后牙冠的严重缺损,是口腔科常见的病例。缺损的原因,一是见于大面积的邻(牙合)面或(牙合)颊面的龋坏,二是见于牙体劈裂。而后者往往是因为干髓术或根管治疗后牙体脆性增加,或充填后忽略调(牙合)过陡的非工作尖,或因重度磨耗形成“臼状”(牙合)面等。这些情况的牙体在骤咬硬物或在外力撞击下,引起牙体劈裂。我 Severe posterior crowns, dental department is a common case. The reasons for the defect, one is seen in a large area of ​​the adjacent (occlusal) surface or (occlusal) buccal caries, and the second is found in the tooth splitting. The latter is often due to an increase in the fragility of the tooth after stemming or root canal treatment, or neglecting a steep non-working tip after filling or a “mortar” surface due to severe wear Wait. Tooth in these cases in the sudden bite hard objects or external impact, causing the tooth splitting. I