ASSOCIATION BETWEEN VITAMIN D RECEPTOR (VDR) GENE POLYMORPHISMS AND EARLY DENTAL IMPLANT OSSEOINTEGRATION: A PROSPECTIVE CLINICAL STUDY

Abstract

Background: Dental implant osseointegration is a multifactorial process influenced by surgical, prosthetic, and host related determinants. Vitamin D, acting through the vitamin D receptor (VDR), regulates calcium homeostasis, osteoblast differentiation, and bone remodelling. Functional polymorphisms in the VDR gene may therefore modulate peri-implant bone healing and the development of early implant stability. Aim: To evaluate the association between four common VDR gene polymorphisms—FokI (rs2228570), BsmI (rs1544410), ApaI (rs7975232) and TaqI (rs731236)—and early implant stability, and to explore the influence of serum vitamin D status on osseointegration. Materials and Methods: One hundred systemically healthy adults receiving a single endosseous implant were enrolled prospectively. Genomic DNA extracted from peripheral blood was genotyped by PCR-RFLP for the four polymorphisms, and serum 25-hydroxyvitamin D was measured. Implant stability was recorded as the implant stability quotient (ISQ) by resonance frequency analysis at placement (primary stability) and at the second-stage/loading review (secondary stability); the gain in stability (ΔISQ) was calculated. Genotype frequencies were tested for Hardy Weinberg equilibrium, and associations with ISQ and osseointegration outcome were assessed by ANOVA, chi square, and multivariate regression (p < 0.05). Results: All four polymorphisms were in Hardy–Weinberg equilibrium. Primary stability did not differ by genotype. The FokI polymorphism was significantly associated with ΔISQ (ANOVA p = 0.002): ff carriers showed a markedly smaller stability gain (3.31 ± 2.17) than FF (5.77 ± 2.34) or Ff (6.10 ± 2.50) carriers. In the adjusted linear model, the FokI ff genotype independently predicted a lower ΔISQ (β = −2.52; 95% CI −4.02 to −1.02; p = 0.001). BsmI, ApaI, and TaqI showed no significant association with any stability measure. Serum vitamin D did not correlate significantly with ISQ or osseointegration outcome in this cohort. Sixteen implants (16%) showed delayed osseointegration and five (5%) were early failures; the FokI ff genotype was associated with delayed osseointegration at a non-significant trend level (adjusted OR 3.67; 95% CI 0.83–16.2; p = 0.086). Conclusion: Within the limits of this study, the VDR FokI polymorphism was independently associated with reduced early implant stability gain, whereas BsmI, ApaI, TaqI, and serum vitamin D level were not. VDR FokI genotyping may help identify patients at risk of slower osseointegration and merits evaluation in larger cohorts.