On the effect of an internal light conductor on the marginal integrity of class-II composite fillings

Objectives The aim of this study was to examine the marginal behavior of class-II double surface fillings made with newly designed light transmitting inserts. These inserts guide the polymerization light directly into the body of the filling. Material and methods Sixty standardized two-surface cavities have been prepared into freshly extracted human molars and filled with Herculite XRV. Fifteen cavities were filled using the incremental technique (positive control group), 15 were filled with one single increment (negative control group) and 15 teeth each were filled with light conducting inserts with and without use of the light conducting system. Before and after thermomechanical stressing in a chewing simulator (50,000 × 50 N and 2000 cycles between 5 °C and 55 °C), the amount of perfect margin was measured by quantitative margin analysis using a SEM. Additionally, following dye penetration (24 h, 0.1% methylene blue), all teeth were cut in the mesio-distal direction and the amount of penetration was measured. Results The group with light transmitting inserts showed 79.8% perfect margin, the positive control group 68.0%, the group with inactive inserts 65.4% and the negative control group 57.8%. MANOVA showed a strong effect (p < 0.001) on the parameters group and thermocycling. The results from dye penetration were similar. Significance Light conducting inserts seem to have a positive effect on the marginal integrity of class-II composite fillings. Results show that this effect is produced by the internal light conductor and not volumetric effect alone.