Depth of Cure and Polymerization Shrinkage of the SonicFill Composite and a Nanohybrid Composite: A Comparative Study

Abstract

Composite restorations may take time longer in application than equivalent amalgam restorations. Longer time in the dental chair may test the patience of children, making the procedure more difficult for the dentist. In an attempt to speed up the restoration process, a new class of resin-based composite material, the bulk-fill RBC, was recently introduced on the market, enabling up to 4- or 5-mm thick increments to be cured in one step. Accordingly, this study was designed to assess depth of cure and polymerization shrinkage of the bulk inserted resin composite (SonicFill) and compare it with resin composite utilizing the incremental packing technique (Herculite XRV Ultra). A total of 20 resin composite discs to test the depth of cure using the Vickers microhardness test and 20 resin composite discs to test the polymerization shrinkage using strain gage test were divided into 8 subgroups (n = 5 for DOC and n = 5 for polymerization shrinkage) according to the two levels of the study; Level 1: resin composite material (either bulk fill or nanohybrid), Level 2: Increment thickness (2mm, as well as thickness obtained by scrapping method (5mm for SonicFill , 3mm for Herculite XRV Ultra).

In regards to the depth of the cure of the material at top surface and relative microhardness, Two-Way ANOVA revealed that resin composite type and increment thickness had a significant effect on microhardness .

For the bottom surface microhardness results showed statically significant difference in mean microhardness values for both materials.

Regarding the polymerization shrinkage, two –way ANOVA revealed that resin composite type and the thickness and the interaction between them had a significant effect on polymerization shrinkage.