Effects of Excavation on Composite Bonding to Laser Prepared Cavities

LASERs are used to prepare teeth, however the affects that this has on the bond strength of composite resin restoration is unclear.

Objective: To evaluate if mechanical excavation influences the bond strength of composite to enamel and dentin prepared by LASER.

Material and Methods: The occlusal surface of 48 human molars were ground to obtain flat enamel (E) or dentin (D) surface, irradiated for 10s by an Er.Cr:YSGG laser (Waterlase-Biolase) [4.5 W, 60% air, 80% water for enamel and 3 W 60% air, 70% water for dentin specimens], the samples were divided randomly into 4 groups (n=12/gp) Eex and Dex: the surfaces were excavated by a spoon excavator, Ec and Dc: without excavation. All samples were etched (37% H3PO4, 20s for enamel and 15s for dentin), washed (30s) and adhesive applied (Adper-Single Bond plus, 3M-ESPE) and light cured (20s). A transparent plastic tube (1.5 mm inner diameter) was filled with 3 mm of composite (Filtek-Supreme plus 3M-ESPE) and placed on the treated surface, light cured (40s), stored (37°C, 24h) then shear bond strength (SBS) tested (1 mm/min) and data were analyzed [ANOVA, Tukey's, p<0.05)]. The mode of failure was evaluated under SEM.

Results: The mean SBS±sd for each group was 21.72±7.94 MPa (Eex), 16.97±7.77 MPa (Ec), 12.3±5.56 MPa (Dex) and 13.629±7.283 MPa (Dc). ANOVA showed no significant intergroup differences all tested groups [(p=0.152 (enamel) p=0.658 (dentin)]. SEM evaluation showed enamel and dentin samples tend to fail more cohesively.

Conclusion: Within the limits of this study it is concluded that mechanical alteration and excavation of enamel and dentin surfaces prepared by Er.Cr.YSGG laser doesn't significantly influence the bond strength of composite resin. SEM's revealed that bond to lased enamel and dentin tends to fail more cohesively and excavation may reduce the thickness of the affected enamel and dentin.