Shear bond strength evaluation of different veneering systems on Ni-Cr alloys.

PURPOSE: The aim of this study was to evaluate the shear bond strength of four esthetic veneering materials on nickel-chromium (Ni-Cr) alloy. MATERIALS AND METHODS: Forty square patterns (10 x 10 x 1.5 mm) were cast with Ni-Cr, divided equally into four groups, and received four treatments for veneering: conventional porcelain-fused-to-metal (PFM), Artglass, Targis/Vectris, and Biodent light-cured prosthodontic composite resins. After sandblasting of the cast metal surfaces with 50 micro m alumina, the composites were applied to the surfaces according to manufacturers' recommendations. Shear bond strength was determined at a crosshead speed of 0.5 mm/min. Results were analyzed statistically with Kruskal-Wallis analysis of variance and multiple comparison tests. RESULTS: Mean shear bond strength values were 34.96 MPa for PFM, 14.17 MPa for Targis/Vectris, 13.64 MPa for Artglass, and 10.56 MPa for Biodent. The PFM group exhibited significantly higher bond strength values compared with the other three groups (p < 0.001). CONCLUSION: PFM showed considerably higher shear bond strength values than the three metal-resin bonding techniques.

Cephalometric evaluation of maxillomandibular relationships in patients wearing complete dentures: a pilot study.

The purpose of this study was to evaluate the changes in vertical and sagittal maxillomandibular relationship of the patients who had been wearing dentures for an extensive period. Fifteen edentulous patients (seven men and eight women; mean age 63.5 years) who had worn dentures for six to 16 years (mean 10 years) were selected for this study. New prostheses were fabricated by conventional methods, and the patients were evaluated cephalometrically before and after the new prosthesis. The results were compared by Wilcoxon signed rank test (P < .05). Results indicated that a prognathic mandible and a pseudo Class III relationship with a reduced occlusal vertical dimension became a normal Class I maxillomandibular relation when the new prosthesis was inserted. A better facial profile was achieved.

Tensile strength of type IV dental stones dried in a microwave oven.

STATEMENT OF PROBLEM: It is known that drying dental stones in a microwave oven can save time, but the strength of the material may be affected by different drying methods. PURPOSE: This study evaluated the diametral tensile strength (DTS) of 5 type IV gypsum products at different time intervals using microwave and air-drying methods. MATERIAL AND METHOD: . A total of 300 cylinder specimens were prepared from 5 type IV dental stones (Moldano, Amberok, Herastone, Shera-Sockel, and Fujirock; n = 60 per stone) in accordance with the manufacturers' recommendations. Half of the specimens of each stone (n = 30) were dried in open air within a temperature range of 20 +/- 2 degrees C; the other half (n = 30) underwent initial setting in a silicone rubber mold in open air for 10 minutes and then were dried in a microwave oven for 10 minutes. Within these groups, 10 specimens were tested under diametral compression at each of the following time periods: 30, 60, and 120 minutes after drying. Three-way analysis of variance and Scheffe's post hoc test were performed for statistical comparisons at a significance level of P<.05. RESULTS: At all time intervals, the diametral tensile strength values for dental stones dried in a microwave oven (mean 2.99 MPa) were significantly higher (P<.01) than the values for specimens dried in open air (mean 2.53 MPa). CONCLUSION: Within the limitations of this study, microwave oven drying had a positive effect on the diametral tensile strength of 5 type IV dental stones.