Clinical evaluations of cast gold alloy, machinable zirconia, and semiprecious alloy crowns: A multicenter study

Abstract

Statement of problem. Few studies have compared the marginal and internal fits of crowns fabricated from machinable palladium-silver-indium (Pd-Ag-In) semiprecious metal alloy. Purpose. The purpose of this clinical study was to evaluate and compare the marginal and internal fits of machined Pd-Ag-In alloy, zirconia, and cast gold crowns. Material and methods. A prospective clinical trial was performed on 35 participants and 52 abutment teeth at 2 centers. Individuals requiring prosthetic restorations were treated with gold alloy or zirconia crowns (2 control groups) or Pd-Ag-In alloy crowns (experimental group). A replica technique was used to evaluate the marginal and internal fits. The buccolingual and mesiodistal cross-sections were measured, and a noninferiority comparison was conducted. Results. The mean marginal gaps were 68.2 gm for the gold crowns, 75.4 mu m for the zirconia crowns, and 76.9 grn for the Pd-Ag-In alloy crowns. In the 5 cross-sections other than the distal cross-section, the 2-sided 95% confidence limits for the differences between the Pd-Ag-In alloy crowns and the 2 control groups were not larger than the 25 mu m noninferiority margin. The control groups displayed smaller internal gaps in the line angle and occlusal spaces compared with the Pd-Ag-In crown group. Conclusion. The marginal gaps of machinable Pd-Ag-In alloy crowns did not meet the noninferiority criterion in the distal margin compared with zirconia and gold alloy crowns. Nonetheless, all 3 crowns had clinically applicable precision.