title: A comparison of the effects of two burs on endodontic access in all-ceramic high lucite crowns.
abstract: OBJECTIVE
  The purpose of this study was to examine and compare the effects of diamond and tungsten carbide burs with respect to the preparation of access through all-ceramic crowns.
  
  
  METHODS
  Thirty extracted maxillary premolars were restored with all-ceramic crowns. Each specimen was assigned to one of two groups: (1) access opening prepared with a round diamond bur; (2) access opening prepared with a carbide fissure bur. Access preparations were scanned by means of scanning electron microscopy; observed were defects categorized as edge chipping, microcracks, and fractures.
  
  
  RESULTS
  Edge chipping around the access was universal. Significant chipping (x > or = 0.1 m) was seen in 43% of access peripheries. Eleven percent of the crowns fractured. chi(2) analysis (P <.05) demonstrated no statistical difference between the bur groups. Results of a t test revealed no statistical difference in edge chipping between the two bur types.
  
  
  CONCLUSIONS
  All-ceramic crowns bonded to extracted maxillary premolars may experience edge chipping, microcracks, and fractures at equal rates whether access is prepared with a round medium coarse diamond bur or a tungsten carbide fissure bur.
authors.affiliation: University of Iowa, Department of Family Dentistry, College of Dentistry, Iowa City, IA 52242-1001, USA.
authors.forename: D R
authors.initials: DR
authors.lastname: Haselton
authors.forename: P M
authors.initials: PM
authors.lastname: Lloyd
authors.forename: W T
authors.initials: WT
authors.lastname: Johnson
mesh_terms: D001641:Bicuspid; D002516:Ceramics; D016009:Chi-Square Distribution; D003442:Crowns / Q000706:statistics & numerical data; D003722:Dental Alloys; D018130:Diamond; D006801:Humans; D066298:In Vitro Techniques; D008437:Maxilla; D008855:Microscopy, Electron, Scanning; D019904:Polymethyl Methacrylate; D011897:Random Allocation; D018915:Root Canal Preparation / Q000295:instrumentation* / Q000706:statistics & numerical data; D013499:Surface Properties; D017973:Tungsten Compounds
chemical_list: D003722:Dental Alloys; D017973:Tungsten Compounds; C002802:tungsten carbide; D018130:Diamond; D019904:Polymethyl Methacrylate