This section is from the book "Dental Medicine. A Manual Of Dental Materia Medica And Therapeutics", by Ferdinand J. S. Gorgas. Also available from Amazon: Dental Medicine.
Compressed air is recommended as essential to the dentist for relieving the pain of many operations, and also for securing better results in the action of certain remedial agents by bringing them in closer contact with the tissues to be anaesthetized. It has been successfully employed by a method which consists in forcing, by compressed air with an even and constant force, an obtunding agent into the tubuli of the dentine, in cases of hypersensitiveness. It is a more simple method of obtunding than that of cataphoresis, electricity being the pressure in the cataphoric method.
Some twenty-five to thirty or forty pounds of air-pressure are sufficient, which can be secured by an apparatus designed for the purpose, which will produce double the amount of pressure in air than in water. A solution of cocaine in sulphuric ether - vapocaine, for example, has the advantage of easy access to the tubuli of the dentine, on account of the ether holding the cocaine and finding its way into the tubuli, when it evaporates leaving the cocaine, which then combines with the fluid present.
Besides its use as an obtundent of sensitive dentine, compressed air may also be used to diffuse medicines in root-canals, and into the pus-pockets of alveolar pyorrhoea, in bleaching teeth, in forcing out blood and pus in pyorrhoea, in forcing back the gum and contents of such pockets, as a spray, and as a dessi-cant of pulp-canals, in drying cavities in teeth, and also drying the mouth in rapidly hardening cement fillings with warm air, in cooling impressions of modeling compound, or wax, in keeping dry the banding of a root by forcing back the blood and gum, in setting crowns and bridge-work, etc. In the apparatus employed, the outlet of air is under control so as to secure an even and constant pressure, and the supply is controlled by a cut-off.