Abstract: Objective To investigate the clinical necessity of periodontal minimally invasive non-surgical therapy (MINST) in upper anterior teeth of patients with thin gingival phenotype. Methods Eighteen cases of grade Ⅲ and Ⅳ periodontitis with thin gingiva, who visited the Department of Periodontology of the Affiliated Stomatological Hospital of Nanjing Medical University from May 2020 to September 2021,were recruited and divided into two groups randomly. Their upper anterior teeth were treated with MINST (MINST group) or conventional subgingival scaling and root planing (SRP group). Changes of clinical parameters, such as probing depth (PD), clinical attachment loss (CAL), gingival recession (GR) and bleeding on probing (BOP) positive rates, were examined and compared between baseline and 3 and 6 months after therapy, as well as intergroup differences. Patients′ perception of discomfort/pain experienced during and after therapy was evaluated using visual analog scale (VAS) immediately and 7 d after procedure. After 6 months, patients′ perception regarding outcomes of the therapy wasalso measured by VAS in the same way. In addition, patients′ aesthetic satisfaction of the treated teeth was also recorded. Results Regardless of PD at the baseline, both groups had significant changes in PD, CAL, BOP positive rates and GR (P＜0.01). For sites of 4 mm≤PD≤6 mm, at 6 months after operation, change values of GR in the SRP group were greater than those in the MINST group (P=0.035). Also, only in SRP group, higher GR values were observed after 6 months compared to measurements after 3 months (P＜0.001). For sites with PD>6 mm, intergroup analysis showed that change values of PD and CAL in MINST group were higher than those in SRP group(P＜0.01). At 6 months after operation, change values of GR in SRP group were higher than those in MINST group(P=0.014). In addition, at 6 months postoperatively, further changes in PD values in both groups (P＜0.05) and in GR values (P=0.025)in SRP group were observed, compared to 3 months. In addition, the complaint of discomfort/pain and root hypersensitivity during the first post-therapy week was more severe in SRP group(P＜0.05), and no significant differences in the perception of therapy outcomes and aesthetic satisfaction levels of the treated teeth were observed between groups. Conclusion For upper anterior teeth with thin gingiva, especially for sites with PD>6 mm, MINST presents obvious advantages in PD reduction, CAL gain, maintaining position of the gingival margin and improving post-operative comfort experience of patients. Therefore, it is necessary to use MINST to achieve better periodontal health. However, it cannot be considered that MINST can achieve higher aesthetic evaluation from patients.

Key words: periodontitis, periodontal minimally invasive non-surgical therapy, subgingival scaling and root planing