Effects of Local Anesthetics on Tissue Penetration Using Diode Lasers in Intraoral Tissues

The purpose of this study was to demonstrate heat transfer within oral soft tissues using different lasers under the effect of local anesthetics (LA). Bovine tongue slices were placed in between two glass slides and at a distance from a thermographic camera. In total, 2-cm-long 240 incisions were made along the surface of the tissue parallel to glass slides and the camera capture field. Incisions were performed using 445-nm and infrared (IR) lasers (970 nm and 980 nm on a continuous wave at 2 W) with 320 µm-initiated (concentrated energy at the tip provided by a blue articulated paper and laser irradiation) and noninitiated (defused energy) fiber (30-sec irradiation period). LA was injected into the specimens before irradiation. The temperature changes in °C (ΔT) and vertical and lateral heat transfer (in mm) were recorded at 10-sec intervals for 30 sec, using thermographic images. The amount of lateral and vertical heat transfer was measured. A repeated analysis of variance statistical comparison test was used to analyze differences between the lateral (width) and the vertical (height) heat transfer for initiated and noninitiated lasers and different lasers. The maximum ΔT in °C utilizing initiated tips of 970, 980, or 445 nm were 11.82 ± 3.46, 7.66 ± 3.24, and 18.94 ± 7.01 and using noninitiated tips were 8.27 ± 1.69, 8.87 ± 2.40, and 12.31 ± 8.65, respectively. Heat transfers (height/width) for initiated were 40.65 ± 10.40/90.65 ± 10.77 mm, 41.50 ± 11.83/83.95 ± 11.20 mm, and 33.70 ± 9.10/95.10 ± 11.17 mm and for noninitiated lasers were 52.95 ± 6.89/96.10 ± 11.17 mm, 47.75 ± 7.41/93.75 ± 14.96 mm, and 31.35 ± 11.40/75.20 ± 19.68 mm, respectively. A statistically significant difference was found between all lasers (p < 0.05) for initiated and noninitiated lasers (except for 970/980 nm for noninitiated lasers). Lower penetration depth (p < 0.05) at 445-nm diode and greater lateral heat spreading (p < 0.05) were identified under LA especially utilizing noninitiated tips without significant difference in IR lasers. LA might negatively influence soft tissues creating scattering when noninitiated tips are used and IR diode laser technology.