Root surface morphological changes after focused versus defocused CO₂ laser irradiation: A scanning electron microscopy analysis

Background: Many studies have observed damages to root surfaces treated by CO₂ laser in continuous mode with a focused beam. The morphologic changes observed were always associated with temperature increase induced by high energy release. Methods: The purpose of this study was to analyze by scanning electron microscopy (SEM) the effects of CO₂ laser in 2 different modes on root surfaces. Study samples consisted of 30 extracted single-rooted periodontally compromised human teeth. Root specimens were randomly assigned to 3 groups: group A (12) treated with CO₂ laser in continuous mode with a focused beam of 0.8 mm; group B (12) treated with CO₂ laser in pulsed mode with defocused beam of 4 mm; and group C (6), untreated controls. Results: Group A (continuous mode) showed severe damages to dentin surfaces such as craters and fissures. Group B (defocused mode) did not result in any damages to the root surfaces, showing flat and smooth surfaces with apparent fusion of the smear layer and dentinal tubules almost completely sealed. The untreated control group was characterized by irregular and amorphous surfaces with several shallow depressions. Conclusions: Although both laser modes resulted in changes to the treated root surface specimens, the changes resulting in a smooth surface from use of defocused pulsed beam may present an advantage in periodontal treatment.