下颌先天性缺失一颗恒切牙的正畸学研究

Orthodontics Research on Congenital Absence of One Mandibular Permanent Incisor

下颌先天性缺失一颗恒切牙在我国有较高发生率,引起下颌先天缺牙的病因繁多,但遗传倾向或家族聚集性被推测为其首要病因,可能与同源盒基因TGFA、MSX1和PAX9的突变有密切的联系。下颌缺失一颗恒切牙后容易引起下颌骨发育不足和下颌切牙向内倾斜,进而导致Ⅱ类面型和Ⅱ类错牙合增多,前牙覆牙合覆盖加大,下颌中线不调,Bolton指数减小等临床表现,给正畸矫治增加了难度。临床上正畸医师常通过对患者面型、牙列拥挤度、磨牙关系、前牙覆牙合覆盖、Bolton指数以及患者自身诉求等方面综合考虑,必要时行诊断性蜡合排列试验协助建立组牙保护牙合,选择拔牙、邻面去釉或开辟间隙修复等方法进行正畸矫治。

In China,there is a relatively high incidence of congenital absence of one mandibular permanent incisor. The causes of congenital absence of mandibular incisor are various,but heredity or familial aggregation has been suggested as the primary cause,which has a close connection with homeobox genes TGFA,MSX1 and PAX9. Congenital absence of one mandibular incisor is easy to cause clinical manifestations of mandibular deficiency and incisor retroclination,which would lead to class Ⅱ facial profile and the increase of classⅡ malocclusion,overjet and overbite of anterior teeth,discrepancy of mandibular midline,decrease of Bolton index and so on. Such clinical manifestations bring more difficulties to orthodontics treatment. Therefore,clinical orthodontists usually make treatment of extraction,interproximal enamel reduction or creating a space for restoration basing on the comprehensive assessments of patients＇ facial types,crowding of teeth,molar relationship,overjet and overbite of anterior teeth,Bolton index and patient＇s own demands,and diagnostic waxing is set up if necessary.