title: Precision of fit of two margin designs for metal-ceramic crowns.
abstract: BACKGROUND
  Although metal-ceramic restorations are widely used, there is a lack of information about how the fit is affected by margin designs.
  
  
  OBJECTIVE
  This study measured and compared the precision of fit of metal-ceramic crowns with two margin designs.
  
  
  METHODS
  Thirty-two extracted human premolar teeth were prepared for complete-coverage restorations with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with improved stone type V. MC crowns were fabricated with a porcelain-butt margin on the buccal aspect (n = 32) and a feather-edge metal margin on the lingual aspect (n = 32), which served as a control group. Precision of fit was measured three times at the mid-buccal and mid-lingual margins of each crown with a profilometer. The data were statistically analyzed with the paired t-test (alpha < .05).
  
  
  RESULTS
  Mean marginal gap size of porcelain-butt margins was 27.93 microm (+/-15.84) and of feather-edge metal margins 42.43 microm (+/-24.12). The marginal gap size of feather-edge metal margins was statistically significantly greater than that of porcelain-butt margins (p = 0.0045).
  
  
  CONCLUSIONS
  The marginal fit of porcelain-butt margins was significantly better than that of feather-edge metal margins.
  
  
  CONCLUSIONS
  Porcelain-butt margins in this study had a better marginal fit than feather-edge metal margins, and thus have given clinicians evidence to prefer the use of porcelain-butt margins.
authors: Department of Endodontics, Prosthodontics, and Operative Dentistry, University of Maryland, Baltimore College of Dental Surgery, Baltimore, MD 21201, USA. Penwadee@umaryland.edu
authors: Penwadee
authors: P
authors: Limkangwalmongkol
authors: Gerard J
authors: GJ
authors: Chiche
authors: Markus B
authors: MB
authors: Blatz
mesh_terms: D003442:Crowns; D003734:Dental Casting Investment / Q000737:chemistry; D003735:Dental Casting Technique; D003760:Dental Impression Materials / Q000737:chemistry; D003761:Dental Impression Technique / Q000295:instrumentation; D003776:Dental Porcelain / Q000737:chemistry; D017267:Dental Prosthesis Design; D006801:Humans; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D011145:Polyvinyls / Q000737:chemistry; D012833:Siloxanes / Q000737:chemistry; D013499:Surface Properties; D019231:Tooth Preparation, Prosthodontic / Q000145:classification
chemical_list: D003734:Dental Casting Investment; D003760:Dental Impression Materials; D016876:Metal Ceramic Alloys; D011145:Polyvinyls; D012833:Siloxanes; C034183:vinyl polysiloxane; D003776:Dental Porcelain