Laser-osteotomy induced changes in bone

Abstract

Abstract Objective: To describe changes caused by clinically used lasers during osteotomy procedures. Temperature rise and potential thermal damage to tissue during ablation of bone using a super-pulsed carbon dioxide laser of 9.6-μm wavelength and an Er:YAG laser, equipped with a water-cooling spray and scanner system were studied. Background data: There has been no recent study comparing the super-pulsed CO 2 laser using a 9.6 μm wavelength to the Er:YAG laser with regard to their thermal effects on bone. In addition, the use of such laser systems under clinical conditions and histological evaluation in human bone has not been reported so far. Methods: In this study, two different types of samples were investigated to yield data most consistent with a typical clinical situation. Porcine slices and mandibular bone segments were studied at a drilling depth with a range of 0.5–0.7 and 0.6–0.97 mm, respectively. A control group treated with a conventional hand piece was compared to the laser groups. Lasers were also used in an OR-setting to evaluate clinical use and yield histological samples from human bone. Results: In the CO 2 laser groups demonstrating the highest elevation in temperature of the studied bone slices a mean temperature rise of less than 1.88 °C was noted. The Er:YAG revealed the highest mean temperature rise with 3.3 °C. Conventional drilling with a comparable drilling rate resulted in a mean rise of 1.43 °C. The laser groups of mandibular bone segments revealed a constant decrease in temperature hence the conventional drill rose to a mean temperature of 3.7 °C. Scanning electron microscope observations were lacking the typical morphological changes seen in earlier studies, specifically extensive melting, charring or cracking. Microscopic histology revealed minimal tissue changes limited to a few μm. Conclusions: A maximum rise of mean temperature to 1.88 °C, well below the critical margin of 7 °C, in closest proximity to the bone marrow and the morphological unaltered bone surfaces, demonstrate the safety and tissue preserving capability of the superpulsed 9.6 μm CO 2 laser. All three modalities are considered to preserve tissue not exceeding critical temperatures. The laser caused an even lower temperature rise than conventional drilling when used for osteotomies on bone segments. Moreover, the laser showed acceptable efficacy with drilling times comparable to the conventional dental drill. The clinical use of a 9.6 μm CO 2 laser as a bone-cutting tool can be considered to preserve tissue with minimum histologic effects.