Non-Metallic Plastic Materials for Filling Teeth.
* * * “The employment of the earlier dentists of gums, mastic and sandarac, in etherial and alcoholic solutions for the stopping of cavities of decay, is the first approach history records of plastic fillings. About the year 1848, however, the first substantial progress was made in this direction by the use of gutta-percha as a temporary filling material. A little later, the well-known compound, Hill's stopping, was introduced, which is a modification of gutta-percha by the addition of certain mineral elements to make it harder, therefore more available for permanent fillings.
* * * About thirty years ago, oxychloride of zinc was introduced, the first of a now well-known class of filling materials, viz.: the zinc plastics. Next in order came oxyphosphate of zinc, followed by enumerable modifications and combinations.
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“It cannot be denied that the introduction of gutta-percha and the zinc plastics was the beginning of an era in operative dentistry that made it possible to attain results never before brought about. Prior to that time little, if anything, had been accomplished in the direction of protecting pulps from the effect of thermal irritation. The solution of this problem alone is of such intrinsic worth as to make any material, capable of contributing to that end, of inestimable value. All preparations of the zinc plastics, likewise gutta-percha, at least so far as the writer has knowledge, are more or less non-conductors of caloric, therefore valuable for this purpose, and it is almost an unpardonable offense to ignore their use in all large cavities as a protection to pulps. * * * Gutta-percha, however, unless in solution of chloroform or other volatile solvent, is not wholly safe, unless the greatest care is exercised to prevent its introduction into the cavity in too heated a condition. This is a serious obstacle, as the minimum degree of heat necessary to plasticity may, especially if the pulp is near the surface, be sufficient to permanently injure this organ. The pressure generally necessary to adapt this substance to place, is another objection. So, nothing short of the greatest caution in its use will give certain results. Gutta-percha as a filling material, compared with the zinc plastics for inside use, and amalgam for outer surfaces, has a limited sphere of usefulness. * * * The oxychloride cement has an escharotic action on organized tissue, which makes it unsafe as a nerve capping; but when used in connection with an intervening layer of a non-irritant, it becomes useful for this purpose. It is decidedly antiseptic, but readily soluble in oral fluids, and is distinguished as “the most preservative, and at the same time the most perishable of all filling materials.” The antiseptic quality is a valuable feature for root fillings, and as these are supposed to be protected from the fluids of the mouth, their solubility is unimportant.
“The zinc phosphates are less irritating in their action on organized tissue, are denser in structure and less soluble in the oral fluids, and for general purposes are preferable and in more general use than the zinc chlorides.
“Briefly, then, to sum the matter up, what is the value of zinc plastics in dental practice, and to what extent should they be used? * * All large cavities should have a layer of this substance intervening between metallic fillings and their deeper portions, if possible, to protect the pulp from thermal irritation. * * * As a covering contiguous to exposed pulps, the more neutral and non-irritating of these preparations possess more good qualities than any other substance, chiefly on account of their adaption without pressure and the non-generation of heat.
“For filling root canals, zinc plastics are unsurpassed. The method I have practiced for a long time with more satisfactory results than any other, is to carry these to the apex on shreds of cotton of a fineness suitable to the case in hand, using necessarily the non-sticky variety. The facility and greater certainty with which the apex may be reached, combined with the imperviousness and antiseptic properties, make them the ideal root filling. For use in connection with crown and bridge-work, we have nothing to compare with them, and can only say they stand alone. For entire fillings in teeth that promise pathological complications, or for obvious reasons require temporary operations, they are a most valuable material. Taking them all in all, they occupy an important place in dentistry, and we could illy afford to return to the methods in vogue before their introduction. But like all good things, zinc plastics are often abused and their use is not always followed by the best results. * * I am opposed to temporary fillings as a substitute for something better, except possibly in children's cases, or where pathological or certain sexual conditions prohibit. The principal provocation for criticism is the indiscriminate practice of prostituting a good thing for uses other than its proper one. The outcome of such practice can result only against the general good of the profession, through the ultimate disappointment and loss to the innocent victim. The remedy that suggests itself against such abuse is to be more explicit in imparting advice on these matters. When temporary fillings must be inserted, impress the patient forcibly as to their limited utility. If such fillings are preferred on account of their inexpensiveness, or for any other reason, be emphatic in calling them temporary fillings and nothing more.”
DISCUSSION.
Prof. J. Taft said he had never used amalgam as a filling material. Oxyphosphate acts differently in different hands. Had seen an oxyphosphate last eighteen years. It should not be used close to the gum, or in proximal positions. Is one of the very best materials for porcelain inlays. A good oxyphosphate will last as long as an ordinary gold filling. He uses it very often as an intermediate filling material. Much is due to the manner in which it is mixed. It should be thoroughly mixed. Some will granulate when used immediately, but if it is worked between the fingers, it becomes quite plastic and in that condition it is better and easier used. Heat accelerates, while cold retards setting.
Dr. J. R. Callahan asked if either the oxychloride or the oxyphosphate hardened the dentine.
Dr. J. S. Cassidy said oxychloride would harden by dehydration; much depends upon the healthy condition of the saliva. Mechanical abrasion has little to do with its loss. Chemical action is its chief cause. More loss takes place in mouths whose saliva is vitiated by putrefaction than by fermentation.
Prof. Taft said cleanliness is very important in mouths containing cement fillings.
Dr. H. J. McKellops spoke upon the oxyphosphates and their effect upon the dentine. If inserted in cavities and allowed to remain a year or so, when taken out the dentine will be found very hard and a gold filling may be inserted. It is one of the best materials for filling, and is especially applicable for children's teeth. Eructions from the stomach are very destructive to phosphate fillings. He says oxychloride is not the best root filling, especially in small roots. The mercury of amalgam will render a pulpless tooth very brittle.
Prof. H. A. Smith:—Good manipulation is requisite to success in plastic fillings; the parts should be thoroughly combined. He had seen a large crown oxyphosphate filling which had been inserted eight years ago, in Germany. They were good filling materials, but had their place.
Dr. L. E. Custer, Dayton. Ohio:—Before we can understand the action of the oral fluids upon the cement, or the action of the cement upon the tooth structure, we must first get an idea of what oxyphosphate of zinc is. When the two portions are united, the powder has such an influence upon the fluid as to cause it to crystallize, which in turn incorporates the powder in it. It is a chemical reaction so far as the liquid changes its form to a liquid of crystallization and also liberates heat, but it is a mixture as the powder does not change its form—it is still oxide of zinc. Being of this nature, it is easily acted upon by external agents, and at the same time the free phosphoric acid acts upon the tooth structure. He had found that alkalies acted upon the cement by neutralizing the acid of crystallization, which liberated the oxide of zinc as a precipitate. Strong acids overpower the phosphoric acid and act upon the oxide, the latter disappearing in the solution. So, as had been referred to by Dr. Cassidy, we will find a more rapid loss in mouths in which putrefaction is going on, because putrefaction being distinguished from fermentation only by the presence of nitrogen, and it has been shown by Dr. Watt that one stage in the formation of nitric acid was the formation of ammonia. Ammonia disintegrates the cement by neutralizing the acid of crystallization.
Dr. Arnold said he filled roots with oxychloride by using fibres of cotton on a small broach.
Dr. McKellops defied anyone to fill pulp canals with oxychloride of zinc, as well as with a solution of gutta-percha. He said there was often more than one opening at the apex. He can tell when the gutta-percha has reached the apex by watching the countenance of the patient.
Dr. Gray said he enlarged the root canal and filled with iodoform and oil of cassia.
Dr. F. A. Hunter, Cincinnati, Ohio, said he was never sure that he filled but two roots perfectly, and those were where the gutta-percha appeared at the opening of the sinus leading from the roots.
Dr. W. H. Sillito, Xenia, Ohio, asked if it was not the oxychloride of zinc which had the therapeutic effect.
The annual election of officers ensued with the following result: President. Dr. M. H. Fletcher, Cincinnati; First Vice-President, Dr. L. E. Custer, Dayton; Second Vice-President, Dr. Otto Arnold, Columbus; Corresponding Secretary, Dr. H. T. Matlack, Covington, Ky.; Recording Secretary, Dr. H. T. Smith, Cincinnati; Treasurer, Dr. Frank A. Hunter. Cincinnati.
(TO BE CONTINUED.)