Occlusal bite force changes during 6 months of orthodontic treatment with fixed appliances

Background: Occlusal bite force (OBF) is reported to change during fixed appliance orthodontic treatment. Aims: The aim of the present study was to determine bite force changes during the first 6 months of fixed appliance orthodontic treatment and to investigate the relationship between patients' subjective pain levels and recorded changes in OBF. Methods: Forty-seven subjects (34 females, 13 males) were recruited from the Dental Teaching Centre at the Jordan University of Science and Technology. The subject's ages ranged between 18 and 26 years (average 19.0 +/- 3.36 years). Bite force was measured using a portable OBF gauge at nine time intervals (T0 - T8). At each OBF recording, subjects were asked to describe their subjective pain level using a visual analogue scale (VAS). A repeated-measures analysis of variance and a Bonferroni post-hoc comparison test were applied to determine differences at the various time intervals. Results: Bite force significantly reduced during the first month of orthodontic treatment and approximately 50% of pretreatment OBF was lost by the end of the first week. However, bite force recovered to pretreatment levels by the end of the sixth month. Visual analogue pain scores were higher during the first 2 weeks of treatment and were positively correlated with the OBF loss. Conclusion: OBF reduced during the first month of orthodontic treatment but, with time, recovered to pretreatment levels. (Aust Orthod J 2012; 28: 197-203)