title: Biomechanical behavior of endodontically treated premolars using different preparation designs and CAD/CAM materials.
abstract: OBJECTIVE
  To evaluate the effect of restoration design ('2.5-mm deep endocrown', '5-mm deep endocrown' or '5-mm deep post&crown') and CAD/CAM material type (composite or lithium disilicate glass-ceramic) on the load-to-failure of endodontically treated premolars in absence of any ferrule.
  
  
  METHODS
  The crowns of 48 single-rooted premolars were cut and the roots were endodontically treated. Teeth were randomly divided into six groups (n=8); teeth in each group were restored using one of the two tested materials with standardized CAD/CAM fabricated endocrowns (with either 2.5-mm or 5-mm deep intra-radicular extension) or conventional crowns (5-mm deep post&crown). After cementation using luting composite, the specimens were immersed in distilled water and subjected to 1,200,000 chewing cycles with a load of 50N applied parallel to the long axis of the tooth (0°). After cyclic loading, a compressive load was applied at 45° to the tooth's long axis using a universal testing machine until failure. Load-to-failure was recorded (N) and the specimens were examined under a stereomicroscope with 3.5x magnification to determine the mode of failure.
  
  
  RESULTS
  All specimens survived the 1,200,000 chewing cycles. A significant interaction between restoration design and CAD/CAM material was found using two-way ANOVA. In the '2.5-mm deep endocrown' groups, the composite achieved a significantly higher load-to-failure than the lithium disilicate glass-ceramic, while no differences between materials were found in the '5-mm deep endocrown' and '5-mm deep post&crown' groups. More unfavorable failures (root fractures) were observed for higher load-to-failure values.
  
  
  CONCLUSIONS
  Only following a '2.5-mm deep endocrown' design, composite appeared more favorable than lithium disilicate glass-ceramic as crown material; this may be explained by their difference in elastic modulus.
  
  
  CONCLUSIONS
  Shallow endocrown preparations on premolars present less surface for adhesive luting and a difference in crown material becomes apparent in terms of load-to-failure. The use of a more flexible composite crown material appeared then a better option.
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven (UZ Leuven), Dentistry, Leuven, Belgium; Federal University of Santa Catarina (UFSC), Department of Operative Dentistry, Florianópolis, SC, Brazil. Electronic address: diogolise@hotmail.com.
authors.forename: Diogo
authors.initials: D
authors.lastname: Pedrollo Lise
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven (UZ Leuven), Dentistry, Leuven, Belgium. Electronic address: annelies.vanende@gmail.com.
authors.forename: Annelies
authors.initials: A
authors.lastname: Van Ende
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven (UZ Leuven), Dentistry, Leuven, Belgium. Electronic address: jan.demunck@kuleuven.be.
authors.forename: Jan
authors.initials: J
authors.lastname: De Munck
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven (UZ Leuven), Dentistry, Leuven, Belgium; Sao Paulo State University (UNESP), School of Dentistry, Department of Restorative Dentistry, Araçatuba, Brazil. Electronic address: tha.suzuki@gmail.com.
authors.forename: Thaís Yumi
authors.initials: TY
authors.lastname: Umeda Suzuki
authors.affiliation: Federal University of Santa Catarina (UFSC), Department of Operative Dentistry, Florianópolis, SC, Brazil.
authors.forename: Luiz Clovis
authors.initials: LC
authors.lastname: Cardoso Vieira
authors.affiliation: KU Leuven (University of Leuven), Department of Oral Health Sciences, BIOMAT & University Hospitals Leuven (UZ Leuven), Dentistry, Leuven, Belgium. Electronic address: bart.vanmeerbeek@uzleuven.be.
authors.forename: Bart
authors.initials: B
authors.lastname: Van Meerbeek
mesh_terms: D001641:Bicuspid; D001697:Biomedical and Dental Materials; D002484:Cementation; D002516:Ceramics / Q000737:chemistry; D019245:Compressive Strength; D017076:Computer-Aided Design; D003442:Crowns; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D019553:Tooth, Nonvital
chemical_list: D001697:Biomedical and Dental Materials; C520133:IPS e.max CAD LT; C493120:lithia disilicate; D003776:Dental Porcelain; C023506:Glass ceramics
keywords: CAD/CAM; Composite; Compressive load; Cyclic aging; Endocrown; Lithium disilicate