title: A preliminary evaluation of the structural integrity and fracture mode of minimally prepared resin bonded CAD/CAM crowns.
abstract: OBJECTIVE
  This study was a preliminary evaluation of two minimal preparation designs proposed for ceramic and composite resin bonded CAD/CAM crowns. It compared the structural integrity and fracture mode of teeth restored with traditionally and minimally prepared resin bonded CAD/CAM crowns fabricated from the same material hypothesizing that teeth restored with minimal resin bonded crowns would demonstrate the same fracture strength to teeth restored with traditional resin bonded crowns.
  
  
  METHODS
  Forty intact maxillary molar teeth were used and divided in four groups. Two groups were prepared according to a traditional crown preparation design and two groups were prepared according to minimal preparation designs. A resin composite (Paradigm MZ100, 3M ESPE) and a leucite glass-ceramic (ProCAD, Ivoclar Vivadent) were used for the fabrication of the crowns using CEREC Scan. Crowns of ceramic were cemented using Variolink II (Ivoclar Vivadent) and crowns of composite with Rely X Unicem Aplicap (3M ESPE) and loaded until fracture. Load data was analysed using ANOVA comparing crowns of the same restorative material. The mode of fracture was also recorded and analysed (Kruskal-Wallis).
  
  
  RESULTS
  For the composite system the mean fracture load and SD was 1682N (+/-315) for the traditional and 1751N (+/-338) for the minimal crowns. For the ceramic system the mean fracture load and SD was 1512N (+/-373) for the traditional and 1837 (+/-356) for the minimal crowns. No statistically significant difference was found between the two designs for each system. Nonparametric analysis (Kruskal-Wallis) of the fracture mode showed no statistical significant difference between designs for either material (p>.05).
  
  
  CONCLUSIONS
  Within the limitations of this experimental design, it was found that minimally prepared resin bonded CEREC crowns demonstrated equal fracture resistance and mode of fracture to that of crowns bonded to traditionally prepared teeth.
authors.affiliation: Department of Adult Dental Care, School of Clinical Dentistry, University of Sheffield, Claremont Crescent, S10 2TA, Sheffield, UK. e.tsitrou@gmail.com
authors.forename: Effrosyni A
authors.initials: EA
authors.lastname: Tsitrou
authors.forename: Maria
authors.initials: M
authors.lastname: Helvatjoglu-Antoniades
authors.forename: Richard
authors.initials: R
authors.lastname: van Noort
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D017076:Computer-Aided Design; D003442:Crowns; D001840:Dental Bonding / Q000379:methods*; D003776:Dental Porcelain / Q000737:chemistry; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013997:Time Factors; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D014867:Water / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: D000538:Aluminum Silicates; D003188:Composite Resins; C454801:ProCAD Ceramic; C483701:Rely X Unicem; D019279:Resin Cements; C452079:paradigm MZ100; D014867:Water; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink; C023506:Glass ceramics; D015040:Zirconium