Biomodification of coronal bovine dentin with chitosan solutions associated with modified nano-hydroxyapatite and Biosilicate®.

Objectives: This study aimed to test experimental chitosan-based solutions, with modified nano-hydroxyapatite (n-HA) and Biosilicate as mineral sources with and without L-Aspartic acid (L-Asp) as the polymer-induced liquid-precursor (PILP), on mineral deposition and activity and expression of matrix metalloproteinase (MMP) on demineralized coronal bovine dentin and collagen fiber reinforcement.

Methods: Six chitosan-based experimental gel solutions were used as treatment: Sol1-2 % chitosan; Sol2-2 % chitosan+ 5.5 % n-HA; Sol3-2 % chitosan+ 0.02 % L-Asp+ 5.5 % n-HA; Sol4-2 % chitosan+ 1 % Biosilicate; Sol5-2 % chitosan+ 0.02 % L-Asp+ 1 % Biosilicate; Sol6-2 % chitosan+ 0.02 % L-Asp. Demineralized bovine dentin specimens and collagen fiber were treated for 5 min and immersed in artificial saliva for 14 days. Dentin fragments were analyzed to determine their chemical composition with Attenuated total reflectance - Fourier transform infrared spectroscopy (ART-FTIR) and to evaluate the activity and expression of two key gelatinases (MMP-2 and MMP-9) with zymography and immunofluorescence. Dentin slices were used to assess dentin density by transmitted light microscopy. Collagen fiber was tested through microtensile test. Data analysis was performed by ANOVA and Kruskal-Wallis.

Results: Samples treated with Sol1 and Sol3 showed more carbonate after demineralization; and Sol2 and Sol3 presented the highest values of collagen cross-link. The gelatinolytic activity of Sol2 and Sol3 showed statistically similar results to sound dentin (p > 0.05). Sol1, 2, and 4 resulted in a higher mineral density. Sol2, 3, and 6 showed the highest values for tensile strength.

Significance: Therefore, the treatment of demineralized dentin with modified nano-hydroxyapatite resulted in the reinforcement of collagen fiber, mineral deposition in dentin architecture, and the inhibitor of metalloproteinases.