Postretention changes in canine position. Results of a long-term follow-up

Long-term stability of orthodontic treatment and patient satisfaction. A systematic review

OBJECTIVE

To evaluate morphologic stability and patient satisfaction at least 5 years after orthodontic treatment.

MATERIALS AND METHODS

Published literature was searched through the PubMed and Cochrane Library electronic databases from 1966 to January 2005. The search was performed by an information specialist at the Swedish Council on Technology Assessment in Health Care. The inclusion criteria consisted of a follow-up period of at least 5 years postretention; randomized clinical trials, prospective or retrospective clinical controlled studies, and cohort studies; and orthodontic treatment including fixed or removable appliances, selective grinding, or extractions. Two reviewers extracted the data independently and also assessed the quality of the studies.

RESULTS

The search strategy resulted in 1004 abstracts or full-text articles, of which 38 met the inclusion criteria. Treatment of crowding resulted in successful dental alignment. However, the mandibular arch length and width gradually decreased, and crowding of the lower anterior teeth reoccurred postretention. This condition was unpredictable at the individual level (limited evidence). Treatment of Angle Class II division 1 malocclusion with Herbst appliance normalized the occlusion. Relapse occurred but could not be predicted at the individual level (limited evidence). The scientific evidence was insufficient for conclusions on treatment of cross-bite, Angle Class III, open bite, and various other malocclusions as well as on patient satisfaction in a long-term perspective.

CONCLUSIONS

This review has exposed the difficulties in drawing meaningful evidence-based conclusions often because of the inherent problems of retrospective and uncontrolled study design.

Posterior and anterior components of force during bite loading

Late anterior crowding of teeth has been associated with the anterior component of force (ACF) developed during biting. Possible physiologic mechanisms countering ACF, including the presence of a posterior component of force (PCF), are hypothesized. In this self-controlled study, 60 subjects aged 27.05+/-3.9 years were examined for ACF and PCF that were calculated as the change in tightness of a mandibular dental contact points from non-biting to biting state. Both ACF and PCF were found to develop simultaneously. However, the PCF was 4-7 folds smaller than the ACF (p<0.001). The ACF progressively declined by 10-20 folds (p<0.001) from the posterior to anterior dentition. The lateral incisor-canine contact point had the greatest ACF decline (63-74%). ACF effect on the anterior dentition is counteracted by a protective mechanism consisted of PCF, progressive dissipation of ACF, and canine blockage.