阻生第三磨牙生长方向与牙根数目关系的探讨

目的对临床拔除的1035颗阻生第三磨牙的生长方向（阻生类型）与牙根数目的关系进行分析与探讨。方法记录1035颗阻生第三磨牙拔除前阻生类型（生长方向）和拔除后牙根数目。结果阻生类型中，下颌以近中阻生最多见（50．559／6），其次为垂直阻生（45．05％），远中阻生最少（4．40％）；上颌以颊向阻生最多见（60．12％），其次为垂直阻生（35．58％），腭向阻生和远中阻生最少。下颌牙根数目有四类：两根（60．99％）、融合根（34．62％）、多根（3．859／6）和单根（0．55％）；上颌牙根数目有五类：融合根（56．44％）、三根（20．25％）、两根（17．79％）、四根（4．29％）和单根（1．23％）。下颌近中阻生、垂直阻生和远中阻生中两根比率、融合根比率分别为64．13％、33．70％，59．75％、32．93％，37．50％、62．50％。上颌颊向阻生、垂直阻生、腭向阻生和远中阻生中融合根比率分别为56．12％、56．9％、50％、66．67％。结论阻生第三磨牙的牙根数目与生长方向（阻生类型）有关，这一结果对临床顺利拔除阻生第三磨牙有重要指导意义。

Study of the Relationship between Growing Direction and Root Number

Objective To study the relationship between growing direction （impacted type） and root number of 1035 impacted third molar. Methods Record the impacted type （growing direction） of the 1035 impacted third molar before pulling out and the root number after pulling out. Results The proportion of the impacted type of mandible are as follow： mesioangular impaction is 50. 55%, vertical impaction is 45.05%, distoangular impaction is the least（4. 40%）. The proportion of the impacted type of maxilla are as follow： buccoangular impaction is 60. 12%, vertical impaction is 35.58%, palatoangular impaction and distoangular impaction are the least. The root of the mandibular third molar can be divided into 4 types： 2 roots（60.99%）, fused root（34.62%）, multi-root （3.85%） and 1 root（0. 55%）, The root of the maxillar third molar can be divided into 5 types, fused root（56.44%）, 3 roots（20.25%）, 2 roots（17.79%）, 4 roots（4. 29%） and 1 root（1.23%）. The proportion of 2 roots and fused root of mesioangular impaction, vertical impaction and distoangular impaction in mandible are 64.13%, 33.70%, 59.75%, 32.93%, 37. 50%,62. 50%. The proportion of fused root of buccoangular impaction,vertical impaction,palatoangular impaction and distoangular impaction in maxilla are 56.12%,56.9% ,50%,66.67%. Conclusion The root number of the impacted third molar is concerned with the growing direction （impacted type）. This result is of great guiding significance to the successful removal of impacted third molar.