Use of zinc phosphate cement as a luting agent for Denzir？ copings: an in vitro study

Twelve Procera copings and twenty-four Denzir copings were made. After the copings had been made, twelve of the Denzir copings were sandblasted on their internal surfaces. All copings were then cemented with zinc phosphate cement to carbon steel dies and transferred to water or artificial saliva. Two weeks after cementation, half of the samples were tested. The remaining samples were tested after one year in the storage medium. All tests were done in tension and evaluated with an ANOVA.Sandblasted and un-sandblasted Denzir copings performed as well as Procera copings. Storage in water or artificial saliva up to one year did not decrease the force needed to dislodge any of the coping groups. Three copings fractured during testing and one coping developed a crack during testing. The three complete fractures occurred in Procera copings, while the partly cracked coping was a Denzir coping.No significant differences existed between the different material groups, and the retentive force increased rather than decreased with time. Fewer fractures occurred in Denzir copings, explained by the higher fracture toughness of the Denzir material. Based on good clinical results with zinc phosphate cemented Procera crowns, we foresee that zinc phosphate cement luted Denzir copings are likely to perform well clinically.CADCAM technologies have found increased use in dentistry during the past 15 years. Cerec, a system invented by M？rmann and Brandistini [1,2], was the first commercially available CADCAM system. Cerec was designed for making ceramic inlays and veneers, and these should be etched and bonded to the tooth with resin based luting agents [3,4]. Resin bonding was promoted because it improved retention and sealed gaps around Cerec restorations. Such gaps were often wider around the early Cerec restorations than they were around cast restorations. In addition, clinical experience evolving at that time suggested that the fracture rate of ceramic restorations decreased if they w