2012 年 10 巻 4 号 p. 276-290
Posterior cross bite in the deciduous dentition stage is unlikely to heal on its own even as the jaw grows. If left untreated, it could continue through to the mixed dentition stage and permanent dentition stage, cause facial asymmetry and invite temporomandibular joint dysfunction as well as modify the dental arch. Early treatment of subjects with deciduous dentition stage posterior cross bite is considered necessary, however the cause of the cross bite, craniofacial morphological characteristics and the position of individual teeth and tooth axes are still not fully understood and a consensus between experts on the ties between diagnosis and treatment is not necessarily seen. In this study we focused on the molar group tooth axes and analyzed models of 15 children with cross bite and models of children with healthy occlusion, compared the relationship between dental arch and tooth axis and examined palatal morphology and postero anterior cephalogram with the purpose of clarifying the aspect of posterior cross bite in the deciduous dentition stage. Results were as follows. In dental arch size measurement, there was a trend of the distance between each measurement being larger in the cross bite side of the cross bite group than the non-cross bite side. When compared with the control group, the distance in both the cross bite side and non-cross bite side of the cross bite group was significantly smaller. In maxillary and mandibular deciduous molar tooth axis measurement, no significant differences were observed in the maxillary and mandibular first and second deciduous molar tooth axis measurements between the cross bite group and the control group. In measurement of the angle between the maxillary and mandibular molar tooth axes (lingual), no significant differences were observed in the angle between the maxillary and mandibular first deciduous molar tooth axes and the angle between the maxillary and mandibular second deciduous molar tooth axes between the cross bite group and the control group. In palatal surface distance measurement, although there was no significant difference between the cross bite side and non-cross bite side of the cross bite group, the measurement of the control group was significantly higher than both the cross bite side and non-cross bite side of the cross bite group. In analysis by postero anterior cephalogram, no significant difference in maxillary and mandibular right and left jaw width and posterior symmetry was seen between the cross bite side and non-cross bite side of the cross bite group. The midline of the tooth deviated by 2.40 mm and the midline of the maxillary and mandibular jaw deviated by 3.25° on the cross bite side in the cross bite group.
