In vitro release of phosphoric acid ester from self-etching primer

Self-etching primers have simplified the process of direct bonding of dental resins, by eliminating the rinsing step after etching in conventional bonding, for example. Although it is generally assumed that all of the applied self-etching primer is incorporated into the resin, the possibility that a substantial amount remains free and extractable into a person's saliva has not been investigated. The aim of the present study was to examine this issue by bonding brackets to extracted teeth with self-etching primers under controlled conditions and determining the proportion of the applied phosphoric acid ester that is subsequently extractable by high-performance liquid chromatography. Approximately half of the applied acid ester was extractable and thus not integrated into the polymeric network following standard light curing. This was reduced to 40% when the curing time was doubled. Acid ester leaching was a rapid process that was essentially completed within an hour.