Vitor G Paula1, Fabio C Lorenzoni2, Estevam A Bonfante3, Nelson R F A Silva4, Van P Thompson5, Gerson Bonfante1. 1. Department of Prosthodontics, University of São Paulo - Bauru College of Dentistry, Bauru, SP, Brazil. 2. Department of Prosthodontics, UNIGRAN University, Dourados, MS, Brazil. 3. Department of Prosthodontics, University of São Paulo - Bauru College of Dentistry, Bauru, SP, Brazil. Electronic address: estevamab@gmail.com. 4. Department of Restorative Dentistry, Federal University of Minas Gerais, UFMG, Belo Horizonte, MG, Brazil. 5. Department of Biomaterials, Biomimetics and Biophotonics, King's College London, Guy's Hospital, London, United Kingdom.
Abstract
OBJECTIVE: To compare 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. METHODS: Composite resin replicas of a first molar full crown preparation were fabricated. Zirconia copings were milled as conventional (0.5mm even thickness, Zr-C, n=20,) or modified (lingual margin of 1.0mm thickness, 2.0mm height connected to two proximal struts of 3.5mm 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 10(6) 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). RESULTS: 2-parameter 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 10(6) 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. SIGNIFICANCE: Improved 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.
OBJECTIVE: To compare 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. METHODS: Composite resin replicas of a first molar full crown preparation were fabricated. Zirconia copings were milled as conventional (0.5mm even thickness, Zr-C, n=20,) or modified (lingual margin of 1.0mm thickness, 2.0mm height connected to two proximal struts of 3.5mm 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 10(6) 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). RESULTS: 2-parameter 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 10(6) 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. SIGNIFICANCE: Improved 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.
Authors: Camila da Silva Rodrigues; Iana Lamadrid Aurélio; Marina da Rosa Kaizer; Yu Zhang; Liliana Gressler May Journal: Dent Mater Date: 2019-03-04 Impact factor: 5.304
Authors: Camila da Silva Rodrigues; Iana Lamadrid Aurélio; Sara Fraga; Marina da Rosa Kaizer; Yu Zhang; Liliana Gressler May Journal: Dent Mater Date: 2021-04-15 Impact factor: 5.687
Authors: Vinicius Pavesi Fardin; Gerson Bonfante; Paulo G Coelho; Edmara T P Bergamo; Dimorvan Bordin; Malvin N Janal; Nick Tovar; Lukasz Witek; Estevam A Bonfante Journal: J Appl Oral Sci Date: 2022-04-22 Impact factor: 3.144