Objective: to investigate the clinical efficacy of pulsed holmium laser(Nd:YAG laser)in the treatment of acute pericardial periodontitis, and to observe the effect of Nd:YAG laser on microbial changes in the periorbital pocket.Methods:126 patients with acute pericoronitis were randomly divided into control group (conventional treatment group) and experimental group (conventional treatment+laser-assisted treatment group).Only partial crown irrigation was performed in the control group.The blind bags were continuously washed with 3.0% hydrogen peroxide and 0.9% normal saline for 3 days(once per day).The experimental group was dealed with Nd:YAG laser for 3 days (once per day)and taken the exudate of the blind pocket on the 1st day before and after laser treatment.The pain degree,mouth opening and gingival index (GI value)of the two groups were evaluated before treatment and after the 1, 2, 3, 5and 7th day of treatment. The changes of dominant bacteria before and after laser-assisted treatment were observed on the 1st day. We compared the effectiveness of the two groups after 7th day of treatment.Results:After 1, 2and 3 days of treatment, the pain index, degree of mouth opening improvement and gingival index were better in the experimental group than in the control group.The difference was statistically significant(P<0.05).There was no significant difference between the two groups after 5 and 7 days of treatment (P>0.05).The number of microbes in the peri-cryophytes of the experimental group was significantly decreased before and after treatment on the 1st day (P<0.05).There was no significant difference between the two groups after one week(P>0.05).Conclusion:Through clinical observation and microbiological analysis the application of Nd:YAG laser in the treatment of acute wisdom tooth pericoronitis can effectively reduce the pathogenic bacteria in the periorbital pocket, reduce pain and inflammation.Meanwhile we can improve the degree of opening, shorten the course of disease.Nd:YAG laser in the treatment of acute wisdom tooth pericoronitis is simple and safe.To a certain extent,the use of antibiotics is reduced and it is suitable for a wide range of people,and it is worthy of being widely used in clinical practice.