Composite Bond strength to Primary Dentin Prepared with Er,Cr:YSGG Laser

Objective: Hard tissue cutting lasers have been shown to conservatively and effectively remove caries, often without the use of anesthesia. These characteristics are of particular interest in the treatment of pediatric dental patients. After caries removal, most primary teeth are restored using composite resins. The purpose of this investigation was to compare the bond strength of composite resin to laser cut primary dentin using different laser power settings with and without etching. Methods: Vertical cuts were made on the crowns of 30 freshly extracted primary teeth with a #56 fissure bur to expose 3 x 3 mm areas of dentin. The surfaces were subjected to laser surface treatments with an Er,Cr:YSGG hydrokinetic laser (Waterlase MD, Biolase Technology Inc). Equal numbers of surfaces (20) were treated at 0.5W, 0.75W, and 1.0 W. One-half of the lased surfaces were then etched with 37% phosphoric acid for 15 seconds. Cylinders of a hybrid composite (Herculite XRV) were then bonded to all treated surfaces with PQ1 (Ultradent) as the bonding agent. After light curing the composite resin, shear bond strength tests were performed on an Instron test machine. Differences among groups were determined using ANOVA and t-tests. Results: Bond strengths of composite with PQ1 bonding agent to etched and non-etched laser cut surfaces at 0.5 W (17.2±3.3, 15.8±2.5 MPa respectively) were statistically the same. As the power setting increased to 0.75 W and 1.0 W, with etching bond strengths were statistically similar to the 0.5 W values. However, non-etched laser cut surface bond strength values decreased. Conclusions: The results reveal that primary dentin treated with Er,Cr:YSGG hydrokinetic laser at 0.5 W does not require etching for bonding. As the energy level increases, it is beneficial to add etchant as part of the conditioning regiment to provide adequate bonding.