Yoshihara K, et al. - Researchers probed the chemical interaction of glycero-phosphate dimethacrylate (GPDM) with hydroxyapatite (HAp) using diverse chemical analyzers and ultra-structurally characterized the interface of a GPDM-based primer formulation with dentin. Data suggested that a weak bond between GPDM and HAp, unlike the strong bond formed by MDP to HAp. GPDM could be an adequate monomer for an etch-and-rinse adhesive, due to its high hydrophilicity, but appeared less appropriate for a ‘mild’ self-etch adhesive that besides micro-retention ionically interacts with HAp, or for a self-adhesive restorative material.