Curing effectiveness of a light emitting diode on dentin bonding agents

This study tested the hypothesis that dentin bonding agents (DBAs) cured with a light emitting diode (LED) light curing unit (LCU) would not show a statistically significant different dentin shear bond strength (DSBS) relative to a halogen LCU, when the LED and halogen LCUs had a supposedly similar irradiance. Five commercial DBAs were tested: ScotchBond Multipurpose, Single Bond, One Step, Clearfil SE Bond, and Adper Prompt. The LCUs used in this study were a VIP (Bisco) for the halogen light and an Elipar FreeLight (3M ESPE) for the LED. First, the emission spectrum and spectral irradiance of both LCUs were investigated. Next, the DSBS of the DBAs cured with each LCU was measured. Two-way analysis of variance was used to analyze whether there were differences in DSBS resulting from the type of LCU and DBA used. The halogen LCU showed a higher total irradiance value relative to the LED LCU, but the difference of spectral irradiance was reduced in the efficient wavelength ranges for camphoroquinone activation. Although the DBAs cured with both types of LCUs showed similar DSBS values, Clearfil SE Bond showed the highest DSBS value when cured with a halogen light. Therefore, the null hypothesis of this study was rejected, indicating that the curing effectiveness of the LED LCU on some DBAs can be lower than that of a halogen LCU in terms of bond strength.