A follow-up study of early interceptive treatment of primary anterior crossbites.

The purpose of this study was to investigate the outcome of early interceptive treatment of primary anterior crossbites with posterior occlusal acrylic resin blocks in combination with a 2 × 4 appliance, and to examine the differences in craniofacial morphology between the stable and relapse groups. Lateral cephalograms of 46 subjects (17 males and 29 females; average mean age 4 years 2 months ± 5 months) with a primary anterior crossbite were obtained before (T0) and immediately after (T1) treatment and at a 6 year follow-up (T2). The patients were assigned to either a stable (n = 35; 13 males and 22 females) or a relapse (n = 11; 4 males and 7 females) group according to the amount of overjet when the permanent incisors had erupted. The differences in craniofacial morphology between the groups were compared using a two-tailed t-test. The results revealed that the relapse subjects had a more forward position of the mandible relative to the cranial base and maxilla, a longer mandible and an increased gonial angle at T0. At T1, both groups had a positive overjet, but the treatment changes were different. Between T1 and T2, the maxillary length (A'-Ptm') increased less in the relapse group, the angle between the posterior border of the mandibular ramus and SN plane (Ram-SN) decreased and gonial angle increased and vice versa in the stable group. When posterior bite raising and 2 × 4 appliance therapy are used to correct primary anterior crossbites, all patients showed an immediate positive treatment response, whereas approximately one-quarter of subjects relapsed into a reverse overjet when the permanent incisors had erupted, mainly because of a more severe Class III craniofacial morphology at T1 and unfavourable growth during T1-T2.