Monday, November 5, 2012
Zirconia Cementation Update
The generally accepted practice of conventionally cementing monolithic ceramic restorations is clinically effi cient and is the most popular method of placing our all-zirconia TLZ, BruxZir, and lithiumdisilicate eMax restorations. In a recent edition of Inside Dental Technology, however, Dr. Ed McLaren takes issue: “The problem is that these cements are much more soluble than resin-based cements. If, over time, the cement solubilizes and fails, exposing the glass cement to saliva, the restoration can undergo hydrolytic degradation which weakens the material.” He recommends bonding these restorations, particularly in situations where the preparation is non-retentive. Dr. Russell Giordano, Boston University Goldman School of Dental Medicine, an authority on dental materials agrees. It has been established that bonding almost doubles the load and increases resistance to failure. Low pressure, sandblasting the interior of the restoration at the laboratory with alumina, and the use of primers, such as AZ Primer (Shofu Dental Corporation), Clearfi l™ Ceramic Primer (Kuraray), Metal/Zirconia Primer (Ivoclar Vivadent), and Z-Prime Plus® (BISCO), signifi cantly improve adhesion. Recently, The Dental Advisor gave Bisco’s Z-Prime Plus a 5-Star rating and claimed that it doubles zirconia bond-strength. Z-Prime is a priming agent that enhances the adhesion between zirconia and composite resin cements, in both self-cure and light-cure modes. Based on what we’ve recently learned about the effects of primers, therefore, we recommend their use on both full-contour zirconia and porcelain fused-to-metal restorations, particularly with minimally retentive preparations.