If this preliminary process has been satisfactorily conducted, the next step will be that of filling the canal at its upper third. Gold is claimed to be the best material for this. The question may be asked, why fill the upper third? Because it is absolutely necessary for success that the root should be bleached as well as the crown. It must be remembered that the pulp chamber requires the same careful treatment as that given to the canal. It must be thoroughly cleansed of all debris to its fullest extent, and that, in the incisors and cuspid teeth, is almost to the enamel line of the cutting edge. Having proceeded thus far, the case is now prepared for the further process of bleaching. The next point to be considered is the insertion of the material. Before this is attempted the canals and crown should be well washed with a solution of ether, borax, sodium bicarbonate, or ammonia, to remove fatty matter. It should then be well washed with distilled aqua. The tooth is then dried, the rubber dam having been applied at the beginning of the operation. There are several methods of bringing the acid used in connection with the lime. This apparently simple matter is really quite difficult. One process is, to saturate the entire canal and pulp chamber with the acid before inserting the chlorinated lime. Another is, to dip the instrument into the weak acid solution and then into the lime, and pack rapidly into the cavity; and still another is, to make a paste by the use of distilled aqua and pack this in the tooth, and then apply a stronger acid by means of cotton wrapped around the point used. There are difficulties attending all these modes. The point desired must be kept constantly in view—that of having acid sufficient and of proper strength to break up the compound and set free the chlorine used, and to preserve as much as possible of the latter for bleaching. Before commencing the packing, everything should be ready, so the cavity can be sealed at once. Convenience of adaptation must govern the choice of the material used for closing the cavity. Gutta-percha, oxyphosphate or oxychloride of zinc may be used with good results, but the zinc preparations are harder to remove than the gutta-percha. After sealing the cavity, the tooth must be left for a day or two. On the return of the patient, remove all of the application, avoiding the use of steel instruments. Syringe out the canal with distilled aqua. If the bleaching has not gone far enough, a second application must be made, and this be repeated until a satisfactory result is obtained. The importance of using distilled water must be insisted upon. The reason for this must be apparent, for in many waters the minerals held in solution, especially those impregnated with iron, will defeat the desired object.