Thermal Compatibility of Veneering Porcelains on Zirconia Ceramic Implant Abutments

Objectives: The firing of porcelain onto zirconia abutments can provide esthetic screw-retained implant crowns. This in vitro study evaluated the thermal compatibility of 4 veneering porcelains with the ZirDesign™ (AstraTech) yttria stabilized zirconia abutment. Stock abutments were ground to dimensions of a maxillary central incisor. The effects of abutment modification by aluminum oxide abrasion, base/liner application, diamond grinding to thin abutment walls were assessed.

Methods: ZirDesign abutments were ground to standardized dimensions using Brasseler Duracut Coarse Diamond burs in water-cooled high-speed handpiece to 0.75 mm facial wall thickness and one group to 0.4 mm. Zirconia veneering porcelains and liners studied were: (VM9), Vita, Effect Bonder; (EMX) e.MAXCeram, IvoclarVivadent, ZirLiner; (CZR), Noritake, Shade Base; (LAV), LavaCeram, 3M ESPE, Framework Modifier. Abutment groups were abraded with 50um alumina@40psi. A jig with a fixture analogue positioned the abutment to standardize buildup of veneering porcelain to full crown contour. Following completion of porcelain buildup, specimens were submitted to 20 body firings examining with transillumination for cracking after each firing.

Results: [8 specimens/group tested] KEY: Porcelain, WT= Wall Thickness, Abr=Abrasion, LP=Peeling of Liner During Firing, Cr=Cracking During Porcelain Buildup, Surv= % Survival of 20 Firings.

CZR- Abr(-):LP=5/8, Cr=0, Surv=100%; Abr(+):LP=0, Cr=0, Surv=100%.

EMX- Abr(-):LP=0, Cr=0, Surv=100%; Abr(+):LP=0, Cr=0, Surv=100%. WT=0.4 mm - Abr(+):LP=0, Cr=0, Surv=100%.

LAV- Abr(-):LP=0, Cr=0, Surv=100%; Abr(+):LP=0, Cr=0, Surv=100%.

VM9- Abr(-):LP=8/8, Cr=1/8, Surv=100%; Abr(+):LP=0, Cr=5/8, Surv=100% for remaining 3 tested.

Conclusions: Nonabrasion of abutments resulted in peeling of bonder for VM9, CZR. Abrasion improved adherence of bonder during firing of VM9, CZR. Abrasion caused cracking in 63% of VM9 specimens during fabrication sintering. For abraded EMX at 0.4mm wall thickness no cracking occurred. Three porcelain groups survived 20 firings indicating excellent thermal compatibility with abraded zirconia abutments for fabrication of screw-retained implant crowns.

Study funded by Astra Tech Dental, Waltham, MA, USA.