Morphological changes of bovine mandibular bone irradiated by Er,Cr:YSGG laser:: An in vitro study

Objective: The purpose of this study was to investigate the morphological changes of bovine madibular bone following Er,Cr:YSGG laser irradiation in different methods in vitro. Background Data: Recently, an erbium, chromium/yttrium, scandium, garmet (Er,Cr:YSGG) laser device that emits a laser beam at the wavelength of 2.78 mum was introduced. This type of infrared laser proved to ablate dental hard tissues effectively. However, the different effects of bone ablation by this laser in different irradiation methods were still unknown. Materials and Methods: Adult bovine mandibular bones were cut into 24 small pieces, 3-4 cm in length. The parameters of Er,Cr:YSGG laser irradiation were as follows: wavelength was 2.78 pm, pulse duration was 140-200 musec, repetition rate was 20 pulse/sec, power was 4 W, spot size was 1.26 X 10(-3) mm(2), and energy density was 160 J/cm(2). Irradiation methods were different in four groups (six specimens in each group): group A, fixed position and contact mode; group B, fixed position and noncontact mode; group C, nonfixed position and contact mode; and group D, nonfixed position and noncontact mode. Results: Ablation depth in group A was significantly greater than in group B (p < 0.01). In group A, thermal damage was apparent. In group B, C, and D, thermal damage was minimal. Conclusion: ErCr:YSGG laser allows for precise surgical bone cutting and ablation with minimal thermal damage to adjacent tissue. Irradiation in different methods may achieve different ablation rates and thermal damage.