518 Curing efficiency of 2,4,6-trimethylbenzoyldiphenylphosphine oxide initiator in composite resins

Friday, September 14, 2012: 4 p.m. - 6 p.m.
Location: Veranda 2 (Finlandia Hall)
Presentation Type: Oral Session
V. MILETIC, Department of Restorative Odontology and Endodontics, University of Belgrade School of Dental Medicine, Belgrade, Serbia, and A. SANTINI, Edinburgh Postgraduate Dental Institute, The University of Edinburgh, Edinburgh, United Kingdom
Objectives: The objective of this study was to determine the degree of conversion (DC) of unfilled and filled resins with different concentrations of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin® TPO; BASF Corporation, Charlotte, NC, USA) cured with a polywave LED light-curing unit (LCU).

Methods: Unfilled resins were prepared by mixing 1 mmol of BisGMA and 1 mmol of TEGDMA (Esstech Inc., Essington, PA, USA). Increasing concentrations of Lucirin® TPO in the range of 1.25*10-3 – 12*10-2 mmol (0.05wt%-4.97wt%) were added to each mixture. Filled resins were prepared by adding 75wt% Tetric EvoCeram fillers (Ivoclar Vivadent, Schaan, Liechtenstein) to the unfilled resins. Standardized samples in Teflon moulds, 5 mm in diameter and 2 mm thick, were cured using a polywave LED LCU (bluephase® G2; Ivoclar Vivadent, Schaan, Liechtenstein) at a 1 mm tip-to-surface distance. The DC was determined using micro-Raman spectroscopy based on changes in peak intensity of 1640 cm-1 and 1610 cm-1 peaks, assigned to the aliphatic and aromatic groups in the cured and uncured materials, respectively. The data were analysed using ANOVA and regression analysis (α=0.05).

Results: Increased initiator concentrations increased logarithmically the DC of unfilled and filled resins. The DC of unfilled resins was 73-91% at the top and 63-81% at the bottom surfaces and that of filled resins was 53-81% at the top and 47-70% at the bottom surfaces. Unfilled resins containing more than 1.08wt% Lucirin® TPO showed similar DC values (p>0.05). The same was found in filled resins with more than 1.50wt% Lucirin® TPO (p>0.05). The bottom-to-top ratios were in excess of 85% in all groups.

Conclusions: Lucirin® TPO showed a high reactivity upon irradiation with a polywave LED LCU resulting in clinically acceptable range of DC values. Fillers significantly reduced conversion but had no effect on the logarithmic relationship between initiator concentration and the DC.

This abstract is based on research that was funded entirely or partially by an outside source: This study was undertaken in The University of Edinburgh. Dr Miletic's accommodation, substistence and travel were funded by the IADR Toshio Nakao Fellowship and Research grant ON172007 Ministry of Education and Science, Serbia

Keywords: Composites, Dental materials and Lucirin TPO