Universidade de Passo Fundo

About: Universidade de Passo Fundo is a education organization based out in Passo Fundo, Brazil. It is known for research contribution in the topics: Population & Context (language use). The organization has 3464 authors who have published 4323 publications receiving 43906 citations.

Color difference thresholds in dentistry.

Abstract: Purpose The aim of this prospective multicenter study was to determine 50:50% perceptibility threshold (PT) and 50:50% acceptability threshold (AT) of dental ceramic under simulated clinical settings. Materials and Methods The spectral radiance of 63 monochromatic ceramic specimens was determined using a non-contact spectroradiometer. A total of 60 specimen pairs, divided into 3 sets of 20 specimen pairs (medium to light shades, medium to dark shades, and dark shades), were selected for psychophysical experiment. The coordinating center and seven research sites obtained the Institutional Review Board (IRB) approvals prior the beginning of the experiment. Each research site had 25 observers, divided into five groups of five observers: dentists—D, dental students—S, dental auxiliaries—A, dental technicians—T, and lay persons—L. There were 35 observers per group (five observers per group at each site ×7 sites), for a total of 175 observers. Visual color comparisons were performed using a viewing booth. Takagi–Sugeno–Kang (TSK) fuzzy approximation was used for fitting the data points. The 50:50% PT and 50:50% AT were determined in CIELAB and CIEDE2000. The t-test was used to evaluate the statistical significance in thresholds differences. Results The CIELAB 50:50% PT was ΔEab = 1.2, whereas 50:50% AT was ΔEab = 2.7. Corresponding CIEDE2000 (ΔE00) values were 0.8 and 1.8, respectively. 50:50% PT by the observer group revealed differences among groups D, A, T, and L as compared with 50:50% PT for all observers. The 50:50% AT for all observers was statistically different than 50:50% AT in groups T and L. Conclusion A 50:50% perceptibility and ATs were significantly different. The same is true for differences between two color difference formulas ΔE00/ΔEab. Observer groups and sites showed high level of statistical difference in all thresholds. Clinical Significance Visual color difference thresholds can serve as a quality control tool to guide the selection of esthetic dental materials, evaluate clinical performance, and interpret visual and instrumental findings in clinical dentistry, dental research, and subsequent standardization. The importance of quality control in dentistry is reinforced by increased esthetic demands of patients and dental professionals.

The clinical success of all-ceramic restorations.

Abstract: Background The authors conducted a comprehensive literature review to compile and compare clinical evidence for the treatment of teeth using all-ceramic restorations Types of Studies Reviewed The authors searched the English-language peer-reviewed literature using MEDLINE and PubMed with a focus on research published between 1993 and 2008 They also conducted a hand search of relevant dental journals They reviewed randomized controlled trials, nonrandomized controlled studies, longitudinal experimental clinical studies, longitudinal prospective studies and longitudinal retrospective studies Results Evidence suggests that for veneers, intracoronal restorations and complete-coverage restorations for single-rooted anterior teeth, clinicians may choose from any all-ceramic system on the basis of esthetic needs (many systems have had greater than 90 percent success at six years) Well-studied molar restorations include those made of alumina and, increasingly, zirconia and bonded lithium disilicate Reasonable evidence has shown the effectiveness of anterior three-unit fixed partial dentures made of lithium disilicate, alumina and zirconia For three-unit restorations involving a molar, expert consensus suggests that only zirconia-based systems are indicated Clinical Implications Available evidence indicates the effectiveness of many all-ceramic systems for numerous clinical applications Bonding has been shown to increase clinical success Studies of zirconia prostheses indicate problems with porcelain cracking

Antioxidant responses of wheat plants under stress

Abstract: Currently, food security depends on the increased production of cereals such as wheat (Triticum aestivum L.), which is an important source of calories and protein for humans. However, cells of the crop have suffered from the accumulation of reactive oxygen species (ROS), which can cause severe oxidative damage to the plants, due to environmental stresses. ROS are toxic molecules found in various subcellular compartments. The equilibrium between the production and detoxification of ROS is sustained by enzymatic and nonenzymatic antioxidants. In the present review, we offer a brief summary of antioxidant defense and hydrogen peroxide (H2O2) signaling in wheat plants. Wheat plants increase antioxidant defense mechanisms under abiotic stresses, such as drought, cold, heat, salinity and UV-B radiation, to alleviate oxidative damage. Moreover, H2O2 signaling is an important factor contributing to stress tolerance in cereals.