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目的探讨在不同根面牙体预备方式、不同树脂厚度等条件下的衔铁-牙根复合体应力分布状况。方法 2002年1—4月在北京理工大学力学实验室建立4种不同根面预备和衔铁黏结方式的有限元模型,模型一:根面仅作平整预备,无边缘斜面;模型二:根面预备为凹形,边缘预备45°斜面肩台,衔铁与根面接触;模型三:同模型二,但衔铁与根面之间有一层厚0.5mm的树脂黏结剂;模型四:根面预备为嵌入式,衔铁黏结在其中,吸附面和根面在同一水平面上。采用4种不同方向进行根面加载。加载由有限元分析软件自动执行,并导出所需的应力值进行力学分析。结果不同牙体预备方式和黏结方式,应力主要集中分布在根桩颈部和基牙颈部。有限元力学分析结果显示,垂直载荷下每种模型各部分应力值较小,分布也较为合理,各模型应力值差别不明显;斜向载荷下各应力值增大约1～3倍。在各种加载条件下,不同牙体预备和黏结方式间VonMises应力值差异不大;拉力载荷下,衔铁与根面之间的树脂厚度增加,根面树脂内最大VonMises应力值也增加。各种载荷下,嵌入式牙体预备方式的牙本质内应力相对其它模型均较小。结论黏结式衔铁的黏结固位力可靠,受力后应力分布较为合理;衔铁颈部是需要加强的部位,临床黏结时树脂不要过厚。
Objective To investigate the stress distribution of the armature-root complex under different root preparation conditions and different resin thicknesses. Methods From January to April, 2002, four different finite element models of root preparation and armature bonding were established in the Mechanics Laboratory of Beijing Institute of Technology. Model 1: The root surface was only prepared for smoothing without edge bevels. Model 2: A concave, edge preparation of 45 ° bevel shoulder, the armature and the root surface contact; model three: the same model two, but the armature and the root surface between a layer of 0.5mm thick resin adhesive; model four: Type, armature bonding in which, adsorption and root surface in the same level. Four different directions for root loading. The loading was performed automatically by FEA software and the required stress values were derived for mechanical analysis. Results Different tooth preparation methods and bonding methods, stress mainly concentrated in the root of the root and the abutment neck. The results of finite element analysis show that the stress values of each model are smaller and the distribution is more reasonable under the vertical load, and the stress values of the models are not obviously different. The stress increases about 1 ~ 3 times under the oblique load. Under different loading conditions, Von Mises stress values of different dental preparation and bonding methods are not significantly different. Under tensile load, the thickness of the resin between the armature and the root surface increases, and the maximum Von Mises stress in the root surface resin also increases. Under various loads, the internal dentin stress of embedded tooth preparation is smaller than other models. Conclusion Adhesive keeper possesses a reliable bond strength and a more reasonable stress distribution. The neck of the keeper needs to be strengthened, and the resin should not be too thick when clinically bonded.