Dentin Induction Assessment of a Ca-PO4 Containing Bonding Agent

A bonding agent (CP-BA), containing calcium phosphates, the acidic monomer PMGDM, HEMA and acetone has been developed. CP-BA was designed for the remineralization of mineral-deprived dentin surfaces after acid-etching performed during bonding procedures. CP-Ba could also be applied on pulp exposures to improve the remineralization from a resin-based Ca-PO₄ pulp capping cement, which had been compromised by a bonding agent barrier.

  Objective: To determine the potential of CP-BA for reparative dentin formation using a novel in vitro dentin induction assay assessing dentin sialophosphoprotein (DSPP) promoter activity. Methods: Stably transfected odontoblasts (MO6-G3 cells) containing mouse 2.6kbDSPP promoter luciferase (Luc) contruct (J Dent Res 83(Spec Iss A):3047, 2004) were exposed to crushed or leached acetone-free CP-BA specimens (a-MEM media) and material components (HEMA & PMGDM/HEMA) in DMSO  ranging from 1:10 to 1:1000 or 0.5x10^-4 to 0.5x10^-6 mol/L, respectively. Cells were plated, grown in a-MEM with 10% FCS, antibiotics, and 50 mg/mL ascorbic acid in 95% air and 5% CO₂, and test compounds added.   After 24 h cells were lysed, centrifuged and Luc activity measured normalized by protein concentrations. The data were analyzed using a regression curve and the accuracy determined by the variance of regression.  Results: The data indicated that all tested components stimulated dentin induction as determined by Luc activity increase.  Compared to the background activity, the leached samples, at all concentration tested, stimulated DSPP promoter activity to the highest extent ranging from 3 to 4 fold.  PMGDM and the crushed acetone-free set CP-BA were also capable of stimulating DSPP promoter activity at the lower concentrations tested. Conclusions: CP-BA and its components have beneficial dentin induction properties partly attributed to the inductive properties of PMGDM. These data are in agreement with preliminary in vivo pulp-capping results showing that 45 % of CP-BA-treated teeth had dentin bridges. Support: NIDCR-DE13298, ADAF, and NIST.