Lectures on operative dental surgery and therapeutics . ge of the elastic material,whencoming in proximity with the curved periphery of thecavity is met and contested by the gold reef established atthe cervical border—the pressure being almost imperrceptible in its contractility on the tooth and partscontiguous. The cornua of the golden crescent are sowidely separated as to prevent the rubber trespassingagain upon the edges of the vertical walls of thecavity. 79 Looking at the figure, it will be seen that from the dis-tance to which the cavity extends below the generalgingival border, any clam
Lectures on operative dental surgery and therapeutics . ge of the elastic material,whencoming in proximity with the curved periphery of thecavity is met and contested by the gold reef established atthe cervical border—the pressure being almost imperrceptible in its contractility on the tooth and partscontiguous. The cornua of the golden crescent are sowidely separated as to prevent the rubber trespassingagain upon the edges of the vertical walls of thecavity. 79 Looking at the figure, it will be seen that from the dis-tance to which the cavity extends below the generalgingival border, any clamp which miglit be applied on thecervico-buccal aspect would inevitably cause pain bypressure on the lingual gum. In such an instance, it iscompulsory to place the clamp in a vertically-obliqueposition, while its tendency to contract causes it toadvance upon the lingual wall of the tooth, acting in anaggressive manner upon the gum, and resulting—asalready stated—in discomfort to the patient, which in-creases the difficulties to be contended Fig. 29. a Shows the rubber contracting ujoon the collar-like formation offcold //, which is built, crescentic shape, upon the cervical portion of thetooth ; the outer portions indicating points to which the filling is tobe built previous to relaxing pressure upon the rubber. il d, Ligatures. But there being an entire absence of painful pressure inthe method now described, it becomes possible, cwterispatihii.^, to combat the influences tliat otherwise mightfrustrate every measure put forth. Before concluding my remarks upon the rubber, I mayadd that it should not be kept on hand in any great 80 quantity, as it suffers a subtle deterioration by age, be-comes rotten, and therefore valueless in cases where itsuse is most essential. Experiments made on the india rubber of commerceprove its degenerating qualities, for when exposedto light it has been found to absorb oxygen ;five hundred grains of virgin caoutchouc, cut into theform of
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