253 Optimizing Light-cured Composite Properties with Camphroquinone and Butylhydroxytoluene Combinations

Thursday, March 22, 2012: 2 p.m. - 3:15 p.m.
Presentation Type: Poster Session
H. NASSAR, Indiana University School of Dentistry, Indianapolis, IN, and T. CHU, Restorative Dentistry, Indiana University, Indianapolis, IN
Objectives: To investigate the effects of camphroquinone (CQ) and butylhydroxytoluene (BHT) combinations on the curing and mechanical properties of light-cured composite resin. Methods: Resin composite material was prepared by mixing Bis-GMA, UDMA, and TEGDMA at a 1:1:1 ratio. BHT was added as an inhibitor at four concentrations (0.0%, 0.5%, 1.0%, and 1.5%). Four concentrations of CQ (0.1%, 0.5%, 1.0%, and 1.5%) were used to serve as an initiator. Sixteen groups of resin composite resulted (A through P); with different concentrations of BHT and CQ. For each group, six properties were tested. Flexural strength (FS) and flexural modulus (FM) were tested using a bending test with rectangular beam specimens; degree of conversion (DC) was determined using fourier transform infrared spectroscopy; and a tensometer was used to measure the polymerization shrinkage stress (PS), contraction stress rate (SR), and gel time (GP) for each resin group. The effects of CQ and BHT combinations on each of these properties were evaluated using two-way analysis of variance (ANOVA). Results: Groups with low CQ and BHT showed moderate values for FS, FM, SR and MS with DC around 70%. Increasing the BHT concentration caused minor changes in FS and FM, moderate decrease in SR and MS, and a sharp decrease in DC and high GP values. Increasing the CQ content gave a steady incline in values for FS and FM accompanied with a slight reduction in GP that was followed by a moderate increase up to 7 sec. In groups with high CQ and BHT, a clear improvement of mechanical properties was noted. Also, at high CQ and BHT, SR and MS values were comparable to baseline. Conclusions: The curing and mechanical properties of resin composite can be tailored through CQ and BHT combinations with high CQ and high BHT showing the most promising results.

Keywords: Composites and camphroquinone, butylhydroxytoluene