���䲻ͬԤ����ʽ��ȫ�ڹ�λ��Ӱ����о�

目的    研究颈袖不同预备方式对全冠固位力的影响。方法    选取上颌离体切牙40颗，均为2009年8月至2010年2月杭州口腔医院收治的牙周病患者因松动无法保留而拔除的牙齿。根据颈袖不同预备方式随机分为A、B、C、D组，每组10颗牙。对离体牙牙冠舌侧颈1／3进行研磨形成0°（A组）、2°（B组）、5°（C组）切向聚合度的颈袖；D组为对照组，无颈袖存在。在2343型电子万能测试机上，测量拉力与牙体长轴方向夹角为0°和15°时冠脱位所受到的最大拉力值。结果    不同拉力方向下，A、B、C组的固位力明显高于D组，差异均有统计学意义（P < 0.05）。拉力与牙体长轴方向的夹角为0°时，A、B、C组的固位力随着切向聚合度的增加而降低，A组固位力与B组之间差异无统计学意义（P > 0.05），而与C组间差异有统计学意义（P < 0.05）；拉力与牙体长轴方向的夹角为15°时，A、B、C组的固位力也随着向聚合度的增加而降低，差异均有统计学意义（P < 0.05）。结论    颈袖预备有利于全冠的固位，特别适合于抵抗全冠的旋转脱位。

The effect of different cervical sleeve preparation on retention force of full crown

Objective To investigate the effect of different cervical sleeve preparation on the retention force of full crown.Methods Forty extracted maxillary incisors were randomly divided into two parts to receive the measurement of retention force with 0° and 15° angle between the tension and long axis of tooth.Twenty teeth in each part were randomly divided into four groups：Group A,B,C and D.The incisal convergence angle of cervical sleeve in Group A,B and C were 0°,2° and 5°.Group D without cervical sleeve served as control group.Results The retention force of Group D was lower than that of Group A,B and C,and the difference was significant in 0° and 15° angle between the tension and long axis of tooth（P 0.05）.No significant difference was found between Group A and B in the retention force with 0° angle between the tension and long axis of tooth（P 0.05）,while there were significant differences between Group A and C（P 0.05）.The retention force of Group A,B and C with 0° and 15° angle between the tension and long axis of tooth were gradually decreased with the increase of cervical sleeve convergence angle,and the difference was significant in three groups with 15° angle between the tension and long axis of tooth（P 0.05）.Conclusion Cervical sleeve preparation is beneficial to the retention of full crown,and is especially suitable to resist rotatory dislocation of full crown.