Page 51 - My FlipBook

TUIJK TEETH IJllIDGE-WOIlK JJ5

together with the teeth, but both in these and in
large bridges it may be good practice to cement
only the abutments, the teeth being temj)orarily
fixed with gutta-percha and cemented on only after
these are perfectly set in the mouth. Thus we are
easily and quickly enabled to avoid irritating edges
in the mouth as also incorrect articulation.
At visible jjoints the openings where the pivots
emerge should be covered with silicate cement.
For preventing the gold from irritating the gum,
both the wire and the lower margins of the collars
may be covered with a plating of platinum.
According to Dr. Thiersch, the following method
may be used to platinize :
Roll ;j'3 grms. of platinum into the shape of a
plate as thin as possible, cut it into small pieces, and
dissolve in 50 c.c. of nitro - muriatic acid. The
surplus acid having been removed in the water-bath,
there are obtained about 10 grms. of chloride of
platinum, a dry, crystalline, yellow- or brown-coloured
mass.
Now prepare two solutions, the first consisting of
1 litre of distilled water, '10 grms. of phosphate of
ammonia, 100 grms. of phosphate of soda, and 4
grms. of chloride of platinum ; the second solution
consisting of 4 grms. of chloride of platinum dis-
solved in 100 grms. of distilled water, 20 grms. of
phosphate of ammonia in 200 grms. of distilled
water. On mixing both solutions and stirring u)), a
yellow precipitate will be formed. Add to this mixture