Vitamin D and Bone Physiology: Demonstration of Vitamin D Deficiency in an Implant Osseointegration Rat Model

Purpose: The patient population varies in nutritional deficiencies, which may confound the host response to biomaterials. The objective of this study was to evaluate the effect of a common deficiency of vitamin D on implant osseointegration in the rat model. Materials and Methods: Male Sprague‐Dawley rats were maintained under the cessation of vitamin D intake and UV exposure. The serum levels of 1,25(OH)₂D₃, 25 OHD₃, Ca, and P were determined. Miniature cylindrical Ti6Al4V implants (2‐mm long, 1‐mm diameter) were fabricated with double acid‐etched (DAE) surface or modified DAE with discrete crystalline deposition (DCD) of hydroxyapatite nanoparticles. DAE and DCD implants were placed in the femurs of vitamin D‐insufficient and control rats. After 14 days of healing, the femur‐implant samples were subjected to implant push‐in test and nondecalcified histology. The surfaces of recovered implant specimens after the push‐in test were further evaluated by scanning electron microscopy (SEM). Results: The decreased serum level of 25 OHD₃ demonstrated the establishment of vitamin D insufficiency in this model. The implant push‐in test revealed that DAE and DCD implants in the vitamin D‐insufficient group (15.94 ± 8.20 N, n = 7; 15.63 ± 3.96 N, n = 7, respectively) were significantly lower than those of the control group (24.99 ± 7.92 N, n = 7, p < 0.05; 37.48 ± 17.58 N, n = 7, p < 0.01, respectively). The transcortical bone‐to‐implant contact ratio (BIC) was also significantly decreased in the vitamin D‐insufficient group. SEM analyses further suggested that the calcified tissues remaining next to the implant surface after push‐in test appeared unusually fragmented. Conclusions: The effect of vitamin D insufficiency significantly impairing the establishment of Ti6Al4V implant osseointegration in vivo was unexpectedly profound. The outcome of Ti‐based endosseous implants may be confounded by the increasing prevalence of vitamin D insufficiency in our patient population.