The effect of axial grooves on the resistance form of cast restorations.

Fifteen sets of castings were fabricated to machined stainless steel dies of 5 degrees, 10 degrees, and 15 degrees of taper and 3, 4, 6, 8, and 10 mm of preparation length. Each casting was loaded vertically on its sloped surface in an attempt to unseat the casting. Only the castings of 3 and 4 mm of preparation length and 10 degrees and 15 degrees taper were unseated. Two experiments were performed on these four sets of dies to test parallel proximal and parallel buccolingual grooves. Dies with grooves oriented on the proximal surfaces provided complete resistance to horizontal dislodgement, whereas dies with grooves oriented on the buccal and lingual surfaces provided only partial resistance to horizontal displacement and potential failure of the castings.