Influence of Er:YAG Laser Surface Treatment and Primer Application Methods on Microtensile Bond Strength Self-Etching Systems

OBJECTIVE: The aim of this in vitro study was to evaluate how surface preparation and primer application technique can influence the microtensile bond strength of self-etching system. BACKGROUND DATA: One of the possible applications of dental lasers includes increasing the quality of bond strength. MATERIALS AND METHODS: 12 extracted, sound human molars were ground flat to expose occlusal dentin and were then divided into six groups (G1-G6)(n = 30-36) according to surface preparation and primer application (active or passive): G1-diamond bur (DB) + active primer (AP); G2-DB + passive primer (PP); G3-Er:YAG laser (EL) + AP; G4-EL + PP; G5-#600-grit paper disc (PD) + AP; G6-PD + PP. After adhesive procedure, 5-mm high composite buildups were created with Z 250. After storage in water at 37 degrees C for 24 h, teeth were vertically sectioned into serial 1- mm2 sticks. Samples were tested for tension in an Instron machine at 0.5 mm/min. Nine additional molars were prepared to morphological analysis. Regular grit diamond bur, Er:YAG laser, or #600-grit SiC paper was used for SEM observations of dentin surfaces of each group before and after treatment with self-etching primers. Microtensile data were submitted to statistical analysis. RESULTS: G1-43.85 +/- 9.60 MPa; G2-24.28 +/- 8.90 MPa; G3-24.11 +/- 4.05 MPa; G4-23.30 +/- 4.21 MPa; G5-55.64 +/- 8.50 MPa; G6-56.45 +/- 12.05 MPa. CONCLUSIONS: (1) Er:YAG laser and diamond burs are able to create distinct smear layers; however the resistance of dentin/adhesive interface is similar. In this way, we can use both instruments clinically without diminishing bond strength; (2) the #600-grit sandpaper disc least affects resistance and is highly recommended for in vitro studies to achieve standard preparation of dentinal surface; (3) active primer application is the method most recommended, despite the type of dentin preparation instrument used.