Differential Response of Salivary MMP-8 and MMP-9 to Full-Mouth Disinfection: Implications for Biomarker Sensitivity in Periodontal Therapy

Background/Objectives: Matrix metalloproteinases (MMP-8 and MMP-9) are key mediators of periodontal tissue degradation and have been proposed as salivary biomarkers of disease activity. However, their comparative responsiveness to non-surgical periodontal therapy remains insufficiently clarified. This study aimed to assess short-term changes in salivary MMP-8 and MMP-9 following full-mouth disinfection (FMD), to evaluate their association with clinical periodontal parameters, and to explore potential differences according to depressive comorbidity. Methods: Eighty patients were included and divided into two groups: 40 patients without depressive disorder (PAR group) and 40 patients with depressive disorder (DEP group). Clinical periodontal parameters (probing depth and clinical attachment loss) and salivary levels of MMP-8 and MMP-9 were assessed at baseline and 12 weeks following FMD. Salivary MMP-8 and MMP-9 levels were determined using the enzyme-linked immunosorbent assay (ELISA). Results: Significant reductions in probing depth and clinical attachment loss were observed following therapy (p < 0.01). Salivary MMP-9 levels decreased significantly in both groups (PAR: 2.4 to 1.1 ng/mL, p = 0.002; DEP: 2.6 to 1.5 ng/mL, p = 0.004), whereas MMP-8 did not show statistically significant changes (p > 0.05). Moderate positive correlations were identified between MMP-9 and clinical parameters (r = 0.46–0.51), while MMP-8 showed no significant associations. No significant differences in treatment response or biomarker dynamics were observed between groups. Conclusions: The findings indicate a differential salivary biomarker response to periodontal therapy, with MMP-9 showing greater responsiveness than MMP-8 under the conditions of this study. These results suggest a potential role for salivary MMP-9 in reflecting short-term periodontal changes; however, further longitudinal and controlled studies are required to establish its clinical applicability. Depressive comorbidity did not appear to influence short-term outcomes, although this finding should be interpreted cautiously due to the lack of a standardized severity assessment.