title: Fracture resistance of different partial-coverage ceramic molar restorations: An in vitro investigation.
abstract: BACKGROUND
  The authors conducted a study to evaluate the influence of preparation design on reliability and fracture resistance of press-ceramic posterior partial-coverage restorations (PCRs) under fatigue. They compared the results for PCRs fabricated of a new press ceramic (IPS e.max Press-VP 1989/4, Ivoclar-Vivadent, Schaan, Liechtenstein) with results for ceramic inlays and unprepared molars.
  
  
  METHODS
  The authors randomly divided 96 human upper molars into six equal groups. Control group NP specimens remained unprepared. Control group IN specimens received a mesio-occlusal-distal (MOD) inlay preparation. The test groups received PCR preparation designs based on group IN's inlay design, with additional cuspal reduction that increased from group to group. The authors fabricated 16 ceramic inlays and 64 PCRs of IPS e.max Press and luted them adhesively. All specimens underwent masticatory fatigue loading (1.2 million cycles, 1.6 hertz, 98 newtons), 5,300 thermal cycles and observation for fracture patterns. Afterward, the authors loaded all surviving specimens until fracture.
  
  
  RESULTS
  No fractures occurred during the exposure to the masticatory simulation. After undergoing loading in a universal testing machine, the groups showed no significant differences in fracture strength values (P = .6026). Thus, the different preparation designs of the PCRs demonstrated no significant influence on the restorations' fracture resistance. The median failure loads ranged from 1,567 to 1,960 newtons.
  
  
  CONCLUSIONS
  All-ceramic PCRs for molars made of IPS e.max Press were shown to be fracture-resistant, results comparable with those of natural unprepared teeth.
  
  
  CONCLUSIONS
  When a posterior ceramic PCR is indicated, the clinician should perform a defect-oriented preparation that preserves tooth structure. Further clinical investigations are recommended to verify the authors' in vitro results.
authors.affiliation: Department of Prosthodontics, Albert-Ludwigs-University, Freiburg, Germany. christian.stappert@nyu.edu
authors.forename: Christian F J
authors.initials: CF
authors.lastname: Stappert
authors.forename: Wael
authors.initials: W
authors.lastname: Att
authors.forename: Thomas
authors.initials: T
authors.lastname: Gerds
authors.forename: Joerg R
authors.initials: JR
authors.lastname: Strub
mesh_terms: D000704:Analysis of Variance; D003737:Dental Cavity Preparation / Q000379:methods*; D003776:Dental Porcelain / Q000737:chemistry*; D019232:Dental Restoration Failure; D006801:Humans; D007284:Inlays / Q000379:methods*; D008963:Molar; D018709:Statistics, Nonparametric; D016474:Weight-Bearing
chemical_list: C508050:IPS e.max Press; D003776:Dental Porcelain