Serum Vitamin D Status and Risk of Early and Late Dental Implant Failure: A Systematic Review of Multivariate-Adjusted Primary Studies with Explicit Vitamin D Cut-off Classification

Statement of problemDental implant failure remains a significant clinical concern, with early loss often attributed to impaired osseointegration. Recent research has considered the role of serum vitamin D in implant integration, yet the precise relationship between vitamin D status and implant loss, particularly when distinguishing early and late failures, is not fully established. PurposeThe objective of this analysis was to evaluate the association between explicit serum vitamin D cut-off values and clinically confirmed dental implant failure, with a particular focus on differentiating early (pre-loading) from late (post-loading) failures. The review also sought to determine whether primary studies used multivariate adjustment for potential confounders. Material and methodsThe draft of this revision was registered in PROSPERO (CRD420251049631, https://www.crd.york.ac.uk/PROSPERO/view/CRD420251049631). A comprehensive literature search was conducted using AI-assisted tools to identify primary research studies, including randomized controlled trials and cohort studies, published in English, Spanish, French, German, or Italian. Eligible studies required explicit vitamin D threshold categorization, clinically verified implant loss, and clear differentiation of early and late failures. Data extraction included study design, vitamin D categorization, analytical methods, and outcomes. ResultsIdentified studies predominantly consisted of retrospective and prospective cohorts examining early implant failures, frequently using cut-offs such as >30 ng/mL, 10-30 ng/mL, and <10 ng/mL for serum vitamin D. Results suggested a higher frequency of early failures in individuals with severe vitamin D deficiency; however, all studies relied on univariate analyses without multivariate adjustment for confounders. Late implant failures were rarely addressed. ConclusionsCurrent evidence indicates a possible association between low serum vitamin D and early dental implant failure, but the lack of robust statistical adjustment prevents definitive conclusions. High-quality studies with rigorous confounder control and explicit early versus late failure analysis are needed.