title: Influence of restoration thickness and dental bonding surface on the fracture resistance of full-coverage occlusal veneers made from lithium disilicate ceramic.
abstract: OBJECTIVE
  The purpose of this in-vitro study was to evaluate the influence of ceramic thickness and type of dental bonding surface on the fracture resistance of non-retentive full-coverage adhesively retained occlusal veneers made from lithium disilicate ceramic.
  
  
  METHODS
  Seventy-two extracted molars were divided into three test groups (N=24) depending on the location of the occlusal veneer preparation: solely within enamel, within enamel and dentin or within enamel and an occlusal composite resin filling. For each test group, occlusal all-ceramic restorations were fabricated from lithium disilicate ceramic blocks (IPS e.max CAD) in three subgroups with different thicknesses ranging from 0.3 to 0.7mm in the fissures and from 0.6 to 1.0mm at the cusps. The veneers were etched (5% HF), silanated and adhesively luted using a self etching primer and a composite luting resin (Multilink Primer A/B and Multilink Automix). After water storage at 37°C for 3 days and thermal cycling for 7500 cycles at 5-55°C, specimens were subjected to dynamic loading in a chewing simulator with 600,000 loading cycles at 10kg combined with thermal cycling. Unfractured specimens were loaded until fracture using a universal testing machine. Statistical analysis was performed using Kruskal-Wallis and Wilcoxon tests with Bonferroni-Holm correction for multiple testing.
  
  
  RESULTS
  Only specimens in the group with the thickest dimension (0.7mm in fissure, 1.0mm at cusp) survived cyclic loading without any damage. Survival rates in the remaining subgroups ranged from 50 to 100% for surviving with some damage and from 12.5 to 75% for surviving without any damage. Medians of final fracture resistance ranged from 610 to 3390N. In groups with smaller ceramic thickness, luting to dentin or composite provided statistically significant (p≤0.05) higher fracture resistance than luting to enamel only. The thickness of the occlual ceramic veneers had a statistically significant (p≤0.05) influence on fracture resistance.
  
  
  CONCLUSIONS
  The results suggest to use a thickness of 0.7-1mm for non-retentive full-coverage adhesively retained occlusal lithium disilicate ceramic restorations.
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany. Electronic address: msasse@proth.uni-kiel.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Sasse
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Krummel
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Klosa
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, School of Dentistry, Christian-Albrechts University, Arnold-Heller-Str. 16, 24105 Kiel, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D000134:Acid Etching, Dental; D001732:Bite Force; D003188:Composite Resins / Q000737:chemistry; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis; D003801:Dental Veneers; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008963:Molar; D013314:Stress, Mechanical; D013499:Surface Properties; D019246:Tooth Preparation / Q000379:methods*
chemical_list: D003188:Composite Resins; C493120:lithia disilicate; D003776:Dental Porcelain
keywords: All-ceramic; Ceramic thickness; Dental bonding surface; Fracture resistance; Full-coverage molar restoration; Self etching primer