Factors contributing to the variability of anterior overbite opening after standardized posterior bite raiser placement: a prospective single-arm pre-post clinical study.

BACKGROUND

Posterior bite raisers are frequently used in orthodontics, yet the magnitude of the resulting anterior overbite change shows substantial interindividual variability. This study aimed to identify dental and cephalometric characteristics that explain interindividual variability in anterior overbite opening following standardized posterior bite raiser placement.

METHODOLOGY: Forty-seven subjects (7-56 years of age) with a recent lateral cephalogram were recruited. Digital intraoral impressions of the dentition were taken before and after temporary placement of a 2mm-diameter stainless-steel posterior bite raiser in the central fossae of both mandibular first permanent molars. Overbite changes and dental characteristics were recorded on digital dental casts, while skeletal parameters were measured on the corresponding lateral cephalogram. Regression analyses were performed to identify associations between anterior bite opening and individual dental or cephalometric characteristics.

RESULTS

Placement of 2mm posterior bite raisers decreased anterior overbite by an average of 2.2mm, but with large interindividual variation (0.3-4.0mm). The magnitude of anterior opening was significantly associated with the molar relationships (p<.001), whereby patients with Class I molar relationships showed greater opening (2.5mm, range 0.6-4.0mm) than those with Class II molar relationships (1.7mm, range 0.2-3.8mm). Occlusal morphology also influenced the outcome, as deeper mandibular fossae were correlated with reduced anterior opening (p<.01). Skeletal cephalometric variables were not significantly associated with the quantity of bite opening.

CONCLUSIONS

The anterior opening induced by posterior bite raisers is highly variable among individuals and primarily determined by local dental morphology and intercuspation rather than skeletal characteristics. Recognizing these dental predictors may help clinicians anticipate the vertical response to posterior bite disocclusion during orthodontic treatment.