Evaluating the Potential to Remineralize Dentin Using PILP-releasing Dental Cements

Objectives: Recent advances in our understanding of mineralization of collagen fibrils have provided novel methods to reintroduce apatite mineral into firbils, which led to the recovery of mechanical properties of demineralized dentin to values between 60 and 100% of normal dentin modulus and hardness when applied in vitro. The polymer-induced liquid precursor system (PILP) involves the use of a heavily charged polymer, e.g. poly-Aspartic Acid (pAsp) which stabilizes saturated calcium phosphate solutions by the formation of nanoparticles comprised of pAsp surrounded by an ion cloud concentrated in calcium and phosphate. In solution these nanoparticles attach to collagen and release their ion content into the fibrils to subsequently form oriented apatite nanoparticles intrafibrillarly. Here we tested novel cement formulations for their ability to continuously release PILP nanodroplets at the dentin-cement interface and to restore dentin properties for use as a future restorative material with reparative functions.
Methods: Two types of glass-ionomer based cements were used and supplemented with 0, 20 and 40% of pAsp: Product A) Biocem (Nu-Smile Inc.); B) Glass Powder (GP). Effect of pAsp on setting time was evaluated. Cements were applied to artificial dentin lesions with a depth of about 140 um and stored in SBF solutions for up to 14 days. Nanoindentation was applied across the cement-dentin interface to evaluate the ability for remineralization of collagen and to reconstitute dentin properties.
Results: Biocem forms stable cements with the addition of pAsp. GP requires 40% of pAsp additions to solidify and set as a cement. Nanomechanical profiles indicate that both Biocem and GP remineralize dentin collagen as indicated by an increase in modulus from 0.3 to above 4 GPa after 14 days of remineralization.
Conclusions: Additions of pAsp to glass ionomer cements may present a viable approach to remineralize portions of carious lesions and to recover substantial amount of the natural tissue thus conserving tissue and possibly reducing the risk of pulp exposure.