Mechanical, Chemical and Bond Strength Properties of Bisphenol-A Free Composites

Objectives: The aim of this study was to evaluate mechanical, chemical and bond strength properties of bisphenol-A free (BPA-free) resin-based composite (RBC) containing an elastomeric monomer.
Methods: BPA-free RBCs were blended either containing 60/25/14wt% of UDMA, PEG400 and TEGDMA (UDMA) or 35/25/25/14wt% of UDMA, PEG400, Exothane 24 and TEGDMA (UDMA-EXO) monomers. Camphorquinone (0.5wt%) and DMPOH (0.5wt%) were added as the photoinitiator system and, 52wt% of 7.5µm BaBAlSi glass and 13wt% 40nm fumed silica were added as filler loading. A multiwave LED (VALO, Ultradent) was used to photo-activate all samples. Mechanical properties (n=10) were assessed by ultimate tensile strength (UTS), flexural strength (FS), flexural modulus (FM) e Knoop hardness (H) tests. Chemical properties (n=10) were assessed by degree of conversion (DC), chemical softening (CSoft), water sorption (Wsp) and water solubility (Wsl). For Microtensile bond strength test, twenty box shaped Class I (4 mm in depth) preparations were fabricated in the pulp chamber of sound human third molars. The restorations were made (two layers of 2-mm in thickness) using either a UDMA or UDMA-EXO experimental composites (n=10). After 24 h in water storage, the restorations were sectioned in beams (0.81 mm² area) and tested for dentin microtensile bond strength (µTBS). Data were submitted to ANOVA and Tukey’s test (α=0.05, β=0.2) for all tests.
Results: The Table 1 shows all means for all performed tests. The results showed that BPA-free RBCs containing UDMA-EXO showed lower FS and FM than UDMA, but no differences were found for CS and Wsol. However, UDMA-EXO showed lower CSoft and Wsp and higher H, DC and microtensile bond strength than UDMA.
Conclusions: Thus, it was possible to conclude that despite the reduction in mechanical properties, the use of an elastomeric monomer could improve chemical properties and increase bond strength of BPA-free RBCs.