Comparison of the mechanical properties of dentin and enamel determined by different nanoindentation techniques: conventional method and continuous stiffness measurement

The obtaining of mechanical properties as elastic modulus and hardness of enamel and dentin has been an important topic of study in material science. Due to the small size of the samples, nanoindentation test becomes an ideal technique for determining the mechanical properties of these structures. Despite numerous studies, there is no agreement on the values of elastic modulus and hardness. The present study analyzes the mechanical properties variability of enamel and dentin for two different bovine teeth by a conventional nanoindentation test. Also, this work compares the elastic modulus and hardness by two different nanoindentation techniques: conventional method (CM) and continuous stiffness measurement method (CSM). Two bovine incisor teeth were extracted, cleaned and stored at 4 degrees C immersed in distilled water during one month. They were transversally sectioned and the crowns were cross-sectioned into 2 mm thick slices, obtaining 6 sections from each tooth. All sections were polished and kept fully hydrated in artificial saliva at room temperature for 24 hours. On each section, CT and CSM nanoindentation tests were carried out to obtain the elastic modulus and hardness of enamel and dentin. Both elastic modulus and hardness decrease as indentation load increases. However differences on mechanical properties values have been obtained depending of the nanoindentation technique applied.