The tooth: An analogue for biomimetic materials design and processing

Objective. Overview the development of human tooth; enamel, dentoenamel junction and dentin in regard to hierarchical structure property relationships and how these component structures can serve as templates for the design of tough materials. Methods. The dental, engineering and ceramic literature (PubMed, Science Direct, Google Scholar) covering the last 20 years was over viewed regarding enamel and dentin characterization, structure -property studies, as well as, publications related to bioinspired materials with relationship to tooth structure. Relevant publications were selected for inclusion. Results. Enamel has been studied and modelled at 3 hierarchical levels, prism structure, parallel prism interactions and enamel decussation effects. Missing is a 4th level where the previous three hierarchies are combined with the 3D arrangement of these levels in enamel areas. Aspects of the enamel prism infrastructure and prism decussation have been used in 3D printing of Bouligand ceramic structures. The dento-enamel junction serves to arrest cracks and reduce the stress in enamel as a graded elastic modulus layer, leading to development of dental ceramics with increased strength and fatigue resistance. Dentin is a compliant structure that supports enamel mechanically and may, through providing interstitial fluid at the DEJ, allow repair of microcracks in enamel. Adequate models of dentin properties remain to be developed as it remains highly variable in tubule lumen size and the degree of mineral density around and between tubules. Significance. The structure of teeth, particularly the 4 hierarchical levels of enamel, creates a vital, hard, tough damage tolerant system for inspiring new materials. (C) 2019 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.