Objective To compare the clinical efficacy of endoscope-assisted scaling and root planing（SRP） and photodynamic therapy（PDT） combined with SRP in the treatment of severe periodontitis. Methods A total of 80 patients with severe periodontitis treated in a hospital in Liaoning Province from April 2018 to March 2020 were randomly divided into observation group and control group

with 40 cases in each group. The patients in the control group were treated with PDT combined with SRP

and the patients in the observation group were treated with SRP under periodontal endoscope. The clinical efficacy and adverse reactions were compared between the two groups. At the same time

the periodontal index

the level of inflammatory cytokines in gingival crevicular fluid and the visual analogue scale（VAS） were compared between the two groups before and after treatment. Results The total effective rate of the observation group was 92.50%

which was higher than that of the control group（75.00%）

and the difference was statistically significant（P<0.05）. The bleeding index（BI）

probing depth（PD） and attachment loss（AL） of the two groups after treatment were lower than those before treatment

and the difference was statistically significant（P<0.05）

but there was no significant difference between the two groups（P>0.05）. After treatment

the levels of IL-17

TNF-α and hs-CRP in gingival crevicular fluid in the two groups were lower than those before treatment

and those in the observation group were lower than those in the control group

and the difference was statistically significant（P<0.05）. After treatment

the levels of interleukin-17（IL-17）

hypersensitive C-reactive protein（hs-CRP） and tumor necrosis factor-α（TNF-α） in gingival crevicular fluid in the two groups were lower than those before treatment

and those in the observation group were lower than those in the control group

and the difference was statistically significant（P<0.05）. The VAS scores at 12 to 72 hours after treatment in both two groups were lower than those before treatment

and those in the observation group were lower than those in the control group

and the difference was statistically significant（P<0.05）. The incidence of adverse reactions in the observation group was 5.00%

which was lower than that in the control group（22.50%）

and the difference was statistically significant（P<0.05）. Conclusion The efficacy of periodontal endoscope-assisted SRP in the treatment of severe periodontitis is better than that of PDT combined with SRP

and it can help to improve the whole oral periodontal index

the level of inflammatory cytokines in gingival crevicular fluid

and also help to relieve pain. Thus

it is worth popularizing in clinical application.