Winkler M M, Katona T R, Paydar N H
Dental Materials Division, Indiana University-Purdue University at Indianapolis, School of Dentistry 46202, USA.
J Dent Res. 1996 Jul;75(7):1477-83. doi: 10.1177/00220345960750070701.
An important disadvantage of current dental resin composites is polymerization shrinkage. This shrinkage has clinical repercussions such as sensitivity, marginal discoloration, and secondary caries. The objective of this study was to compare three filling techniques in terms of the transient stresses induced at the resin composite/tooth interface during polymerization. The techniques were: bulk filling (B), three horizontal increments (HI), and three wedge increments (WI). A simple Class V cavity preparation was modeled in finite element analysis. Polymerization shrinkage was simulated by a thermal stress analogy, thereby causing 1% shrinkage due to an arbitrary coefficient of thermal expansion. Interface normal and shear stresses were calculated at nine steps during polymerization, proceeding from 0% to 100% volume of cured resin. The importance of the interface transient stresses was revealed by the finding that, in most cases, their peak values exceeded the final or residual stress. Also, the WI and B techniques consistently exhibited the highest and lowest maximum transient stresses, respectively. These results from the simple model of a Class V restoration suggest that bulk filling of light-cured resin composites should be used in restorations which are sufficiently shallow to be cured to their full depth.
当前牙科树脂复合材料的一个重要缺点是聚合收缩。这种收缩会产生一些临床影响，如敏感、边缘变色和继发龋。本研究的目的是比较三种充填技术在聚合过程中在树脂复合材料/牙齿界面处引起的瞬态应力。这些技术分别是：整块充填（B）、三次水平分层充填（HI）和三次楔形分层充填（WI）。在有限元分析中模拟了一个简单的V类洞制备。通过热应力类比来模拟聚合收缩，因此由于任意热膨胀系数导致1%的收缩。在聚合过程的九个步骤中计算界面法向应力和剪应力，从固化树脂体积的0%到100%。通过发现在大多数情况下，它们的峰值超过了最终应力或残余应力，揭示了界面瞬态应力的重要性。此外，WI技术和B技术分别始终表现出最高和最低的最大瞬态应力。这个简单的V类修复模型的这些结果表明，光固化树脂复合材料的整块充填应用于足够浅以完全固化至全深度的修复体中。
