Can TPO as Photoinitiator Replace "Golden Mean" Camphorquinone and Tertiary Amines in Dental Composites? Testing Experimental Composites Containing Different Concentration of Diphenyl(2,4,6-trimethylbenzoyl)phosphine Oxide

The aim of this research was to compare the biomechanical properties of experimental composites containing a classic photoinitiating system (camphorquinone and 2-(dimethylami-no)ethyl methacrylate) or diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO) as a photoinitiator. The produced light-cured composites consisted of an organic matrix-Bis-GMA (60 wt.%), TEGDMA (40 wt.%) and silanized silica filler (45 wt.%). Composites contained 0.27; 0.5; 0.75 or 1 wt.% TPO. Vickers hardness, microhardness (in the nanoindentation test), diametral tensile strength, resistance to three-point bending and the CIE L* a* b* colorimetric analysis was performed with each composite produced. The highest average Vickers hardness values were obtained for the composite containing 1 wt.% TPO (43.18 ± 1.7HV). The diametral tensile strength remains on regardless of the type and amount of photoinitiator statistically the same level, except for the composite containing 0.5 wt.% TPO for which DTS = 22.70 ± 4.7 MPa and is the lowest recorded value. The highest average diametral tensile strength was obtained for the composite containing 0.75 wt.% TPO (29.73 ± 4.8 MPa). The highest modulus of elasticity characterized the composite containing 0.75 wt.% TPO (5383.33 ± 1067.1 MPa). Composite containing 0.75 wt.% TPO has optimal results in terms of Vickers hardness, diametral tensile strength, flexural strength and modulus of elasticity. Moreover, these results are better than the parameters characterizing the composite containing the CQ/DMAEMA system. In terms of an aesthetic composite containing 0.75 wt.%. TPO is less yellow in color than the composite containing CQ/DMAEMA. This conclusion was objectively confirmed by test CIE L* a* b*.