Effect of phosphorylated chitosan and carbodiimide on the surface wettability, surface free energy and surface morphology of the eroded dentin

Abstract

Background. Biomodifiers can reinforce the collagen matrix, improving the biomechanical and bio-chemical properties of dentin. Objectives. The present study aimed to evaluate how 2.5% phosphorylated chitosan (P-Chi) and 0.5 mol/L carbodiimide (EDC) affect the surface wettability, surface free energy and surface morphology of the eroded dentin. Material and methods. Bovine tooth specimens (N = 144) were randomly divided into 6 groups according to the dentin substrate (sound or eroded) and surface treatment (2.5% P-Chi, 0.5 mol/L EDC or no biomodification (control)). Half of the specimens (n = 72) were submitted to erosive challenge by immersion in 0.3% citric acid (pH 3.2) for 2 h. For the surface wettability analysis (n = 12), the contact angles between the dentin surface and the 3M™ Scotchbond™ Universal adhesive were measured with a goniometer. For the surface free energy analysis (n = 3), the contact angles between the dentin surface and 3 organic solvents of distinct polarities (water, formamide and diiodomethane) were recorded. Surface morphology (n = 3) was analyzed with the use of scanning electron microscopy (SEM). The data was statistically analyzed using the two-way analysis of variance (ANOVA) (α = 0.05). Results. Neither 2.5% P-Chi nor 0.5 mol/L EDC influenced the dentin surface wettability (p > 0.05). Surface free energy decreased in the eroded substrate after biomodification with EDC (p < 0.05). Biomodification with P-Chi demineralized the dentin surface and increased the dentin tubule embouchure. Conclusions. It can be concluded that 2.5% P-Chi and 0.5 mol/L EDC did not impact the surface wettability of the eroded dentin. However, EDC promoted lower surface free energy, while P-Chi altered surface morphology, causing demineralization and the opening of dentin tubules.