title: The failure load of CAD/CAM generated zirconia and glass-ceramic laminate veneers with different preparation designs.
abstract: BACKGROUND
  Fracture of feldspathic porcelain laminate veneers represents a significant mode of clinical failure. Therefore, ceramic materials that withstand a higher load to fracture, especially for patients with parafunctional habits, are needed.
  
  
  OBJECTIVE
  The purpose of this study was to examine the correlation of material (zirconia, TZP, glass-ceramic, IEC, and feldspathic porcelain, FP) design (incisal overlapped preparation, IOP, and three-quarter preparation, TQP), and fracture mode to failure load for veneers supported by composite resin abutments.
  
  
  METHODS
  A typodont tooth prepared with 2 designs (IOP, TQP) and the corresponding 2 definitive dies were used to fabricate the composite resin abutments (30 for IOP and 30 for TQP). Ten veneer specimens for each system (Y-TZP, IEC, and FP), were fabricated for each design. The veneers were cemented, invested, and tested in compression until failure by using a universal testing machine. Significant differences were evaluated by 2-factor ANOVA (α=.05).
  
  
  RESULTS
  No statistical mean load difference was noted between the preparation designs for Y-TZP (IOP: 244 ±81 and TQP: 224 ±58 N), IEC (IOP: 306 ±101 and TQP: 263 ±77 N), and FP veneers (IOP: 161 ±93 and TQP: 246 ±45 N). No statistical difference in the mean load was found among the 3 veneer materials for each preparation design except between IEC (306 ±101 N) and FP (161 ±93 N) veneers for TQP.
  
  
  CONCLUSIONS
  Preparation design did not influence the failure load of the veneer materials. Zirconia veneers were the least likely to fracture but the most likely to completely debond; feldspathic porcelain veneers exhibited the opposite characteristics.
authors.affiliation: College of Dentistry, Taibah University, Kingdom of Saudi Arabia, Taibah University, Kingdom of Saudi Arabia. tghazzawi@taibah.edu.sa
authors.forename: Tariq F
authors.initials: TF
authors.lastname: Alghazzawi
authors.forename: Jack
authors.initials: J
authors.lastname: Lemons
authors.forename: Perng-Ru
authors.initials: PR
authors.lastname: Liu
authors.forename: Milton E
authors.initials: ME
authors.lastname: Essig
authors.forename: Gregg M
authors.initials: GM
authors.lastname: Janowski
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000538:Aluminum Silicates / Q000737:chemistry; D002484:Cementation / Q000379:methods; D002516:Ceramics / Q000737:chemistry*; D017076:Computer-Aided Design; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D055119:Elastic Modulus; D006801:Humans; D007180:Incisor; D008422:Materials Testing; D018583:Pliability; D017680:Potassium Compounds / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D015019:Yttrium / Q000737:chemistry*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D017680:Potassium Compounds; D019279:Resin Cements; C493120:lithia disilicate; C499362:yttria stabilized tetragonal zirconia; D003776:Dental Porcelain; C016447:feldspar; C103502:Variolink; D015019:Yttrium; C023506:Glass ceramics; D015040:Zirconium; C028541:zirconium oxide