Abstract: ［Abstract］ Objective〖HTSS〗To investigate the effect of orthodontic treatment on the changes of gingival protein R(Rgp) and to analyze the risk of gingivitis.
〖HTH〗〖WTHZ〗Methods〖HTSS〗A total of 118 adolescent patients who underwent orthodontic treatment were randomly selected. The gingival crevicular fluid was taken before, after, and at 1, 2, 3, and 6 months after correction. The 16S rDNA PCR technique was used to detect Porphyromonas gingivalis（P.g） and Rgp. Chi-square test was used to compare the detection rates of P.g and Rgp between groups, and Spearman rank correlation analysis was used to analyze the relationship between gingivitis and P.g and Rgp detection rates.
〖HTH〗〖WTHZ〗Results〖HTSS〗Among the 118 subjects, the positive rate of P.g detection before, after, 1, 2, 3, and 6 months after correction was 29.66%, 53.39%, 72.03%, 60.17%, 38.14%, compared with the pre-correction, after correction. The positive rate of P.g detection increased gradually in the first month and 2 months, and decreased in the third month(P＜0.05). The positive rate of Rgp in the positive detection of P.g before and after correction, 1, 2, 3, and 6 months after correction were 34.29%, 53.97%, 69.41%, 67.61%, 42.22%. Compared with the pre-correction, the positive rate of Rgp detection increased gradually after 2 and 3 months of correction(P＜0.05). There was a positive correlation between gingival index and detection time, P.g. and positive rate of Rgp(rs=0.352， 0.461， P＜0.05).
〖HTH〗〖WTHZ〗Conclusion〖HTSS〗In the early stage of orthodontic treatment, the appliance can increase P.g and Rgp, and begin to decline in the third month. The sixth month is slightly higher than before correction, and oral hygiene should be emphasized during orthodontic treatment, which is conducive to the prevention of gingivitis.

Key words: orthodontic appliances, gingival protein R, Porphyromonas gingivalis