Assessment of post-orthodontic occlusal contacts with wrap-around and clear overlay retainers

A prospective study to evaluate short-term changes in occlusal force and contact surface area associated with retainer wear. Total 32 subjects, randomly assigned to two experimental groups, a clear overlay group and a wrap-around retainer group, were followed to assess occlusal changes. Assessments were made utilizing the T-Scan II (Tekscan, Inc., 307 West First St., South Boston, MA 02127) method of occlusal analysis at 3 time periods; T0, at debond all subjects received lower fixed canine to canine retainer and upper clear overlay retainers; T1, 2 weeks later 14 subjects received wrap-around retainers and the clear overlay retainer group was checked (18 subjects); T2, occlusal contact assessment 2 months later for both groups. During T0-T1, the occlusion with clear overlay retainers showed a significant decrease in posterior surface area contact (p < 0.05) as well as a decrease in force that was not statistically significant. During the following 6 weeks (T1-T2), the Wrap-around retainer showed significant increases in posterior force and area (p < 0.001). However, overall during time period T0-T2 neither retainer group showed a significant change in relative distribution of occlusal force or surface area (p > 0.05). An independent sample (15 subjects) showed high intraclass correlations (r > 0.90) between replicate measurements of relative force, indicating low technical errors when multiple measurements are used. In conclusion, there were no significant net changes in occlusal forces or areas after 6 weeks of comparison between the wrap-around and clear overlay retainers following orthodontic therapy. In addition, it was shown that the T-Scan is a reliable apparatus for analysis of relative force.