Evaluation of resin-enamel interface micromorphology in respect of different Er,Cr:YSGG laser parameters

Background and objective: Enamel irradiation with an erbium,chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser has been reported to cause micromorphological alterations within resin-enamel interfaces and subsurface enamel. The present study was conducted to evaluate the effects of different output power/pulse repetition rate parameter combinations of Er,Cr:YSGG laser on the micromorphology of resin-enamel interfaces and subsurface enamel. Materials and methods: Thirty-five bovine incisors were used in the present study. Er,Cr:YSGG laser was used on enamel with different output power/pulse repetition rate parameter combinations as follows: 6 W/20 Hz, 6 W/35 Hz, 6 W/50 Hz, 3 W/20 Hz, 3 W/35 Hz, 3 W/50 Hz. Following adhesive and composite procedures, specimens were sectioned and either acid-etched with 37% phosphoric acid for 1 min or immersed in 55% nitric acid for 12 h. Then the resin-enamel interfaces were investigated by scanning electron microscopy (SEM). Results: Micromorphological findings by SEM revealed that when enamel surfaces were irradiated with all 6-W groups and 3 W/20 Hz-combinations, large resin structures indicating subsurface microcracks were generally evident within interfaces and subsurface enamel. However, when irradiated with 3 W/35 Hz and 3 W/50 Hz-combinations, the observed resin-enamel interfaces were similar to those of the acid-etched only group. Conclusion: Deploying Er,Cr:YSGG laser with lower power and high pulse repetition rate combinations may reduce damage to resin-enamel interfaces and subsurface enamel. However, assessment of the relationship between these findings and bond strength requires further study.