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Title: Collagen ultrastructure in primary teeth affected with Osteogenesis Imperfecta and Dentinogenesis Imperfecta
Author: Shinawi, Albatool M. J.
ISNI:       0000 0004 7228 5295
Awarding Body: UCL (University College London)
Current Institution: University College London (University of London)
Date of Award: 2017
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The main organic component in dentine is collagen type I, which provides mechanical support and strength. Any cross-linking or genetic mutations occurring during collagen formation can cause incorrect collagen fibril formation. Osteogenesis Imperfecta associated with Dentinogenesis Imperfecta (DI type I) and Dentinogenesis Imperfecta in teeth alone (DI type II) are genetic disorders which may affect the ultrastructure of dentinal collagen fibrils. Very little is known about the possible changes in collagen ultrastructure and impact on physical properties of dentine, particularly in primary teeth. Aim: Identify the ultrastructure and investigate the mechanical properties of dentinal collagen; 1. Measurement of bulk dentine hardness. 2. Exposure of collagen by applying a demineralisation protocol. 3. Investigation of the differences in collagen ultrastructure between DI types I&II and control primary teeth. Methods: Primary teeth were categorized in three groups with five teeth per group: Control, DI type I and DI type II. Samples were sectioned and the median hardness was measured by Wallace Indenter and calculated. Samples were prepared using a demineralisation with different agents and deproteinisation techniques in each group; 37% Phosphoric acid for 15 seconds, then 6.5% Sodium Hypochlorite for 5 seconds, and 17% EDTA for 30 minutes to expose collagen networks. Fourier Transform Spectroscopy (FTIR) was used to analyse demineralisation. Exposed collagen fibril ultrastructure was characterised by using Scanning electron microscopy (SEM) and Atomic force microscopy (AFM). Results: Dentine hardness value significantly decreased in DI types I and II compared to the control group (P ≤ 0.0001). FTIR showed phosphate peak reduction and amide I peak intensification after demineralisation in all groups with Phosphoric acid, indicating effective demineralisation. In control teeth, fibrils were exposed with uniform arrangement and collagen D-band periodicity was homogenous. In DI type I, collagen fibrils were identified but D-banding periodicity was not clearly visible. The collagen fibrils in DI type II were difficult to identify, due to smear layer formation subsequent to demineralisation. Demineralisation with EDTA was performed on both DI teeth groups to expose collagen ultrastructure. Collagen fibrils were identified but D-banding periodicity was not clearly visible. Both DI types collagen fibrils demonstrated local swellings in multiple areas. Conclusion: There was a significant difference in dentine hardness between control and DI primary teeth (P ≤ 0.0001). On a microscopic level there were differences in collagen structure between the three groups.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available