Thermal Penetration Depth of Pulsed Lasers in Gingival Tissues: An In Vitro Study

With laser irradiation emerging as an adjunctive treatment utilized in nonsurgical periodontal therapy, it is important to understand the variance of penetration depth among the different laser wavelengths. To evaluate the thermal penetration depth, as a photothermal effect, of carbon dioxide (CO₂)-, erbium: doped yttrium-aluminum-garnett (Er:YAG)-, and erbium, chromium: yttrium-scandium-gallium-garnett (Er,Cr:YSGG)-lasers on the bovine gingiva in an in vitro model. Four mandibles from freshly slaughtered cows were utilized in this study. Buccal and lingual root debridement was provided using three different laser wavelengths, all in pulsed settings. A CO₂- (10,600 nm), Er:YAG- (2940 nm), and Er,Cr:YSGG- (2780 nm) were utilized to irradiate pockets of two mandibular posterior teeth in each group. Laser power output settings were set to 2 W. The posterior teeth were irradiated for 30 sec buccal and 30 sec lingual of each tooth for all selected treatment test groups. Instrumentation with curettes was performed as a control group. Gingival flaps, including the entire gingiva, were fixed in 10% formalin and stained via Elastin van Gieson. Sections were examined microscopically to evaluate thermal damage and statistically compared using mixed effect model with Tukey adjustment. The CO₂-laser irradiation presented a statistically significant lower mean compared to Er,Cr:YSGG-laser (p < 0.0001). Er,Cr:YSGG-laser had a higher penetration depth compared to Er:YAG-laser (p < 0.0001). There was no statistically significant difference found in penetration depth between CO₂- and Er:YAG-laser irradiation. It can be concluded that all tested pulsed lasers had minimal penetration depth into the gingiva. However, the pulsed CO₂- and Er:YAG-lasers presented lower thermal effects compared to Er,Cr:YSGG-laser in vitro.