[Fractographic analysis of clinically failed anterior all ceramic crowns].
OBJECTIVE
To identify the site of crack initiation and propagation path of clinically failed all ceramic crowns by fractographic analysis.


METHODS
Three clinically failed anterior IPS Empress II crowns and two anterior In-Ceram alumina crowns were retrieved. Fracture surfaces were examined using both optical stereo and scanning electron microscopy. Fractographic theory and fracture mechanics principles were applied to disclose the damage characteristics and fracture mode.


RESULTS
All the crowns failed by cohesive failure within the veneer on the labial surface. Critical crack originated at the incisal contact area and propagated gingivally. Porosity was found within the veneer because of slurry preparation and the sintering of veneer powder.


CONCLUSIONS
Cohesive failure within the veneer is the main failure mode of all ceramic crown. Veneer becomes vulnerable when flaws are present. To reduce the chances of chipping, multi-point occlusal contacts are recommended, and layering and sintering technique of veneering layer should also be improved.
Department of Prosthodontics, Guanghua School of Stomatology, Hospital of Stomatology, Sun Yat-sen University & Guangdong Provincial Key Laboratory of Stomatology, Guangzhou 510055, China.
Qian
Q
DU
Min-bo
MB
Zhou
Xin-ping
XP
Zhang
Ke
K
Zhao
D002516:Ceramics; D003442:Crowns; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003801:Dental Veneers; D019544:Equipment Failure Analysis; D006801:Humans; D008855:Microscopy, Electron, Scanning; D016062:Porosity
C483026:In-Ceram Alumina; D003776:Dental Porcelain