Study compares contact wear and fracture strength among CAD/CAM all-ceramic single crowns

Thursday, November 23, 2017



A recent German study has investigated the strength of screw- and cement-retained CAD/CAM all-ceramic single crowns. The study looked at different veneering concepts to compare contact wear and fracture strength.

Mechanical failures can sometimes occur in ceramic restorations. One of the most common technical issues is ‘chipping’, where there is a fracture in the porcelain veneer. According to some clinical studies chipping rates for veneered all-ceramic restorations can range between 6.3% and 15.2%. This chipping risk is associated with the conventional manufacturing processes for creating fixed dental prostheses.

Because of this, the authors of this study looked at computer-aided design/computer-aided manufacturing (CAD/CAM) fabricated restorations. They operated under the assumption that the mechanical behaviour of all-ceramic crowns would depend on the materials, fabrication method and also the mode of retention of the prosthetic structure.

In total, fifty implants were placed. Five groups of CAD/CAM all-ceramic crowns were fabricated, with each group using a different method of veneering. All implants were then exposed to artificial aging, load until fracture and a scanning microscopy (SEM) analysis.

The results revealed a range of different outcomes depending on the method of veneering used. It was found that the screw-retained zirconia crowns with a modified coping design caused the least contact wear. The crowns with lithium disilicate veneering showed the highest substance loss and also seemed to preserve implants better. Lastly, the results showed that the mode of retention had no impact on the fracture load.

This study was published in Clinical Oral Investigations.