Effect of crystalline phase assemblage on reliability of 3Y-TZP.

Statement Of Problem: Strengthening mechanisms of zirconia ceramics stabilized with 3 mol% yttria (3Y-TZP) are complex and dictated by the crystalline phase assemblage. Although their clinical performance for dental restorations has been excellent, there is evidence that framework fractures do occur and have been underreported. Meanwhile, the relationship between phase assemblage and reliability of 3Y-TZP is not properly understood.

Analysis of thermal distributions in veneered zirconia and metal restorations during firing.

Objective: The present work evaluated the thermal behavior of porcelain-metal and porcelain-zirconia restorations during fast and slow firing and cooling.

Methods: All-ceramic (porcelain on zirconia) and porcelain-fused-to-metal (PFM) molar crowns were fabricated with 1 or 2mm porcelain thickness. Thermocouples were attached to the cementation (T1) and occlusal (T4) surfaces of the restoration and embedded at the framework-porcelain interface (T2) and inside the porcelain (T3) to acquire temperature readings by time.