Studies on Evaluating Method for Adhesive Durability of Posterior Composite Resin.

建立了一种评价后牙复合树脂与牙体粘结强度的新方法。在这种方法中，使用了具有填充树脂的圆柱形空腔的样品。聚合固化后，用平底圆柱形冲头将树脂挤出。由此得到的粘结强度与实际情况的关系比传统的剪切试验更接近实际情况。通过多次实验，发现树脂与牙本质的粘结强度为1.31 Mpa，与牙釉质的粘结强度为5.82 Mpa。这两个数值分别是剪切试验值的46%和26%。我们还进行了估算，发现在树脂/牙齿界面处出现了非常大的拉应力。这些拉伸应力在剪切试验中不会出现，并被认为是导致建议的推出法粘结强度降低的原因。研究了后部复合树脂在反复压缩载荷下的粘结耐久性。制备了四种型腔，即箱形、带斜面的箱形、托盘、带斜面的托盘，并用复合树脂填充。考察了两种灌装程序，一种是一次灌装的常规方法，另一种方法是分两步完成灌装。试件承受反复压缩载荷，通过染料渗透试验评价粘接耐久性。结果表明，反复加载对边际渗漏有促进作用。托槽的边缘渗漏比盒形槽小，对提高两种槽洞的耐久性都有很好的效果。充填过程对试件的耐久性影响不大，二次充填试件的耐久性比常规一步充填试件的耐久性差。

We developed a new method for the evaluation of bond strength of posterior composite resin to tooth. In this method, specimens having cylindrical cavities filled with resin are used. After polymerization and curing, resin are pushed out by flat-based cylindrical punch. Bond strength thus obtaired are considered to have more close reiationships to the actual ciinic condition than those obtained by conentional shear test. We conducted several experiments and found that bond strength of resin to dentin was 1.31Mpa, and that to enamel was 5.82MPa. These values were 46% and 26%, respectively, of those obtained by shear test. We also carried out estimations and found that very large tensile stresses occur at resin/tooth interface. These tensile stresses do not occur in specimens utilized in shear test, and are considered to responsible for the reduction of bond strength noted with the proposed push-out method.The adhesive durability of posterior composite resins under repeated compressive loads was investigated. Four types of cavities, i.e. box, box with bevel, saucer, saucer with bevel were prepared and filled with composite resins. Two filling procedures were examined, one was conventional method in which filling was done at one time, while in other method, filling was completed in two steps. Specimens were subjected to repeated compressive loads, and adhesive durability was evaluated by dye penetration test. It was found that the marginal leakages were promoted by repeated loadings. The saucer cavity showed less marginal leakage than box cavity, and bevel excellent effects on the improvement of durability of both types of cavities. Filling procedure has little effect on durability, and specimens filled by two-step method show poorer durability than specimens filled by two-step method show poorer durability than specimens filled by conventional one-step method.