Statement of problem: Various strategies have been proposed to reduce the cement space of foundation restorations for endodontically treated teeth. However, they may add more operative steps, or the dentist must keep ...
Statement of problem: Various strategies have been proposed to reduce the cement space of foundation restorations for endodontically treated teeth. However, they may add more operative steps, or the dentist must keep different sizes of drills and posts in stock. A 2-piece universal adjustable post system has been developed to overcome this problem, but whether the system has acceptable fatigue survival performance is unclear. Purpose: The purpose of this in vitro study was to evaluate the fatigue survival and stress distribution of endodontically treated teeth without a ferrule and restored with different glass fiber post strategies versus a recently introduced universal 2-piece fiber post system. Material and methods: Bovine incisor roots were randomly assigned to 3 groups as per the post used (n=13): adapted glass fiber post with post space preparation of the same size, composite resin-custom glass fiber post (CTM), and universal 2-piece glass fiber-reinforced composite resin post (UNI). The posts were adhesively luted, the composite resin core was added, and a composite resin crown was produced with computer-aided design and computer-aided manufacturing (CAD-CAM), and then adhesively luted to each core. A fatigue test was performed with the stepwise stress method (10 000 cycles/step;20 Hz;load=100 N to 750 N;step=50 N) until fracture, and the failure mode analyzed. The stress distribution was evaluated by finite element analysis with the maximum principal stress criteria by following the parameters of the in vitro test. The solids were considered homogeneous, linear, and isotropic, except for the glass fiber post (orthotropic), and a load of 450 N at 30 degrees was applied. The fatigue failure load and the number of cycles for failure were analyzed with Kaplan-Meier and Mantel-Cox (log rank test) (α=.05). The finite element analysis results were analyzed with colorimetric graphs. Results: The highest fatigue failure load and the number of cycles for failure were
The aim of this study is to assess the effect of the timing of adjustment on the fatigue flexural behavior and surface characteristics of lithium disilicate-based ceramics. Discs (Ø = 15 and 1.2 mm thickness) of ...
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The aim of this study is to assess the effect of the timing of adjustment on the fatigue flexural behavior and surface characteristics of lithium disilicate-based ceramics. Discs (Ø = 15 and 1.2 mm thickness) of four lithium disilicate-based ceramics (IPS *** CAD, Ivoclar AG; Rosetta SM, HASS Corp; T-Lithium, Shenzhen Upcera Dental Technology Co Ltd; Goozir, Shenzhen Yurucheng Dental Materials Co) were obtained and randomly allocated into three groups based on the timing of adjustment factor: CTRL-directly crystallized without any additional treatment; PRE-subjected to adjustment precrystallization; post-adjusted postcrystallization. The specimens underwent cyclic fatigue biaxial piston-on-three-balls flexural testing (n = 10; 20 Hz frequency, 10,000 cycles per step, initial stress of 100 MPa, and step-size of 25 MPa). Fatigue flexural strength (FFS) and the number of cycles for fatigue failure (CFF) were recorded and submitted to factorial (two-way analysis of variance [ANOVA]), survival (Kaplan-Meier and Mantel-Cox tests) and Weibull analysis. Surface roughness data were collected and submitted to two-way ANOVA and Tukey's posthoc tests. Fractographic and topographic features were descriptively and qualitatively analyzed. Both the adjustment (p < 0.0001 and F = 49.18) and material (p < 0.0001 and F = 11.99) factors showed a statistically significant impact on the FFS and CFF, as did their interaction (p = 0.03 and F = 2.51), indicating higher values for the CTRL and PRE groups compared to the post group, and for the T-LITHIUM, EMAX, and GOOZIR materials compared to ROSETTA. Regarding the Weibull modulus, all groups showed similar statistical values. Surface roughness was also influenced by both factors (p < 0.05-PRE > post > CTRL). ROSETTA exhibited higher Ra values than EMAX and higher Rz values than both EMAX and TALMAX. Fractures always originated at surface defects in the tensile stress concentration region. Topographic features revealed prominent scratches
Antioral cancer drugs need a greater antiproliferative impact on cancer than on normal cells. Demethoxymurrapanine (DEMU) inhibits proliferation in several cancer cells, but an in-depth investigation was necessary. Th...
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