上颌第四磨牙实为多生牙,也叫额外牙,是指正常牙数之外多生的牙齿[1]。国内外报道额外牙发生率为2%~4%,是比较常见的先天畸形[2-3]。多生牙多数发生在上颌切牙区、其次是在前磨牙区,最后是磨牙区。现将笔者所在单位门诊接诊的一例双侧上颌第四磨牙异位病例的临床资料报道如下。 The fourth maxillary fourth molar actually juvenile teeth, also known as additional teeth, refers to the normal number of teeth outside the polygamous [1]. The incidence of extra teeth at home and abroad reported 2% to 4%, is more common congenital malformations [2-3]. Much of the polyp occurs in the maxillary incisor area, followed by the premolar area, and finally the molar area. Now the author’s unit outpatient admissions a case of bilateral maxillary fourth molar ectopic cases of clinical data reported below.