FOCUSED ION BEAM - DIGITAL IMAGE CORRELATION ANALYSIS OF RESIDUAL STRAINS AT THE HUMAN DENTINE-ENAMEL JUNCTION INTERFACE
Tan Sui, Alexander Korsunsky
MBLEM University of Oxford, UK
As a hydrated biological mineral composite, human dental tissue mainly consists of dentine and enamel based on mass and volume, each one of which has a hierarchical structure and versatile mechanical properties. Durable bond between dentine and enamel is provided by the dentine enamel junction (DEJ), an important biological interface that is a lifelong success story: while intact and free from disease, failure in this interface does not occur despite the harsh thermomechanical loading in the oral cavity. It is still not fully clear of the underlying reasons for such remarkable strength and durability from structural and mechanical perspectives. One hypothesis is that a layer of inelastic strain forms adjacent to the DEJ during odontogenesis due to the presence and evolution of residuals tresses. However, significant experimental and interpretational challenges to date have limited any meaningful quantification of residual stress in the vicinity of the DEJ at the appropriate spatial resolution. In this study, a recently developed flexible and versatile method utilizing focused ion beam (FIB) milling with digital image correlation (DIC) is applied to measure the residual elastic strain at (sub)micron-scale. We report the results that span the transition from human dentine to enamel, and incorporate the material lying at and in the vicinity of the DEJ. Link between internal architecture and the residual elastic strain state at the micrometre scale is observed, which is useful for understanding the remarkable performance of the DEJ. This will further help improve or design biomimetic materials for clinical and engineering applications.