Harith, NSB; (2013) Dentinal Ultrastructure In Osteogenesis Imperfecta and Dentinogenesis Imperfecta. Doctoral thesis , UCL (University College London).

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Abstract

Osteogenesis Imperfecta (OI) associated with Dentinogenesis Imperfecta, type I (DI) is a rare genetic condition, where mutations of COL1A1 and COL1A2 genes result in variations of the collagen α-chains. The collagen fibrils are expected to be abnormally thin. These alterations have been shown to affect the bones, but have not yet been elucidated in the dentinal collagen. Objectives: Evaluation of demineralisation protocols to expose dentinal collagen for permanent and primary teeth and to characterise the morphology of dentinal collagen ultrastructure in primary DI type I using Atomic Force Microscopy (AFM). Methods: Primary (6) and permanent (6) control teeth plus one DI type I primary tooth have been used.To reveal the dentinal collagen structure, four demineralisation approaches have been evaluated: 1) two blocks of dentine were treated with 10 vol% citric acid for 15seconds and 6.5 vol% NaOCLaq for 120s; 2) dentine blocks treated with commercial etchant and 6.5 vol% NaOCLaq. These demineralised dentine were characterized using Raman spectrocopy and AFM ; 3) teeth demineralised in 17% Ethylenediaminetetraacetic acid (EDTA) for 12 months before being histology sectioned and stained with Picrosirius red; and 4) dentine block was treated with 17% EDTA for 10 minutes. Both demineralised samples were characterised using scanning electron microscopy (SEM). Results: All demineralisation protocols achieved partial or complete demineralisation of the dentine. Demineralisation with commercial etchant and NaOCI produced visibly defined collagen fibrils in primary and permanent teeth. A shorter time was sufficient for demineralisation in primary teeth. In OI associated DI primary tooth; AFM images revealed an area of thickened dentinal collagen fibrils that distributed at only one a direction with a wide distribution of D-banding distance, suggesting less regular banding pattern. Conclusion: The difference in dentinal collagen fibril arrangement and D-banding distance in the affected primary tooth may lead explain the altered mineralization.

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