Fracture strength and fractographic analysis of zirconia copings treated with four experimental silane primers

This study evaluated and compared the effect of new four experimental silane coupling agents on the fracture strength of zirconia copings. The findings were supported with fractographic and finite element analyses. All together 125 zirconia copings with a ?wall thickness of 0.6mm were fabricated on identical nickel-chromium master dies and then divided randomly into five groups (n=25). Four test groups were prepared according the experimental silane primer (labeled: OIWA1, OIWA2, OIWA3 and OIWA4) ?and one control group without silanization. The silane monomers used were: ?3-methacryloxypropyltrimethoxysilane (in OIWA1), ?3-acryloxypropyltrimethoxysilane (in OIWA2), ?3-?isocyanatopropyltriethoxysilane (in OIWA3) and styrylethyltrimethoxysilane (in OIWA4). Tribochemical sandblasting (silica-coating) treatment was performed to the inner surface of the copings in the ?test groups. All the specimens were silanized at the inner surfaces of the zirconia copings. Self-?adhesive universal resin cement was used to cement the copings to ?the underlying master die. Zirconia copings were vertically loaded on the ?cusp ?area until the first crack failure was occurred using Precision Universal Tester ?at a ?constant crosshead speed of 1mm/min. Then, the machine ?was manually controlled to cause more failure ?to further determine the texture of fracture. Three dimensional finite element analysis and fractography were performed to support the fracture strength findings. Based on the finite element analysis results, zirconia silanized with ?3-acryloyloxypropyltrimethoxysilane showed the highest fracture strength with a mean of ?963.75?N (SD 4.5N), while zirconia copings silanized with ?3-methacryloyloxypropyltrimethoxysilane showed a mean fracture strength value of ?925.65N (SD 2.4N). Styrylethyltrimethoxysilane-silanised zirconia showed mean fracture strength of 895.95N (SD 3.5N). Adding silane coupling agents to the resin-zirconia interface increased the fracture strengths significantly (ANOVA, p<0.05). Silanization with four new experimental silane primers in vitro produced significantly ?greater fracture strength than the control group not treated with the test silane.

Employers’ expectations of the employability skills needed in the sport and recreation environment

This study aimed to test the applicability of the Survey of Employability Skills Needed in the Workforce (SESNW) (Robinson, 2006) in Greek sport employers. One hundred ninety three employers from three sectors participated in the study. Consecutive EFAs led to six robust factors of employability skills, labeled Professional Behavior & Development, Leadership & Influence, Problem Solving, Organization & Time Management, Communication Ability and (Inter)Personal skills. All factors were highly rated by the employers were no differences occurred between employment sectors. By understanding the competencies expected by employers, Universities may better align undergraduate programs with industry needs, enhancing the graduates' employability. © 2016 Elsevier Lt

Long Term Fatigue Behavior of Zirconia Based Dental Ceramics

This study evaluated the influence of cyclic loading on zirconia bar-shaped specimens after being subjected to three different surface treatments: particle abrasion with either 50 μm or 110 μm alumina and grinding with diamond points, while polished specimens served as a control. Statistical analysis revealed significant reduction (38-67%) in flexure strength (P &lt; 0.001) after three million cycles of dynamic loading for all surface treatments. Scanning electron imaging revealed grain boundary thickening, grain pull-out, and micro-cracking as the main structural defects. The results suggest that various surface treatments of zirconia based dental ceramics may significantly influence their long term fatigue resistance in the oral environment

An In Vitro Investigation of Veneered Zirconia-Based Restorations Shade Reproducibility

© 2016 by the American College of Prosthodontists Purpose: To examine the effects of the veneering technique on the shade reproducibility of zirconia-based crowns. Materials and Methods: An artificial tooth was prepared with a 1.2 mm heavy chamfer finish line and 8° taper. The prepared tooth was scanned using CAD/CAM technology to fabricate 45 cobalt chromium (CoCr) testing dies. One CoCr die was scanned, and 45 zirconia copings were milled and devided according to the veneering technique into 3 groups of 15 specimens each: layering veneering (LV) using Vita Vm9, overpressing veneering (OV) using Vita Pm9, and digital veneering (DV) using Vita Triluxe forte. All veneering layers had the same shade (A2). The specimens were cemented onto the testing dies using glass inomer cement. A spectrophotometer was used to measure the shade coordinates (L, C, h, a, b) for a Vita A2 shade tab and for each specimen. Both the CIE Lab (ΔEab) and the CIE DE2000 (ΔE00) color difference formulas were applied to compare the shade tab and the study groups. One-way ANOVA and multiple comparison Bonferroni tests were applied for statistical analysis of the results. Results: Means and standard deviations (SDs) of ΔEabwere 2.3 ± 1.3 for LV, 3.5 ± 0.8 for OV, and 4.0 ± 0.7 for DV. Means and SDs of ΔE00were 1.4 ± 0.8 for LV, 2.1 ± 0.5 for OV, and 3.1 ± 0.4 for DV. ΔEabof LV group was significantly lower (p \u3c 0.05) than both OV and DV groups, whereas the difference in ΔEabbetween OV and DV groups was not significant (p = 0.39). The differences in ΔE00between all groups were significant (p \u3c 0.05). Conclusions: LV group was superior to other groups in terms of shade reproducibility. The ΔEaband the ΔE00values of LV and OV groups were within clinically acceptable ranges; however, the ΔEaband the ΔE00values of group DV were beyond the clinically acceptable ranges. The ΔE00formula demonstrated a statistically significant difference between OV and the DV groups, while the ΔEabformula did not. The zirconia veneering technique had a significant influence on the shade reproducibility of zirconia-based crowns