Experimental studies on the nature of property gradients in the human dentine

Abstract

We conducted an investigation into the nature of dentine mineralization and mechanical property gradients with the aid of experimental techniques such as the fluoroscopic X-ray microanalysis and instrumented microindentation, respectively. It was found that the tooth adapts to a complex structure with significant gradients in properties. We observed a significant correlation between the degree of mineralization within the dentine and the mechanical properties. The natural gradation in mechanical properties is explained by the stress analysis within anatomical-sized tooth specimens done using digital photoelasticity. These results are explained within the context of the functional requirements that are imposed on the tooth. This study highlights tooth structure as a biologically adapted, functionally graded material.

Stress distributions in human teeth modeled with a natural graded material distribution

“…(3), which was derived from pure HA tablets, can still be applied without corrections for the organic matrix and water content for converting the attenuation coefficient of dentin into the corresponding elastic modulus. The results showed that the distribution of elastic modulus in the dentin followed a similar trend to that in enamel, where the outer dentin was harder than the inner dentin, as found in previous studies [6,23,26].…”

“…Fong et al [5] also reported that the nanohardness across the DEJ gradually decreased from 4.8 GPa to 0.8 GPa, with the elastic modulus following a similar profile. Kishen et al [6] found a significant correlation among the mineral density, hardness and elastic modulus in human dentin using fluoroscopic X-ray imaging and microindentation. Their results showed that the hardness and elastic modulus of root dentin increased gradually from the central region to the outer surface of the root.…”

“…Moreover, Cuy et al [10] found that the lingual cusp (the one that is chiefly responsible for breaking down food) of a maxillary molar had a thicker, stiffer layer of enamel. Therefore, researchers have hypothesized that the graded distribution of mechanical property within human teeth was developed to adapt to their particular functional needs [6,10]. The following example further demonstrates that tooth structures are optimized for the mechanical loads that they sustain.…”

“…The following example further demonstrates that tooth structures are optimized for the mechanical loads that they sustain. A digital photoelastic analysis showed high concentration of bending stresses in the cervical region of a mandibular incisor [6]. It was found that this region of high stress concentration also had higher mineral density, hardness and elastic modulus.…”

Laboratory validation of a new gas-enhanced dentine liquid permeation evaluation system

“…The unique tubular structure of dentine is mainly related to evolutionar functional adaptation to enable mastication by transducing bite pressures into tensile forces in the collagen matrix [1]. In addition, fluid-filled dentinal tubules allow for transducing stimuli to the underlying pulp [2].…”