Principles and practice of operative dentistry . mercury. If the operator knows the exact formula of the alloy which he is using,the proportion of mercury necessary to completely amalgamate the alloyis readily determined by the above. If, however, he does not possess theformula, he can ascertain by an experimental mix the amount of mer-cury necessary to obtain the best results in working any grade of amalgam. 372 OPERATIVE DENTISTRY. The amount of mercury required for the amalgamation of dental alloysis greatly increased as the amount of silver passes beyond sixty per cent.,so that with an all
Principles and practice of operative dentistry . mercury. If the operator knows the exact formula of the alloy which he is using,the proportion of mercury necessary to completely amalgamate the alloyis readily determined by the above. If, however, he does not possess theformula, he can ascertain by an experimental mix the amount of mer-cury necessary to obtain the best results in working any grade of amalgam. 372 OPERATIVE DENTISTRY. The amount of mercury required for the amalgamation of dental alloysis greatly increased as the amount of silver passes beyond sixty per cent.,so that with an alloy containing seventy per cent, of silver it was verydifficult to form a workable mass with fifty per cent, of mercury ; whilewith eighty per cent, of silver it becomes necessary to use as much assixty per cent, of mercury. In mixing amalgams by weight, the amount of the alloy necessary forthe case in hand should first be weighed, and then the exact proportion byweight of mercury added to it. These should be placed in a mortar and • Fig. Flagg wafering pliers. mixed with the pestle until the mercury is thoroughly incorporated,making an even mass of firm consistency. It is then taken in the palm ofthe hand and kneaded into a mass, and compressed in a piece of chamois-skin or silk fabric, by wringing withFig. 451. the fingers or with a pair of flat-nosed pliers, or with Flaggs wafering pliers,shown in Fig. 450. If the mix has been properlyproportioned, no mercury can be ex-pressed by gentle pressure with thepliers, and but very little under severepressure. The practice of addingmore mercury than is needed in mix-ing an amalgam, and then expressingit in order to obtain a good workingmass, is to be deprecated, from thefact that the mercury is the solventor fusing element in the amalgam, andwhenever any portion of it is takenfrom the mass, by just that much thecomposition of the amalgam is altered and its physical characteristicschanged. Dr. Black advocates the plan of mixin
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