Retention And Relapse
Definition of Retention
Retention is defied as “Maintaining newly moved teeth in position long enough to aid in stabilizing their corrections”.
Definition of Relapse
Relapse is defied as “The loss of any correction achieved by orthodontic treatment” or “Relapse is defied as tendency of orthodontically treated teeth to rearm back to their original position”.
Schools of Thought of Retention
- There are various philosophies to explain post-treatment stability.
- These are referred to as the “school of retention”.
Read And Learn More: Retention and Relapse in Orthodontics: Causes, Types, Functions
The Occlusion School of Thought
According to Kingsley—“Proper occlusion is a key factor in determining the stability of the newly moved teeth”.
The Apical Base School
- It is formulated by Alex Landstrom, McCauley and Nance.
- In 1920 Alex Landstrom suggested that apical base is important factor in the correction of malocclusion.
- McCauley added that the intercanine and intermolar width should be maintain during orthodontic treatment.
- Nance noted that the arch length cannot be permanently increased to a major extent.
The Mandibular Incisor School
Grieves and Tweeds suggested that post-treatment stability was increased when mandibular incisors were placed upright on slightly retroclined over the basal bone.
The Musculature School
It states that functional muscle balance is necessary in order to ensure post-treatment stability.
Causes of Relapse after Orthodontic Treatment
- Soft Tissue Factors
- After orthodontic treatment gets completed, teeth remain in unstable position.
- Pressure from the sof tissue leads to the relapse.
- Teeth should be placed in the new position of balance.
- Muscular factors
- Teeth acquiring new position take some time to get stabilize.
- Any abnormal habit which persists will alter the equilibrium and causes relapse of teeth.
- Supporting Tissues
Both gingival and periodontal tissues get changed or altered subsequent to orthodontic tooth movement and need time for their reorganization.
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- Reorganization of periodontal fibers
- During the movement of tooth, PDL space and collagen fiber bundles are altered.
- After the removal of fixed appliances there is restoration of normal periodontal architecture. This is due to the reorganization which take place when tooth start responding individually to functional forces like masticatory force.
- Reorganization of PDL occurs over a 3 to 4 months period.
- As reorganization occurs, there is active stabilization of tooth due to the PDL metabolism which comes in effect.
- Reorganization of gingival fibers
- Reorganization of gingival fibers occur slowly.
- Collagen fibers complete their reorganization in 4 to 6 months.
- Supracrestal elastic fibers remodel slowly and they take nearly one year to reorganize.
- That’s why pericision is recommended in teeth corrected for rotations.
- Reorganization of periodontal fibers
- Occlusal Factors
- Tooth size discrepancy
- Tooth size discrepancy between both the maxillary and mandibular teeth causes relapse after the correction.
- Features of maxillary tooth material excess are deep overbite, combination of increased overbite and overjet, anterior crowding, improper buccal occlusion.
- Features of mandibular tooth material excess are end-to-end incisor relationship, space in maxillary anterior region, mandibular anterior crowding and improper buccal occlusion.
- Axial inclination
- Tooth size discrepancy
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- Excessive lingual tipping of anterior teeth causes deep bite.
- It is necessary to provide proper angulation between maxillary and mandibular incisors.
- Transverse discrepancy
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- Tendency for relapse associated with palatal expansion techniques is more. So long-term retention is needed.
- Third molars
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- Role of third molars in causing late mandibular incisor crowding is doubtful.
- Extraction of lower third molar has beneficial effects in decreasing mandibular anterior crowding.
- Extraction of third molars provides space for distal and lingual movement.
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- Facial growth and occlusal development
- Dentoalveolar adaptation maintains occlusal relationship even with skeletal malrelationship.
- If skeletal growth continues in a marked fashion, occlusal changes will occur.
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