Method: Flexural strength and elastic modulus were measured using beam specimens (2x2x25mm) of neat photoinitiated BT (control) along with samples containing 1, 5, 10, or 20wt% of either TOSU Addend1 or Addend2. Beams were irradiated with a dental lamp for 4min (2min top, 2min bottom), stored 24hrs prior to testing on a mechanical tester (4-pt bend, loading rate 3.7mm/min). Polymerization stress of samples containing 50wt% unmodified glass filler or 50wt% filler plus 5wt% of either TOSU Addend1 or Addend2 was measured between two abraded glass rods (5mm diameter) coated with cyanoacrylate-glue held 1mm apart by a mechanical tester. The composites were irradiated using three dental curing lamps (80s). Maximum load (recorded for 30mins post irradiation) was divided by cross-sectional area to calculate polymerization stress.
Result: The addition of up to 5wt% of TOSU addends to BT (Addend1: strength [95.53±2.48MPa], modulus [2.47±0.17GPa]; Addend2: strength [103.64±10.88MPa], modulus [2.51±0.09GPa]) did not significantly decrease mechanical strength (p<0.05, n=8) from the neat BT control (strength [103.81±10.59], modulus [2.72±0.09GPa]). The addition of 5wt% addends to BT composite filled with 50wt% unmodified glass significantly decreased polymerization stress (p<0.05, n=6) from control [5.15±0.70MPa] to Addend1 [3.45±0.34MPa] and Addend2 [3.98±0.63MPa].
Conclusion: The addition of TOSU addends significantly lowers polymerization stress in methacrylate composites while maintaining good mechanical properties. Supported in part by: NIH-NIDCR Grant T32 DE07294 and NIH-NIDCR Grant R21 DE018336.
Keywords: Composites, Dental materials, Polymerization, Polymerization Stress and Stress
See more of: Dental Materials 7: Polymer-based Materials-Physical Properties and Performance