Er:YAG laser focal distance variation in enamel/resin interface

Objectives: The aim of this study was to assess “in vitro” the influence of Er:YAG laser focal distance variation on the shear bond strength of a composite resin to the enamel of primary teeth. Methods: Fifty buccal surfaces of extracted human canines kept in a 0.4% azide sodium solution were grounded and assigned into five groups (n=10). The control group was conditioned with 37% phosphoric acid (CA). In the lased groups, the enamel surface treatment was performed by irradiating with Er:YAG laser (80mJ/2Hz) and varying the focal distance (12, 14, 16 and 17 mm), followed by acid etching. The Single Bond/ Filtek Z250 (3M) resinous system was employed for the manufacture of specimens. The shear bond strength tests were performed in a universal testing machine (EMIC) at a crosshead speed of 0.5 mm/min. Failure mode was assessed using a X40 magnification stereomicroscope Data were submitted to statistical analysis by ANOVA. Results: The means in MPa were: CA: 18.76 (±6.68); 12mm: 12.73 (±5.46); 14mm: 15.9 (±6.81); 16mm: 20.1 (±6.94) and 17mm: 15.15 (±6.81). There was no statistically significant difference (p<0.05) between the tested groups. Conclusions: It was concluded that Er:YAG laser focal distance variation didn't influence the adhesive resistance of the resinous system to enamel, even when compared with the control group (acid conditioning solely).