Ex Vivo Evaluation of Gingival Ablation with Various Laser Systems and Electroscalpel.

Objective: The aim of this study was to perform a systematic and multifaceted comparison of thermal effects during soft tissue ablation with various lasers and an electroscalpel (ES). Materials and methods: Er:YAG, Er,Cr:YSGG, CO2, Diode, Nd:YAG lasers (1 W, pulsed or continuous wave), an ES, and a scalpel (Sc; control), were employed for porcine gingival tissue ablation. Temperature changes during ablation were measured by using an infrared thermal imaging camera and a thermocouple. After ablations, the wounds were observed using stereomicroscopy and scanning electron microscopy (SEM), and histological sections were analyzed. Compositional analysis was also performed on ablated sites by SEM wavelength dispersive X-ray spectroscopy. Results: The surface temperature during irradiation was highest with CO2 (over 500°C), followed by Diode (267°C) and Nd:YAG (258°C), Er:YAG (164°C), ES (135°C), and Er,Cr:YSGG (85°C). Carbonization was negligible (Er:YAG), slight (Er,Cr:YSGG), moderate (Nd:YAG and ES), and severe (CO2 and Diode). Under SEM observation, Er:YAG and Er,Cr:YSGG showed smooth surfaces but other devices resulted in rough appearances. Histologically, the coagulated and thermally affected layer was extremely minimal (38 µm in thickness) and free from epithelial collapse for Er:YAG. Compared with other devices, less compositional surface change was detected with Er:YAG and Er,Cr:YSGG; additionally, the use of water spray further minimized thermal influence. Conclusions: Among various power devices, Er:YAG laser showed the most efficient and refined gingival ablation with minimal thermal influence on the surrounding tissues. Er:YAG and Er,Cr:YSGG lasers with water spray could be considered as minimally invasive power devices for soft tissue surgery.

Evaluation of bone healing following Er:YAG laser ablation in rat calvaria compared with bur drilling.

The Er:YAG laser is currently used for bone ablation. However, the effect of Er:YAG laser irradiation on bone healing remains unclear. The aim of this study was to investigate bone healing following ablation by laser irradiation as compared with bur drilling. Rat calvarial bone was ablated using Er:YAG laser or bur with water coolant. Er:YAG laser effectively ablated bone without major thermal changes. In vivo micro-computed tomography analysis revealed that laser irradiation showed significantly higher bone repair ratios than bur drilling. Scanning electron microscope analysis showed more fibrin deposition on laser-ablated bone surfaces. Microarray analysis followed by gene set enrichment analysis revealed that IL6/JAK/STAT3 signaling and inflammatory response gene sets were enriched in bur-drilled bone at 6 hours, whereas the E2F targets gene set was enriched in laser-irradiated bone. Additionally, Hspa1a and Dmp1 expressions were increased and Sost expression was decreased in laser-irradiated bone compared with bur-drilled bone. In granulation tissue formed after laser ablation, Alpl and Gblap expressions increased compared to bur-drilled site. Immunohistochemistry showed that osteocalcin-positive area was increased in the laser-ablated site. These results suggest that Er:YAG laser might accelerate early new bone formation with advantageous surface changes and cellular responses for wound healing, compared with bur-drilling.

In vitro and clinical evaluation of optical coherence tomography for the detection of subgingival calculus and root cementum.

This study evaluated the effectiveness of swept-source optical coherence tomography (ss-OCT) for detecting calculus and root cementum during periodontal therapy. Optical coherence tomography (OCT) images were taken before and after removal of subgingival calculus from extracted teeth and compared with non-decalcified histological sections. Porcine gingival sheets of various thicknesses were applied to the root surfaces of extracted teeth with calculus and OCT images were taken. OCT images were also taken before and after scaling and root planing (SRP) in human patients. In vitro, calculus was clearly detected as a white-gray amorphous structure on the root surface, which disappeared after removal. Cementum was identified as a thin, dark-gray layer. The calculus could not be clearly observed when soft tissues were present on the root surface. Clinically, supragingival calculus and cementum could be detected clearly with OCT, and subgingival calculus in the buccal cervical area of the anterior and premolar teeth was identified, which disappeared after SRP. Digital processing of the original OCT images was useful for clarifying the calculus. In conclusion, ss-OCT showed potential as a periodontal diagnostic tool for detecting cementum and subgingival calculus, although the practical applications of subgingival imaging remain limited.