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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.
The negatively charged cell wall of many microorganisms attracts the positively charged chromophore which causes the specimen to absorb the stain giving it the color of the stain being used. Positive staining is more commonly used than negative staining in microbiology. The different types of positive staining are listed below. [1]
Dental impressions are negative imprints of teeth and oral soft tissues from which a positive representation can be cast. They are used in prosthodontics (to make dentures), orthodontics, restorative dentistry, dental implantology and oral and maxillofacial surgery. [3]: 136–137
DAPI can be used for fixed cell staining. The concentration of DAPI needed for live cell staining is generally very high; it is rarely used for live cells. [7] It is labeled non-toxic in its MSDS [8] and though it was not shown to have mutagenicity to E. coli, [9] it is labelled as a known mutagen in manufacturer information. [2]
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 ...
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 ...
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]
[1] [2] [3] The Diff-Quik procedure is based on a modification of the Wright-Giemsa stain pioneered by Harleco in the 1970s, [1] and has advantages over the routine Wright-Giemsa staining technique in that it reduces the 4-minute process into a much shorter operation and allows for selective increased eosinophilic or basophilic staining ...