A zinc oxide-modified hydroxyapatite-based cement facilitated new crystalline-stoichiometric and amorphous apatite precipitation on dentine.

Abstract

Aim: To evaluate the remineralization ability of two dentin canal sealer cements. Methodology: Dentin surfaces were subjected to: i) 37% phosphoric acid (PA) or ii) 0.5 M ethylenediaminetetraacetic acid (EDTA) conditioning prior to the application of two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide (oxipatite), respectively. Samples were stored in simulated body fluid during 24 h or 21 d. Remineralization of the dentin surfaces were studied by Raman spectroscopy, mapping with K-means cluster and hierarchical cluster analysis were done. Nano-roughness and collagen fibrils width measurements were performed by means of an atomic force microscopy. Results: PA+oxipatite promoted both the highest dentin mineralization and crystallographic maturity at the dentin surface. Non-crystalline amorphous-like apatites were also formed. Dentin treated with PA+calcypatite attained the roughest surface with minimal fibril width. Crosslinking of collagen only raised in the group PA+oxipatite, after 21 d. The maximum relative mineral concentration and structure of collagen referred to amide I and ratio amide III/AGEs was achieved after using PA+calcypatite at 21 d time point. EDTA produced a lower stoichiometric hydroxyapatite with decreased maturity, at the expense of the carbonate band widening, though it favored the nucleation of carbonated calcium phosphate. Conclusions: Surfaces treated with PA+oxipatite attained the highest dentin remineralization with both crystalline-stoichiometric and amorphous apatites, at long term. EDTA conditioning facilitated amorphous-bulk mineral precipitation. This amorphization, more intense after using oxipatite, provided an ion-rich environment favoring in situ dentin remineralization.