Abstract: PURPOSE: To evaluate the effects of different timing of fixed orthodontics on enamel demineralization and periodontal conditions. METHODS: A total of 180 patients with fixed orthodontic treatment admitted from January 2021 to December 2023 were selected and divided into three groups according to the duration of orthodontic treatment: group A (n=60) with a treatment period of less than 6 months, group B (n=60) with a treatment period between 6 to 12 months, and group C (n=60) with a treatment period between 12 to 18 months. The enamel demineralization was evaluated by International Caries Detection and Assessment System (ICDAS), and ICDAS score was obtained. The periodontal status was evaluated by bleeding on probing (BOP), probing depth (PD), clinical attachment loss (CAL) and plaque index (PI). The correlation between enamel demineralization (ICDAS score) and changes of periodontal status (BOP, PD, CAL, PI) was analyzed by Pearson correlation analysis. The influencing factors of enamel demineralization in patients undergoing fixed orthodontics were analyzed by multivariate logistic regression analysis. RESULTS: There was no significant difference in the severity of enamel demineralization among the three groups (P>0.05). The total incidence of enamel demineralization (group A < group B < group C) was significantly different from the ICDAS score (group A < group B < group C)(P<0.05). There were significant differences in BOP, PD, CAL and PI among the three groups, and all were group A < group B < group C(P<0.05). ICDAS score was moderately positively correlated with BOP and PD, weakly to moderately positively correlated with CAL, and highly positively correlated with PI (P<0.05). The correction time, PI, frequency of high-glucose diet and local application of fluoride were independent influencing factors of enamel demineralization in patients undergoing fixed orthodontics (P<0.05). CONCLUSIONS: A long duration of fixed orthodontics will increase the risk of enamel demineralization and affect periodontal health of patients. PI, frequency of high-glucose diet and local application of fluoride can affect enamel demineralization. Personalized plans and regular follow-up programs should be formulated based on the individual conditions of patients, and oral hygiene guidance and prevention should be strengthened.

Key words: Fixed orthodontics, Correction time, Enamel demineralization, Periodontal status, Correlation, Influencing factor