EFFECT OF RESIDUAL HEAT IN DENTIN ADHESION AFTER Er,Cr:YSGG LASER

Objectives: The purpose of this in vitro study is to evaluate the residual heat on dentin surface irradiated with Er,Cr:YSGG laser within different parameters using a high resolution thermographic camera and the influence in dentin adhesion using a microtensile bond strength test.

Methods: Forty-nine dentin slices (2 mm) were obtained from third molars. The temperature analysis was done through a thermographic camera. Nine slices of dentin were randomly distributed in 3 groups according to the parameters used (G1- 44,3 J/cm², G2 - 47,8 J/cm², G3 - 54,9 J/cm²). The occlusal side of the dentin slice was divided in four quadrants, allowing 4 measurements of 5 seconds (each) in the same sample, resulting into twelve measurements per group. For the microtensile bond strength test, 40 slices of dentin were randomly distributed into 4 groups (n=10), being G1, G2 and G3 the same as described previously and G4 did not receive laser irradiation and served as a control group. After laser irradiation or not, the samples were restored using 35% phosphoric acid, Single Bond dental adhesive and Z-350 composite resin. After storage of 24 hours at 37^oC and 100% humidity, the samples were sectioned into beams (1mm²) and exposed to tensile strength.

Results: It was observed a significant increase in temperature (Δt = 13.83^oC) (p<0.0001) in group G3. The groups G1 and G2 had a similar temperature rise (G1 - 3.96^oC and G2 - 3.62^oC). The highest bond strength was observed in the control group G4 (29.20 MPa) when compared to all laser treated groups.

Conclusion: The heat transmission in dentin (2mm thick) demonstrated safe only in the groups G1 and G2. Within the parameters of this study, the residual heat in dentin created by the Er,Cr:YSGG laser had an unfavorable effect on adhesive procedures.

In part sponsored by NIDCR DE007057.