超过正常数目而形成的牙齿叫做额外牙。这是牙齿发育在数目上的一种异常。如果这种牙与邻牙非常相似,也可称为多生牙。额外牙可以正常萌出,埋伏阻生,牙体倒置,呈异位或不正常的途径萌出。这类牙可以引起种种并发症,如引起邻牙拥挤,延期萌出,间隙、扭转、囊肿损害和吸收。因此,尽早作出诊断,予以适当治疗是非常必要的。额外牙的发生情况据国外文献报道,额外牙的发生率儿童为0.3～3.8％,且存在明显种族差异。Mckibben与Brearly通过X线照片研究发现1500个白种人儿童,年龄在3～12岁的发生率为1.53％。Nismarder与Sujaku调查日本儿童的发生率高于3％。Laws More than the normal number of teeth formed is called extra teeth. This is an abnormality in the number of teeth. If this tooth is very similar to the adjacent teeth, also known as polygamy. Extra teeth can eruption, implicated obstruction, inverted teeth, ectopic or abnormal path eruption. Such teeth can cause complications such as crowding of adjacent teeth, delayed eruptions, gaps, twisting, cyst damage and absorption. Therefore, to make a diagnosis as soon as possible, to be properly treated is very necessary. The occurrence of extra teeth According to foreign literature, the incidence of extra teeth in children was 0.3 to 3.8%, and there is a clear ethnic difference. Mckibben and Brearly through the X-ray study found that 1500 Caucasian children, aged 3 to 12 years the incidence was 1.53%. Nismarder and Sujaku surveyed Japanese children at> 3%. Laws