevent recurrence.

Theorem 3:Malocclusion should be overcorrected as a safety factor.

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

Theorem 5:Bone and adjacent soft tissues must be allowed to reorganize around newly positioned teeth.

Theorem 6:If lower incisors are placed upright over basal bone, they are more likely to remain in good alignment.

Theorem 7:Corrections carried out during periods of growth are less likely to relapse.

Theorem 8:The farther the teeth have been moved, the less likelihood of relapse.

Theorem 9:Arch form, particularly in the mandibular arch, cannot be permanently altered by appliance therapy.

----Someone Added----Theorem 10:Many treated malocclusions require permanent retaining devices.

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Normal Age Related ChangesFirst:Sinclair and Little 1983 A decrease in arch length.A decrease in intercanine width esp females from 13 20.Intermolar widths were fairly stable.Small decrease in OJ and OB.An increase in lower incisors irregularity.

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T0 : mixed dentitionT1: early permanentT2: adult 18Irregularity index Arch length Intercanine widthIntermolar width21

Normal age related changesSecond:Iowa Facial Growth Bishara et al 1997Maxillary and Mandibular arch length and Intercanine width all increase until age 13 then decreases esp. in females.

Maxillary and Mandibular intermolar width increases until age 13 then becomes static with little decrease in females.

Factors that affect POST treatment stabilityAlteration of arch form.

Periodontal and gingival tissues.

Mandibular incisor dimensions.

Influence of environmental factors and neuromusculature.

Consideration of continuing growth.Post treatment tooth positioning and establishment of functional occlusion.

Role of developing third molars.

Influence of the elements of the original malocclusion.

Arch width and form should be maintained during ortho ttt

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Alteration of Arch From

It is generally agreed that arch from and width should be maintained during orthodontic treatment.

Evidence shows that intercanine and intermolar widths decrease during the postretention period, especially if expanded during treatment. For this reason, the maintenance of the arch form rather than arch development is generally recommended.

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HAAS 1980 and SANDSTORM 1988, found that maintenance of 3 4 mm intercanine width and upto 6 mm intermolar width was possible when expansion was carried out simultaneously with maxillary apical base expansion.

De La Cruz et al. 1995, carried out a 10 year post retention study on 87 pts to determine the long term stability of orthodontically induced changes in maxillary and mandibular arch form. The results showed that although there was considerable individual variability, arch form tended to return toward the pretreatment shape. They concluded that the patients pretreatment arch form appeared to be the best guide to future stability.

Periodontal and gingival tissuesOrthodontic correction of tooth rotations is proposed to result in stretching of the collagen fibers.

The PDL organization is important for stability.

But supracrestal fibers remodeling is very slow and can exert forces capable of displacing a tooth at one year after removal of orthodontic app.

Brain 1969 and Edwards 1970 advocated gingival fiber surgery Circumferential Supracrestal Fiberotomy to allow release of soft tissue tension and reattachment of the fibers in a passive orientation.

Circumferential Supracrestal Fiberotomy27

Mandibular Incisors DimensionsIt was reintroduced by Peck and Peck AO 1972 after a study of 45 untreated normal occlusions.They advocated reduction of mandibular incisors to a given faciolingual/ mesiodistal ratio to increase stability. Their work was criticized since their recommendations were based on a study involving untreated rather than treated cases. In addition, there were young pts with ideal lower incisor alignment. And it is possible that these cases would show crowding if followed long term.Gilmore and Little AJO 1984, studied 134 treated and 30 control cases w minimum 10 yrs post retention. They showed that:

A weak association between long-term irregularity and either incisor width or faciolingual/mesiodistal ratio.

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Influence of Environmental factors and NeuromusculatureLittle et al AJO 1985 and Houston et al 1990 in 2 studies:The initial position of the lower incisors has been shown to provide the best guide to the position of stability.

If lower incisor advancement is a treatment objective, permanent retention is essential for maintenance of the result.

Growth modification treatmentFollowing the use of head gear or functional appliances, Retention using a modified Activator appliance has been reported as effective in maintaining Class II correction.Weislander AJO 1993

2. Growth Facial growth continues throughout life, generally in the same direction as that occurring during adolescence, but to a much smaller degree Behrents 1985Recommendation:Retain if possible, until growth cease.

Long term removable or fixed retainer to avoid LLS crowding Sadowski 1994

Consideration of Continuing Growth

Litowitz AO1948, cases exhibiting greatest amount of growth during treatment showed less relapse.

Nanda and Nanda ajo1992, Agreed with Riedel and stated that any skeletal changes that occur during retention may attenuate, exaggerate or maintain the dento-skeletal relationship.Found that pubertal growth spurt for pts with skeletal deep bite occurs on average 1.5 2 years later than open bite cases. Therefore, a longer retention period for deep bite patients.

Riedel AO1960, Growth may aid in the correction of orthodontic problems but may also cause relapse of treated cases.

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Post treatment tooth positioning and establishment of functional occlusionAdequate Interincisal contact angle may prevent overbite relapse and good posterior intercuspation prevents relapse of both crossbite and anteroposterior correction.

Average interincisal: 130 150.533

Role of Developing Third MolarsImplies a passive role of the third molars in the development of late crowding by hindering that adjustment.

Recent studies show a statistically significant but not a clinically significant role of third molars in post retention crowding.

In summary: Minor importance of third molars contribution in development of incisor crowding.

Woodside 1970Broadbent 1941Richardson 198234

Influence of the original malocclusionIt is suggested that Overbite Relapse tends to occur in the first 2 years post treatment.

Most studies do not support a greater relapse in CLASS II div 1 cases when compared with other malocclusion groups.

A slight change in OJ toward pretreatment values was demonstrated in all malocclusion groups.Kaplan AJO 1966, advocated Overcorrection.

Little et al AJO 1981, greater than 50% of the rotations or displacements relapsing in an opposite direction.

Role of Transverse DiscrepanciesThe expansion appliance must be maintained passively or removable appliance placed to aid in transverse retention.

Clinician must overcorrect transverse discrepancy 36

Factors that will help minimize Relapse: Destang and kerr 2003During treatment Planning:

Consider extraction of severely displaced teeth in the plan of extraction pattern.2. During Active treatment: Move upper incisors to within lower lip control.

Correct rotations early in treatment.

Tuverson 1980 suggested reshaping of contact points to aid stability.

Overcorrection of the malocclusion.

Maintain existing arch form.

Maintain intercanine width.

Avoiding posterior expansion .

Maintain AP position of lower incisors.

3. During Finishing stage:

Maximize Interdigitation.

Correct incisors to achieve normal edge. Centroid relationship

Correct Root torque & ensure root Parallelism.

Consider IPS for triangular teeth.

Labial Frenectomy prior to debond to minimize re opening of diastema.

CSF within 4 - 6 months after debonding.

Inter proximal stripping Circumferential supracrestal fiberotomy 38

4. During retention phase:

Prolong retention Bonded retainer for PDL compromised cases and cases of high risk of relapse.

Retain if possible until growth cease.

Elimination of habits.

Factors Affect Choosing the Type of RetainerInformed consent about the possibility of relapse and the rationale of retention.

Age adult pts.

Type of malocclusion.

Type of treatment and tooth movement.

PDL status.

Duration of treatment.

Patients motivation.

Informed consent According to the BOS British Orthodontics Society advice sheet ,It is the responsibility of the treating clinician to explain in details the possibility of relapse and the rationale of retention before commencing and orthodontic treatment.40

Adult PatientsIf PDL status is normal and no occlusal settling is required, there is no evidence to support any changes in retention protocol for the adult patients compared with adolescent patient.

Patient with a history of Periodontal Disease or Root ResorptionPermanent retention is advised.

There is evidence of an increased risk of deterioration of lower incisor alignment post-retention in cases with root resorption or crestal bone loss.Sharpe 1987

For those with minimum to moderate disease, a more routine retention protocol can be used.Zachrisson Therefore well benefit from prolonged retention42

Correction of Post. and Ant. CrossbitesWhen the incisor overbite and posterior intercuspation are adequate for maintaining the correction, no retention is necessary. Kaplan Ajo 1993

Correction of Deep OverbiteThe use of anterior bite plane until the completion of facial growth has been recommended.

Retention After Deep Bite Correction Requires control of overlap of incisors during retention.This is accomplished by using a removable upper retainer combined with a bite plane.As vertical growth continues into the late teens, the retainer is often needed for several year.

The retainer does not separate the posterior teeth45

Correction of Anterior Open BiteIncorporating posterior bite blocks has been recommended for prolonged retention.

Currently there is a lack of scientific evidence to support this 46

Retention after Anterior Open Bite CorrectionExcessive vertical growth and eruption of posterior teeth often continue until late teens or early twenties.

Controlling eruption of upper molars is therefore the key to retention in open bite patients.

High pull head gear to the upper molars, in conjunction with a standard removable retainer to maintain tooth position, is one effective way to control open bite relapse.

A better alternative is an appliance with bite blocks between the posterior teeth an open bite Activator or Bionator.

In severe open bite, conventional maxillary and mandibular retainers for daytime wear, and an open bite bionator as a night retainer from the beginning of the retention period.

Activator: which stretches the patients soft tissues to provide a force opposing eruption.

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Spaced Dentition Permanent retention has been recommended following orthodontic treatment to close generalized spacing or midline diastema in an otherwise normal occlusion.Graber

Retention after CLASS II correction

Overcorrection of the occlusal relationships as a finishing procedure is an important step in controlling tooth movement.

Even with good retention, 1 2 mm of anteroposterior change caused by adjustments in tooth positions is likely to occur after active treatment stops.

As a general guideline,

If more than 2 mm of forward repositioning of lower incisors, permanent retention is required.

It is important not to move lower incisors too far forward.

Incisors to far forward: Due to class 2 elastics

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This relapse tendency can be controlled in one of the two ways:

The first, is to continue head gear to the upper molars on a reduced basis at night in conjunction with a retainer to hold the teeth in alignment.

The second method, is to use a functional appliance of the activator or bionator type to hold both tooth position and occlusal relationship.

This type of retention is needed for 12 24 months or more with patients with a severe skeletal problem initially.

This is quite satisfactory in well motivated patients who have been wearing head gear during ttt .

A potential difficulty is that the functional appliance will be worn only part time at night and daytime retainers of conventional design will be needed to control tooth position during the first few months.

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The guideline is: The more severe the initial Class II problem and the younger the patient at the end of active treatment, the more likely that either head gear or a functional appliance will be needed as a retainer.

Retention after CLASS III correction

Applying a restraining force to the mandible, as from chincap tends to rotate the mandible downward, causing growth to be expressed more vertically and less horizontally, and Class III functional appliances have the same effect.

If face height is normal or excessive after orthodontic treatment and relapse occurs from mandibular growth, surgical correction after the growth has expressed itself may be the only answer.

In mild Class III problems, a functional appliance or a positioner may be enough to maintain the occlusal relationships during post treatment growth.

Relapse from continuing mandibular growth is very likely to occur and such growth is extremely difficult to control.

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Retention of Lower Incisor AlignmentIf the mandible grows forward or rotates downward, the effect is to carry the lower incisors into the lip, which creates a force tipping them distally.

Incisor crowding also accompanies the downward and backward rotation of the mandible seen in open bite problems.

A retainer in the lower incisor region is needed until growth has declined into adult levels.

It is also suggested, retention should be continued, at least on a part-time basis, until third molars have either erupted into normal occlusion or have been removed.

Continued skeletal growth alter the position of the teeth. For this reason continued mand. Growth in normal or Class III patients is strongly associated with crowding of the lower incisors.

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Summary of post treatment changesIntercanine width reduction is seen, whether expansion was made or not.

Intermolar width tends to return to pretreatment value.

Mandibular anterior crowding continues into the fifth decade.

Of all treatment modalities studied only 3 showed acceptable long term mandibular incisor alignment:Early mixed dentition ttt without fixed appliance therapy.Non extraction therapy with generalized spaces.Lower incisor extraction cases.

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Maxillary SurgeriesWillmar1974, performed LE FORT 1 osteotomy on 106 pts with the use of surgically placed metal markers. Insignificant 10% reported relapse on anterior marker.

Washburn, Schendel and Epker 1982, performed superior maxillary repositioning on 15 young pts. Jaw relationship was maintained even in pts who experienced postsurgical growth.

Mandibular SurgeriesHuang and Ross AJO 1982, evaluated short term and long term effects of surgical lengthening of retrognathic, growing mandible in children.

22 pts (12 boys and 10 girls), at the mean ages: boys at 14.1 and girls at 13.4 years.

The results were:The response varied with the amount of lengthening performed, but did not vary with age, sex, cause.Lengthening more than 11 mm, was accompanied by extensive relapse with major remodeling of the condyle or posterior symphysis.Lengthening less than 9 mm, was followed be little or no relapse.No significant growth of mandible after the age of 11.The mandible returned to its preoperative growth direction within 2 years postsurgical.

Retention Planning

Retention PlanningIt is divided into 3 categories, depending on type of treatment instituted:

Limited retention.

Moderate retention in terms of both time and appliance wearing.

Permanent and semi permanent retention.

Conditions where Limited retention is required Corrected Crossbites:Anterior: with adequate OB, retroclined or upright tooth & favorable growth.Posterior: with adequate cuspal interdigitation and OB, inclination of buccal teeth & favorable growth.Dentitions that have been treated by serial extraction:High canine extraction cases.

Corrections that have been achieved by retardation of maxillary growth.

Dentitions in which the maxillary and mandibular teeth have been separated to allow for eruption of teeth previously blocked out.

Where Moderate retention is required CLASS I NON EXTraction cases.

CLASS I or II EXTraction.Generally desirable to use a maxillary Hawley type retainer until normal function adaptation has occurred.sometimes its desirable to use either a maxillary Kloehn-type head gear, or a Labiobuccal type of appliance with cervical or occipital resistance applied at night.

Moderate retentionCorrected deep overbites in either CLASS I or CLASS II malocclusions:

Retention in a vertical plane.

Bite plane on a maxillary retainer is desirable. Worn continuously for the first 4 6 months, including meal time.

Vertical dimensions should be held until growth can catch up.

Moderate retention

Early correction of rotated teeth to their normal positions:Before root formation has been completed.

The Corrected CLASS II Div 2 malocclusion, requires extended retention to allow for the adaptation of musculature.

Where Permanent retentionEXPANSION cases has been choice of treatment,esp. mandibular arch.

Cases of GENERALIZED SPACING, after space closure.

Instances of SEVERE ROTATION or SEVERE LABIOLINGUAL MALPOSITION , by bonded retainer.

DIASTEMA, particularly in adult patients.

Timing of RetentionIt should be: FULL TIME for the first 3 4 months, except that the retainers should be removed on meal times. unless circumstances like periodontal bone loss require permanent splinting.

PART TIME basis for at least 12 months, to allow time for remodeling of gingival tissues.

If significant growth remains, continued PART TIME until completion of growth.

All patients treated in early permanent dentitions will require retention of incisor alignment until late teens.

Retention is needed for all patients who had fixed orthodontic appliance to correct intra-arch irregularities. 68

Requirement of Retaining AppliancesShould restrain each tooth that has been moved into the desired position.

Should permit the forces associated with functional activity to act freely on the retained teeth.

It should be as self cleansing as possible.

It should be constructed in a manner to be as inconspicuous as possible, yet should be strong enough.

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Types and Design of RetainersRemovable Retainers:

Hawley Retainer.Spring or Barrer Retainers.Begg Retainer.Thermoplastic Retainer VFR.Positioner.Damon Splint.HG, FABP, Chin Cup, Functional appliance and Modified Activator.Fixed Retainers:

The Fixed Appliance itself.Dental Bridge: like Resin bonded or Fixed. used in hypodontia cases.Banded Retainer.Bonded Retainer.

REMOVABLE RETAINERS

1. Hawley Retainer

No ClaspBall Clasp0.032 C Clasp0.032Soldered- .032 Labial Bow 3x3

- "T-Traditional Pink" Acrylic

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1. Hawley Retainer

Adams0.028 wire SSWrapAround0.02 wire SSReverse Curve Loop

QCM WrapAround

1. Hawley RetainerTypes:

U-loops.

Reverse U-loops better control of Canines.

Labial Bow Soldered to the molar cribs. Advantages:

Posterior occlusal settling in the initial 3 months.

Bite plane can be added to maintain Overbite reduction.

Acrylic tooth can be added.

Can be activated. To close residual spaces.

Maintain lateral expansion.

3. Fewer wires to interfere with occlusion.Labial bow for simple tooth movement.

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2. Spring or Barrer RetainerAcrylated bows both labially and lingually .Designed to allow minor adjustment of rotated incisors.

The original appliance extended only to the canines; however, due to the risk of swallowing or aspiration, a modification which includes cribs on the first molars has been described. if the teeth are realigned on the working model by the technician.

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3. Begg RetainerLabial bow soldered to a thinner wire.

Minor tooth movements can be achieved.

When setttling is desirable.

No wires crossing occlusion, free to settle*Bite plane can be added *Acrylic tooth can be added*Support is also provided by palatal hooks at the canines. Modified Versions may include acrylic on the bow 3-3 and/ or C clasps on the second molars.76

4. Thermoplastic Retainer

Full posterior coverage.Worn for short time.Fabricated from 1.5 mm polyvinylchloride sheet.Advantages:

Aesthetic.Easy to construct.Cheap.Active tooth movement.Acrylic tooth can be added.Better control for incisor alignment than Hawley.Disadvantages:

Cant retain expansion cases, unless supported by thick wire.Cant retain extrusion and intrusion.No settling.If partial cover is used, pt may develop AOB.Inc. risk of decalcification.

2.otherwise it will interfere with settling.3. Heating at 475 degrees .. Vacuum pressure at 1.5 b for 50 secs.If the pt on cariogenic diet77

5. Positioner

Uses:

Minor correction after debond. Beneficial at the end Begg ttt. If the pt decided to discontinue ttt. As a Retainer.The pt is advised to practice repeated cycles of clenching then relaxation to encourage tooth movement.

By 3 weeks, it becomes passive retainer. Problems:

Costly.

No rotational or overbite correction.

Needs pts cooperation.

Elastomeric or Rubber retainer.Custom made.Formed around the teeth and the coronal part of gingiva.Costume made: made on articulated models that have been sectioned and realigned. Begg: inc intrusion / tipping of teeth / root uprightening.

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6. Damon Splint Advantages:

Holds teeth and arches in corrected positions.

Retentive splints for CLASS II, CLASS III, bilateral Crossbites and Orthognathic cases.

Assists in tongue training.

Basically, its upper and lower essix retainers connected.

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7. HG, FABP, Chin cup, Functional appliance & Modified activator

After correction of Severe Skeletal problems in Growing pts.

To complete treatment in presence of 2 3 mm CLASS II discrepancy.

Appropriate to construct the appliance to an edge to edge relationship, reduce the vertical opening to 3 mm and to keep the block interfaces vertical at 90.

FIXED RETAINERS For long term retention of the Labial Segment, esp. reduced periodontal support and for midline Diastema.Proffit

Failure rates 47%.Bearn AJO 1995Indications:

Maintenance of Lower Incisor Position.Diastema maintenance.Maintenance of Implant Space.Keeping Extraction Space Closed in Adults.

During late growth

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1. The Fixed Appliance itself

2. Dental Bridge

Used in Hypodontia cases.

3. Banded Retainer

Bands placed on the lower premolars with a connecting soldered heavy arch wire 0.030, closely adapted to the lower labial segment.

4. Bonded RetainerAdvantages

Easy.Aesthetic.Doesnt interfere with speech.Less reliant upon compliance.Reduce risk of development of lower labial segment.Allow some physiologic movement.No evidence of long-term periodontal problems, but calculus can build up around them.Disadvantages

Time consuming.Technique sensitive.Interfere with bite deep bite.Caries.Prevent settling.Dont retain transverse expansion.High failure rate 23%.

IndicationsProlong retention.PD compromised.Adults poor compliance.CLP pts, with RA to maintain transverse relationship.AOB.Palatal canines.Diastema and Generalized spaces.Extraction space closure in adults.

Proclined lower labial incisors.

Alteration in intercanine width.

Severely displaced teeth.Prophylactic in lower arch.

4. Bonded RetainerRigid

Bonded on Canines only.

IndicationsSevere pretreatment lower inc. crowding or rotations.Planned alteration in intercanine width.After advancement of lower inc. during active ttt.After NON extraction, in mildly crowded pts.After correction of deepbite.

0.030 0.032 inch.

Sandblasted round S.S wire.

FlexibleBonded on each tooth individually.Allow physiological tooth movement.Materials: .015, .0175, .0195 or .0215 multistrand.Orthoflex chain, made from gold or SS.Fiber glass strips.

Nimri 2009 found that no difference between multistrand and round, except more plaque on mutistrand.

Advantages of multistrand:The irregular surface offers inc, mechanical retention. Without the need of retentive grooves.2. The flexibility of the wire allows physiological movement of teeth.3. Less failure rate than round wires.

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4-4:1. Vertical step bet, canine and premolar pre ttt2. Inter premolar width is inc. during ttt in non ext cases3. To prevent slipped contact bet 3 & 44. Ext cases to prevent space reopening

Labial:Restoration present lingually2. Deep bite3. Ext cases4. Temp. retention while fabricating Maryland bridge89

Dr James Hilgers 91

ConclusionMaintaining the treatment result following orthodontic treatment is one of the most difficult aspects of the entire treatment process. Normal maturational changes, together with post-treatment tooth alterations, conspire against long term stability. All treated malocclusions must eventually be returned from control by appliances to control by the patients own musculature. Permanent retention is increasingly being recommended as the only way to ensure long-term stability of an orthodontic treatment result. Proper goals of treatment, careful mechanotherapy, precise occlusal equilibration, and well-chosen retention procedures play a role in achieving occlusal homeostasis.

ReferencesSinclair PM, Little RM. Maturation of untreated normal occlusions.Retanium Splint Placement https://www.youtube.com/watch?v=0qrLca760WkSupra crestal Fibrotomy https://www.youtube.com/watch?v=HdOkoKEieos

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