History of Teeth whitening and teeth bleaching
Discoloration of a tooth is the result of the death of its pulp, the disorganization of the red blood-corpuscles, and the dissemination of the hemoglobin through the dentinal tubuli. It should be understood, however, that in this connection no reference is made to those metallic stains resulting from the oxidation of amalgam fillings containing large amounts of silver or cadmium, or from other conditions which may be operative in the mouth, like the chromogenic action of certain bacteria, tobacco, medicines containing iron, etc. Chemistry has not as yet discovered any reliable and effective method of removing the metallic stains caused by the oxidation of metal fillings, etc.
The death of the pulp does not of necessity result in discoloration of the tooth, but loss of its translucency or vital appearance is always a resultant of pulp devitalization. This appearance once lost can never again be restored by any means known to chemistry or dental art. Discoloration may be removed and the tooth whitened, but a natural appearance in color or translucency can never be obtained. The removal of discoloration may be accomplished by two methods: first, by chemic agents, and secondly, by the color effect obtained by the introduction of a white filling material into the enlarged cavity and pulp-canal. By such means it is possible to greatly improve the color, and this improvement is most marked in those teeth which are most discolored.
The first noticeable change in the color of a tooth which has had its pulp devitalized by any of the various causes which may produce this condition is that of a pinkish tint.
The Truman Method: Dr. James Truman (1864) introduced the first successful method of bleaching discolored teeth. His method consists substantially of liberating chlorine form chlorinated lime by the addition of a weak solution of acetic, tartaric, or oxalic acid. Dr. Truman has suggested several ways by which the chlorinated lime and the acid may be brought together. "One process is to saturate the entire canal and the pulp chamber with the acid before inserting the chlorinated lime: another is to dip the instrument in the weak solution of acid, and then in the lime, and pack it rapidly into the cavity; and still another is to make a paste by the used of distilled water, and pack this into the tooth and then apply a stronger acid solution by means of cotton wrapped around the point used."
The cavity is then quickly sealed with gutta-percha, zinc oxychloride, or zinc oxyphosphate. This method to be repeated every two or three days until the required shade is obtained.
The failures which occur by the use of this method are due, in the opinion of Dr. Truman, to defective manipulation, principally in the employment of steel or any metal instruments, as by their use metallic compounds are formed with the chlorine and permanent discolorations result, and in the non employment of distilled water in the various manipulations, for reasons that are manifest.
After the desired color is obtained, the tooth must be filled with some material which will by its antiseptic and coagulating qualities prevent the future decomposition of the contents of the dentinal tubuli. Dr. Truman thinks zinc oxychloride possesses these qualities in a remarkable degree, and experience proves it to be a most satisfactory substance for this purpose. After the cement has set it should be protected with a gold filling.
In the employment of chlorinated soda for the purpose of bleaching a tooth, the dentin is dehydrated as thoroughly as possible by the usual means, and afterwards saturated with the solution. A piece of absorbent cotton may then be saturated with a weak acid solution, placed in the cavity, and sealed in. The chemical action is substantially the same as when chlorinated lime is employed, the liberation of chlorine which combines with the hydrogen element of the color molecule, and sets free the oxygen element in a nascent state.
Another method of bleaching teeth with chlorine is that invented by Dr. Wright, of Richmond Virginia. This method consisted of forcing a continuous stream of chlorine gas-previously prepared in the laboratory-into the pulp-canal and cavity of the tooth by an elaborate apparatus made especially for the purpose. The method was very efficient and rapid in its action, but the complications of the apparatus and the trouble of preparing the gas were obstacles which prevented its general adoption, and it was therefore abandoned.
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