Chemically pure tin is furnished to the dentist in three forms,- foil, fibrous mats, and rolled strips. Foil is the form most generally used. This is beaten after the same manner as gold, and is furnished to the profession usually in two weights, No. 3 and No. 4, the figures representing the weight of the foil in grains. No. 3 foil is the weight in most general use.
The fibrous mats or " fibrous tirin is made from fine shavings of tin loosely pressed into mats. This form of tin has a tendency to crumble, and is therefore not so readily introduced into the cavity as foil, neither has it any advantages which are not possessed in an equal or higher degree by the foil.
Rolled strips of tin are about the weight of No. 20 gold-foil, and are used in the same manner as ribbons of non-cohesive foil.
Tin is one of the oldest filling-materials, and until the introduction of amalgam was the only substance at the disposal of the dentist for filling that class of teeth which were not considered worthy of the precious metal, or which for pecuniary reasons the patient could not afford to have filled with gold.
It is much more ductile and easier of introduction than gold. It can be more readily adapted to frail cavity walls, and when properly intro duced makes a perfectly moisture-tight plug. It does not readily oxidize, and but for its objectionable color and softness would be the very best material for filling frail teeth. Tin-foil when first made is cohesive to a certain degree, but this property is soon lost on being exposed to the atmosphere, and cannot be restored by annealing.
The therapeutic action of tin upon tooth-structure is decidedly antiseptic when oxidation takes place. For this reason it cannot be too highly recommended for lining the cervical wall in approximal gold fillings, and as a filling-material in those cases in which there is a persistent recurrence of caries, associated with a thick, ropy, tenacious saliva, which in all probability is due to the presence of gelatin-forming micro-organisms within the mouth.
Tin does not conduct thermal changes so readily as gold, and consequently causes much less irritation to sensitive dentin. This fact led many of the older operators to line the bottom of all hypersensitive cavities, and those in which the pulp was nearly exposed, with a layer of tin-foil.
Its most important use is for filling the temporary teeth and first permanent molars of children. The ease and rapidity with which it may be inserted and condensed, as well as its preservative qualities upon tooth-structure, make it the best material for this purpose that the dentist has at his command.
This is an instructive summary of the qualifications and the duties of the present day Dental Assistant -- The Diplomat standing between the dentist and lost income. | read more |