Effect of the CO2 laser on enamel surface roughness after debonding ceramic brackets and the application of nanohydroxyapatite: in-vitro study

Objective Evaluate the effect of the CO 2 laser on enamel surface roughness after debonding ceramic brackets and applying nanohydroxyapatite. Methodology Sixty extracted premolars were randomly assigned to four groups ( n = 15): G1, G2, G3, G4. Ceramic brackets were bonded to the buccal surface for G1 and G2 groups. Before debonding, the CO 2 laser group (G2) was irradiated with a power of 6 W for 5 s; shear bond strength was calculated using a universal testing machine and the adhesive remnant index with a stereomicroscope. Enamel roughness for the four groups was assessed using a profilometer; then, each group was subdivided for the application of nanohydroxyapatite paste and stored in saliva or deionized water. The surfaces were re-evaluated after 15, 30, and 60 days; the Friedman and Nemenyi post-hoc tests were used for statistical analysis, while Kruskal–Wallis and Dunn's multiple comparison post-hoc tests with Holm's correction adjustment to compare between groups. Results The group irradiated with CO 2 laser significantly reduced bond strength and roughness parameters upon debonding compared to the bracket group ( p < 0.001). No significant differences were observed in roughness reduction between the group treated with the CO 2 laser and the application of nanohydroxyapatite paste; however, the surface roughness decreased in the bracket group G1b. Conclusions CO 2 laser irradiation reduced the force required for debonding ceramic brackets and minimized enamel surface roughness compared with conventional debonding. This contributes to the development of enamel-preserving orthodontic treatments; however, this property does not improve when applying nanohydroxyapatite paste.