Impact of solutions and storage time on the chemical and mechanical properties of human dentin.

Abstract

Background: Considering the importance of standardization of the pH of control solutions and its impact on the chemical composition and mechanical properties of dentin during storage over a specified period, this study aimed to analyze the pH of control solutions and how it affects the chemical composition and mechanical properties of dentin stored over a given period.

Material and methods: Six control solutions-coconut water, mineral water, distilled water, deionized water, artificial tears, and saline-were kept in a bacteriological incubator at 37°C, with their pH measured using a pH meter (mPA-210 from MS Tecnopon ®) for seven days: T0 (initial), T1 (2 hours), T2 (24 hours), T3 (48 hours), and T4 (7 days). In the second phase, the two solutions with the most stable pH in the first phase were selected and aligned with the critical pH of dentin (pH ≥ 6.5). Human third molars were sectioned and divided into two groups (n=13): distilled water and deionized water. The pH of the solutions, the chemical composition, and the microhardness of the dentin were evaluated by pH meter, Fourier transform infrared spectroscopy (FTIR), and Knoop microhardness (KH), respectively, at the aforementioned time points. The values were analyzed by two-way ANOVA (storage time and solution), followed by the Tukey test.

Results: Both solutions presented pH incompatible with the dentin until T2, and the samples presented a 40% reduction in microhardness at T4. Additionally, a reduction in carbonate and an increase in amides were observed in the dentin, indicating changes in the mineral and organic phases.

Conclusions: It is concluded that both the solutions and the storage time negatively affect the chemical composition and microhardness of the dentin, highlighting the importance of carefully selecting the control solutions and the storage time in in vitro studies. Key words:Dentin, hardness, FTIR, pH, storage solution.