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Occlusal contacts and maximum voluntary bite force in subjects with Essix and wraparound retainers

Aim: To determine the differences in occlusal contact (OC) and maximum voluntary bite force (MVBF) changes in subjects with Essix and wraparound retainers. Materials and Methods: Sixty subjects aged 14-20 years wearing Essix (13 males and 17 females ; mean age 16.3±1.9), and wraparound (11 males and 19 females, mean age 16.0±1.7) retainers. Measurements were undertaken after fixed appliance removal (T1) and after 6 (T2), and 10 weeks of retention (T3). MVBF was determined unilaterally with the occlusal force meter GM10 (Nagano, Keiki, Japan). The subjects bit on the instrument four times on each side and repeated the procedure in reversed order. OC was determined using Hawe Transparent Strips No 690, straight (Kerrhawe SA, Bioggio, Switzerland). The strip was placed on lower teeth, and OC was recorded when it could not be pulled out between the antagonists. Statistical analyses were performed with mixed types of multifactorial variance analysis (ANOVA) and Bonferroni post hoc tests. Results: There was statistically significant increase (p<0.001) in MVBF in wraparound wearers during all readings. In Essix wearers the increase was more significant between T1 and T2 (p=0.002) than between T2 and T3 (p=0.039). OC did not differ between readings when Essix was used, and when wraparound was used there was a significant increase between T1 and T2 (p=0.003). When the appliances at each reading were compared, no statistically significant differences were fond with regard to both OC and MVBF. Conclusions: There were more increase in MVBF and the OC during the 10 week retention period when wraparound was used, but there was no significant difference between the appliances at each reading. Thus both wraparound and Essix can be successfully used for retention.

occlusal contacts; bite force; orthodontic retainer

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