下颌第三磨牙牙尖、阻生类型与牙根的相互关系

摘要

目的　本文对1090颗下颌阻生第三磨牙牙合面牙尖、阻生类型与牙根的相互关系进行了探讨。结果　牙合面牙尖呈六型，分别是三尖型(0.55%)、四尖型(26.42%)、五尖型(53.58%)、六尖型( 18.16%)、七尖型(0.83%)和八尖型(0.46%)。牙根呈四型，分别是融合根型(35 .14%)、双根型(57.34%)、三根型(7.34%)和四根型(0.18%)。牙合面牙尖数目少，融合根比例高，三尖型主要是融合根型； 牙尖根数目增加，双根和三根比例上升。七尖型、八尖型没有融合根型。阻生尖型以近中位最多见(31.62%)，垂直位(29.08%)，颊向位(16.88%)，远中位、舌向位和水平位均不足9%。远中位融合根比例高达47.06%；近中位、垂直位和水平位双根比例高，分别为64.35%、58.04%和57.73%；颊向位和垂直位三根比例高，分别达13.04% 和11.35%，其余各类型中三根的比例均不足9.5%。结论　各阻生类型均符合牙合面牙尖数少融合根比例高，牙合面牙尖数多，双根和三根的比例高的规律。%Objective．To study the relationship between the cusps,impacted type and roots 1090 mandibular third molar tooth.Results．The cusps of the mandibular third molar tooth can be divided into 6 types,they are 3 cusps (0.55%),4 cusps (26.42%),5 cusps (53.58%),6 cus ps (18.16%),7 cusps (0.83%)and 8 cusps (0.46%).The root of the mandibular third molar tooth can be divided into 4 types,they are 1 root (35.14%),2 roots (57.34% ),3 roots (7.34%) and 4 roots (0.18%).The less the cusps of teeth crown,the higher the proportion of one root.The cusps is increase,the proportion of one root is decrease and the proportion of two roots or three roots is increase.7 and 8 cusps have not 1 root.The proportion of impacted type are as follow:mesioangular impaction is 31.65%.Vertical impaction is 29.08%,buccoangular impaction is 16.88% ,distoangular impaction,linguoangular impaction and horizontal impaction is less then 9%.The proportion of one root of distoangular impaction is the largest (47 .06%),the proportion of two roots of mesioangular impaction.Vertical impaction,horizontal impaction is 64.35%,58.04%,57.73%.Respectively.The proportion of three roots of buccoangulaz impaction and vertical impaction separately reach 13.04% and 11.35%.The proportion of three roots of rest types is less than 9.5%.