The Effect of Er Laser Treatment on the Surface Roughness of Enamel and Bacterial Adhesion

<b><i>Objective:</i></b> To investigate the effects of laser-treated enamel surface roughness on the adhesion of <i>Streptococcus mutans</i>. <b><i>Methods:</i></b> A total of 176 premolars extracted for subtractive orthodontic treatment were collected. Samples were randomly divided into four groups: control group, 35% phosphoric acid, Er:YAG laser, Er,Cr:YSGG laser. Surface roughness was detected using three-dimensional white light interferometric surface topography (<i>n</i> = 8/group), and surface morphology was observed by scanning electron microscope [(SEM), <i>n</i> = 8/group]. Samples were cultured in <i>S. mutans</i> solution for 12 h, 1 day, and 2 days. The colony forming units on the enamel surface were calculated (<i>n</i> = 8 per time point). The biofilm and activity of <i>S. mutans</i> were observed by SEM (<i>n</i> = 2/group) and confocal laser scanning microscope (<i>n</i> = 2/group). Correlation analysis was carried out between bacterial adhesion on the enamel surface at different time points and the surface roughness of the enamel treated by different methods. <b><i>Results:</i></b> After Er:YAG and Er,Cr:YSGG laser etching, the surface roughness of enamel increased (<i>p</i> < 0.05), but there was no difference in <i>S. mutans</i> adhesion and biofilm morphology after 1 day compared with traditional phosphoric acid etching (<i>p</i> > 0.05). <i>S. mutans</i> adhesion was positively correlated with the enamel roughness in the early stage. <b><i>Conclusions:</i></b> Er:YAG and Er,Cr:YSGG laser etching may be an alternative to traditional phosphoric acid etching.