Bonding ability of magnesium doped hydroxyapatite based insert with Clearfil dental adhesive

Decayed or damaged tooth structure is widely being repaired with the resin based dental composites (RBCs) in the clinical practice. However, relatively high failure rate and short lifespan are common in the case of the larger posterior teeth restorations, caused by the polymerization shrinkage of RBCs. In order to reduce the polymerization shrinkage inorganic dental inserts were introduced. The aim of this study was to fabricate dental inserts based on hydroxyapatite doped with 5 mol. % of magnesium ions (MgHAP) and determine their bonding ability with a restorative material widely used in the clinical practice – Clearfil Universal adhesive. The MgHAP powder and insert were characterized using energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) analysis and scanning electron microscopy (FE-SEM). Bonding ability of the inserts with restorative material was measured by shear bond strength (SBS) test, and the type of fracture was determined by the optical microscope. The obtained mean SBS value of the MgHAP inserts was 12.7 MPa, with mostly cohesive type of the fracture present. These inserts present promising dentin substitutes for application in the restorative dentistry.