Tissue response following CO2 laser application in apical surgery: light microscopic assessment in dogs.

The potential advantages of CO2 laser in apical surgery have not been established histologically. Therefore, the long-term effects of CO2 laser on the apical and periapical tissues were examined histologically in dogs 6 months after apical surgery. Lased specimens and unlased controls showed periapical inflammatory and osteogenic reactions. Lased root surfaces revealed craters with a superficial charred layer closely associated with new cementum-like matrix. The subjacent dentin appeared tubule-free and eosinophilic. Lased bone trabeculae showed a charred layer with a deeper osteocyte-free zone. The charred layer was covered by new bone. Detached charred segments in the marrow space and periapical inflammatory infiltrate were intimately associated with multinucleated giant cells, some containing minute char particles. Such cells were absent from the root and trabecular char linings. In addition, the charred surfaces were free of hard tissue resorption. These results suggest that CO2 laser does not hinder healing when applied in apical surgery.