AbstractBackgroundThe aim of this study was to investigate the potential association between vitamin D deficiency and matrix metalloproteinase‐9 (MMP‐9) levels in gingival crevicular fluid (GCF) across various periodontal health and disease statuses.MethodsA total of 200 volunteers were divided into two groups according to serum vitamin D concentration (25(OH)D < 10 ng/mL and 25(OH)D ≥ 10 ng/mL). Periodontal health status was determined based on a full‐mouth periodontal examination and radiographic evaluation. Participants in both groups were categorized according to periodontal diagnoses, encompassing periodontal health, gingivitis, and periodontitis. Following sampling, the MMP‐9 levels in GCF were determined by the enzyme‐linked immunosorbent assay (ELISA) method.ResultsThe GCF MMP‐9 levels were found to be higher in individuals with serum 25(OH)D < 10 ng/mL, in both the healthy and gingivitis and periodontitis groups, compared to those with 25(OH)D ≥ 10 ng/mL. Nevertheless, a statistically significant distinction was observed exclusively within the gingivitis and periodontitis groups. Correlation analysis and robust regression analyses provided additional evidence supporting the predictive role of periodontal disease status and vitamin D concentration in local MMP‐9 levels. These associations remained significant after adjusting for age and sex in robust regression analysis (p = 0.002). Furthermore, the inclusion of periodontal clinical parameters in the regression analysis revealed notable associations of clinical attachment loss with local MMP‐9 levels, along with periodontal disease status and serum vitamin D concentration (p < 0.001).ConclusionThe findings of our study suggest a potential mechanistic relationship between serum vitamin D levels and periodontitis.PLAIN LANGUAGE SUMMARYVitamin D deficiency is a widespread issue globally due to urban living, less outdoor time, seasonal changes, aging, and sunscreen use, leading to inadequate sun exposure. Low vitamin D levels are linked to several health problems, including hypertension, diabetes, heart diseases, and periodontal diseases, which affect the gums and bones around teeth and can cause tooth loss if untreated. Although the link between vitamin D and periodontal disease is unclear, it may involve the enzyme matrix metalloproteinase‐9 (MMP‐9). Our study examined 200 people, dividing them into two groups based on vitamin D levels. We assessed their gum health and measured MMP‐9 levels in their gingival crevicular fluid, a liquid that seeps out from the tiny space between gums and teeth. We found that people with lower vitamin D levels had higher MMP‐9 levels, especially those with gum disease. Our analysis showed that both vitamin D levels and gum health significantly impact MMP‐9 levels, with gum health being the more influential factor. Maintaining good gum health and adequate vitamin D levels is crucial for managing MMP‐9, an enzyme critical for tissue remodeling during healing and inflammation. However, excessive MMP may rapidly destroy periodontal tissues.