Concentration of 10-MDP in Composites Influences Bond and Biaxial Strength

Objectives: To assess the influence of different concentrations of adhesive monomer 10-MDP used in an experimental self-adhesive composite on the push-out bond strength and biaxial flexural strength.
Methods: Experimental composites were prepared by combining urethane dimethacrylate (UDMA), poly(propylene glycol) dimethacrylate (PPGDMA) and 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP) monomers (0%, 5%, 10%, 15%) with filler particles at a powder-liquid ratio of 3:1. Flexural strength of dry disc specimens (10 mm diameter and 1 mm thickness; n=10) were determined using a ball on ring jig. Push-out bond strength was carried out using ivory as a dentine model and cylindrical shaped composite restorations (n=10).
Results: All values of biaxial flexural strength were above 100 MPa, ranging from 139.2 ± 7.6 (5% 10-MDP) to 111.2 ± 10.6 (20% 10-MDP). Strength results show a decreasing trend with higher concentrations of the 10-MDP monomer. Conversely, push-out bond strengths increased from 6 MPa ± 4.7 to 11.3 MPa ± 2.6 with increasing 10-MDP from 5 to 15%.
Conclusions: The 10-MDP monomer can provide self-adhesive composites with good bonding to dentine, but levels may need to be limited to ensure mechanical properties are not compromised.