Objective  To observe the morphological transformation and Ca/P changes of the periodontally disease root surfaces irradiated by Er, Gr:YSGG Laser. Methods 

18 periodontally diseased teeth and 6 wisdom teeth were collected in vitro. After 18 periodontally diseased teeth were planed, 12 teeth were randomly selected as the  laser treatment group, the others as the acid treatment group. The 6 wisdom teeth were selected as the healthy control.Then the evaluation for root surfaces

morphological transformation was conducted by SEM. An energy spectrum analyzer was used to analyze the Ca/P ratio of root surfaces. Results  The root surfaces were clean and even in the laser treatment group. Smear layer could also be effectively eliminated in the laser treatment group and the acid treatment group, but the SEM results were different. Atom content analysis showed that the Ca/P ratio of the laser treatment group and the acid treatment group had no distinct difference. Conclusion  It is effective to remove smear layers and infected cementum of surface layers with Er, Cr：YSGG irradiating on the planed periodontal root surfaces

 Er, Cr:YSGG laser, periodontal disease, root surface, smear layer, Ca/P ratio