Depth of Cure and Microhardness of Nanofilled, Packable and Hybrid Dental Composite Resins

Resin-based composites are used worldwide in dentistry as they are used in a huge variety of clinical applications, as an esthetic restorative material with excellent physical and mechanical properties when adequate polymerization is obtained. In this study, depth of cure and microhardness of three composites were measured and compared. A total of sixty human mandibular first molars were used. The teeth were divided into three main groups (20 teeth each) according to the composite resins that were used. In group I, Surefil (packable composite) was used as the restorative material. In group II, Esthet-X-improved (nanofilled composite) was used, while in group III Glacier (hybrid composite) was used. Each group was subdivided into four subgroups (five teeth each) according to the storage intervals (24 hours, one week, two weeks, and three weeks). In each group, occlusomesial cavities were prepared with diamond burs and restored with the composite, according to manufacturer's instructions. In all specimens, composite was applied to the cavity using incremental technique. All the restored teeth were subjected to in vitro thermal cycling and mechanical loading simulating a total of six months in vivo function. Depth of cure was evaluated using penetrometer and microhardness was measured using Vicker’s microhardness tester. A significant difference in depth of cure and microhardness were found between the three composites used. Depth of cure and microhardness of the packable composite was better than the other two composites used. There was a fairly good correlation between the microhardness and the depth of cure for the three composite materials.