The apparent fracture toughness and elastic modulus-to-hardness ratio of metalceramic restorations was found to be significantly greater than that of individual porcelain specimens, presumably due to residual compressive stresses in their surface. A method of making a substructure for a dental restoration, which dental restoration has a substructure of an essentially dental metal and, fired thereon, a coating of an essentially dental ceramics, comprising applying a mixture of a dental metal powder and a thermoplastic polymeric material having a melting point above 50° C. ![]() Mean E/H was 20.2 for the crowns and 11.6 for the disks. Mean K c was 1.91 MPa.m 1/2 for the restorations and 0.98 MPa.m 1/2 for the individual specimens. Three Knoop indentations were also made for E/H measurement. An oil film was used to minimize slow crack growth due to atmospheric moisture. ![]() The specimens were gold-coated to enable the radial cracks formed on indentation with a Vickers microhardness tester to be more easily seen. Five metal-ceramic crowns were also made using Olympia metal and Vita VMK opaque and body porcelains. ![]() Five specimens of Vita VMK 68 body porcelain were made by hand condensation and vacuum-fired according to the manufacturer's instructions. An indentitation technique was used to compare the apparent fracture toughness (K c) and modulus of elasticity-to-hardness ratio (E/H) of metalceramic crowns with individual porcelain specimens.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |