Orthodontic Relapse and Retention: Strategies for Maintaining a Beautiful Smile

Posted on Aug 24, 2024 in Biology

Why Retention is Needed

Gingival and periodontal tissue require time post-treatment to reorganize. Soft tissue pressures are likely to cause relapse if teeth are placed in an unstable position. Growth post-treatment may also cause relapse.

Timing of Tissue Reorganization

  • PDL: 3-4 months
  • Collagenous gingival fibers: 4-6 months
  • Elastic supracrestal fibers: 1 year

Basic Theories of Relapse and Retention

1. Relapse is less likely if corrections are made during times of growth.

  • Influence of growth of the maxilla and mandible can only occur in growing patients.
  • Advantages of early treatment.

2. Lower incisors are more likely to remain in good alignment if positioned upright over basal bone.

  • Perpendicular to the mandibular plane.
  • In terms of stability, it is better to place too much lingual inclination rather than too much labial inclination.
  • Pretreatment lower incisor proclination is associated with less long-term crowding; this is thought to be due to weaker labial muscular forces.

3. Overcorrection is recommended in malocclusions.

  • Class II to edge-to-edge
  • Deep bite cases
  • Rotated teeth

This should create enough space initially for the tooth to erupt into. Transseptal fibrotomy is also recommended in severe cases.

4. Relapse is less likely to occur if the cause of the malocclusion is eliminated.

  • Thumb, finger, or lip habit
  • Tongue posture
  • Nasopharyngeal obstruction leading to mouth breathing leading to an open bite

5. Obtaining proper occlusion is an important factor in maintaining corrected positions.

  • Overfunction of maxillary canines on mandibular canines can cause 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).

6. The farther a tooth is moved, the less likely it is to relapse.

  • As a tooth moves farther from its original position, an equilibrium is formed, producing a more ideal occlusion.
  • Little evidence to support this statement.

7. Appliance therapy cannot permanently alter arch form (especially in the lower arch).

  • Treatment should maintain the initial arch form, as it will tend to return to its pretreatment shape.

8. Reorganization of bone and adjacent tissues is required around newly positioned teeth.

  • Use a fixed or rigid appliance or an appliance that is inhibitory and not tooth-dependent.

9. Corrected 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 extended period to prevent relapse.

Types of Retention

Removable Retainers

  • Hawley Retainer Modification:
    1. For premolar extraction cases in order to avoid space opening from wires crossing the occlusion:
      1. The bow can be soldered to clasps on first molars.
      2. Place C-clasps on second molars and allow the bow to run around the entire arch.
      3. The labial bow can run between the lateral and canine and solder the clasp to control canines.
  • Wraparound Retainer (“Clip-on”):
    • Wire-reinforced plastic bars along the labial and lingual surfaces of dentition.
    • May not allow PDL reorganization as teeth are not able to move individually; firmly holds the arch.
    • Less comfortable than Hawley.
    • Not as good in overbite maintenance.
    • Indicated in perio cases where splinting is needed.
  • Positioner:
    • Can be made as a retainer or used for finishing and then maintained as a retainer.
    • Disadvantages as a retainer:
      • Bulky and difficult to wear full-time.
      • Do not retain incisor position as well as a conventional retainer because patients usually won’t wear full-time.
      • Overbite increases due to limited patient wear.
    • Advantages as a retainer:
      • Reestablishes normal tissue when gingival hyperplasia is present.
      • Maintains occlusal relationship and intra-arch position.
      • Unlikely to break.
      • Can be made with jaws rotated down and back to prevent Class III relapse.
      • Can be constructed to prevent relapse in skeletal Class II and open bite cases.
      • Growth control is less effective than a part-time functional appliance or headgear.
  • Essix:
    • Advantages:
      • Esthetic
      • Patient is more likely to wear.
      • Inexpensive
      • Quick fabrication
      • Minimal bulk
      • High strength
      • No adjustments
      • Usually does not interfere with speech or function.
  • Damon Splint:
    • Basically, upper and lower Essix retainers connected.
    • Retentive splint for Class II, Class III, and bilateral crossbite treatment.
    • Assists in tongue training.
  • Fixed Retainers:
    1. Maintaining lower incisor position: Even mild mandibular growth between the ages of 16-20 can cause lower incisor relapse. A fixed lingual bar bonded only to canines can prevent distal tipping of lower incisors.
    2. Holding diastema closed: Utilize lighter wire (17.5 or 19.5 mil twist). Bond above the cingulum – out of occlusion. Can prevent bite deepening if lower incisors erupt.
    3. Implant or pontic space maintenance: Reduces mobility of teeth, making it easier to place a bridge. Holds space if prolonged periodontal treatment is required post-ortho, prior to the placement of restoration.
    4. Retaining closed extraction spaces: Placed on facial surfaces of posterior teeth. Mainly used in adults, as they tolerate this better than removable retainers. More reliable than a removable retainer.

Active Retainers

A removable appliance that corrects irregularities and is maintained as a retainer.

  • Spring Retainer: Realign malpositioned incisors.
    1. Will usually need to perform IPR prior to appliance placement to prevent proclining incisors into an unstable position.
    2. IPR flattens contacts, increasing stability.
    3. Can reduce incisors 0.5 mm/side.
    4. If teeth are severely crowded, retreatment with bonded brackets is recommended; followed by fixed retention.
  • Modified Functional Appliance: Manage relapse potential in Class II or Class III cases.
    1. Activator or Bionator:
      • Upper and lower retainers joined by inter-occlusal bite blocks.
      • Maintain teeth within the arch while slightly altering the occlusal relationship.
      • Example: If an adolescent slips back 2-3 mm into Class II after early correction, this appliance can be used to recover proper occlusion.
      • No value if used in adults (as no vertical growth remains).
      • Moves teeth (no skeletal change).

Relapse Due to Growth

  • Order of completion: Width, then anterior-posterior, then vertical.
  • As anterior-posterior and vertical continue longer, growth in these directions is more likely to cause long-term problems.
  • Retention Class II: Relapse in these patients is most likely due to a combination of dental and skeletal changes.
    1. Dental changes (short-term relapse): 1-2 mm of anterior-posterior change tends to occur immediately following treatment, especially when Class II elastics are used. Overcorrection is important in preventing relapse. Forward movement of lower incisors more than 2 mm will require permanent retention.
    2. Skeletal changes (long-term relapse): Depends on age, sex, and maturity. If the original growth pattern continues, treatment that involved growth modification will most likely result in a loss of at least some correction. Patients most likely to require these treatments:
      1. The younger the patient at the end of treatment.
      2. The greater the initial Class II problem.
      3. Much easier to prevent relapse than to correct later.
      4. Bionator/Activator: Maintain occlusal relationship. The bite registration is taken in CR, so the appliance is “passive.” Not edge-to-edge like when used for “active” Class II correction.
  • Retention Class III: Relapse occurs mainly from mandibular growth. Chincups and functional appliances rotate the mandible downward, causing more vertical growth. Not as effective as maintaining Class II. If relapse occurs in normal or excessive face height patients: may need surgical correction after growth. In less severe Class III cases: Utilize a functional appliance or positioner. Will maintain the occlusal relationship in these cases. May position jaws down and back to prevent relapse.
  • Retention Deep Bite: Must control overbite during the retention period. Construct an upper removable retainer with a baseplate to prevent lower incisors from over-erupting; posterior occlusion is maintained. After stability is achieved, worn at night only.
  • Retention Anterior Open Bite:
    • Patients with a habit (thumb or tongue): Relapse occurs by a combination of molar elongation and incisor depression.
    • Patients without a habit: Relapse is due to the elongation of posterior teeth, mainly upper molars; not incisor-related. Important to control the eruption of upper molars. High-pull headgear with the use of conventional removable retainers. Appliance with posterior bite blocks (open bite activator or bionator) at night and conventional retainers during the day. Preferred because of better patient acceptance and control of lower molars.
  • Retention Lower Incisors:
    • Skeletal changes: Mandible grows downward, forward, or downward and backward, leading to increased lip pressure on incisors, leading to them being tipped distally.
    • Dental changes: Third molar eruption (no evidence). Late mandibular growth (major contributor). Should be retained until mandibular growth has ceased (girls: late teens, boys: early twenties).