Correlating the mechanical properties to the mineral content of carious dentine--a comparative study using an ultra-micro indentation system (UMIS) and SEM-BSE signals.

The deterioration of the mechanical properties of carious dentine was assumed to be associated with the decrease in mineral content due to the carious process. This study aimed to compare the mechanical properties of carious dentine studied by an ultra-micro-indentation-system (UMIS) and the mineral content determined using backscattered scanning electron (BSE) imaging. Eight axial sectioned and fine polished primary molar teeth with untreated carious dentine were measured for hardness and elastic modulus using the UMIS. On each specimen two centrally located linear arrays of indentations were made from the pulp to lesion cavity floor, followed by the capture of a BSE image using a solid-state detector. The BSE intensity at the same spot as the indentation array on each specimen was analysed and compared to the UMIS results. The results show that the mechanical properties of dentine are dependent on its mineral content. The decrease in mechanical properties of carious dentine, namely hardness and elastic modulus are directly linked to the reduction in its mineral content (r2 = 0.93 and 0.92, respectively). The relationship between dentine hardness and elastic modulus values (y) can be expressed as an exponential function of the mineral content in wt.% (x) that is y = ae(bx).