Fracture strength of machined ceramic crowns as a function of tooth preparation design and the elastic modulus of the cement

Abstract Objectives To determine, by means of static fracture testing the effect of the tooth preparation design and the elastic modulus of the cement on the structural integrity of the cemented machined ceramic crown-tooth complex. Methods Human maxillary extracted premolar teeth were prepared for...

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Bibliographic Details
Published in:Dental materials 2014-02, Vol.30 (2), p.234-241
Main Authors: Shahrbaf, Shirin, van Noort, Richard, Mirzakouchaki, Behnam, Ghassemieh, Elaheh, Martin, Nicolas
Format: Article
Language:English
Subjects:
Advanced Basic Science
Anatomic design
Bicuspid
CAD/CAM
Ceramics
Crowns
Dental Cements
Dentistry
Elastic modulus
Elasticity
Flat design
Humans
Materials Testing
Maxillary premolar
Mechanical test
Resin luting agent
Vita MK II
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Summary:Abstract Objectives To determine, by means of static fracture testing the effect of the tooth preparation design and the elastic modulus of the cement on the structural integrity of the cemented machined ceramic crown-tooth complex. Methods Human maxillary extracted premolar teeth were prepared for all-ceramic crowns using two preparation designs; a standard preparation in accordance with established protocols and a novel design with a flat occlusal design. All-ceramic feldspathic (Vita MK II) crowns were milled for all the preparations using a CAD/CAM system (CEREC-3). The machined all-ceramic crowns were resin bonded to the tooth structure using one of three cements with different elastic moduli: Super-Bond C&B, Rely X Unicem and Panavia F 2.0. The specimens were subjected to compressive force through a 4 mm diameter steel ball at a crosshead speed of 1 mm/min using a universal test machine (Loyds Instrument Model LRX.). The load at the fracture point was recorded for each specimen in Newtons (N). These values were compared to a control group of unprepared/unrestored teeth. Results There was a significant difference between the control group, with higher fracture strength, and the cemented samples regardless of the occlusal design and the type of resin cement. There was no significant difference in mean fracture load between the two designs of occlusal preparation using Super-Bond C&B. For the Rely X Unicem and Panavia F 2.0 cements, the proposed preparation design with a flat occlusal morphology provides a system with increased fracture strength. Significance The proposed novel flat design showed less dependency on the resin cement selection in relation to the fracture strength of the restored tooth. The choice of the cement resin, with respect to its modulus of elasticity, is more important in the anatomic design than in the flat design.
ISSN:0109-5641
1879-0097
DOI:10.1016/j.dental.2013.11.010