title: Retrospective and clinical evaluation of retrievable, tooth-implant supported zirconia-ceramic restorations.
abstract: OBJECTIVE
  Permanent cementations of zirconia-ceramic restorations may conflict with the rationale for retrievability of implant-supported restorations. The aim of this study was to test the hypothesis that retrievable, tooth-implant supported FDPs made of veneered zirconia ceramic cores are a viable treatment alternative.
  
  
  METHODS
  Restorations of patients in private practice and dental clinic were evaluated by reviewing patient records retrospectively and performing a final clinical examination. Permanently cemented copings protected the tooth abutments. The zirconia-ceramic restorations were semi-permanently cemented to the copings and the implant abutments using acrylic-urethane cement. In addition to Kaplan-Meier analyses for complications, the effect of age, gender, signs of bruxism, jaw and number of units on complications was estimated using Cox regression analyses (significance p < 0.05).
  
  
  RESULTS
  The follow-up period for 23 patients (nine with signs of bruxism) with four anterior and 27 posterior zirconia-ceramic restorations (3-12 units) ranged from 12.7-47.9 months. Core fractures of two posterior prostheses in patients with signs of bruxism yielded a 40-month survival rate of 93.5%. There were 10 cohesive chippings within the veneering porcelain for seven patients (six patients with signs of bruxism), which resulted in 40-month chipping rates of 5.6% among non-bruxers and 100% among patients with signs of bruxism. The hazard ratio for signs of bruxism was 20 (95% confidence interval: 2.1-188.3, p = 0.009).
  
  
  CONCLUSIONS
  Retrievable, tooth-implant supported restorations made of zirconia-ceramics should be used with caution because of some core fractures and a considerable number of minor veneer fractures. The fracture risk was very high among patients with signs of bruxism. Due to the low number of occasions for intentional retrievals, a recommendation to use semi-permanently cemented, all-ceramic FDPs would still be premature.
authors: Department of Prosthodontics, Gerodontology and Biomaterials, Center of Oral Health, University Medicine of Greifswald, Germany. mundt@uni-greifswald.de
authors: Torsten
authors: T
authors: Mundt
authors: Friedhelm
authors: F
authors: Heinemann
authors: Christof
authors: C
authors: Schankath
authors: Christian
authors: C
authors: Schwahn
authors: Reiner
authors: R
authors: Biffar
mesh_terms: D002516:Ceramics / Q000737:chemistry*; D015921:Dental Implants; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D015040:Zirconium / Q000737:chemistry*
chemical_list: D015921:Dental Implants; D015040:Zirconium