Destructive tests on welds in metallic materials - Hardness testing of narrow joints welded by laser and electron beam (Vickers and Knoop hardness tests)

The paper describes a method for a controlled change in the power of an electron beam during a pulse of submillisecond duration, using a source "SOLO" with a plasma cathode. The beam power is controlled by changing the amplitude of the beam current with a corresponding change in the concentration of the emission plasma. This control method allows generating submillisecond beams of variable power (up to 10 MW at a maximum rate of change of no more than 0.5 MW/µs), which can be used for processing various metallic materials in order to change the functional properties of their surface with the ability to control the rate of input of beam energy into the surface of these materials.

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Effect of repeated cycles of chemical disinfection in microhardness of acrylic resins of complete denture base

RGO - Revista Gaúcha de Odontologia ◽

10.1590/1981-863720170002000023310196 ◽

2017 ◽

Vol 65 (3) ◽

pp. 196-201

Author(s):

Elisa das Graças MARTINS ◽

Rafael Tobias MORETTI NETO

Keyword(s):

Sodium Hypochlorite ◽

Knoop Hardness ◽

Sodium Hypochlorite Solution ◽

Chlorhexidine Digluconate ◽

Water Control ◽

Denture Base ◽

Acrylic Resins ◽

Hardness Tests ◽

Before And After ◽

Edentulous Patients

ABSTRACT Objective: To evaluate the microhardness of specimens of acrylic resins VipiCril® (thermally polymerized resin) and Bosworth New Truliner® (self-polymerized resin), before and after immersion in solutions of 0.12% chlorhexidine digluconate, 1% sodium hypochlorite, Corega Tabs® and water (control), testing the null hypothesis that the mouthwashes and chemicals used to disinfect complete dentures do not interfere with the superficial microhardness, and can therefore be used as adjuncts to oral hygiene of edentulous patients. Methods: Sixty specimens of resin VipiCril®(thermally polymerized resin) and 60 specimens of resin Bosworth New Truliner® (self-polymerized resin) measuring 16 mm of diameter and 6 mm of height were prepared, which were randomly divided into four groups of 15 specimens each, undergoing Knoop hardness tests (KHN) both before and after cycles of immersion in solutions of 0.12% chlorhexidine digluconate, 1% sodium hypochlorite, Corega Tabs® and water (control). Results: The specimens of resins VipiCril and Bosworth immersed in solutions of 0.12% chlorhexidine, Corega Tabs® and water showed decreased microhardness. Conclusion: The 1% sodium hypochlorite solution caused least damage to the denture structure, not leading to decrease of the superficial microhardness.

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