Laboratory evaluation of experimental restorative systems containing 4-META

To determine the in vitro shear bond strengths and quantitative microleakage of four experimental bonding restorative systems used in conjunction with Metafil-A, an experimental composite that does not contain 4-META, and Metafil-Ex, a 4-META containing experimental composite.

120 test specimens were prepared on dentin treated with Amalgambond Activator followed by the application of an experimental primer consisting of 35% glyceryl methacrylate. In 60 teeth the mixed Amalgambond Base and Catalyst was then applied while in the remaining 60 teeth this step was omitted. Cylinders of either Metafil-A or Metafil-Ex were bonded to the dentin surfaces and the test specimens removed from the assembly apparatus after 1 minute or after 15 minutes and the latter specimens were stored in saline at 37 degrees C for 24 hours prior to determining the shear bond strength in an Instron machine at a crosshead speed of 0.5 mm/minute. Sixty Class V preparations were made on the facial surfaces of the roots of extracted human premolars and the preparations restored with the four restorative systems. The quantitative microleakage was determined by a spectrophotometric dye-recovery method.

The shear bond strengths were significantly lower when the 4-META-containing Amalgambond Base and Catalyst were not applied and were unmeasurable when Metafil-A was used as the composite. The quantitative microleakage of the latter system was significantly greater than when the other restorative systems were used.