FINITE-ELEMENT STRESS-ANALYSIS OF 3 FILLING TECHNIQUES FOR CLASS-V LIGHT-CURED COMPOSITE RESTORATIONS

An important disadvantage of current dental resin composites is polyme rization shrinkage. This shrinkage has clinical repercussions such as sensitivity, marginal discoloration, and secondary caries. The objecti ve of this study was to compare three filling techniques in terms of t he transient stresses induced at the resin composite/tooth interface d uring polymerization. The techniques were: bulk filling (B), three hor izontal increments (HI), and three wedge increments (WI). A simple Cla ss V cavity preparation was modeled in finite element analysis. Polyme rization shrinkage was simulated by a thermal stress analogy, thereby causing 1% shrinkage due to an arbitrary coefficient of thermal expans ion. Interface normal and shear stresses were calculated at nine steps during polymerization, proceeding from 0% to 100% volume of cured res in. 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 exhibi ted the highest and lowest maximum transient stresses, respectively. T hese results from the simple model of a Class V restoration suggest th at bulk filling of light-cured resin composites should be used in rest orations which are sufficiently shallow to be cured to their full dept h.