To prevent osteotomy deviation off the septum, the crown is sectioned (Fig.2) and the coronal end of the septum is to be exposed.  The crack line extends to the pulpal chamber.  The teeth #19,20 and 31 are missing.去掉牙冠显示裂纹够深的（图二箭头）。

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Xin Wei, DDS, PhD, MS 1st edition 07/09/2020, last revision 10/01/2020