Condylar Bone Quality in Growing Children Is Associated With Genetic Polymorphisms in Genes Involved in Calcium and Phosphate Maintenance

Single nucleotide polymorphisms (SNPs) play a crucial role in regulating vitamin D, parathyroid hormone (PTH), and calcitonin concentrations, which are involved in bone health. Some reports suggested that fractal analysis is useful in the morphometric analysis of the mandible trabecular bone in panoramic radiographs. Therefore, we investigated if SNPs in genes that influence vitamin D, calcitonin, and PTH levels are involved in condylar bone quality during the active growing phase of the mandible. Fractal dimension was obtained from the condyle region of interest (ROI) using panoramic radiographs and used to measure the complexity and the microarchitecture of the bone. Fractal dimension using the box-counting algorithm was then calculated. In order to avoid information bias, a script to automate the commands in the software ImageJ was generated to ensure consistency and minimize the potential for human error during the data analysis process. SNPs in vitamin D receptor (<i>VDR</i>), cytochrome P450 family 27 subfamily B member 1 (<i>CYP27B1</i>), cytochrome P450 family 24 subfamily A member 1 (<i>CYP24A1</i>), vitamin D binding protein (<i>VDBP</i>), SEC23 homolog A (<i>SEC23A</i>), calcitonin receptor (<i>CALCR</i>), and parathyroid hormone (<i>PTH</i>) were analyzed. DNA extracted from saliva was used for genotyping analysis of <i>VDR</i> (rs7975232, rs2228570, and rs1544410), <i>CYP27B1</i> (rs4646536), <i>CYP24A1</i> (rs927650), <i>VDBP</i> (rs4588), <i>SEC23A</i> (rs8018720), <i>CALCR</i> (rs1801197), and <i>PTH</i> (rs6256, rs307247, and rs694). A statistical analysis was performed with an alpha error tolerance of 5%. A total of 100 children were included; 50 (50%) were boys and the age ranged from 5 to 14 years old. Fractal dimensions were compared among genotypes. The GT (mean = 1.20 and standard error = 0.03, <i>p</i> = 0.024) and TT genotypes (mean = 1.16 and standard error = 0.06, <i>p</i> = 0.047) in the gene VDBP (rs4588) presented lower fractal dimension. The GG genotype in SEC23A (rs8018720) (mean = 1.34 and standard error = 0.03, <i>p</i> = 0.011) and the TC genotype in PTH (rs694) showed an increased fractal dimension (mean = 1.29 and standard error = 0.03, <i>p</i> = 0.020). In conclusion, SNPs in VDBP, SEC23A, and PTH encoding genes are associated with mandibular condylar trabecular bone structure in children.