Influence of Er: YAG laser cooling flow used for cavity preparation on shear bond strength of resin composite to dental substrates

Abstract

The present study has the aim to evaluate in vitro the influence of water flow rate on shear bond strength of a composite resin to enamel and dentin after Er:YAG cavity preparation .Ten bovine incisors will be selected and roots will be removed. Crows will be sectioned in 4 pieces, resulting in 40 samples that will be individualy embedded in polyester resin using PVC cylinders. After polymerization, specimens will be ground under water cooling in a polishing machine using # 320 to 600-grit silicon carbide paper to enamel planification. An additional polishment will be accomplished with # 1200-grit SiC paper for 30 seconds to produce a standardized smear layer. After enamel shear bond strength test, the specimens will be ground the same way described before to expose superficial dentin surface. The bonding sites (enamel and dentin) will be delimited (3 mm diameter) and samples will be randomly assigned into 4 groups (n=10) acording to the water flow rate employed on Er:YAG laser cavity preparation: I- Er:YAG + water flow rate of 1mL/mim; II- Er:YAG + water flow rate of 1,5 mL/mim; III- Er:YAG laser + water flow rate of 2,0 mL/mim; IV- bur (high speedy turbine) - control group. After cavity preparation, samples will be conditioned with 37% phosphoric acid for 15 seconds. The Single Bond (3M) adhesive system will be applied and a Teflon matrix will be placed and filled with composite resin Z-250 (3M) and light-cured. Specimend will be kept in artificial saliva under 37o C , for 24 hours. The shear bond strength test will be performed with a universal testing machine (0,5 mm/mim). Data will be subjected to statistical analysis using the most adequated method.