Difference between heartwood and sapwood
Forest Products Laboratory (U.S.)
1919
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5 records were found.
Titanium has been widely used for dental implant applications because their attractive properties such as low Young modulus, good fatigue strength, excellent corrosion resistance and biocompatibility. However it cannot meet all clinical requirements. 1-2 When inserted in the oral environment, dental implants are submitted to a complex degradation phenomena occurring due to the interaction of tribological and corrosive phenomena which can result on its failure. In
fact, most of the failures are a result of the combined action of mechanical solicitations (sliding or abrasive wear, erosion, impact, fretting or fatigue processes) and chemical solicitations as a consequence of contact with saliva, cells or bacteria. Consequently, dental implants become part of a tribocorrosion system, and the investigation of the tribocorrosion mechanisms i...
Low-fusing dental porcelains are commonly used for the fabrication of aesthetic restorations to prevent oxidation of NiCrMo, CoCrMo and titanium substructures. The aim of this study was to characterize one feldspar-based commercial porcelain in order to obtain information on the chemical composition, thermal expansion and particle size distribution. Opaque and dentin commercial porcelains have been selected for this purpose. The chemical analyses were carried out by XRD and X-ray fluorescence. The particle size distribution of the porcelains was measured by a particle analyzer associated to the CILAS 2.56 software. Finally, the thermal expansion was characterized by dilatometry. Analyzing the chemical composition, it was observed that the porcelain presented high ZrO2 content. On the other hand, the majority of the porcelains present l...
Titanium and titanium alloys have been widely used in orthopeadics and dental implants because of their excellent properties such as low modulus, good fatigue strength, good corrosion resistance and biocompatibility. However, their poor wear resistance still limits their application. When inserted in the oral environment dental implants are under a complex degradation phenomenon as a result of the combined action of chemical and mechanical solicitations, which can result in its failure. The relatively poor wear resistance of titanium may be improved by surface modification, namely by anodic oxidation. Also, as suggested by recent works carried out using animal models, bone regeneration may be enhanced by acting on the surface topography of the implant, essentially if the an oxide is present at the surface.
The present study aims to in...
Partial fixed prosthodontic restoration is used to rehabilitate both the form and function of partial or total compromised teeth and must remain permanently joined to the remaining teeth. The most useful material in prosthodontics is feldspar porcelain, commercialized as aluminosilicate powders. Dental porcelains depict limited mechanical strength to rehabilitate extensive spaces. The association of porcelain with Ni-Cr metallic infrastructures allows the metallic component to compensate for the brittle nature of porcelain, thus preserving the thermal insulation, aesthetics and, most important, reducing the possibility of cracking during mastication efforts. Cohesive flaws caused by low mechanical strength connect the metallic substructure to the oral environment, characterized by the presence of an electrolytic solution (saliva), aggr...
External corrosion is one of the most common causes of oilwell casing failure. Hostile
environments can be due to acidizing treatments. Although it is common to add corrosion inhibitors
and oxygen scavengers in acidic solutions to control external casing corrosion, their real efficiency
is unknown yet. Therefore, it is important to establish how aggressive to steel are the different
hostile environments to help decide which acidic systems can be used. A comparative evaluation of
the corrosion of steel immersed in hardened cement slurries submitted to commonly acidizing
agents is suggested. The performance of Special Class Portland Cement Slurries reinforced with
polished SAE 1045 steel was evaluated by electrochemical measurements as a function of time.
Open circuit potential, polarization curves and electrochemical impedance spectrosc...
