磨牙倾斜角度和萌出间隙对第三磨牙萌出的影响

目的研究影响第三磨牙阻生或萌出的一些客观因素。方法选择86例(男37例,女49例)平均年龄25.4岁,上下颌第三磨牙均存在的患者,将其分为萌出组和阻生组,利用曲面断层片对患者上下颌第三磨牙的近中倾斜角、牙冠近远中径、磨牙后间隙、磨牙后间隙和牙冠近远中径的比值进行测量分析。结果上颌萌出组萌出间隙较阻生组大1.95mm,第二磨牙和第三磨牙长轴交角相差12.53°,萌出组第三磨牙近远中径比阻生组小0.69mm,有统计学差异。下颌萌出组萌出间隙L-ES(R)较阻生组平均值大3.33mm;第三磨牙与牙合平面交角阻生组较萌出组大32.48°;萌出组与阻生组的磨牙后间隙/牙冠近远中径平均值分别为1.05、0.85,3项指标差异均有显著性(P<0.01)。下颌第三磨牙近远中径相差0.3mm,无统计学意义。结论第三磨牙萌出受萌出间隙和磨牙间交角的影响,对于上颌第三磨牙,磨牙交角影响更大,对于下颌第三磨牙无足够的间隙萌出,是导致下颌第三磨牙阻生的重要原因。

Effects of eruption space and molar agulations on third molar eruption

Objective To find evidences for clinical treatment program by investigating the variables in the third molar between the subjects with impacted third molars and those with erupted ones. Methods 86 subjects (37 males,49 females) with an average age of 25.4 years old were chosen and divided into impacted and erupted groups. Standardized panoramic radiographs were taken and the indexes of the third molar angulation, mesiodistal crown width , eruption space, and the ratio between them were analyzed.Results In the maxilla, the eruption space of erupted group was 1.95 mm larger than that of the impacted group ([WTBX]P<0.01).The average difference of the angle between the long axis of the third molar and the second molar was 12.53 degrees(P<0.01). Mesiodistal crown width of the erupted group was smaller than that of the impacted group and the difference was 0.7 mm(P<0.05). In mandible, the eruption space of erupted group was larger than that of the impacted group and the difference was 3.33 mm (P<0.01). The average difference of the angle between the long axis of the third molar and the occlusal plane was 32.48 degrees(P[WTBZ]<0.01). The average ratios between the eruption space and mesiodistal crown width in the impacted and erupted groups were 0.85 and 1.15, respectively (P<0.01). The impacted and erupted groups had no significant differences in respect to mesiodistal crown width of the third molar. Conclusion The eruption space and third molar angulation could affect the eruption of third molar. Molar angulation is more important to the maxillary third molar. To mandibular third molar inadequate eruption space or more mesioangulation of the third molar results in molar impaction.