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

To evaluate the remineralization ability of two endodontic sealer cements.

Mid-coronal dentine surfaces were subjected to: (i) 37% phosphoric acid (PA) or (ii) 0.5 mol L^-1 ethylenediaminetetraacetic acid (EDTA) conditioning prior to the application of two experimental hydroxyapatite-based cements, containing sodium hydroxide (calcypatite) or zinc oxide oxiapatite respectively. Samples were stored in simulated body fluid for 24 h or 21 days. Remineralization of the dentine surfaces were studied by Raman spectroscopy (mapping with K-means cluster and hierarchical cluster analysis) was undertaken. Nanoroughness and collagen fibril width measurements were performed with an atomic force microscopy. ANOVA and Student-Newman-Keuls test were performed (α=0.05).

Phosphoric acid+oxiapatite promoted both the highest dentine mineralization (P < 0.05) and crystallographic maturity at the dentine surface. Noncrystalline amorphous-like apatites were also formed. Dentine treated with PA+calcypatite attained the roughest surface (P < 0.05) with minimal fibril width (P < 0.05). Cross-linking of collagen only became greater in the group PA+oxiapatite after 21 days. The maximum relative mineral concentration and structure of collagen linked to the amide I and ratio amide III/AGEs was obtained after using PA+calcypatite at 21-days time-point (P < 0.05). EDTA produced a lower stoichiometric hydroxyapatite (P < 0.05) with decreased maturity, at the expense of carbonate band widening, although it favoured the nucleation of carbonated calcium phosphate.

Dentine surfaces treated with PA+oxiapatite attained the highest dentine remineralization with both crystalline-stoichiometric and amorphous apatites, at 21 days. EDTA conditioning facilitated amorphous-bulk mineral precipitation. The amorphization was more intense after using oxiapatite and provided an ion-rich environment favouring in situ dentine remineralization.