Vitamin D deficiency is known to affect many people and diseases. Even in the biggest pandemic of recent years, Vitamin D deficiency is thought to be associated with COVID-19 disease because of its effects on both innate and adaptive immunity and studies have been conducted on this issue [21, 22]. Another important role of vitamin D is maintaining bone strength and mineral balance. Vitamin D deficiency can cause rickets, osteomalacia, and an increased incidence of bone fracture. If calcium absorption from the intestine is insufficient, PTH and 1,25(OH)2D3 can stimulate osteoclastogenesis. Thus, there is a transition of calcium from bone to blood [1, 8, 9].
In this type of studies examiner reproducibility is needed for the results to be more reliable and interpretable. Therefore, all the measurements performed by the same radiologist at different times and high intra-observer agreement was observed.
There are several studies about the methods for analyzing the bone in terms of qualitative and quantitative parameters in dentistry [23,24,25,26,27,28,29,30,31,32,33]. In a study by Alman et al. [30] it was reported that FD analysis performed in the mandibular regions has a good diagnostic ability to detect patients with low bone mineral density. Also in another study, Magat et al.[34] evaluated FD analysis using both CBCT and panoramic radiography. They suggested that since CBCT has higher radiation dose and lower image resolution, panoramic radiography is more advantageous for the examination of trabecular bone. In the literature, there are also many studies that panoramic morphometric indices were used successfully to deduce possible disease or drug-related osteoporotic conditions in craniofacial bones [31, 35].
According to our knowledge, this study is the first to quantify radiomorphometric indices and analyze FD on panoramic radiographs in patients with vitamin D deficiency.
Demiralp et al.[33] reported that FD values were higher in patients using bisphosphonates. This may be due to decreased bone resorption in people using bisphosphonates. In some studies FD values were found to be lower in patients with chronic renal failure [32], thalassemia major [36], sickle cell anemia [37] compared to patients in the control group. According to the study of Ustaoglu et al., lower FD values were reported in the regions of subcortical area in condyle, supracortical area above angulus, and above the mandibular canal distal side to the second premolar in patients with antiepileptic drug-induced osteoporosis [12]. The study reported by Göller et al. found that mean FD value of mandible and value of supracortical area above angulus and anterior mental foramen was significantly lower in patients using aromatase inhibitors [38]. In a study conducted by Coşgunarslan et al., the FD values of ramus and angulus mandible were significantly lower in patients using selective serotonin reuptake inhibitors (SSRIs). There was no significant difference between the study and control groups for the mean FD value of mandibular cortical bone [10]. Contraversely in another study conducted on women with celiac disease by Neves et al. [39], no statistically significant difference was found in FD value between the study and control groups. In the present study, the mean FD value and and FD2 value were lower in the groups with vitamin D deficiency and it was statistically significant (p < 0.05). This supports the view that vitamin D deficiency causes a decrease in bone mineral density and increases alveolar porosity.
In the literature, there are many studies investigating bone mineral density with panoramic radiography by MCI, MCW, PMI [13, 19, 31,32,33, 40,41,42]. According to the results of the studies, the MCW value was found to be lower in patients with osteoporosis [17, 32, 41, 43, 44]. In our study, we used the new radiomorphometric indices used by Barra et al.[18] instead of MCW. According to the results of our study, there was no difference in CTM values between the groups (p > 0.05). Barra et al.[18] reported that the MI and PI indices in CBCT can be used to determining low bone mineral density in postmenopausal women.
In the literature there are studies that found no difference in PMI in the control and study groups [10, 11, 36, 39], as well as studies that found that the PMI was higher in the control group compared to the study group [12, 38]. In the present study the PMI value in Group 1 was higher than the others.and there was a statistically significant difference between the groups (p < 0.05).
In our study, there was a significant difference in MCI between the groups. (p < 0.05). Similarly, Cakur et al. reported that MCI is significantly related to vertebral bone mineral density in osteoporotic women [45]. Also in another study among postmenapausal women with osteoporosis, Klemetti et al. found that MCI is strongly associated with buccal cortex bone mineral density [24]. Contraversely in some studies that evaluates MCI, there was no difference between the groups [11, 12, 36, 38].
Vitamin D levels have been investigated in some studies regarding the existence of its association with periodontal disease and their results showed that serum levels of vitamin D were significantly lower in patients with periodontitis than those in healthy subjects [46, 47]. Gong et al. concluded that 1,25-Dihydroxyvitamin D deficiency accelerated alveolar bone loss by inhibiting osteoblastic bone formation and enhancing periodontal tissue degeneration in calcium and phosphorus as well as age-independent manner [48]. In addition, poor bone mineralization may be a factor that facilitate the destruction in periodontal disease. Furthermore, Mangano et al. [15] researched correlation between early implant failure and low serum levels of vitamin D and showed a higher incidence of the implant failure rate. Osteoporotic changes occurred by vitamin D deficiency may be one of the reasons for failure in dental treatment such as implant surgery or periodontal therapy. Vitamin D supplementation may positively affect dental treatment results in those with vitamin D deficiency.
There are some limitations of this study. First one is that since it is a retrospective investigation there were not enough patients for insufficient group with the Vitamin D values between 21 and 29 ng/ml. Therefore, the insufficient group was ommitted from the study. Another limitation is that we studied on only the mandible, new comprehensive investigations can be conducted including maxilla to have more information about the effects of vitamin D deficiency on jaws.
In conclusion; according to results of radiologic examinatinations in present study, Vitamin D deficiency effects the trabeculation, porosity, mineral bone density of mandible. Fractal analyze and the other morphometric indices can be used for evaluating the alveolar structure in panoramic radiographs. To have more detailed information about the effects of vitamin D deficiency on alveolar bone further studies is needed for mandible and maxilla with larger populations.