In vitro analysis of the fracture resistance of CAD-CAM monolithic zirconia molar crowns with different occlusal thickness.
To compare the fracture resistance and mode of failure of CAD-CAM monolithic zirconia crowns with different occlusal thickness.



Forty CAD-CAM monolithic zirconia crowns with different occlusal thickness were randomly distributed into 4 experimental groups: 2.0mm (group 1), 1.5mm (group 2), 1.0mm (group 3) and 0.5mm (group 4). The restorations were cemented onto human molars with a self-adhesive resin cement. The specimens were loaded until fracture; the fracture resistance and mode of failure were recorded. The data were statistically analyzed with the one-way ANOVA followed by the Fisher׳s Exact test with Bonferroni׳s correction (p=0.05).



The fracture resistance values of all the specimens exceeded the maximum physiological occlusal loads in molar regions. All the crowns showed cohesive microcracks of the zirconia core; only 1 crown with a thickness of 0.5mm was interested by a complete fracture.



The occlusal thickness of CAD-CAM monolithic zirconia crowns did not influence either the fracture resistance and the mode of failure of the restorations; the occlusal thickness of CAD-CAM monolithic zirconia crowns can be reduced up to a lower bound of 0.5mm keeping a sufficient strength to withstand occlusal loads; CAD-CAM monolithic zirconia crowns showed sufficient fracture resistance to be used in molar regions, even in a thin configuration (0.5mm).
Department of Medical Biotechnologies, School of Dental Medicine, University of Siena, Viale Bracci, 53100 Siena, Italy. Electronic address: errestino@libero.it.
Roberto
R
Sorrentino
Department of Medical Biotechnologies, School of Dental Medicine, University of Siena, Viale Bracci, 53100 Siena, Italy. Electronic address: triulzio.clementina@gmail.com.
Clementina
C
Triulzio
Department of Medical Biotechnologies, School of Dental Medicine, University of Siena, Viale Bracci, 53100 Siena, Italy. Electronic address: marella86@hotmail.it.
Maria Gabriella
MG
Tricarico
Department of Medical Biotechnologies, School of Dental Medicine, University of Siena, Viale Bracci, 53100 Siena, Italy. Electronic address: bonadeogianni@gmail.com.
Giovanni
G
Bonadeo
Department of Dentistry, University "Vita Salute San Raffaele" of Milan, Via Olgettina 60, 20132 Milan, Italy. Electronic address: gherlone.enrico@hsr.it.
Enrico Felice
EF
Gherlone
Department of Medical Biotechnologies, School of Dental Medicine, University of Siena, Viale Bracci, 53100 Siena, Italy. Electronic address: ferrarm@gmail.com.
Marco
M
Ferrari
D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D008963:Molar; D015040:Zirconium / Q000737:chemistry*
D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide
CAD–CAM; Crown; Fracture resistance; Monolithic; Occlusal thickness; Zirconia