Polymerization characteristics, flexural modulus and microleakage evaluation of silorane-based and methacrylate-based composites

To compare the behavior of a new low-shrinkage silorane-based composite (P90) with two conventional methacrylate-based composites, in terms of polymerization shrinkage, polymerization stress, gel point, flexural modulus and microleakage.

The materials tested were P90 (3M ESPE), AP-X (Kuraray), Quixfil (Dentsply). Polymerization shrinkage was measured using the Accuvol method. Polymerization stress was assessed using a stress-strain analyzer. Polymerization shrinkage (%) and force (N) were continuously recorded for 300 seconds. Polymerization shrinkage and stress after 300 seconds and gel point were recorded. Flexural modulus was obtained by three-point bending. A laboratory microleakage test was performed. Class V cavities prepared on labial surfaces of 70 freshly extracted human teeth were randomly assigned to the seven groups (N=10): P90/PSA (P90 System Adhesive), AP-X/CBA (Clearfil SE Bond Adhesive), Quixfil/XBA (XP Bond Adhesive), P90/CBA, P90/XBA, AP-X/PSA, Quixfil/PSA. The teeth were immersed in 1% basic fuchsin dye for 24 hours at room temperature. All teeth were cut in a labial-lingual direction and the penetration of dye along the wall of cavities was observed under a stereoscopic light microscope. Statistical analysis was performed with one-way ANOVA, Kruskal-Wallis ANOVA test and post hoc tests (P< 0.05).

The low-shrinkage silorane-based composite (P90) exhibited significantly lower polymerization shrinkage, polymerization stress, flexural modulus and a later gel point than the conventional methacrylate-based composites. In the microleakage test, P90/PSA, AP-X/CBA, AP-X/PSA demonstrated the lowest microleakage scores without a significant difference among them (P> 0.05). Quixfil/XPA exhibited the highest microleakage scores.