title: Retention forces and seating discrepancies of implant-retained castings after cementation.
abstract: OBJECTIVE
  The purpose of this in vitro study was to evaluate the influence of cement type and application technique on seating discrepancies and retention forces of noble alloy castings cemented on titanium abutments.
  
  
  METHODS
  Eugenol-free zinc oxide (Freegenol), zinc phosphate (Harvard), glass ionomer (KetacCem), polycarboxylate (Durelon), and self-adhesive resin (RelyX Unicem) cements were used. The inner surfaces of the castings were either completely coated or half-coated with cement. Abutments were used as delivered with a machined surface for the first part of the study. Groups of 8 castings were cemented in both ways. For the second part of the study, the abutments were air-abraded (aluminum oxide, 50 microm particle size), and groups of 8 completely coated castings were cemented with all cements. Marginal discrepancies were measured before and immediately after cementation. Tensile tests were conducted to measure the retention forces. Statistical analysis was performed with pair-wise comparison using the Wilcoxon rank sum test modified by Bonferroni-Holm.
  
  
  RESULTS
  Change in seating discrepancies did not differ significantly among the different application techniques. The median retention forces for completely-coated castings were 177 N for eugenol-free zinc oxide, 346 N for zinc phosphate, 469 N for glass ionomer, 813 N for polycarboxylate, and 653 N for self-adhesive resin. With respect to retention force, 3 significantly different groups (P < .05) were identified: (1) zinc oxide, (2) zinc phosphate/glass ionomer, and (3) polycarboxylate/self-adhesive resin. No differences in retention between the 2 coating techniques were found for any cement. However, air abrading the abutments resulted in increased retention of the castings for some of the cements.
  
  
  CONCLUSIONS
  Half-coating of the restorations with cements did not result in reduced retention values compared to the complete coating technique, but air abrasion resulted in increased retention with some cements.
authors.affiliation: Department of Prosthodontics, Propaedeutics and Dental Materials, Dental School, Christian-Albrechts-University at Kiel, Germany. mwolfart@proth.uni-kiel.de
authors.forename: Mona
authors.initials: M
authors.lastname: Wolfart
authors.forename: Stefan
authors.initials: S
authors.lastname: Wolfart
authors.forename: Matthias
authors.initials: M
authors.lastname: Kern
mesh_terms: D020906:Air Abrasion, Dental; D003738:Dental Cements / Q000737:chemistry*; D017268:Dental Prosthesis Retention / Q000379:methods*; D019094:Dental Prosthesis, Implant-Supported / Q000379:methods*; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D003738:Dental Cements