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.
Sodium Peroxide is obtained by adding the peroxide of hydrogen to an excess of caustic soda solution of twenty per cent., and then pouring into alcohol. Chemically considered, it is the analogue of peroxide of hydrogen.
It is a strongly alkaline and caustic white solid, soluble in water, when it produces an increase of temperature and evolves a certain amount of oxygen, with scarcely any loss of the latter if the peroxide of sodium is added to the water in small quantities and gradually stirred in; when the solution is made hurriedly by the addition of large quantities of the powder to the water at a time, the evolution of heat, due to the energy of the combination, causes rapid elevation of the temperature of the solution and the decomposition of the peroxide.
It is necessary to protect this preparation of sodium from moisture, and if exposed to the air its weight increases twenty per cent. in twenty-four hours. The presence of water and contact with organic matter produces inflammation in such matter, hence it is necessary to handle this drug with care.
Peroxide of sodium very closely resembles peroxide of hydrogen in the readiness with which it separates from the extra atom of oxygen it contains, and its bleaching property depends upon this extra atom of oxygen, which, when liberated, seizes upon the hydrogen of the organic color-compound, thus destroying its identity. While peroxide of hydrogen contains but three or four per cent. of available bleaching oxygen, peroxide of sodium contains about twenty per cent., and as a bleaching agent, antiseptic, disinfectant and sterilizer, it has an additional advantage over peroxide of hydrogen, by possessing a saponifying and solvent action upon the oils, fats and animal tissue present in the dentinal structure of the teeth.
On account of its being freely soluble in water, and uniting with it so energetically as to evolve considerable heat, such action can be controlled by adding the powdered peroxide of sodium slowly and in small quantities to the water, which should always be done in making solutions, as decomposition and loss of oxygen result when such care is not taken, and the solution is allowed to become hot. A standard solution can be reduced to any desired strength by adding definite proportions of water. Strong solutions of peroxide of sodium are powerfully caustic and dissolve animal tissue and saponify oils and fats.
Peroxide of sodium when carefully employed, has proven highly successful as a bleaching agent for discolored teeth, and a detergent disinfectant and sterilizer in the treatment of putrescent conditions of the pulp chamber and canals, as it penetrates the tubuli and dissolves the fibrils as well as the fatty constituents. Peroxide of hydrogen contains about three or four per cent. of available oxygen, while peroxide. of sodium contains twenty per cent., and in addition is a powerful saponifier: hence its superiority as a bleaching agent. A solution varying in strength from full saturation to one containing about five per cent. of the saturated solution, has been employed by Dr. E. C. Kirk in the treatment of pulpless teeth with putrescent canal-contents, and especially in such cases where the whole structure of the dentine was permeated and colored by an offensive and fermenting mass of decomposing organic matter, with often a blind abscess as an accompaniment to add to the foulness present, with satisfactory results. He recommends flooding the pulp-chamber and canals with a fifty per cent., or even a saturated solution, of peroxide of sodium, with the rubber-dam in position to prevent contact of the solution with the soft tissues of the mouth, the activity of the preparation being at once shown by the evolution of gas similar to the action of peroxide of hydrogen, but with less violence and rapidity. Peroxide of sodium is also very effective as a bleaching agent for carious and discolored dentine. For bleaching purposes, Dr. Kirk recommends saturating the dentine with a strong solution of peroxide of sodium (50 per cent.), following this by treatment with a dilute acid, such as hydrochloric, sulphuric or acetic, or a ten per cent. solution of trichloracetic acid; the preference is given to hydrochloric. In addition to such properties, peroxide of sodium completely sterilizes the dentine by acting as a mechanical cleanser, and a solvent of the organic debris and fats, in the form of small shreds of pulp-tissue and organic matter in a partially decomposed state. Dr. Kirk also recommends, after the application of the peroxide of sodium, inserting into the canals, for a moment on cotton, a diluted solution of hydrochloric or sulphuric acid, afterward washing and drying with hot air, and then immediately filling them. For the upper teeth he recommends that the application of the solutions be in pledgets of asbestos fibre, as the cotton is rapidly disintegrated by strong solutions.
Dr. Harold Clark describes his method of preparing a saturated solution of peroxide of sodium as follows:
"I put two ounces of distilled water in a small four ounce lemonade glass and prop it up in a basin of water so that the level of the water in the glass be just below the level of the rim of the basin. I place the latter under the cold water tap so that a small stream may run continuously into the basin about the glass. In this way its contents are prevented from rising in temperature. The violent reaction occurring when peroxide of sodium is put in water, raises the temperature of the water, driving off the oxygen which we desire to retain in the solution. By surrounding the glass with cold water and sifting the peroxide of sodium in small quantities every half hour until the solution becomes semi-opaque we obtain in the course of two or three days a saturated solution."
Dr. L. P. Van Woert suggests the following method of preparing a satisfactory solution of peroxide of sodium: "Take a common tumbler about half full of distilled water, place it in the centre of a good-sized pudding-dish, and pour all the cold water around it possible, without floating the glass. Add the sodium peroxide in very small portions - about what could be taken upon the point of the large blade of a pocket-knife - dusting in the water slowly to cause as little agitation as possible, and this amount should not be added oftener than once in a half hour, being careful to have the sodium peroxide finely powdered. This to be continued until the preparation begins to look opaque as powder is added. Let it stand over night and it is then ready for use. If a lump about the size of a small bean is dropped into water, you will notice on the margin of the line of agitation a ring of color resembling iodine. If the peroxide is put in the water, as I have suggested, there will be very little surface agitation and none of the discoloration, the result of which is a solution that has never failed. This takes several days to make, but it will more than pay for the time consumed, in its prompt action as a bleacher and sterilizer. I have placed this solution in the hands of a number of gentlemen, to be used in the treatment of abscessed roots, and up to the writing of this not a single failure has been reported. The general impression is that sodium peroxide is for bleaching only, while it is the most valuable preparation ever found for the treatment of dead teeth, if used in the following manner: Cleanse the root-canals of such septic matter as possible to get at with instruments, and dry them with hot air ; then carry small ropes of cotton, saturated with a full strength solution, as near the foramen as you can, using orange-wood, shaped like fine probes, and cover with a temporary stopping, letting the whole remain for two days, after which wash with hot water, and fill in the usual manner." When peroxide of sodium is introduced into a pulp-canal a chemical reaction takes place, and like peroxide of hydrogen, it is an active oxidizer from the facility with which it parts with one atom of oxygen; it is also a saponifier and solvent of the pulp tissue, and of oils and fats. Its effects on the fibrils are to dissolve and saponify them as a bleaching agent, for its action far into the dentinal tubuli.