Effects Of Active Vitamin D Deficiency And Subsequent Alterations Of Milk Contents On Tooth And Mandible Development

Effects of Active Vitamin D Deficiency and Subsequent Alterations of Milk Contents on Tooth and Mandible DevelopmentMaster degree candidate: Qian WangSupervisor: Professor Dengshun MiaoObjectives: To determine whether effects of active vitamin D deficiency and subsequent alterations of milk contents on tooth and mandible development in sucking pups.Methods: Calcium and 1,25-dihydroxyvitamin D3【1,25(OH)₂D₃】levels were measured in the milk from 25-Dihydroxyvitamin D3 1α-hydroxylase heterozygous [1α(OH)ase^+/-] and homozygous [1α(OH)ase^-/-] dames to assess effect of 1,25(OH)₂D₃ on the milk contents. The phenotypes of teeth and mandibles were compared between 2-week-old 1α(OH)ase^+/- and 1α(OH)ase^-/- pups fed by 1α(OH)ase^+/- and 1α(OH)ase^-/- dames, respectively, by radiography, micto-CT scanning and 3-dimentional reconstruction, histology, histochemistry and immunohistochemistry.Results: Milk calcium levels were decreased in 1α(OH)ase^-/- dames compared to 1α(OH)ase^+/- dames. Dental volume and dental alveolar bone volume in mandibles were reduced in 1α(OH)ase^-/- pups compared to their 1α(OH)ase^+/- littermates, and were also reduced in pups fed by 1α(OH)ase^-/- dames compared to pups fed by 1α(OH)ase^+/- dames, which were the hightest in 1α(OH)ase^+/- pups fed by 1α(OH)ase^+/- dames and were the lowest in 1α(OH)ase^-/- pups fed by 1α(OH)ase^-/- dames. The thickness of predentin and biglycan positive area were increased significantly in the first molars in 1α(OH)ase^-/- pups compared to 1α(OH)ase^+/- pups fed by either 1α(OH)ase^+/- or 1α(OH)ase^-/- dames, and both were increased more dramatically in 1α(OH)ase^+/- and 1α(OH)ase^-/- pups fed by 1α(OH)ase^-/- dames compared to the genotype-macthed pups fed by 1α(OH)ase^+/- dames. The DSP positive area was decreased significantly in the first molars in 1α(OH)ase^-/- pups compared to 1α(OH)ase^+/- pups fed by either 1α(OH)ase^+/- or 1α(OH)ase^-/- dames, and it was decreased more dramatically in 1α(OH)ase^+/- and 1α(OH)ase^-/- pups fed by 1α(OH)ase^-/- dames compared to the genotype-macthed pups fed by 1α(OH)ase^+/- dames. The number and surface of TRAP positive osteoclasts were increased slightly in the dental alveolar bone in 1α(OH)ase^-/- pups compared to 1α(OH)ase^+/- pups fed by either 1α(OH)ase^+/- or 1α(OH)ase^-/- dames, and both were increased significantly in 1α(OH)ase^+/- and 1α(OH)ase^-/- pups fed by 1α(OH)ase^-/- dames compared to the genotype-macthed pups fed by 1α(OH)ase^+/- dames. Conclusion: Active vitamin D and high milk calcium intake each stimulates mineralization and development of teeth and mandibles and have cooperative action.