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In microscopy, negative staining is an established method, often used in diagnostic microscopy, for contrasting a thin specimen with an optically opaque fluid. In this technique, the background is stained, leaving the actual specimen untouched, and thus visible. This contrasts with positive staining, in which the actual specimen is stained.
Unlike negative staining, positive staining uses basic dyes to color the specimen against a bright background. While chromophore is used for both negative and positive staining alike, the type of chromophore used in this technique is a positively charged ion instead of a negative one. The negatively charged cell wall of many microorganisms ...
Tooth whitening or tooth bleaching is the process of lightening the colour of human teeth. [1] Whitening is often desirable when teeth become yellowed over time for a number of reasons, and can be achieved by changing the intrinsic or extrinsic colour of the tooth enamel. [2]
Failure to completely clean out the necrotic soft tissue of the pulp system may cause staining, and certain root canal materials (e.g., gutta percha and root canal sealer cements) can also. [1] Another possible factor is the lack of pulp pressure in dentinal tubules once the pulp is removed, leading to incorporation of dietary stains in dentin. [1]
Rubber cups, also called prophy cups, are used in the hand-piece. Polishing paste, prophylactic paste, usually containing fluoride, is used with the rubber cups for polishing. Rubber cups should not be used over the cementum area as it may remove a layer of cementum at the cervical area. There are two popular types of prophy cups: 4 webs and 6 ...
Phosphotungstic acid is used in histology as a component for staining of cell specimens, often together with haematoxylin as PTAH. It binds to fibrin, collagen, and fibres of connective tissues, and replaces the anions of dyes from these materials, selectively decoloring them. Phosphotungstic acid is electron dense, opaque for electrons.
Impression paste is traditionally used to take the working (secondary) impressions for a complete denture. When used with a special tray it requires 1 mm of spacing to allow for enough thickness of the material; this is also termed a close fitting special tray. [2] It is available as a two-paste system: Base paste: zinc oxide; Catalyst paste ...
Furthermore, negative staining with nigrosin can reveal some microorganisms that cannot be stained by regular methods. Nigrosin WS is used in tests for viability because living cells exclude the dye, but it enters dead cells. [5] Nigrosin has minor application in industrial evaporation as a light-absorbing water-soluble pigment. [6]