In the present pilot case-control study in a sample of Puerto Rican adults, periodontitis cases had significantly lower levels of serum 25 (OH) D compared to controls; furthermore, for every unit increase in serum 25 (OH) D levels, the odds of severe and moderate periodontitis was significantly reduced by 12 %. To our knowledge, this is the first study to evaluate the relationship between serum 25 (OH) D levels and periodontal disease in a group of Hispanics. The periodontal status of the cases recruited in this study appears representative of the Puerto Rican population at large, as reported in epidemiological studies [4]. Similarly, the vitamin D status of the controls recruited in the present study matches the previously reported status of much larger Puerto Rican adult population samples [19–21].
Other studies have also found an association between vitamin D status and periodontal disease. In a case-control study on pregnant women, involving 117 cases (clinically moderate to severe periodontitis) and 118 controls (periodontally healthy), cases presented with lower median 25 (OH) D levels (23.6 ng/ml) relative to controls (40 ng/ml; p??0.001) [27]. Pregnant women with periodontal disease were more likely to have serum 25 (OH) D levels 30 ng/ml (65 % of cases versus 29 % of controls; p??0.001); furthermore, pregnant women with 25 (OH) D levels 30 ng/ml had a twofold increase in the odds of moderate to severe periodontal disease (adjusted OR 2.1; 95 % CI 0.99, 4.5). Similarly, a prospective study of 42,730 adults aged 40–75 years participating in the Health Professionals Follow-Up Study and followed for 20 years found that participants in the highest quintile of the predicted 25 (OH) D score had a 20 % lower incidence of tooth loss compared with the lowest quintile of 25 (OH) D score (HR 0.80, 95 % CI 0.76, 0.85; P??0.001) [28]. However, a case-control study of Finnish adults, with 55 cases (chronic periodontitis) and 30 controls (periodontally healthy), did not find an association between 25 (OH) D levels and periodontal health status [29]. This latter study found that participants with low 1,25 (OH) 2D were more likely to be in the case group (OR?=?0.97, 95 % CI?=?0.95-1.00). The lack of association between 25 (OH) D levels and periodontal disease in the Finnish study was attributed in part to the overall lower serum 25 (OH) D levels among study subjects.
Vitamin D insufficiency plays a role in dental (altered formation) and oral bone pathologies (altered formation, periodontal disease and jaw osteonecrosis), the mechanisms of which rely on the specific behavior of oral cells and dental cells, which are responsive to vitamin D [30]. Oral epithelial cells are capable of converting inactive vitamin D to the active form of 25 (OH) D, which has been shown to induce expression of the antimicrobial peptide LL-37 and other host defense mediators [31]. This may represent a mechanism by which vitamin D enhances innate immune defenses against periodontal pathogenic bacteria. In fact, another study found that optimal ranges of serum vitamin D may reduce susceptibility to gingival inflammation and that gingivitis may be a useful clinical model to evaluate the anti-inflammatory effects of vitamin D [5]. This finding was supported by the results of a more recent randomized clinical trial, which showed that vitamin D has a dose-dependent anti-inflammatory effect on gingivitis [32]. Furthermore, vitamin D may also reduce periodontal disease through its general anti-inflammatory and immunomodulatory effects [33, 34].
Study limitations and strengths should be taken into consideration when interpreting the reported results. Sample size and lack of inclusion of other confounders (e.g., socio-economic status and physical activity) are two of the study limitations. Nevertheless, all participants were recruited from the university external outpatient clinics, a service provided at a lower cost to the community, thereby ensuring a homogenous sample with similar socio-economic status. In terms of study strengths, the same selection process was used to recruit both cases and controls, while periodontal status of all participants was assessed by a NIDCR-calibrated dentist. In addition, we used serum 25 (OH) D levels to assess vitamin D status, which reflects both dietary intake and sun exposure, and these were measured in the same laboratory with identical methodology.