Effects of erbium,chromium : YSGG laser irradiation on canine mandibular bone

Background: Only relatively few reports have described the morphological ef fects on bone produced by erbium, chromium: yttrium, scandium, gallium, gar net (Er,Cr:YSGG) laser irradiation, and none has investigated the atomic ch anges or estimated the temperature increases involved. The objectives of th is study were to investigate the morphological, atomic, and temperature cha nges in irradiated areas during and after laser irradiation, and to evaluat e the cutting effect on canine mandibular bone in vitro. Methods: Two canine mandibular bones were cut into 3 to 5 cm pieces and irr adiated by an Er,Cr:YSGG laser utilizing a water-air spray at 5 W and 8 Hz for 10 or 30 seconds. During and after laser irradiation, temperature incre ases in the irradiated areas were measured by thermography. The samples wer e then observed by stereoscopy and scanning electron microscopy to determin e morphological changes and by energy dispersive x-ray spectroscopy to eval uate atomic alterations. Results: Regular holes or grooves having sharp edges and smooth walls were produced, but no melting or carbonization was observed. The maximum tempera ture increase was an average 12.6 degreesC for 30-second irradiation. The c ontinuous time of a temperature increase of more than 10 degreesC was consi stently less than 10 seconds. An atomic analytical examination revealed tha t the calcium: phosphorus ratio was not significantly changed between the l ased and unlased areas (P >0.01). Conclusion: These results showed that the Er,Cr:YSGG laser cuts canine mand ibular bone effectively without burning, melting, or altering the calcium: phosphorus ratio of the irradiated bone.