title: Metal-ceramic bridges from commercial dental laboratories: alloy composition, cost and quality of fit.
abstract: The quality of construction of fixed bridge prostheses directly affects their long-term survival. The cost, alloy composition and marginal fit of bridges made by 30 commercial dental laboratories is assessed. Duplicate models of a three unit bridge preparation were sent to 30 different laboratories, as if required for a patient receiving treatment under the General Dental Service. Material was sent via general dental practitioners, requesting metal-ceramic bridges made from 45% Au alloy, precious metal or non-precious metal. Proximal contacts were overbuilt at 65% of sites and pontic tissue contacts were excessive in all but one bridge. Eight laboratories did not use alloys corresponding to the request made. The mean marginal gaps of non-precious metal bridges (145 microns) were significantly greater than those for 45% gold alloy (106 microns). Marginal fit was poor and a number of factors have been observed, with other postulated, which may have contributed to this problem.
authors.affiliation: Department of Restorative Dentistry, University of Sheffield, Western Bank.
authors.forename: S E
authors.initials: SE
authors.lastname: Northeast
authors.forename: R
authors.initials: R
authors.lastname: Van Noort
authors.forename: A
authors.initials: A
authors.lastname: Johnson
authors.forename: R B
authors.initials: RB
authors.lastname: Winstanley
authors.forename: G E
authors.initials: GE
authors.lastname: White
mesh_terms: D002516:Ceramics; D003722:Dental Alloys / Q000737:chemistry / Q000191:economics / Q000592:standards*; D003735:Dental Casting Technique / Q000592:standards; D003830:Denture, Partial, Fixed / Q000191:economics / Q000592:standards*; D006047:Gold Alloys / Q000592:standards; D006801:Humans; D007754:Laboratories, Dental / Q000592:standards*; D003765:Models, Dental / Q000592:standards; D010165:Palladium; D011787:Quality of Health Care; D006113:United Kingdom
chemical_list: D003722:Dental Alloys; D006047:Gold Alloys; D010165:Palladium