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

提出了一种评价后牙复合树脂与牙体结合强度的新方法。在这种方法中，使用具有填充树脂的圆柱形腔的试样。树脂经聚合和固化后，由平基圆柱冲床推出。与传统的剪切试验结果相比，由此得到的粘结强度与实际情况的关系更为密切。我们通过多次实验发现树脂与牙本质的结合强度为1.31Mpa，与牙釉质的结合强度为5.82MPa。这些值分别为剪切试验所得值的46%和26%。我们还进行了估计，发现树脂/齿界面处出现了非常大的拉应力。这些拉伸应力不会发生在剪切试验中使用的试样中，并且被认为是导致提出的推出方法所指出的粘结强度降低的原因。研究了后置复合树脂在反复压缩载荷作用下的粘接耐久性。制备了箱形、带斜角的箱形、碟形、带斜角的碟形四种型腔，并用复合树脂填充。研究了两种充填方法，一种是一次性充填的常规方法，另一种是分两步充填的方法。试件承受反复压缩载荷，并通过染料渗透试验评估粘接耐久性。结果表明，重复加载对边际泄漏有促进作用。碟形空腔的边缘泄漏比箱形空腔少，斜角对两种空腔的耐久性都有较好的提高效果。充填方式对耐久性影响不大，两步法充填的试件耐久性低于两步法充填的试件，且其耐久性低于常规一步法充填的试件。

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.