title: Mechanical fatigue degradation of ceramics versus resin composites for dental restorations.
abstract: OBJECTIVE
  For posterior partial restorations an overlap of indication exists where either ceramic or resin-based composite materials can be successfully applied. The aim of this study was to compare the fatigue resistance of modern dental ceramic materials versus dental resin composites in order to address such conflicts.
  
  
  METHODS
  Bar specimens of five ceramic materials and resin composites were produced according to ISO 4049 and stored for 14 days in distilled water at 37°C. The following ceramic materials were selected for testing: a high-strength zirconium dioxide (e.max ZirCAD, Ivoclar), a machinable lithium disilicate (e.max CAD, Ivoclar), a pressable lithium disilicate ceramic (e-max Press, Ivoclar), a fluorapatite-based glass-ceramic (e.max Ceram, Ivoclar), and a machinable color-graded feldspathic porcelain (Trilux Forte, Vita). The composite materials selected were: an indirect machinable composite (Lava Ultimate, 3M ESPE) and four direct composites with varying filler nature (Clearfil Majesty Posterior, Kuraray; GrandioSO, Voco; Tetric EvoCeram, Ivoclar-Vivadent; and CeramX Duo, Dentsply). Fifteen specimens were tested in water for initial strength (σin) in 4-point bending. Using the same test set-up, the residual flexural fatigue strength (σff) was determined using the staircase approach after 10(4) cycles at 0.5 Hz (n=25). Weibull parameters σ0 and m were calculated for the σin specimens, whereas the σff and strength loss in percentage were obtained from the fatigue experiment.
  
  
  RESULTS
  The zirconium oxide ceramic showed the highest σin and σff (768 and 440 MPa, respectively). Although both lithium disilicate ceramics were similar in the static test, the pressable version showed a significantly higher fatigue resistance after cyclic loading. Both the fluorapatite-based and the feldspathic porcelain showed equivalent initial and cyclic fatigue properties. From the composites, the highest filled direct material Clearfil Majesty Posterior showed superior fatigue performance. From all materials, e.max Press and Clearfil Majesty Posterior showed the lowest strength loss (29.6% and 32%, respectively), whereas the other materials lost between 41% and 62% of their flexural strength after cyclic loading.
  
  
  CONCLUSIONS
  Dental ceramics and resin composite materials show equivalent fatigue strength degradation at loads around 0.5σin values. Apart from the zirconium oxide and the lithium disilicate ceramics, resin composites generally showed better σff after 10,000 cycles than the fluorapatite glass-ceramic and the feldspathic porcelain. Resin composite restorations may be used as an equivalent alternative to glass-rich-ceramic inlays regarding mechanical performance.
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander University of Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen, Germany. Electronic address: rbelli@dent.uni-erlangen.de.
authors.forename: Renan
authors.initials: R
authors.lastname: Belli
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander University of Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen, Germany.
authors.forename: Eva
authors.initials: E
authors.lastname: Geinzer
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander University of Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Muschweck
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander University of Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen, Germany.
authors.forename: Anselm
authors.initials: A
authors.lastname: Petschelt
authors.affiliation: Laboratory for Biomaterials Research, Dental Clinic 1 - Operative Dentistry and Periodontology, Friedrich-Alexander University of Erlangen-Nürnberg, Glueckstrasse 11, 91054 Erlangen, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Lohbauer
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D003776:Dental Porcelain / Q000737:chemistry; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D008422:Materials Testing; D017680:Potassium Compounds / Q000737:chemistry; D013499:Surface Properties; D015040:Zirconium / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; D017680:Potassium Compounds; C493120:lithia disilicate; D003776:Dental Porcelain; C016447:feldspar; C023506:Glass ceramics; D015040:Zirconium; C028541:zirconium oxide
keywords: Ceramics; Fatigue; Flexural strength; Resin composite; Staircase approach