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

Abstract

Objective Evaluate the effect of the CO2 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 CO2 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 CO2 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 CO2 laser and the application of nanohydroxyapatite paste; however, the surface roughness decreased in the bracket group G1b. Conclusions CO2 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.