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

Tomomasa Nomura, DMD,(a) Ichiro Ikeda, DMD, PhD,(a) Masayuki Otsuki, DDS, PhD,(a) and Junji Tagami, DDS, PhD(a,b)

(a)Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School of Medical and Dental Sciences, and (b)Global Center of Excellence Program, International Research Center for Molecular Science in Tooth and Bone Diseases, Tokyo Medical and Dental University, Tokyo, Japan

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.)

Key Words: composite resin, LED light curing unit, microtensile bond test