[Effects of different die materials on fracture and failure behaviors of all-ceramic crowns].
OBJECTIVE
To investigate the influence of different die materials on fracture strength and failure mode of IPS e.max Press crowns in mechanical test.


METHODS
Thirty-six IPS e.max Press crowns were divided into 3 groups. They were cemented to extracted maxillary first premolars in Group 1, to epoxy dies in Group 2, and to porous NiTi alloy dies in Group 3 respectively. All the crowns were subjected to compressive load in an universal mechanical testing machine. The maximum fracture strength(N) was recorded and fracture modes of the tested crowns were classified. Fractographies of the failed crowns were observed with a stereomicroscope.


RESULTS
Statistical analysis results showed that the mean fracture strength of the IPS e.max Press crowns on extracted natural teeth [(1159.7 +/- 256.0) N] and porous NiTi alloy dies [(1229.6 +/- 326.7) N] were obviously higher than that of epoxy dies [(883.5 +/- 198.1) N, P = 0.016 and 0.003]. Observations of the fractographies of failed crowns showed that the crowns on epoxy die fractured mesio-distally and no plastic deformation and characteristic cracks were observed. However, crowns in the other groups showed cone cracks at the contact area on occlusal surface and radical cracks initiated from the adhesive interfaces.


CONCLUSIONS
Die material has a significant influence on fracture resistance and fracture mode of the IPS e.max Press crowns. The crowns cemented to porous NiTi alloy dies show a similar fracture mode as those on extracted natural teeth.
Wu
Xiao-Ping
XP
Department of Prosthodontics, Guanghua School and Hospital of Stomatology & Institute of Stomatological Research, Sun Yat-sen University, Guangzhou 510055, China.
Li
Da-Sheng
DS
Zhang
Jun
J
Ma
Xiao
X
Zhao
Ke
K
Zhang
Xin-Ping
XP
D001641:Bicuspid; D002516:Ceramics; D003442:Crowns; D003776:Dental Porcelain; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000379:methods*; D008422:Materials Testing; D008437:Maxilla; D009532:Nickel; D019279:Resin Cements; D014025:Titanium
C508050:IPS e.max Press; D019279:Resin Cements; D003776:Dental Porcelain; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium