title: Marginal integrity of direct and indirect castings for implant abutments.
abstract: OBJECTIVE
  Current implant systems with screw-retained abutments permit direct laboratory fabrication of castings. Computer aided drafting systems further enhance the fabrication of computer-milled abutments (CMAs) and castings. The purpose of this study was to compare marginal accuracy, as measured by gap size, of castings made directly on CMAs with those made indirectly on epoxy and stone dies.
  
  
  METHODS
  Castings were made directly for 10 CMAs. Marginal gap measurements were made with the castings seated on the abutments (group A). Castings were also made indirectly on stone and epoxy dies obtained from impressions of the abutments. Marginal gap measurements were made with these indirectly made castings seated on their CMAs (groups B and E). In addition, the directly made castings were transferred between CMAs and marginal gap measurements made (group D). Marginal gap measurements of the groups were compared with analysis of variance (ANOVA) and pair-wise comparisons (Scheffé test).
  
  
  RESULTS
  Groups A and D had marginal gaps of less than 100 microm. These marginal gaps were significantly smaller (P < .05) than the gaps of groups B and E, made on dies, which were approximately 200 to 500 microm.
  
  
  CONCLUSIONS
  With CMAs, it is possible to make an exact duplicate of the abutment. This permits the laboratory to make castings on duplicate abutments with greater precision than can be obtained using the indirect technique. Direct fabrication of castings resulted in smaller marginal gaps, which in turn allows a better marginal seal and improved retention of castings.
authors.affiliation: Restorative Dentistry, New Jersey Dental School, Newark, New Jersey 07103, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Ganz
authors.forename: Nainesh
authors.initials: N
authors.lastname: Desai
authors.forename: Saul
authors.initials: S
authors.lastname: Weiner
mesh_terms: D000044:Dental Abutments; D003735:Dental Casting Technique; D015921:Dental Implants; D018772:Dental Marginal Adaptation
chemical_list: D015921:Dental Implants