A CLINICAL STUDY OF THE INTERNAL FIT OF ZIRCONIA AND GOLD PLATINUM CAD/CAM FRAMEWORKS FIXED DENTAL PROSTHESIS

Statement of problem: A new CAD/CAM technology for the fabrication of metal copings for metal –ceramic restorations has been introduced. However, no sufficient data on the internal fit of metal- ceramic restorations produced by this method is available yet.
Purpose: This study was performed to compare the internal gap between abutment teeth and posterior fixed dental prosthesis (FDPs) fabricated utilizing yttria-stabilized tetragonal zirconia polycrystals and Gold Platinum metal ceramic alloy frameworks.
Materials and Methods: A randomized controlled clinical trial was performed, twenty FPDs were fabricated with yttria –stabilized zirconia poly crystals (Y-TZP –IPS e.max zir CAD) and metal –ceramic (MC Au-Pt) as follow(n=10): thirty patients were randomly selected for internal fit measurements. The internal fit of the FPDs frameworks were measured using replica technique. Data was analyzed with (ANOVA) test, followed by Tukey’s post hoc test.
Results: The internal gap, according to the thickness of the replica, was measured under magnification at the following locations: cervical, axial, and occlusal (cusp-tips and central). The internal gaps of FPDs with zirconia frameworks were significantly larger in cervical, axial, and centro-occlusal regions (cervical: 69.549± 10.484 µm vs. 60.493 ± 15.940 µm axial : 75.678 ± 8.996 µm vs. 53.356 ± 12.916 µm ; and centro-occlusal: 78.159± 10.272 µm vs. 69.343 ± 4.446 µm). The cervical gaps next to the pontics were significantly larger compared with those of the outer walls in both types of FPDs (zirconia: mean difference 71.655 ± 4.583 µm; metal-ceramic: mean difference 52.891± 5.665 µm ).
Conclusion: Posterior three-unit FPDs milled zirconia frameworks fabricated according to the manufacturer’s specifications exhibited larger internal gaps than those constructed using milled Gold Platinum metal-ceramic technique.
Clinical implications: Both milled Gold platinum metal ceramic, and zirconia may be an alternative for 3- unit frameworks in terms of internal fit. Zirconia showed inferior results but within the range of clinical acceptability.