Influence of time and hydration (ageing) on flexural strength of Yttrium stabilized Zirconia polycrystals (Y-TZP) fabricated with different CAD-CAM Systems

Objectives: To evaluate the effect of time and hydration (ageing) on flexural strength of yttrium-stabilized zirconia polycrystals (Y-TZP) zirconia fabricated from three different materials. Methods: This in-vitro study was performed from June to September 2019. Y-TZP bars, measuring 2 x 3 x 20 mm were prepared and sintered from three different materials, Group-1: LAVA™ Zirconia (3M™ ESPE, US) (control) Group-2: Vita In-Ceram YZ (VITA, Germany) and Group-3: Aadva™ Zirconia (Zr) (GC Advanced technologies Inc.). 30 zirconia bars per group were prepared using sectioning of blocks with isomet saw. Followed by sintering in furnaces for recommended temperature cycles. One side of bars were polished and beveled for flexural testing. Groups of specimens were divided into subgroups of 3 (n=10) based on the ageing (distilled water in the incubator at 37ºC) durations (48 Hrs and two and half years). Ten specimens in each material groups were not aged (controls). Samples were exposed to a static force in a three-point bend test using a universal instron-testing machine until fracture. Scanning electron microscopic assessment was performed for fractured specimens for ageing. Data was analyzed using ANOVA and Tukey post hoc test. Results: The mean flexural strength at baseline for Group-1: LAVA™ Zirconia, group (632.7 ± 136.5 MPa) 2: Vita In-Ceram YZ (1036.3 ± 229.6 MPa), and Group-3: Aadva™ Zirconia (1171.3 ± 266.3 MPa) were significantly different. Group-2 and Group-3 specimens showed higher strength compared to Group-1 specimens, irrespective of the ageing duration (p<0.05). Analysis of pooled data for flexural strength for materials by aging period (baseline, after 48 hours and after 2 and ½ years) showed that there was significant reduction of strength with increasing duration (p<0.05). Conclusions: Y-TZP showed variations in flexural strength depending on the material type. Ageing duration exhibited significant influence on the flexural strength of Y-TZP when comparing no ageing to two and half years. Vita In-Ceram YZ and Aadva Zirconia (Zr) showed higher and clinically acceptable flexural strength outcomes. doi: https://doi.org/10.12669/pjms.37.3.3996 How to cite this:Al-Aali KA, Alresayes S, Alhenaki AM, Vohra F, Abduljabbar T. Influence of time and hydration (ageing) on flexural strength of Yttrium stabilized Zirconia polycrystals (Y-TZP) fabricated with different CAD-CAM Systems. Pak J Med Sci. 2021;37(3):---------. doi: https://doi.org/10.12669/pjms.37.3.3996 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Meat tenderization using bromelain enzyme extracted from pineapple waste

Tenderization is an important method to improve the quality and palatability of meat. In comparison to conventional chemical and physical methods of meat tenderization, enzymatic treatment is more economical and healthy. In the present study proteolytic enzyme bromelain was used for this purpose. Bromelain enzyme was extracted from pineapple, quantified and optimized concentration was used for treating the muscle fibre of meat. Tenderness was measured. pH and cooking loss were not significantly (P>0.05) decreased, but water-holding capacity and protein content were significantly (P<0.05) increased with the concentration and ageing. Duration of marination was optimized and SDS- PAGE electrophoresis was conducted to estimate protein. The results proved that bromelain enzyme is an effective method of tenderization used to improve the quality of meat.

Investigation of the Influence of Bonding and Thermal Ageing Duration on the Peeling Strength of Knitted Materials’ Bonds

Bonding technology namely as “sew free” technology is usually applied for joining the pieces of sportswear and leisure clothing. Influence of the thermal ageing duration on the peeling strength of woven fabric and knitted materials bonded at 150°C temperature for 10 s, 20 s, 30 s, and 40 s durations with two polyurethane films of 0.175 mm and 0.127 mm thicknesses has been investigated in this research. Based on the research results it was shown that the peeling strength of the textile bonds is dependent on material type and bonding duration, but it is not highly affected by the ageing at 45°C temperature for 150 min, 300 min, and 450 min. During concluding it may be stated that ageing at 45°C temperatures is not main factor influencing the bond quality during its exploitation in high temperature environment.

A Study on the Dielectric Properties of RBDPO Olein under Low Temperature Thermal Ageing

A number of studies have been carried out previously to investigate the suitability of palm oil as dielectric insulation fluid in transformers. Among the important studies is the ageing performance of palm oil. In this paper, a study was carried out to investigate the dielectric properties of Refined Bleached and Deodorized (RBDPO) Olein after subjected to thermal ageing. A low temperature ageing was carried out at 85°C for 5 days. The AC breakdown voltage, dielectric dissipation factor, relative permittivity and resistivity of RBDPO were examined throughout the ageing duration. It was found that the RBDPO performs reasonably well under low temperature ageing.

Beef tenderness variation due to animal production factors and the effects of electrical stimulation, carcass suspension method, chill rate and ageing duration

Purchasing specifications for beef carcasses have been aimed at reducing carcass variability and elevating the visual and keeping qualities of retail cuts. But more recently, the Meat and Livestock Commission's blueprint for improved consistent quality beef has incorporated a number of post-mortem treatments aimed at improving tenderness. Do these treatments which include electrical stimulation, pelvic bone suspension, slow chilling and prolonged ageing, exert an influence on quality which masks the intrinsic variation due to the primary production factors of feed, age, sex and possibly breed, or are the production and post-mortem effects additive? To what extent are the post-mortem treatments themselves additive?