First dentin bonding agent was:

During the 1950s, it was reported that a resin containing glycerophosphoric acid dimethacrylate (GPDM) could bond to a hydrochloric acid–etched dentin surface. Another researcher had used the same monomer chemically activated with sulinic acid and that combination would later be known commercially as Sevitron Cavity Seal (Amalgamated Dental Company, London, England). Sturdevant Operative Dentistry 7th edition page 142-143