Gadi, Lubabah; (2022) Morphological and Ultrastructural Collagen Defects: Impact and Implications in Dentinogenesis Imperfecta. Doctoral thesis (D.Dent), UCL (University College London).

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Abstract

Abstract of Systematic Review Background: Collagen is the building block for extracellular matrix in bone, teeth and other fibrous tissues. Osteogenesis Imperfecta (OI), or brittle bone disease is a heritable disorder that results from defective collagen type I synthesis or metabolism. The disease manifests as bone fragility that leads to multiple fractures The dental manifestation of OI is Dentinogenesis Imperfecta (DI), a genetic disorder that affects tooth structure and clinical appearance with characteristic greyish-brown discolouration. Management of Dentinogenesis Imperfecta can be difficult. Therefore, understanding the ultrastructural defects in dentinal tissues is of clinical importance. Thus, the aim of the project was to answer the question of what the changes in dentinal collagen macro, micro and ultrastructure in Dentinogenesis Imperfecta. Methods: Three data bases were searched for relevant articles: OVID Embase, OVID Medline, and PubMed Medline. Inclusion criteria were any study, written in English, published after 1990, that examined human dentinal collagen of teeth affected by DI. No exclusions were made by study design or examination protocol. A Cochrane data extraction form was modified to fit project aims and used for data collection. Results: The final dataset of the systematic review included seventeen studies. The most prevalent findings on collagen in DI teeth were increased coarse collagen fibres, and decreased fibres quantity. Other findings included random to parallel fibres orientation and irregular organization. Ultrastructural defects were uncoiled collagen fibres and increased spread of D-banding periodicity. Conclusion: Studies in collagen structure in DI reported changes to the surface topography, quantity, organisation, and orientation of the fibres. Moreover, ultrastructural defects such as the packing/coiling and D-banding of the fibrils, as well as differences in the presence of other collagens are also noted. Taken together, this study provides an understanding of the changes in collagen and its impact on clinical translation, paving the way for innovative treatments in dental management.   Abstract of Scoping Review Background: Dentinogenesis imperfecta is known to affect dental tissues, which is mainly reported to be dentin since it is the most dental tissue abundant. Deformed collagen, abnormal dentinal tubules and reduced mechanical strength are criteria well reported on by studies. In less abundance, enamel has also been described as abnormal, defects as irregularly shaped enamel lamellae and reduced mechanical strength have been described. Cementum, nonetheless, is not a common tissue type to be examined when looking for the effects of this genetic disease. The aim of this scoping review is to identify the effect of dentinogenesis imperfecta on cementum, if present and clarify extent of periodontal involvement in DI patients. Methods: The database of PubMed was searched. Search strategies developed, concepts were: collagen ultrastructure, DI and OI. Inclusion criteria were human or animal studies, of any primary or permanent teeth, affected with dentinogenesis imperfecta, isolated or syndromic DI type, that examined cementum defects. No limitations were applied on study type, date of publication, sample size, age or gender of subjects, nor species in case of animal studies. No restrictions applied on methodology of study as demineralization protocol or examination method. Results: six studies were retrieved, four human and two animal studies. Isolated DI was examined in 3 of which, the observations found were hypomineralized cementum, that is generally hypoplastic but with an increase in cellular cementum in the certain regions. The two papers examining syndromic DI cementum had inconsistent results. Conclusion: cementum defects of isolated DI were reported with consistent results, unlike syndromic DI, this can be because the function and defects of Dentin Sialophosphoprotein (DSPP) are further known than the defects in collagen of DI teeth. The evidence on cementum defects was scarce. The limited number of studies could reflect the limited periodontal involvement in DI patients hence the low clinical importance. From this scoping review we speculate the presence of cementum defects yet on a subclinical level.

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