retention and relapse.ppt

7/27/2019 Retention and Relapse.ppt

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Neethu SalamFinal yr(Part 1)


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Retention and Relapse Moyer defined retention as maintaining newly moved

teeth in position,long enough to aid in stabilising theircorrection.

Relapse has been defined as the loss of any correctionachieved by orthodontic treatment.


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Need for retention: Gingival and periodontal tissue require time post-

treatment to reorganize

Soft tissue pressures are likely to cause relapse if teethare placed in an unstable position

Growth post-treatment may cause relapse


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Timing of Tissue Reorganization Once teeth are able to move individually from one another

during mastication, reorganization of tissues can begin:

PDL: 3-4 months Collagenous gingival fibers: 4-6 months

Elastic supracrestal fibers: 1 year

In cases of severe initial rotations: supracrestal fibrotomiesare recommended at or just before appliance removal toprevent relapse


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Principles of Retention Relapse potential may be predicted by evaluation of initial

occlusion; teeth usually want to return to their originalposition; this is due to gingival fibers and unbalanced lip-

tongue forces

Full-time retention is required for 3-4 months to allow forreorganization of PDL

Retention should continue for at least 12 months in non-growing patients or until growth has ceased in growingpatients


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Theories of retention Riedel has discussed a number of popular explanations of

retention and relapse and the available clinical researchevidence about them.He has summerised the different

philosophies and concepts into nine theories.The tenththeory added by Moyers as an extention to the existingtheories.


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Theorem 1Corrected teeth tend to return to their original position

Due to musculature, apical bases, transseptal fibers, and bone

morphology

Teeth should be held in corrected positions for an extendedperiod of time to prevent relapse


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Theorem 2 Elimination of the cause of malocclusion will prevent

relapse Eg: in cases of abnormal habits such as thumb

sucking,tongue thrusting.etc. Tongue posture

It has been stated that even after successfully completing tonguetherapy/exercises correction is not guaranteed

Nasopharyngeal obstructionmouth breathing open bite

In a study byGavito et al., patients who initially started with anopen bite where evaluated 10 years following retention 35%had an open bite 3 mm or more.


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Theorem 3Overcorrection is recommended in malocclusions

Class II edge to edge

Deep bite cases

Rotated teeth

Less chance of relapse if there has never been a rotation;should create enough space initially for tooth to erupt into

Transseptal fibrotomy is also recommended in severe cases


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Theorem 4Obtaining proper occlusion is an important factor in

maintaining corrected positions

Overfunction of maxillary canines on mandibular canines cancause relapse in the lower incisor area

No movement is seen from regular grinding

Movement may occur if there is destruction of bone or a buildup of fibrous tissue (difficult to maintain tooth position)


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Theorem 5Reorganization of bone and adjacent tissues is required

around newly positioned teeth

Use a fixed or rigid appliance or an appliance the is inhibitoryand not tooth dependent


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Theorem 6Lower incisors are more likely to remain in good

alignment if positioned upright over basal bone

Perpendicular to mandibular plane

In terms of stability, it is better to place too much lingualinclination rather than too much labial inclination

Labial inclination is more likely to collapse due to lip pressure

Pretreatment lower incisor proclination is associated with lesslong-term crowding; this is thought to be due to weaker labialmuscular forces


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Theorem 7Corrections carried out during periods of growth are

less likely to relapse

Litowitz found that patients which exhibited the mostgrowth during treatment demonstrated less relapse

Post-treatment growth (esp. mandibular growth) will

cause secondary crowding due to lower incisorretroclination


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Theorem 8The farther a tooth is moved, the less likely it is to

relapse

As a tooth moves farther from its original position anequilibrium is formed producing a more ideal occlusion

Little evidence to support this statement

May actually case damage (root resorption)


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Theorem 9Appliance therapy cannot permanently alter archform (esp. in lower arch)

Should maintain the initial archform, as it will tend to return toits pretreatment shape

Strang stated:

The width as measured across from one canine to another in the

mandibular denture is an accurate index to the mandibularbalance inherent to the individual and dictates the limits of thedenture expansion in this area of treatment


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Lower Incisors: Were found to be stable if proclination occurred in deep bite

cases or if digit/lip habit was the cause of retroclined incisors

Proclination was found to be stable if the initial cause for theretroclination is eliminated during treatment


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Expansion: Has been shown to be more stable (intercanine) in Class II Div II

than Class I or Class II Div I

This theory was refuted byLittle et alwho stated that intercanineand intermolar expansion will relapse in Class II Div II

RPE followed by edgewise system showed good stability of upperintercanine width and upper and lower intermolar width, butpoor lower intercanine maintance 8 years post-retention


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Theorem 10Many treated malocclusions require permanent retaining

devices

This was added by Moyers

This is true for certain malocclusions.


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References Profitt, Contemp. Ortho, 2007

Graber, Orthodontics, 2005

Gowri Shankar,Text book of orthodontics


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Thank You

retention and relapse.ppt

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