Penetration depth study of 830 nm low-intensity laser therapy on living dog tissue

Background and Aim: Recent studies have shown that low-intensity laser therapy (LILT) enhances chronic wound healing, reduces pain, reduces inflammation, and improves post-operative rehabilitation. However, clinical outcomes in the veterinary use of LILT vary between different experimental studies. This is explained by improper laser parameter settings and limits of its penetration depth. This study aimed to investigate the penetration depth of 830 nm LILT on living dog tissue in different operating modes. This entailed continuous wave (CW) versus pulse wave (PW) and with contact versus non-contact techniques of the laser probe at different tissue-laser probe distances. The results can be applied for use in clinical practice. Materials and Methods: Twenty-four dogs that had undergone abdominal surgery were included in this study. The laser parameters were set at 200 mW, fluence of 4 J/cm2 and the laser power output denoted as mean output power (MOP) was measured by a power meter. Results: The MOP of the 830 nm CW laser was significantly higher than the PW laser (p<0.05). The MOP of the contact technique was significantly greater than that of the non-contact technique in both CW and PW modes (p<0.05). The MOP through the skin tissue was between 16.09 and 18.60 mW (8.05-9.30%) for the contact technique and 8.73 and 19.36 mW (4.37-9.68%) for the non-contact technique. In the muscle-skin layer, the MOP was between 0.50 and 1.56 mW (0.25-0.78%) and the MOP was not detected using the non-contact technique with a 5 cm tissue-laser probe distance. Conclusion: Our study indicates that 830 nm LILT (with laser parameter setting at 200 mW, fluence of 4 J/cm2 for both contact and non-contact techniques, and tissue-laser probe distance up to 5 cm) was appropriate for treatments within 14 mm of depth. However, the use of 830 nm LILT for an application in which the target tissue is deeper than 14 mm may limit its positive effect.

Ablation of Selected Dental Materials Using Er,Cr:YSGG Laser

The effect of Er,Cr:YSGG laser for ablation of commercialized adhesive dental materials were studied using 12 sets of tooth samples. The surface morphology and composition of the tooth samples was observed before and after irradiation using FESEM and EDX. Time dependency of exposure is observed in the tooth sample. Adhesive material Grēngloo produced better ablation on long exposure compared to adhesive material Blūgloo. The ablation effect was also compared between presence and absence of water. The enamel surface produced is highly dependent on the technique used to ablate the adhesive material. Without water, enamel surface appeared roughed and depth of crater was also created. In particular, both materials produce different quality of ablation and reacted differently under different laser parameter and setting.