Gene And Histomorphological Analysis Of 1 Case Of Dentinogenesis Imperfecta-Ⅰ

BackgroundDentinogenesis imperfecta（DGI）is a rare autosomal dominant genetic disorder,which can be classified into type I,II and III according to Shields classification.Among them,DGI-II and DGI-III only involve teeth,while DGI-I is a hereditary dentinogenesis imperfecta with osteogenesis,mainly caused by type I collagen gene mutation,but the specific pathogenesis has not been clarified.In this study,we identified the pathogenic genes of a family with DGI-I and analyzed the genetic data and histological structure of DGI teeth,to provide clues for the study of gene and histomorphological characteristics of dentinogenesis imperfecta.Methods（1）Gene testing: After the informed consent was signed,the information of the family was collected and the genetic map of the family was drawn.Peripheral blood was collected for gene detection.（2）DGI teeth and two normal teeth were observed using micro-CT,light microscopy,field emission scanning electron microscope（SEM）and energy dispersive spectrometry（EDS）.After the samples were processed,the enamel and dentin 0.5 mm away from the enamel-dentin junction（EDJ）were subjected to a load of 0.980 N for 10 seconds with a Vickers microhardness tester to obtain the measurement results.Five microhardness measurements were performed respectively and the average value was taken.Result（1）A heterozygous missense mutation c.1171G>A（p.Gly391Ser）in the related gene COL1A2 of osteogenesis imperfecta type III was identified,and the result of pedigree verification showed that the mutation was originated from her father.（2）Micro-CT analysis showed that DGI-I teeth had normal root length with a single root canal,the pulp cavity was reduced,the root canal became narrow,and the root showed irregular cementum defect and fossa.（3）Atypical scalloped structures of enamel-dentin junction were shown in DGI-I teeth under the light microscope.Scanning electron microscopy showed that the enamel rods and dentin tubules were disordered,and the collagen fibers were thinner.（4）Compared with normal teeth,the atomic percentage of carbon and oxygen increased in DGI-I teeth,while the atomic percentage of calcium and phosphorus and Ca/P ratio decreased.（5）Hardness analysis showed that enamel microhardness of DGI-I teeth was similar to normal,while dentin microhardness was smaller than normal.ConclusionThe gene and histomorphological analysis of the case of dentinogenesis imperfecta-I have expanded the phenotypic spectrum of the disease,which may provide a reference for further genetic and histological studies,and may help to understand the pathogenesis of DGI,and provide theoretical basis for oral treatment in patients with DGI.