title: Fracture strength of minimally prepared all-ceramic CEREC crowns after simulating 5 years of service.
abstract: OBJECTIVE
  To examine the strength and mode of fracture of traditionally and minimally prepared all-ceramic resin bonded CAD/CAM crowns after fatigue loading.
  
  
  METHODS
  Thirty human maxillary molars were used and divided in three groups namely; traditional crown preparation group (I), minimal crown preparation group (II) and occlusal veneer preparation group (III). A leucite reinforced glass ceramic (IPS Empress CAD) was used for fabricating the crowns. The CEREC InEOS system (v3.10) was used for scanning, designing and milling. Five years of clinical service were simulated and the fracture strength of the crowns was measured. One-way ANOVA and Kruskal-Wallis test were used for data analysis (α=0.05).
  
  
  RESULTS
  The mean fracture strength and SD in Group I was 1070N (±181) and in Group II 1110N (±222). One-way ANOVA analysis showed no statistically significant difference between the two groups (p>0.05). In Group III all restorations developed cracks during TCML and were not subjected to fracture loading. Three of the traditionally designed crowns (Group I) and 4 of the minimally designed crowns (Group II) developed surface cracks during TCML.
  
  
  CONCLUSIONS
  Minimal all-ceramic resin-bonded crowns can potentially form a viable restorative option as they demonstrated comparable strength to traditional all-ceramic crowns. However, this should be interpreted with caution as a number of crowns showed cracks after 5 years of simulated service. All the occlusal veneers developed cracks during simulation and further investigation is needed for this to be considered a viable option.
authors.affiliation: Academic Unit of Restorative Dentistry, School of Clinical Dentistry, University of Sheffield, Sheffield, UK.
authors.forename: Nikoleta
authors.initials: N
authors.lastname: Skouridou
authors.forename: Sarah
authors.initials: S
authors.lastname: Pollington
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
authors.forename: Effrosyni
authors.initials: E
authors.lastname: Tsitrou
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000179:Acrylates / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D001732:Bite Force; D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003442:Crowns; D001840:Dental Bonding / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D003801:Dental Veneers; D006358:Hot Temperature; D006801:Humans; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D008963:Molar / Q000033:anatomy & histology; D019279:Resin Cements / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000145:classification* / Q000379:methods
chemical_list: D000179:Acrylates; D000538:Aluminum Silicates; D019279:Resin Cements; D012821:Silanes; C078484:Syntac dentine adhesive; D003776:Dental Porcelain; C078519:leucite; C074543:Cerec; C023506:Glass ceramics; C040415:heliobond; D006858:Hydrofluoric Acid