Impact of Diode Laser Operation Mode on Temperature Increase During Soft Tissue Incision

Objectives: Diode laser systems can be used in continuous wave (cw) or pulsed operation mode. The aim of the present study was to evaluate the temperature increase in soft tissues during incision with a 445 nm diode laser system operated in cw and pulsed operation mode.
Methods: Forty soft tissue specimens obtained from pork muscle tissue were mounted on a motorized linear translation stage and incised using a 445nm diode laser (Sirona, Bensheim, Germany) in different operation modes each: (I) 1.5W, continuous wave, (II) 3W, 50% duty cycle, 100 Hz, (III) 3W, 50% duty cycle, 10Hz. Therefore, the handpiece of the laser device was connected to the slide, allowing a constant linear movement (2mm/s) of the laser tip in contact to the soft tissue’s surface. Temperature measurements were performed with an infrared camera system (VarioCam HD, InfraTec, Dresden, Germany), evaluating the average temperature increase of incised tissue in a distance of 5mm from the laser tip. Values were analysed using a non-parametric test for related samples (Wilcoxon). Differences were considered as statistically significant at p<0.05.

Results: A temperature increase could be observed in all groups under study (p<0.05). Statistically significant highest temperature increase could be observed for laser setting I (1.5W, cw) and II (3W, 50% duty cycle, 100Hz) (p>0.05). Temperature increase for laser setting III (3W, 50% duty cycle, 10Hz) was lower than for settings I and II (p<0.05).
Conclusions: The present study indicates that temperature increase in soft tissues during tissue incision is not only dependent on the average power of the laser device but also on the pulse frequency.