This study evaluated the influence of firing procedures and layering thickness of porcelain on internal adaptation of maxillary anterior cantilever zirconia resin-bonded fixed dental prostheses (RBFDPs). Methods: The maxillary right central incisor on a model was prepared for a single-retainer zirconia RBFDP. A total of 36 frameworks of cantilever zirconia RBFDPs were classified into three groups (CB0.5, CB1.0, and CB2.0 groups) based on the thickness of the cut-back on the facial surface (0.5 mm, 1.0 mm, and 2.0 mm, respectively). Feldspathic porcelain was layered onto the facial surface of the zirconia RBFDP frameworks. Internal space widths between the abutment tooth and the framework were measured before and after porcelain firing by a replica technique. The internal space values before and after porcelain firings were compared using the paired t-test within the same group (α = 0.05). Differences in internal space values (distortion) between before and after porcelain firing were compared using one-way analysis of variance and Tukey multiple comparison tests. Results: For all framework designs, internal space values after porcelain firing were significantly higher than those before firing. Among all groups, the CB0.5 group showed the lowest internal distortion values for the whole measured area. The CB2.0 group showed higher distortion values than the CB1.0 group. Conclusions: Porcelain firing procedures negatively impacted the internal space in cantilever zirconia RBFDPs. In addition, the increased volume of layering porcelain had a negative effect on the internal distortion of maxillary anterior cantilever zirconia RBFDPs.
To investigate the effect of luting agent type on fracture loads of implant-supported ceramic prostheses in premolar region. Ninetynine implant-abutment complexes were divided into three different implant-supported prostheses: monolithic yttria-partially stabilized zirconia (Y-PSZ) restorations (MPZ specimens), porcelain layered on yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) restorations (PLZ specimens), and monolithic lithium disilicate ceramic restorations (MLD specimens). Implant-supported prostheses were luted with adhesive resin luting agent (RLA), glass ionomer cement (GIC), or zinc phosphate cement (ZPC). For MPZ and MLD specimens, fracture loads were significantly higher for RLA group than for GIC and ZPC groups. For PLZ specimens, fracture loads did not significantly differ in relation to luting agent. Fracture loads were significantly higher for MPZ specimens than for other test specimens, regardless of luting agent. Use of an adhesive resin luting agent is recommended for placement of premolar implant-supported monolithic Y-PSZ and lithium disilicate ceramic prostheses.
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