Title of article :
Slow cooling protocol improves fatigue life of zirconia crowns
Author/Authors :
Paula ، نويسنده , , Vitor G. and Lorenzoni، نويسنده , , Fabio C. and Bonfante، نويسنده , , Estevam A. and Silva، نويسنده , , Nelson R.F.A. and Thompson، نويسنده , , Van P. and Bonfante، نويسنده , , Gerson، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2015
Abstract :
AbstractObjective
pare the fatigue life and damage modes of zirconia crowns fabricated with and without framework design modification when porcelain veneered using a fast or slow cooling protocol.
s
ite resin replicas of a first molar full crown preparation were fabricated. Zirconia copings were milled as conventional (0.5 mm even thickness, Zr-C, n = 20,) or modified (lingual margin of 1.0 mm thickness, 2.0 mm height connected to two proximal struts of 3.5 mm height, Zr-M, n = 20). These groups were subdivided (n = 10 each) according to the veneer cooling protocol employed: fast cooling (Zr-CFast and Zr-MFast) and slow cooling (Zr-CSlow and Zr-MSlow). Crowns were cemented and fatigued for 106 cycles in water. The number of cycles to failure was recorded and used to determine the interval databased 2-parameter probability Weibull distribution parameter Beta (β) and characteristic life value Eta (η).
s
meter Weibull calculation presented β = 5.53 and β = 4.38 for Zr-MFast and Zr-CFast, respectively. Slow cooled crowns did not fail by completion of 106 cycles, thereby Weibayes calculation was applied. Increased fatigue life was observed for slow cooled crowns compared to fast cooled ones. Groups Zr-MFast and Zr-MSlow presented no statistical difference. Porcelain cohesive fractures were mainly observed in fast cooled groups. Slow cooled crowns presented in some instances inner cone cracks not reaching the zirconia/veneer interface.
icance
ed fatigue life in tandem with the absence of porcelain fractures were observed in slow cooled crowns, regardless of framework design. Crowns fast cooled chiefly failed by porcelain cohesive fractures.
Keywords :
ceramics , Fatigue , Weibayes , Cooling rate , fractography , Zirconia
Journal title :
Dental Materials
Journal title :
Dental Materials