The effect of prism orientation on the indentation testing of human molar enamel

Abstract

Recent nanoindentation studies have demonstrated that the hardness and Young's modulus of human molar enamel decreases by more than 50% on moving from the occlusal surface to the dentin-enamel junction on cross-sectional samples. Possible sources of these variations are changes in local chemistry, microstructure, and prism orientation. This study investigates the latter source by performing nanoindentation tests at two different orientations relative to the hydroxyapatite prisms: parallel and perpendicular. A single sample volume was tested in order to maintain a constant chemistry and microstructure. The resulting data show very small differences between the two orientations for both hardness and Young's modulus. The 1.5 to 3.0% difference is significantly less than the standard deviations found within the data set. Thus, the variations in hardness and Young's modulus on cross-sectional samples of human molar are attributed to changes in local chemistry (varying levels of mineralization, organic matter, and water content) and changes in microstructure (varying volume fractions of inorganic crystals and organic matrix). The impact of prism orientation on mechanical properties measured by nanoindentation appears to be minimal.

Spatial distribution of the human enamel fracture toughness with aging

“…The use of AFM provided a convenient in situ observation of the indentation, which allowed us to improve the reliability of the data based on the indentation morphology. The mean values of the elastic modulus and the hardness and their aging-and location-induced changes were consistent with previous investigations (Cuy et al, 2002;Braly et al, 2007;Park et al, 2008b).…”

Effect of indentation load and time on knoop and vickers microhardness tests for enamel and dentin

“…The standard deviation of hardness in this study showed a broad variation, similar to previous reports 16 . This broad variation of hardness values can be produced by factors such as specimen preparation, diagonal length reading error 16 , variation in chemical composition 20 , age, and location in the tooth 21 . In this study, the KHN and VHN values of enamel are in approximately the same range, while dentin obtained KHN values higher than VHN values for every variation of indentation load and time.…”

Demineralization–remineralization dynamics in teeth and bone

“…X, calcium substitution with metal cation; Y, phosphate substitution with carbonate; and Z, hydroxide substitution with fluoride. [55][56][57] Ca 5 (PO 4 ) 3 (OH)…”