title: Comparison of marginal fit between all-porcelain margin versus alumina-supported margin on Procera Alumina crowns.
abstract: OBJECTIVE
  Procera Alumina crowns are widely used; however, the effect of crown margin design on marginal fit is unknown. This study measured and compared the precision of fit of Procera Alumina crowns with two crown margin designs: all-porcelain versus alumina-supported margins.
  
  
  METHODS
  Sixteen noncarious extracted human premolars were prepared for Procera((R)) Alumina crowns with an internally rounded shoulder preparation. Impressions were made from all teeth, and master dies were poured with type IV dental stone. The specimens were randomly divided into two groups. Procera Alumina crowns were fabricated: eight crowns with circumferential porcelain-butt (all-porcelain) margins and eight crowns with coping (alumina-supported) margins (control). Precision of fit was measured at six points on each crown with a profilometer (profile projector). The data were statistically analyzed with an independent-samples t-test (alpha < 0.05).
  
  
  RESULTS
  The mean marginal gap size (microm) of coping margins was 68.07 +/- 16.08 and of porcelain-butt margins was 101.29 +/- 43.71. There was no statistically significant difference (p= 0.065) of the marginal gap size between coping margins and porcelain-butt margins.
  
  
  CONCLUSIONS
  The results of this study demonstrate that there was no statistically significant difference in the marginal fit of coping and porcelain-butt margins. Both margin designs are within clinically acceptable ranges. Therefore, clinicians may choose to use a coping margin, as it is less labor intensive and requires less time for fabrication, unless there is a specific high esthetic need for a porcelain-butt margin.
authors.affiliation: Department of Endodontics, Prosthodontics, and Operative Dentistry, University of Maryland, Baltimore College of Dental Surgery, Baltimore, MD 21201, USA. penwadee@umaryland.edu
authors.forename: Penwadee
authors.initials: P
authors.lastname: Limkangwalmongkol
authors.forename: Edwin
authors.initials: E
authors.lastname: Kee
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Chiche
authors.forename: Markus B
authors.initials: MB
authors.lastname: Blatz
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D003442:Crowns; D000044:Dental Abutments; D003764:Dental Materials / Q000737:chemistry*; D003775:Dental Polishing / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D017267:Dental Prosthesis Design; D003801:Dental Veneers; D006801:Humans; D008422:Materials Testing; D016876:Metal Ceramic Alloys / Q000737:chemistry*; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*; D019231:Tooth Preparation, Prosthodontic / Q000379:methods
chemical_list: D003764:Dental Materials; D016876:Metal Ceramic Alloys; C077451:Procera; D003776:Dental Porcelain; D014025:Titanium; D000537:Aluminum Oxide