Healing of rat mouth mucosa after irradiation with CO2, Nd:YAG, and CO2-Nd:YAG combination lasers

The healing process of wounds made by a combination laser was studied in 90 rats. The laser system enabled both separate and combined use of CO₂, and Nd:YAG laser irradiations. The laser wounds and the control excision wounds made by alligator forceps appeared on both sides of the tongue. Specimens from the wound sites were taken immediately, 6 h, and 1, 2, 4, 7, 11, 21, 28, and 42 days after surgery. The wound-healing process was studied by macroscopic evaluation before preparing the specimens for light microscopy. Some dilferences were noted in the wound-healing process among the three groups into which the experimental animals were divided. Tissue coagulation damage was most extensive in the Nd:YAG laser sites, where it was observed in its full extent 4 days after surgery. Epithelial cells were seen to begin to proliferate in all the wounds 6 h after surgery. Re-epithelialization was completed by between 7 (CO₂) and 21 days (Nd:YAG) at all the wound sites. The inflammatory cell infiltration was more prominent in the Nd:YAG and the CO_rNd:YAG combination laser wounds than in the COi and excision wounds during healing. Tissue regeneration occurred faster with less contraction in the combination CO₂-Nd:YAG wounds than in Nd:YAG wounds. The best macroscopic healing result was seen in the CO₂, wound sites. The combination laser was effective both at cutting and at coagulating tissue. Combining the CO₂ and Nd:YAG laser irradiation into one beam resulted in a greater incision depth than what could have been expected from using the two lasers separately.