. The science and practice of dental surgery. gum margin,where it is difficult or impossible to maintauiabsolute dryness for any length of time. The Physical Examination of Dental AmalgamAlloys.—Change of volume m a dental amalgammay be determined in various ways. A some-what rough-and-ready method is that of packinga small quantity into a small glass tube, abouti inch in diameter and closed at one such a tube is packed partly fuU, andthe remainder filled in w ith red ink or anilinedye, any contraction of the amalgam wouldbe indicated by the leakage of the colouredfluid between the
. The science and practice of dental surgery. gum margin,where it is difficult or impossible to maintauiabsolute dryness for any length of time. The Physical Examination of Dental AmalgamAlloys.—Change of volume m a dental amalgammay be determined in various ways. A some-what rough-and-ready method is that of packinga small quantity into a small glass tube, abouti inch in diameter and closed at one such a tube is packed partly fuU, andthe remainder filled in w ith red ink or anilinedye, any contraction of the amalgam wouldbe indicated by the leakage of the colouredfluid between the plug and the side of thetube. On the other hand, expansion may benoted by packing a similar tube quite full,taking care that the plug is made flush withthe open end, and a subsequent examinationwith a strong lens. A more accurate and scientific method changes of volume entails the use of a micrometer, a delicately constructed instru-ment, which records on a dial or scale variationsmeasured to j^l^^ inch. Such an instrument. is shown in Fig. 460. A plug of amalgamis made in the motild (Fig. 461) and is placedin position m the micrometer, and the degreesof contraction are noted from time to time.
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectdentistry, bookyear19
