Association between Vitamin D Levels and Dental Caries: A Systematic Review and Dose-Response Meta-Analysis of Cross-Sectional Studies

Background and Aims: Previous observational studies found inconsistent associations between serum vitamin D levels and dental caries risk. A dose-response meta-analysis of cross-sectional studies was performed to investigate the association. Methods: To April 2023, the ISI Web of Science, PubMed, Scopus, and Google Scholar databases were searched for published papers. Finally, 13 cross-sectional studies were considered that provided odds ratios (ORs) with 95% confidence intervals (CIs) for dental caries in relation to serum vitamin D levels across all age groups. Two reviewers conducted a thorough screening of the studies, data extraction, bias risk assessment, and evidence quality. A random-effect model was used to assess the pooled estimated odd ratios (with 95% confidence intervals). A weighted mixed-effects dose-response meta-analysis in one stage was carried out. Results: Dental caries was significantly more likely to occur when serum vitamin D levels were low compared to high (OR: 1.41; 95% CI: 1.18, 1.68; GRADE = poor confidence). With a 10 nmol/L increase in serum vitamin D level, linear dose-response analysis showed a significant 3% (OR: 0.97; 95% CI: 0.96, 0.99) decrease in the likelihood of dental caries. Serum vitamin D levels and dental caries were found to be inversely correlated, with a significant dose-response relationship at levels greater than 78 nmol/L. Conclusion: This meta-analysis showed that vitamin D insufficiency was strongly associated with dental caries, and that a 10 nmol/L increase in blood 25(OH)D levels was linked to a 3% decrease in dental caries. However, the findings may have less clinical significance due to the uncertainty of the evidence.