Exposure and characterisation of collagen ultrastructure in primary teeth affected with Osteogenesis Imperfecta and Dentinogenesis Imperfecta

Common genetic diseases associated with collagen abnormalities include Osteogenesis Imperfecta (OI) and Dentinogenesis Imperfecta (DI). Whilst the effects of collagen abnormalities in OI are fairly well-known in bone, there is limited information regarding their effects on dentine. This study aims to characterise the microstructure of dentinal collagen, using Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) in DI, OI and control primary teeth. The main aim of this study was first to develop a demineralisation protocol to systematically expose dentinal collagen whilst preventing its degradation. Then, topological assessment of the collagen scaffold at the nano scale level and comparison of characteristic morphological markers was done. Sample-specific demineralisation protocols were developed using a combination of 37% phosphoric acid and 6.5% Sodium Hypochlorite to expose the dentinal collagen. The protocol effectiveness was evaluated using Fourier Transform Spectroscopy (FTIR) and Raman spectroscopy. (AFM) and (SEM) images of exposed dentinal collagen were collected, analysed, and compared to identify specific ultrastructural markers. Dentine sections of 4 control, DI type I (DI associated with OI), and DI type II primary teeth were examined under ethical approval. Dentine in both DI type I and type II samples showed significantly less numbers of dentinal tubules with varying shape and size. Unlike control samples, irregular collagen mesh-network arrangements with inconsistent fibril diameter, local swelling, and abrupt discontinuity were noted. These observations may explain poor dentine quality and adhesion difficulties. In conclusion, it was hypothesised that the interpretation of results and the identification of specific OI/DI markers will guide us into better understanding of the nature and management of these rare conditions