Factors influencing bond strengths between unetched glass ionomers and resins.

The use of glass-ionomer cements as a base beneath composite resins has become a popular restorative procedure often referred to as the "sandwich technique." Originally etching of the glass-ionomer surface was recommended to help create the necessary bond between glass-ionomer cement and composite resin. This study investigated the bond strength of various composite resins and their bond agents to unetched glass ionomer. The pH of the bond agents was measured and related as bond strength. The influence of time elapsed between mixing the glass-ionomer cement and placement of the bond agent was also studied. Bond strengths varied from 65.5 kg/cm2 for G-C Dentin Cement with Pyrofil Light Bond A to 3.2 kg/cm2 for G-C Dentin Cement with Bis-Fil-M. The pH range was from 2.28 for Pyrofil Light Bond to 7.62 for Durafill Bond. Low correlation coefficients between bond strength values and pH indicated only limited relationship between the two. The bond strength decreased as the time lapse between the end of the mix and application of the bond agent increased.