Age-related long-term posttreatment occlusal and arch changes.
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OBJECTIVE: To evaluate differences in long-term postretention changes between adolescents and adults. MATERIALS AND METHODS: The sample included 96 subjects, 51 adolescents and 45 adults (14.2 +/- 0.8 and 21.5 +/- 6.8 years of age, respectively, at the end of treatment) retained for 3 years and followed approximately 16 years post treatment, who were randomly selected from two private practices. Prior to treatment, 38 and 58 had Class I and Class II malocclusions, respectively. RESULTS: With the exception of adult midlines, all of the occlusal variables (overjet [0.50-0.77 mm], overbite [0.85-0.95 mm], the maxillary incisor irregularity [0.69-0.80 mm], the mandibular incisor irregularity [0.85-1.50 mm] and the PAR score [0.86-1.92 points]) showed significant increases over time. Adolescents consistently showed greater increases of the occlusal variables than adults, with mandibular incisor irregularity and the PAR index attaining statistically significant (P < .05) levels. Arch length and mandibular intercanine width showed statistically significant decreases over time in both groups; maxillary intercanine and intermolar widths did not change significantly. Overjet increased significantly more in Class II patients than in Class I patients, whereas Class I patients showed significantly greater decreases in mandibular intermolar width than Class II patients. CONCLUSIONS: Over the 16-year posttreatment period, adolescents showed significantly greater increases in mandibular incisor irregularity, and the PAR index than adults. Treated Class I patients demonstrated less increase in overjet and greater decreases in mandibular intermolar width than Class II patients.