Another way of looking at treatment stability

To determine the contribution of normal physiological changes to the overall manifestation of a relapse after orthodontic treatment. We analyzed long-term changes in the dentition of patients with Class I malocclusions after orthodontic treatment compared with a representative group with untreated Class I malocclusions.

Study participants (n  =  66; mean age, 12 years at treatment initiation) were treated for Class I malocclusions. Dental changes were evaluated at 2, 5, 10, and 15 years after treatment. Control participants (n  =  79) had untreated Class I malocclusions (n  =  53 evaluated at ages 12 and 22 years; n  =  26 evaluated at ages 19 and 39 years). Dental changes were evaluated with the Peer Assessment Rating (PAR) index.

In untreated and treated groups, PAR scores increased over time with gender-specific changes. In the untreated groups, the PAR score significantly increased in male participants between the ages of 12 and 22 years (P  =  .04) and in female participants between the ages of 19 and 39 years (P  =  .001). In the treated group, early posttreatment changes were primarily related to the initial treatment response. Later changes in the PAR score could be attributed to physiological changes, with the same gender-specific changes as those observed in the untreated group.

The pattern of physiological changes in dentition for participants between the ages of 12 and 39 was different between sexes. Females showed more relapse than males between 10 and 15 years posttreatment. This distinction should be considered when evaluating long-term orthodontic treatment responses.