Application of the instrumented indentation method in vitro for determining the basic physico-mechanical properties of natural tooth hard tissues

OBJECTIVE: The aim of the study was to determine the physical and mechanical properties of dental hard tissues, enamel, and dentin, in vitro. MATERIALS AND METHODS: The study material consisted of premolars extracted for medical reasons, pre-sawn in half in the sagittal (longitudinal) direction, followed by fixation in a plastic block and polishing to a mirror shine to obtain sections containing enamel, dentin, and the dentinoenamel junction area. The study method consisted of testing the prepared tooth sections by nanoindentation using a NaNo Hardness Tester with a triangular pyramidal Berkovich indenter. RESULTS: The microhardness and elastic modulus of enamel and dentin, as well as the dentin-enamel junction area, were determined. The displacement indices of the surface layers of dentin and enamel under maximum load and after unloading, determined during indentation, made it possible to determine the elastic properties of the tested dental tissues based on the coefficient of elastic recovery. CONCLUSION: The microhardness, elastic modulus, and elastic recovery coefficient of dentin and enamel obtained as a result of an in vitro study using the nanoindentation method showed good reproducibility of the test results and consistency of the obtained nanoscale indicators with the results of tests on macro-samples using standard methods.