Impact of deproteinization methods on the physical and mechanical properties of dentin

This study was performed to evaluate the effects of thermal and chemical deproteinization methods on the micro-hardness and mineral phases of human dentin. Forty extracted non-carious human premolars were cut from below the cementoenamel junction to prepare 5 mm-thick dentin slices, and then randomly divided into four groups of 10 in each according to the treatments. Group A: thermal treatment (300 degrees C, rate of 30 degrees C /min for 10 min); Group B: 50 ml of 1N NaOH; Group C: 50 ml of 30% H2O2, at 37 degrees C for 7 days; Group D: control. Dry ash was obtained to measure the mass loss of organic content. The microhardness value (MHV) of the exposed root dentin was tested with a Vickers microhardness tester. The structure of the residual dentin mineral was examined using a SEM. Crystallinity was assessed by X-ray diffraction spectroscopy. Data were analyzed with one-way ANOVA and Post Hoc Tukey tests. In the comparison of microhardness values between heat, NaOH, H2O2, and control groups, significant differences were noticed between groups (P < 0.05). Since the organic component was largely removed, it can be seen that the main influence on the hardness of dentin could be the inorganic component rather than the protein content. Thermal treatment was able to completely deproteinize human dentin without significant effects on its physical and mechanical properties, while chemical deproteinization significantly changed the mechanical properties and crystallography of human dentin (P < 0.05).