SHEAR-STRENGTH OF COMPOSITE BONDED TO ER-YAG LASER-PREPARED DENTIN

An Er:YAG laser coupled with a cooling stream of water effectively rem oves dental hard tissues. However, before such a system can be deemed clinically viable, some safety and efficacy issues must be addressed. We compared the bonding of composite to dentin following the preparati on of the dentinal surface with either an Er:YAG laser (lambda = 2.94 mu m) or a standard dental bur and with and without a subsequent acid- etching treatment. The crowns of extracted human molars were removed, revealing the underlying dentin. We removed an additional thickness of material with either a dental handpiece or an Er:YAG laser (350 mJ/pu lse at 6 Hz) by raster-scanning the samples under a fixed handpiece or laser. Comparable surface roughnesses were obtained. Several samples from each group received an acid-conditioning treatment. A cylinder of composite was bonded onto the prepared surfaces. The dentin-composite bond was then shear-stressed to failure on a universal testing appara tus. The results indicate that laser-irradiated samples had improved b ond strengths compared with acid-etched and handpiece controls. SEM ph otographs of the surfaces show exposed tubules following the laser tre atment; tubules could also be exposed with acid etching. We conclude t hat Er:YAG laser preparation of dentin leaves a suitable surface for s trong bonding of an applied composite material.