Spatial distribution of the human enamel fracture toughness with aging

Abstract

Enamel AgingMineral content a b s t r a c t A better understanding of the fracture toughness (KIC) of human enamel and the changes induced by aging is important for the clinical treatment of teeth cracks and fractures. We conducted microindentation tests and chemical content measurements on molar teeth from "young" (18≤age≤25) and "old" (55≤age) patients. The KIC and the mineral contents (calcium and phosphorus) in the outer, the middle, and the inner enamel layers within the cuspal and the intercuspal regions of the crown were measured through the Vickers toughness test and Energy Dispersive X-Ray Spectroscopy (EDS), respectively. The elastic modulus used for the KIC calculation was measured through atomic force microscope (AFM)-based nanoindentation tests. In the outer enamel layer, two direction-specific values of the KIC were calculated separately (direction I, crack running parallel to the occlusal surface; direction II, perpendicular to direction I). The mean KIC of the outer enamel layer was lower than that of the internal layers (po0.05). No other region-related differences in the mechanical properties were found in both groups. In the outer enamel layer, old enamel has a lower KIC, II and higher mineral contents than young enamel (po0.05). The enamel surface becomes more prone to cracks with aging partly due to the reduction in the interprismatic organic matrix observed with the maturation of enamel.

Enamel organic matrix: potential structural role in enamel and relationship to residual basement membrane constituents at the dentin enamel junction

“…Specifically, when fracture toughness and crack growth were measured, the inner enamel closer to the DEJ was found to be tougher and to resist crack propagation more than outer enamel (18,19). A positive contribution by the EOM was shown by a reduction in fracture toughness after its removal or alteration (20,21).…”

Enamel microcracks in terms of orthodontic treatment: A novel method for their detection and evaluation

“…Obtained findings indicated that the teeth having EMCs from the older age group possessed higher width and length values compared with the younger one. Aging and the related changes in the mechanical properties of human enamel (increase in hardness, elastic modulus, brittleness, and decrease in fracture toughness with age) might explain the aforementioned difference 25,29,30) . Further analysis revealed that following debonding width and length of all EMCs increased.…”

Dynamic finite element analysis and moving particle simulation of human enamel on a microscale

“…While there were differences between FEA and MPS results in terms of oscillations resulting from the two different approaches as described by Eqs. (15) and (16) for discretization of the continuum model in Eq. (1), the trends observed were remarkably similar for most of the parameters evaluated.…”

“…Recently, the MPS has been extended to the non-linear elastodynamics of compressible and incompressible materials such as viscosity in enamel [14]. When compared with FEA, MPS has the distinct advantage of being a mesh free model, which is more suited to deformation analysis and to simulation of complex material properties such as interprismatic organic matrix of enamel [15]. A current limitations of the MPS method is that to date there have been no systematic comparative studies with FEA.…”