BLEACHING TEETH.
BY DR. K. M. FULLERTON, CEDAR FALLS, IOWA.
The bleaching of teeth has, from the first introduction of a positive method, been met with remarkable indifference and, at times, positive prejudice. Why this should be will remain a problem. The teeth that require bleaching belong mostly to a class condemned for all purposes except that of mastication. The process is generally only applicable to the six anterior teeth, while possibly an occasional bicuspid may be treated with advantage. When these anterior teeth, especially the incisors, are discolored, they are such a positive disfigurement that the operator has only the choice of evils—to bleach or to excise them, and insert an artificial crown. It would seem no difficult matter to come to a decision, or at least to determine to give the natural tooth a chance for future usefulness.
The fear of re-discoloration, or annoying labor, should not be taken into consideration. All operators are liable to meet with sudden discoloration in the regulating of teeth by the strangulation of the pulp at the apical foramen. When this occurs, it is one of the most humiliating of accidents, as it is one of the most annoying to patients. Discoloration is caused by decomposition, through a slow disintegration of the organic material and the deposit of carbonaceous matter. It therefore follows that the products producing color are not necessarily taken into the tubes by imbibition, though doubtless, to a limited extent, this is the case, but are produced by local degeneration through putrefactive processes. This change, though very slow in producing results, eventually gives to the tooth the bluish tinge, or to a tooth long affected by decomposed matter, the dirty, bluish-yellow. It is unnecessary to enter minutely into the more remote causes of discoloration, but we may summarize them as follows:
1st. When death of a tooth is caused by a blow, attacks of caries, too rapid pressure in regulating teeth, etc., the death and devitalization are followed by imbibition of coloring matter through the largest diameter of the tubules and local discoloration of the tube contents in the minuter anastomosing conduits. These changes may occur in teeth affected by caries, or without any external evidence of disease.
2d. The more aggravated cases, when this color has changed to a bluish-yellow, involving the entire structure of the dentine.
3d. Of the latter class, there may be a further subdivision, in which these are complicated with periosteal lesions which more or less interfere with efforts at restoration to original color.
The necessity of making some effort to restore the color of teeth changed by devitalization was apparent to dentists very early in the present century. The constant destruction of pulps with the imperfect methods of practice then prevailing, necessarily increased this unpleasant complication to such a degree that treatment of the anterior teeth became, so far as appearances were concerned, of no value whatever. Under the defective modes of treating pulp canals then prevailing, discoloration was sure to follow the filling of teeth. Any attempt to change color is necessarily dependent for success upon preliminary measures. Without thoroughness here, all subsequent efforts will fail. The early attempts at bleaching, before the settled practice of filling root canals was established, was not a success, and it must ever remain a failure unless the minuter structure of dentine be carefully considered.
It has been demonstrated by artificial injection, and still better by sudden congestions of the pulp, that coloring matter may be carried nearly to the final distribution of the minute ramifications of the tubuli. This is an important point, for, without this vascularity, bleaching would be impossible. With it, the possibility exists of extending the whitening process to the peripheral border of the dentine; or, in other words, to its union with the enamel on the crown, or the cementum on the roots.
The diameter of the tubuli is so minute, always decreasing in size until lost in final distribution, that any agent used must necessarily require considerable time before it can penetrate to the minute tubes, therefore you must not expect to bleach rapidly and meet with good success. The change, if any change be made at all, is simply on the walls of the canal, and cannot penetrate to any depth of tissue. If the discoloration is superficial, this mode will be effected, but not otherwise.