Objectives: Dental professionals have recognized for the last 15 years the benefits of ceramic restorations to restore natural dentition. Due to the reported outstanding mechanical properties and excellent biocompatibility of yttria-stabilized tetragonal zirconia (Y-TZP), it is being offered as a core material to fabricate all ceramic restorations as well as bridges. While the accepted maximum force of a fully dentate patient is 665 N in the molar region, questions still arise as to the efficacy of all-ceramic bridges. This study reports the material strength of zirconia bridges produced by the Procera (NobelBiocare, AB) technology.

Methods: Ten Procera Zirconia bridge substructures were fabricated using a CAD/CAM technique. Resin dies of a prepared premolar and molar resembling natural dentition were fabricated and duplicated. The dies were then embedded in stone reproducing the clinical distance (14mm) between a mandibular second premolar to a mandibular second molar. Using the Procera Forte Scanner, the dies were scanned and bridges designed using the dimensions recommended for the connectors (3mm height by 2.54mm width). The bridges were then cemented with FujiCem (GC America) onto the mounted dies. All samples were loaded to fracture at the center point of the pontic in a vertical direction using an Instron machine with a cross-head speed of 0.5 mm/min.

Results: Bridge fracture occurred between 922.55 N and 1577.03 N at the connector joint. The mean of the maximum load to fracture of the Procera zirconia bridges was 1,289.75 N.

Conclusions: Given the reported maximum human biting force, the results drawn from this study support the use of the Procera zirconia bridge in replacing dentition in any location of the dental arch.

Supported by NobelBiocare/ University of Michigan Center for Excellence

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