Thermal increase in the oral mucosa and in the jawbone during Nd:YAG laser applications. Ex vivo study

Abstract

Objective: Literature reports bactericidal and biostimulant effects for Nd:YAG laser procedures on bone and oral mucosa but the possible overheating can cause damage to anatomical structures. The aim of the study is the evaluation of thermal increase in different levels of oral tissues: mucosa, periosteum and bone during defocused application of Nd:YAG laser at different parameters. Study Design: Superficial thermal evaluation was performed in pig jaws with a thermal camera device; deep thermal evaluation was realized by 4 thermocouples placed at a subperiosteal level and at 1,2 and 4 mm depth in the jaw bone. Laser applications of 1 minute were performed 5 times (with a pause of 1 minute) on a surface of 4 cm2 with a Nd:YAG laser (VSP mode, 320 micrometer fiber, defocused mode) with different parameters. Temperatures were recorded before and after laser applications and after each pause in order to evaluate also the thermal relaxation of tissues. Results: At submucosal level, mean thermal increase was between 1.1°C and 13.2°C, at 1 mm depth between 1.1°C and 8.5°C, at 2 mm depth between 1.1°C and 6.8°C, at 4 mm depth between 1.0°C and 5.3°C. Temperature decrease during the rest time period was variable between 0°C and 2.5°C. Conclusions: Temperatures reached during clinical procedures with parameters reported in the literature in biostimulation protocols (1.25-2 Watts) for the five minutes of application are not dangerous for biological structures. The decrease in temperature during the rest time period is less considerable in the bone in comparison to oral mucosa. Key words:Nd:YAG laser, thermal increase, thermocouple, thermal camera, low level laser therapy.

Adjunctive effects of laser therapy on somatosensory function and vasomotor regulation of periodontal tissues in patients with periodontitis: A randomized controlled clinical trial

“…[24][25][26] Animal studies have verified the safety of an oral mucosal temperature increase of overall 2 • C on healthy tissues and 6.1 • C increase on root surfaces for the periodontal ligament, which were further supported in our clinical investigation in humans. 25,26 The rising temperature can be explained by two underlying mechanisms. One explanation could be that the heat transportation from tissue to tissue is less dissipated as gingival blood flow declined, and another explanation could be due to the emitting light of Nd:YAG laser which is converted into heat by refraction or diffused reflection at the tip end.…”

Histological Effects of an Innovative 445 Nm Blue Laser During Oral Soft Tissue Biopsy

“…The possibility of having a diagnosis, with laser devices, is maintained, despite the thermal effect in the peri-incisional area due to the heat released by the photothermal effect, which increases the temperature of the tissue, at the incision point; so, it is clear that the laser can be used for biopsies of clinically benign lesions [30,31]. Compared to the traditional cold blade approach, however, the laser offers numerous advantages, including a hemostatic effect that defines intraoperative hemostasis, antibacterial effect on the incision path, better patient comfort, second intention healing without sutures and reduced postoperative edema [11]; for this reason, it is considered the gold standard in the approach to clinically benign lesions of oral soft tissues [32,33].…”

High-intensity Nd:YAG laser accelerates bone regeneration in calvarial defect models

“…The current study revealed that there was no significant difference in new bone formation induced by laser irradiation between sets at 0.75 W and 3 W. However, new bone formation at 0.75 W was 5.9% higher than at 3 W. Recently, Vescovi et al . () evaluated thermal increase in different levels of oral tissues, including mucosa, periosteum and bone, during the defocused application of Nd:YAG lasers at different parameters. They concluded that at low power (1.25–2 W) the thermal increase was very limited and not dangerous for healthy tissues.…”