title: Effect of endodontic access cavity preparation on monolithic and ceramic veneered zirconia restorations.
abstract: OBJECTIVE
  Due to the high chipping rates observed in veneered zirconia ceramic restorations, the use of monolithic zirconia restorations has been recommended. This study tried to compare veneered and monolithic zirconia fixed dental prostheses (FDPs) with respect to the amount of damage induced by endodontic access preparation.
  
  
  METHODS
  Monolithic and ceramic veneered (n = 10) three-unit restorations (retainers: first premolar and first molar; pontic: second premolar) were subject to endodontic access cavity preparation in both retainers using a diamond rotary instrument under continuous water cooling. The number of chipping fractures and microfractures detected using the fluorescent penetrant method were recorded. Statistical analysis was based on Wilcoxon rank sum tests with Bonferroni correction (level of significance α = .05).
  
  
  RESULTS
  Only one microfracture could be identified in the group of monolithic FDPs while a maximum of seven microfractures and three chipping fractures per retainer crown were recorded in the group of veneered restorations. At the premolar site, the veneered restorations showed significantly more microfractures (P = .0055) and chipping fractures (P = .0008). At the molar site, no significant difference with respect to microfractures could be detected (P = .0767), while significantly more chipping fractures occurred in the veneered samples (P = .0293).
  
  
  CONCLUSIONS
  Monolithic zirconia restorations seem to be less susceptible to damage when endodontic access cavities have to be prepared as compared to veneered zirconia reconstructions. However, no conclusions can be drawn on the long-term performance of a specific restoration based on this study.
authors.forename: Tanja
authors.initials: T
authors.lastname: Grobecker-Karl
authors.forename: Mirko
authors.initials: M
authors.lastname: Christian
authors.forename: Matthias
authors.initials: M
authors.lastname: Karl
mesh_terms: D017076:Computer-Aided Design; D003776:Dental Porcelain; D017267:Dental Prosthesis Design; D019232:Dental Restoration Failure; D003801:Dental Veneers; D003830:Denture, Partial, Fixed; D006801:Humans; D016876:Metal Ceramic Alloys; D018915:Root Canal Preparation / Q000379:methods*; D015040:Zirconium
chemical_list: D016876:Metal Ceramic Alloys; D003776:Dental Porcelain; D015040:Zirconium; C028541:zirconium oxide