title: Fracture resistance of ceramic veneers with different preparation designs.
abstract: OBJECTIVE
  The purpose of this study was to examine the fracture load of ceramic veneers with different preparation designs.
  
  
  METHODS
  Seventy-five extracted, intact, human maxillary central incisors were prepared according to five preparation designs (P) (n: 15) as follows: (1) P2e: 2-mm incisal reduction, preparation entirely in enamel; (2) P4e: 4-mm incisal reduction, preparation entirely in enamel; (3) P2d: 2-mm incisal reduction, preparation entirely in dentin; (4) P4d: 4-mm incisal reduction, preparation entirely in dentin; and (6) Pc: Unrestored, intact teeth as control. All preparations had a butt joint incisal finish line, rounded internal line angles, and cervical finish lines 1 mm above the cementoenamel junction. Ceramic veneers were fabricated with IPS Empress (Ivoclar Vivadent AG, Schaan, Liechtenstein) and cemented with Syntac Classic Adhesive system and Variolink II (Ivoclar) resin cement. Veneers were loaded until fracture at a 90° angle to the lingual surface of the test tooth following the thermocycling process (5° to 55°, 3500 times). Statistical analyses were performed using analysis of variance (ANOVA) and Tukey's Multiple Range Test.
  
  
  RESULTS
  The mean fracture loads (SD) were (in N) as follows: (1) P2e: 262 (63); (2) P4e: 189 (40); (3) P2d: 239 (53); (4) P4d: 162 (36); and (5) Pc: 277 (66). The amount of incisal reduction exhibited a significant influence on fracture resistance regardless of the preparation depth (p < 0.05).
  
  
  CONCLUSIONS
  Ceramic veneers with preparation designs entirely on dentin with 4-mm incisal reduction yielded lower fracture loads than those prepared with 2-mm incisal reduction. Veneers with 2-mm incisal reduction exhibited fracture resistance similar to that of intact teeth for preparation designs supplied on both enamel and dentin.
authors.affiliation: Department of Prosthodontics, Faculty of Dentistry, University of Marmara, Istanbul, Turkey. drburcinakoglu@hotmail.com
authors.forename: Burçin
authors.initials: B
authors.lastname: Akoğlu
authors.forename: Deniz
authors.initials: D
authors.lastname: Gemalmaz
mesh_terms: D000134:Acid Etching, Dental / Q000379:methods; D000179:Acrylates / Q000737:chemistry; D000180:Acrylic Resins / Q000737:chemistry; D000538:Aluminum Silicates / Q000737:chemistry; D002484:Cementation / Q000379:methods; D002516:Ceramics / Q000737:chemistry; D003743:Dental Enamel / Q000033:anatomy & histology; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003799:Dental Stress Analysis / Q000295:instrumentation; D003801:Dental Veneers; D003804:Dentin / Q000033:anatomy & histology; D017220:Dentin-Bonding Agents / Q000737:chemistry; D006801:Humans; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D019237:Tooth Cervix / Q000033:anatomy & histology; D019246:Tooth Preparation / Q000379:methods*
chemical_list: D000179:Acrylates; D000180:Acrylic Resins; D000538:Aluminum Silicates; D017220:Dentin-Bonding Agents; C075815:IPS-Empress ceramic; D019279:Resin Cements; C078484:Syntac dentine adhesive; D003776:Dental Porcelain; C078519:leucite; C103502:Variolink; C023506:Glass ceramics; C040415:heliobond; D006858:Hydrofluoric Acid