Abstract: Objective To study the changes of peripheral blood helper T cells （Th17） and regulatory T cells （Treg） in oral therapy. Methods Sixty patients with chronic periodontitis treated from June 2018 to June 2019 were selected and randomly divided into a control group and an observation group, with 30 cases in each group. The control group was treated with minocycline hydrochloride, while the observation group was treated with tinidazole additionally. The treatment efficiency and periodontitis-related indicators such as plaque index （PLI）, tooth looseness （MD）, periodontal pocket depth （PPD）, periodontal attachment level （PAL）, gingival index （GI）, peripheral blood Th17 and Treg levels, and incidence of adverse reactions were compared between the two groups. Results After the designed treatment, the total effective rate in the observation group was 92.42% （61/66）, which was higher than 70.97% （44/62） in the control group （P<0.05）; the PLI, MD, PPD, PAL, GI, and the levels of Th17 and Treg in the observation group were lower than those in the control group （P<0.05）. The incidence rate of adverse reactions in the observation group was 6.67% （2/30）, which was lower than 10.0% （3/30） in the control group （P>0.05）. Conclusion The clinical effect of minocycline hydrochloride combined with tinidazole on chronic periodontitis is significant. It can effectively alleviate the clinical symptoms such as tooth mobility, swelling, and pain, optimize immune function, weaken inflammatory response, and have a high safety level; therefore, it is worthy of clinical application.

Key words: Th17, Treg, Minocycline hydrochloride, Tinidazole, Safety