先天缺牙的研究进展

牙齿的发育不全是一种人类常见的发育异常，包括牙齿的萌出异常、数目异常、形态异常及结构异常。先天性的牙齿缺失属牙齿发育异常中的数目异常，是指临床检查牙齿口内部分或全部缺失，既往没有牙齿脱落或拔牙史，X线检查亦未见颌骨内该缺失牙的牙胚。个别牙缺失多见于恒牙列，最常见的是第三磨牙，其次是第二双尖牙及上颌侧切牙；全部的无牙症比较罕见，其常常累及乳牙和恒牙，通常与某些复杂疾病有关，如外胚层发育不全综合征等。多数牙先天缺失影响患者咀嚼功能，并且影响患者的容貌、身体发育和心理健康。

Research advances in tooth agenesis

Tooth agenesis constitutes one of the most common developmental anomalies in man. Oligodontia is defined as congenital absence of six or more teeth. Based on the studies of our team in cooperation with Peking University Center for Human Disease Genomics in the past five years, this article reviews the current research progress in clinical phenotypes and case collection, epidemiological investigation and etiological genetic studies of oligodontia. The symptoms of oligodontia were classified into syndromic and non-syndromic according to the occurrence of tooth agenesis with or without systemic developmental defects. As for the advancement of theories and techniques of molecular genetics, a number of gene mutations have been identified to be the direct etiological factors causing some specified diseases, especially those with developmental defects. Here, this article summarized the outcomes of molecular genetic study of some cases we collected. Of the systemic oligondontia patients, a new four-base-deletion mutation in PITX2 was identified in a large kindred with typical symptoms of Rieger Syndrome; four different gene mutations in ED1 casing X-linked hypohidrotic ectodermal displasia were found in five nucleus families. Compared with the former, non-syndromic oligodontia has more genetic heterogeneity rather than some specific virulence gene. PAX9 and MSX1 are the identified genes associated with family tooth agenesis without systemic syndrome. Also, in our research, three gene mutations in CBFA1 were detected in four cleidocranial dysplasia families, which is a systemic developmental disease including the symptoms of tooth eruption abnormality and accessory teeth.