Clinical Evaluation of Bulk-fill vs Layered Composite Resin in Class I and II Posterior Restorations

In recent years, people are more concerned with the aesthetic qualities of dental restorations and in response to enhancements in the resin technologies, tooth-colored resin composite materials are increasingly being used for posterior teeth instead of amalgam fillings. Developments during the years in chemical composition, filler reinforcement, and adhesive techniques have resulted in many new modified categories of materials. Some researchers recommend the use of the incremental technique, in which the composite material is gradually placed in layers of 2mm or less.

This approach to restore teeth has a number of advantages, for example, it results in better light penetration and better polymerization of composite resin, reduction in cavity configuration factor, reduction in polymerization shrinkage stress and ensures that the resin adheres to the cavity walls. During curing of the resin, a network of polymers is formed, which becomes rigid due to increased cross linking of the polymer chains. Decreasing mobility of the network causes further shrinkage and results in a strain on the resin composite and cavity margins. The resulting stress has been associated with marginal deficiencies, enamel fractures, cuspal movement, and cracked cusps, which in turn may result in microleakage, post-operative sensitivity, and secondary caries. It has been stated that posterior class II and especially class I cavities with a high C-factor will result in greater stresses due to a larger number of bonded surfaces.

However, there are number of disadvantages associated with the use of an incremental approach to place the resin. For example, voids can be trapped in between the increments, bonding failure can occur in between the increments, difficulty in placing the composite material after cavity preparation and the long time taken for the procedure. In an effort to counter these problems, a new restorative material has been introduced in 2009 which is known as 'bulk-fill' composite, in order to increase efficiency of the operator. However, many clinicians who have accustomed to the incremental cure philosophy when placing the light-cured composite quite rightly question what has been changed to make these bulk-fill light-cured composite a variable alternative. According to some researchers, bulk-fill composite offers more advantages compared to the layered composite. These include increased efficiency in working time, reduced polymerization shrinkage and reduces the risk of contamination and voids forming between the resins.

The aim of this study is to evaluate the clinical performance of bulk-fill composite as compared to the layered composite technique in class I and class II restorations over the period of 2 years.