上颌第三磨牙的形态观察

目的 探讨上颌第三磨牙牙尖数目与牙根型、牙根型与根管数目间的关系,为上颌第三磨牙的保留和再利用提供参考。方法 利用电子数显游标卡尺对上颌第三磨牙进行测量分析,观察牙尖数目和牙根的关系,并通过透明标本的制作观察其髓腔形态。结果 上颌第三磨牙根长大于冠长,颊舌径大于近远中径。其（牙合）面以三尖型居多,其次是四尖型。二尖型和三尖型融合根比例大,四尖型和五尖型者,则二根比例较大。根管系统虽较为复杂,但主要是双根管和三根管型。结论 上颌第三磨牙牙尖与牙根、牙根与根管间的关系有一定的规律性。?

Morphology and Clinical Observation of the Maxillary Third Molar

Objective To study the relation between the number of the cusps and roots, roots and canals in the maxillary third molar to provide the reference for clinical reservation and reutilization. Methods wilh the electronic digital calipers, the third molar was measured. Through the pulp transparent specimen, the shape of canals was observed. Results The maxillary third molar's root was longer than the crown, the buccopalatal dimension was greater than the mesiodistal. The majority of their occlusal surfaces had three cusps, next four cusps. The third molars which had two or three cusps were most of fused roots, while those that had four or five cusps were most of double roots. The root canal systems were comparatively complex, but most of them were most of double three canals. Conclusion There was some regularity of cusps and roots, roots and canals in the maxillary third molar.