Comparison of Film Thickness of Restorative Composites Considered for Thermo-Modified Cementation

This study proposes an updated method for the film thickness of 21 resin composites used as cements.

A load of 30 N was subjected to two glass plates stacked on a heated base to simulate clinically relevant pressure and temperature during the seating of inlays/onlays/veneers. The axial position of the actuator was recorded before and after placing 22.15 mm³ of resin composite between the glass slides. The difference between the two measurements was calculated for each specimen. A total of 18 condensable restoratives, 1 injectable restorative, and 2 resin cements were tested, 5 specimens each (n = 5, N = 105). One-way ANOVA was performed for both variables and Games-Howell post hoc test was used for pairwise comparisons.

The film thickness range was 6-200 μm, with the lowest values for restorative composites (AP-X, Z250, and Herculite XRV Incisal LT with 6-8 μm), followed by Gradia Direct (25 μm) and flowable/injectable composite resins, including designated cements (15-27 μm). Inspiro, Ultradent Transcend Universal, and ENA Hri dentin stood below 50 μm (range 28-49 μm). The other materials (range 81-200 μm) cannot be recommended for thermo-modified cementation.

The initial viscosity of restorative composites is not an indication of the film thickness when used for thermo-modified cementation. There is a wide choice of appropriate materials available on the market.

Some restorative composites are able to generate very thin films and can be used as cement with numerous advantages when compared to designated flowable or dual-cure cements.