Effect of high-power LED light curing unit on bond strength of composite resin to dentin

Purpose: This study evaluated the effect of a high-power solid-state light emitting diode (LED) curing unit on the dentin bond strength of a composite resin with self-etching primer adhesives by means of microtensile bond test. Materials and Methods: The flat dentin surfaces of the extracted human molars were prepared. Each surface was treated with either two self-etching adhesive systems (Clearfil SE Bond, Clearfil Tri-S Bond) and a photocure composite was placed. The adhesive and composite were photocured with a high-power LED, a conventional LED, or a halogen light curing unit. In high-power LED group, the exposure time was reduced 3 or 5 s for the adhesive and 5 or 10 s for the composite. The specimens were trimmed to obtain the stick shape specimens and the micro-tensile bond strengths were measured. The spectrum of the wavelength of each light curing unit was also measured. Results: In Clearfil SE Bond group, the microtensile bond strengths of high-power LED light curing unit groups were statistically lower than that of a halogen light curing unit group. In Clearfil Tri-S Bond group, there were no statistical differences in the microtensile bond strengths between halogen and high-power LED light curing unit groups, when the composite was photocured for 10 s. The spectrum of both high-power and conventional LED light curing units had a single sharp peak around 465 nm. The conventional halogen light curing unit showed broad spectra. Conclusion: A high-power LED curing unit affected the dentin bond strength of a composite resin with self-etching primer adhesives. (Int Chin J Dent 2010; 10: 35-40.)