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3Q1. Why do I have to wear a retainer?

Why do I have to wear a retainer?

Theoretically there are four specific reasons why patients must wear retainers after active orthodontic treatment.


1. Three months is required for periodontal ligament fiber to mature after active orthodontic treatment.

During orthodontic tooth movement, periodontal ligament (PDL) fibers are constantly remodeling. The PDL fiber remains in immature, disorganized state as long as the teeth are splinted together by orthodontic archwire. PDL Fiber slowly mature and reorganize during the first 3 month after the removal of the braces when teeth again experience normal occluasl force. During this time, it is critical to maintain the alignment of the teeth.

2. Maturation of collagenous gingival fiber require six months after active treatment. Maturation of elastic gingival fiber require twelve months after active treatment.

Beside PDL fibers, there are numerous gingival fibers that attaches tooth to gum, tooth to tooth, gum to bone and gum to gum. These gingival fibers maintain the memory of where the tooth was (either rotated or crowed), before they were straightened. One way to imagine how gingival fibers maintain the memory of original position of the tooth is to image collagenous fiber as ropes and elastic fibers as rubber bands both of which connected tooth to tooth, tooth to gum, gum to gum, and gum to bone. Once tooth are aligned, there are developed tension on elastic fiber and laxity on the collagenous fiber. The tension on elastic fibers causes the malocclusion to again re-express itself and laxity on collageous fibers allows this re-expression to occur.

Collengenous fiber take 6 month to remodel and elastic fibers takes approximately 12 months to remodel. Therefore, full time retainer wear is necessary for the first 6 months to allow collageonous fiber to remodel so that all fiber laxity have resolved. Night time retainer wear are necessary for the following next 6 months to allow the elastic fiber to remodel so that all tension are resolved.

3. Completion of mandibular growth Age 19-25.

Young adults, especially young men may have late mandibular growth that cause lower anterior crowding or rarely upper anterior spacing. To prevent this from occurring, orthodontist may have patient wear upper and lower retainers few nights a week until patient have reached age 25. Some orthodontist may relieve the contact between the lower anterior teeth by IPR and place fixed lower retainer until patient have reached age of 22-25 then give the patient the option of removing the fixed retainer at that time.

4. For patient with unbalanced oral-facial musculature – lifetime retention.

Certain orthodontic problems are caused by unbalanced muscular forces exerted on the teeth. Continuous or near continuous (more than 14 hours a day) forces on teeth can cause them to move until the net force is again near balance. Unbalanced on teeth can be caused by habits, such as thumb sucking or abnormal tongue rest position. But it can also be caused by excessively strong or large tongue and excessively lax lip. Patient with thumb sucking habit may have anterior open bite or spacing between upper font teeth. By the end of the orthodontic treatment, if the habit has stopped, the correction of the problem would be stable. However, if the habit persist, the patient will need to continue wearing the retainer until the habit cease. If the cause of the anterior open bite is excessively large tongue with loose lip, the patient will have no choice and would need to wear his or her retainer at least few nights a week for lifetime.