A new thermographic and fluorescent method for tuning photoablative laser removal of the gingival epithelium in patients with chronic periodontitis and hyperpigmentation

Objective. To optimize gingival laser photoablation by thermographic and autofluorescent feed-backs. Background. Photoablative laser treatment is commonly used for gingival de-epithelization in patients with chronic periodontitis or hyper-pigmentation. The reduction of collateral thermal damage of periodontal tissues is crucial for optimal treatment outcome. Methods. Nineteen patients with chronic periodontitis, 7 of which showing gingival hyper-pigmentation, were subjected to de-epithelization with an 810 nm diode laser used in continuous (1 W, 66.67 J/cm2) or pulsed wave mode (69 uJ, 18 us, 8000 Hz, corresponding to peak/mean power of 3.8 W/0.6 W, 40 J/cm2), depending on individual gingival features. Photoablation was controlled in real time with a 405-nm violet light probe, which stimulated a yellow auto-fluorescence of the laser-coagulated tissue. The temperature at the target tissue was controlled with an infrared thermographic probe. When appropriate, small biopsies were taken to evaluate epithelial ablation and thermal effects. Results. The energy density transferred to the treated tissue surface was computed based on the irradiation modality of the target tissues. Laser photoablation performed under thermographic control yielded complete removal of the gingival epithelium with minimal injury to the underlying lamina propria. Irradiation-evoked autofluorescence, conceivably due to epithelial keratins, allowed very sharp recognition of the borders between laser-ablated and intact epithelium thus preventing repeated irradiation. Conclusion. This study further supports the favourable characteristics of photoablative diode laser for gingival de-epithelization. Concurrent thermographic and fluorescent analysis can provide a substantial help to the set up of a safe and well tolerated protocol.