Determination of a safe protocol for using laser ablation with indocyanine green dye in endodontic treatment. In vitro, in vivo and human study.

This study aimed to determine a safe protocol for using Laser Ablation therapy (LA) with Indocyanine Green (ICG) to treat infected root canals.

Methods: In vitro study - The root canal of an extracted human lower incisor was prepared to #35/.06 and was filled with 0.05% ICG dye. The λ 810 nm infrared diode laser was activated during the movement of introducing a #20 fiber into the root canals. The maximum temperature reached in the three root thirds was considered for protocols, modifying the power, pulse interval, and pulse duration. In vivo study - Extracted human lower incisor, lower premolar, and upper molar were selected. Their canals were prepared to #35/0.04, and the teeth were inserted into the subcutaneous tissue of Wistar rats. LA with ICG protocol selected in the in vitro study was performed on each root. The root surface temperature was measured in the three thirds. Then, the subcutaneous tissue adjacent to the roots was removed immediately or after 7 days and subjected to histological analysis in H&E stain. Human study - Thirteen lower incisors indicated for extraction from eleven patients were included. The canals of all teeth were prepared and received LA treatment with ICG in a similar way to the in vivo study. After tooth extraction, the apical thirds of the roots were processed for histopathological analysis.

Results: The in vitro study revealed that the increase in power and pulse duration, or the reduction in pulse interval, determined the temperature rise. The protocol with the highest power that showed a temperature increase below 40 °C was the 2.5 W (power), 300 ms (interval), and 100 ms (duration). The in vivo study revealed that the greatest temperature variation was observed in the lower incisor; for this reason, it was selected for the human study. In the human study, a structure of the periodontal ligament with histological and morphological characteristics comparable to those of healthy tissues and similar to the roots of control teeth was observed in the treated teeth (p < 0.05). No harmful effects were observed on the cementum structure, periodontal ligament, and alveolar bone in any teeth evaluated.

Conclusions: It was concluded that the LA protocol used is safe and can be performed during the treatment of infected root canals.