title: Are endodontically treated incisors reliable abutments for zirconia-based fixed partial dentures in the esthetic zone?
abstract: BACKGROUND
  This ex vivo pilot study tested the influence of defect extension and quartz-fiber post placement (QFP) on the ex vivo survival rate and fracture resistance of root-treated upper central incisors served as abutments for zirconia 2-unit cantilever fixed partial dentures (2U-FPDs) exposed to 10 years of simulated clinical function.
  
  
  METHODS
  Human maxillary central incisors were endodontically treated and divided into the following 5 groups (n = 8): (1) access cavity filled with core build-up composite, (2) biproximal class III cavities filled as in group 1, (3) specimens restored as in group 2 with QFP placed, (4) specimens decoronated and core buildup as in group 1, and (5) specimens restored as in group 4 but with QFP as in group 3. On all specimens, 2U-FPDs were placed with dual-curing resin cement. In order to simulate 10 years of clinical function, specimens were exposed to thermal cycling and mechanical loading with subsequent loading to failure. Kaplan-Meier curves were constructed, and log-rank tests were performed. Fracture force and patterns were compared by means of Kruskal-Wallis, Mann-Whitney U (post hoc), and Fisher exact tests, respectively (P = .05).
  
  
  RESULTS
  For specimens only with an access cavity, it was observed that 25% had catastrophic tooth fractures and the lowest load-to-fracture values. In all other groups, chipping combined with or without debonding occurred. Groups did not differ significantly regarding the survival rate (P = .603) and fracture patterns (P = .633), but they did for fracture load including technical failures (P = .017).
  
  
  CONCLUSIONS
  After 10 years of simulated clinical function, both defect extension and placement of QFP had no significant influence on survival of root-treated upper central incisors as abutments restored with zirconia-based 2U-FPDs.
authors.affiliation: Department of Prosthodontics, Geriatric Dentistry and Craniomandibular Disorders, Charité-Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: René
authors.initials: R
authors.lastname: Tunjan
authors.forename: Martin
authors.initials: M
authors.lastname: Rosentritt
authors.forename: Guido
authors.initials: G
authors.lastname: Sterzenbach
authors.forename: Arndt
authors.initials: A
authors.lastname: Happe
authors.forename: Roland
authors.initials: R
authors.lastname: Frankenberger
authors.forename: Rainer
authors.initials: R
authors.lastname: Seemann
authors.forename: Michael
authors.initials: M
authors.lastname: Naumann
mesh_terms: D003188:Composite Resins / Q000737:chemistry; D003442:Crowns; D000044:Dental Abutments; D003764:Dental Materials / Q000737:chemistry*; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003779:Denture Design; D003830:Denture, Partial, Fixed; D004955:Esthetics, Dental; D005898:Glass / Q000737:chemistry; D006801:Humans; D007180:Incisor / Q000473:pathology*; D008422:Materials Testing; D010865:Pilot Projects; D011176:Post and Core Technique / Q000295:instrumentation; D011791:Quartz / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D018915:Root Canal Preparation / Q000379:methods; D055116:Self-Curing of Dental Resins; D013314:Stress, Mechanical; D016019:Survival Analysis; D013696:Temperature; D013997:Time Factors; D014082:Tooth Fractures / Q000503:physiopathology; D019231:Tooth Preparation, Prosthodontic / Q000379:methods; D019553:Tooth, Nonvital / Q000628:therapy*; D015040:Zirconium / Q000737:chemistry*
chemical_list: D003188:Composite Resins; D003764:Dental Materials; D019279:Resin Cements; C009753:fiberglass; D011791:Quartz; D015040:Zirconium; C028541:zirconium oxide