Abstract: Objective To evaluate the fracture resistance of CAD/CAM zirconia all-ceramic crowns.Methods 284 all-ceramic crowns were fabricated for 189 patients.226 restorations of 156 patients were clinically followed up for 2.5-5.5 years.The site of crown,fracture or breakage,loose or dislodgement were observed.Results The fracture rate was 0.9% at 1 year after the insertion date,2.1% after two years,3.3% after three years,7.1% after four years.Overall the fracture rate was 9.7% with 226 restorations.Base crown fracture took place in two cases.A statistically significant difference was found for fractures when the opposing dentition of natural teeth and fixed restorations were compared (P=0.034).The fractures were most commonly noted when the opposing dentition was a fixed metal ceramic or other ceramic restorations.Conclusions The fracture resistance of CAD/CAM zirconia all-ceramic crowns was acceptable clinically and it can be a preferred esthetic restoration.

Key words: CAD/CAM, Zirconia-base, all-ceramic, fracture resistance