The Injection Molded Technique for Strong and Esthetic Class II Restorations
Class II restorations present several challenges to the clinician. The traditional technique for prepping and filling these restorations leaves them prone to leaking, chipping, wholesale fracture, recurrent decay and ultimately, higher failure rates when compared to amalgam. The classic cavity preparation designs first created by G.V. Black represented a significant advance during his day; however, that day was sometime in 1890. We are now seeing evidence that these shapes can weaken the dentition by contributing to tooth fracturing, in spite of the belief that composites will always strengthen the tooth. Furthermore, the practice of applying several separately cured layers of composite in a deep and boxy preparation creates risks for voids, gaps and seaming between layers. Residual stress can build in the tooth and restoration as the composite is layered, and in spite of careful layering the composite often shrinks as the stress builds to eventually create marginal gapping or enamel microfracturing.