Anterior open-bite malocclusion: stability of maxillary repositioning using rigid internal fixation.

A retrospective cephalometric study was performed to investigate the stability of 37 non-growing anterior open-bite cases using mini-plate rigid fixation. The sample was divided into two groups: Group A: maxillary repositioning alone (17 cases) and Group B: bimaxillary surgery (20 cases). Tracings were performed pre-operatively (T1), immediately post-operatively (T2) and at a minimum of one year follow-up (T3) (12-90 months). In Group A, the maxilla was advanced (3.8 +/- 2.8 mm, p < 0.01) and superiorly repositioned at PNS (2.8 +/- 2.3 mm, p < 0.001). In Group B, the maxilla was advanced (3.5 +/- 3.0 mm, p < 0.01) and superiorly repositioned at PNS (3.7 +/- 1.8 mm, p < 0.001); and the mandible (11.7 +/- 3.8 mm, p < 0.001), with no significant change in the vertical plane (p > 0.05). Late relapse due to condylar remodelling or resorption was found as a cause of large horizontal relapse (8.0 < x < 14.0 mm) in three cases (15%), the amount being associated with the amount of operative advancement (r = 0.7, r-sq = 40%, p < 0.01). It was concluded that the correction of anterior open bite by posterior repositioning of the maxilla using rigid fixation is a stable procedure during the follow-up period, and that in bimaxillary cases, post-operative stability depends largely on the stability of the mandibular advancement, which in turn relates to the amounts of advancement, the pre-operative anterior open bite and the mandibular plane angle.