GAP Australasian-Dentist-May June 2019

Category AustrAlAsiAn Dentist 69 administration of vitamin D in the weeks prior to placement of a dental implant could be useful, particularly in patients with severe deficiency states; in these patients, vitamin D supplementation should be maintained for the whole life, in order to guarantee a good remodelling of the bone around the implant. this study has the distinction of being one of the first clinical studies carried out on a large number of patients to investigate the possibility of an association between low blood levels of vitamin D and the incidence of early failure in implantology. By restricting the analysis to early failures, occurring in the first period of healing and therefore prior to placement of the prosthetic restoration, we were able to focus our research and avoid a range of factors (linked to the restoration itself and the prosthetic load) which could have confused the issue in the study. it is, in fact, well known that implant survival and thus osseointegration depend on a large number of factors (related to the surgical and prosthetic protocol, the materials used, and lastly the patient) [4, 5] and it can be difficult to identify which of them might be determining the success or failure of the treatment [7]. in order to avoid this and to limit the confounding factors, the same materials were used for all the patients in this study (the same implant system for all the patients) [1, 3, 8]. in addition, the same surgical protocol was used, involving submerged healing in the absence of prosthetic loading [3]. thus the only possible confounding factors were the different quantity and quality of bone at the implant receiving sites and the patients’ responses: these are unavoidable factors. However, some of those categories of patients most at risk of implant failure (patients undergoing bone regeneration to create the conditions for the positioning of the implant fixtures or those with particular medical conditions whichmight increase the risk of treatment failure) were excluded in the present study. this study has limits. it is a retrospective work, in which the number of patients having a severe deficiency of vitamin D in the blood was low (only 22); thus the presence of even just one less failure in this group would have led to quite different results. it is possible that some residual confounding may have biased the association between vitamin D and implant failures that we observed. For instance, this study did not investigate the influence of other patient- related factors (e.g., the bone quality) which can affect implant survival in the period immediately following implant placement. in addition, if subjects with low levels of vitamin D were also likely osseointegration and on bone regeneration in dentistry [33–35]. this is probably due to the fact that there are many factors which can determine the success or failure of dental implants; the attention of clinicians has been mostly focused on drawing up surgical and prosthetic protocols and identifying new materials and implant surfaces to improve osseointegration, rather than on the analysis of patient-related risk factors [6– 9]. in a recent clinical work, Alvim-Pereira et al. found no relationship between polymorphism of the vitamin D receptor and implant failure [33]. in a randomized, controlled, double-blind study, schulze- sp¨ate et al. investigated the effects of supplementation with a combination of vitamin D3 (5000 iu) and calcium (600mg) on the formation of new bone following maxillary sinus lift [34]. ten patients were assigned to the test group and given vitamin D and calcium; ten other patients were assigned to the control group and received only calcium [34]. six to eight months after surgery for bone regeneration, bone samples were taken for histological analysis during implant placement [34]. Although supplementation with vitamin D3 would have increased the serum levels of vitamin D with potentially positive effects on bone remodelling at the cellular level, no statistically significant difference was demonstrated between the two groups at the histological level [34]. the results of our study would appear to suggest that a severe deficiency of vitamin D in the blood might be related to an increase in the incidence of early implant failure. in fact, the incidence of early implant failure was rather low (2.2%) in patients with normalized levels of vitamin D in the blood (>30 ng/ml), rose to almost double (3.9%) in patients with insufficient serum levels (10–30 ng/ml), and were rather high (9.0%) in patients characterized by severe deficiency states. However, despite the tendency to an increased incidence of early failure in patients characterized by deficiency states, the differences between the three groups of patients were not statistically significant ( P = 0.15). Our study also confirms that the serum values of vitamin D in the local population are rather low: we found that the proportion of patients with insufficient levels was 49.4% and that the percentage with a severe deficiency was 2.7%. the percentage of patients with adequate levels was 47.9%. this is not surprising, as most of the patients treated came from northern italy and southern switzerland, regions where exposure to sunlight is somewhat reduced for long periods of the year. in the light of this, the osseointegration, but it is not yet entirely clear whether supplementation would promote the healing of periimplant bone tissue clinically [24, 33–35]. A recent review of the literature on animal studies has shown that vitamin D supplementation can stimulate new bone formation and increase the contact between the bone and the surface of titanium implants [24]. specifically, Kelly et al. demonstrated that vitamin D deficiency could significantly compromise the establishment of osseointegration of ti6Al4V implants in rats [25]. similar results were reported by Dvorak et al. [26]. in an experimental study on ovariectomized rats, the authors demonstrated that vitamin D deficiency could impair the formation of peri-implant bone; the normalization of blood levels via supplementation of vitamin D stimulated new bone formation [26]. similar results were reported by Zhou et al., who found an increase in osseointegration in osteoporotic rats given vitamin D supplements [27], and Wu et al., who demonstrated an increase in the percentage of contact between bone and implant in diabetic rats given vitamin D supplements [28]. Finally, liu et al. reported that the administration of vitamin D could increase the fixation of dental implants in mice suffering from chronic kidney disease [29]. A further possibility for study, in order to understand the effects of the administration of vitamin D on bone healing of the peri-implant tissues, is that of coating the implant surface with vitamin D [30–32]. salom´o-Coll et al. evaluated the effect of the topical application of vitamin D to the surface of implants inserted in post-extraction sockets in dogs, with histological and histomorphometric analyses of tissues removed at 12 weeks [30]. topical application of vitamin D increased the percentage of bone to implant contact of 10% [30]. similarly promising results were reported by Cho et al. in a histological and histomorphometric study on rabbits, where the coating of anodized implant surfaces with a solution of poly(D,l- lactide-co-glycolide) PlGA and 1 α ,25- dihydroxyvitamin D3 (1 α ,25-(OH)2D3) stimulated the apposition of new bone on fixtures [31]. Finally, in a further experimental work in rabbits, implants with a surface coated in 1,25-(OH)2D3 have shown an improved tendency to osseointegrate compared to non-coated implants; however, this difference was not statistically significant [32]. unfortunately, very few clinical studies have so far investigated the effects of vitamin D deficiency on lInICal