The Pathology and Therapeutics of Pulp

The Pathology and Therapeutics of Pulp-Involved Teeth and a Definite Technique for Filling Root Canals

By J.P. BUCKLEY, Ph. G., D.D.S. Hollywood, Cal.

In the dental profession today we finda few practitioners,thoughthenumber is growing increasingly less, whose honesty of purpose we cannot question, who still believe it unsafe to have a pulpless tooth in the mouth under any condition. Others there are who are willing to take a chance when the tooth in question is in their own mouth or a member of their immediate family, or when it is a strategic one in the mouth of an occasional patient which must be saved at all hazards if a fixed bridge or removable partial denture is to be successfully anchored; or, as frequently happens, when a pulp has died from an accident or under a porcelain jacket crown in an abutment tooth, the loss of which , in the latter case, means the loss of the bridge or partial denture.

Even in these modern days, with all due skill and judgment, the pulp in a tooth sometimes dies under orthodontic treatment. When this happens it is always in the mouth of a young patient whose parents are solicitous of their child’s welfare and appearance. Then again, there is still another group, growing in numbers, I believe, who feel if there occasional teeth can be properly treated and saved, it might be a wise precaution to treat certain other teeth in the mouth which may not occupy these exceptional and favored positions.

In every practice there are cases of pulp-involved teeth where, if the tooth and surrounding structures can be made healthy and normal, it is wise from both a health and economic standpoint to retain these teeth. Let it be understood that the health angle of this problem is not always on the side of extraction. Many times, because of impaired mastication, more damage to health is caused by radical removal of such teeth than from possible focal infection. The problem presented there is always the eradication of the infection. How best to accomplish this end in these cases is where we need both common sense and judgment.

In the old days many of us, perhaps all of us, went entirely too far in our efforts to save teeth. It was the practice of the day. Almost over night all this was changed and the pendulum swung too far in the opposite direction –the sad thing about it is this: Thousands of teeth were needlessly sacrificed on the basis of expediency. Where the expedient or commercial view point, I am sorry to say it, overshadowed the truly professional, teeth to which the least suspicion could be attached were ruthlessly removed.

If we can correctly read the signs of the times and properly interpret the current literature of medicine and dentistry, both professions today.

Active and Passive Hyperemia

In acute active hyperemia the pain occurs only when the irritant is applied, such as heat, cold, or impart of food in mastication, and subsides almost momentarily without treatment. In passive hyperemia the pain is more constant and may start without the application of a known irritant. In inflammation the pain is continuous and of a boring character, frequently lancinating, and is relieved only by actual bleeding, cold applications, or ultimate death. A pulp with active hyperemia may be saved, even though slightly exposed, by proper treatment and protection; but when passive hyperemia is in evidence its conservation is highly questionable, and in inflammation its life is absolutely hopeless. Therefore, we will only discuss here the therapeutics of active hyperemia. The treatment consists in protecting the pulp from the irritant which caused the condition.

If there is a cavity in the tooth which has caused the pulpal disease an anodyne remedy is indicated. For years now I have used here my phenol Compound and one application, carefully sealed in the cavity with cement without pressure, should restore an active hyperemic pulp to normal. If our diagnosis is correct this initial treatment will stop the ache and in a degree desensitize the decayed dentin, making its subsequent removal less painless. At the second sitting the tooth should be kept dry, preferably with the rubber dam –at least it should be kept dry –and the first dressing and softened dentin carefully removed. In these borderline cases the dentin should not be completely desensitized by any agent or means. We need sensation to guise us n our diagnosis.

A word about Phenol Compound may be in order here. The mistake is often made by dentists in thinking of Phenol as an oleaginous product and that its used in a cavity must be followed with alcohol in order to have cement adhere. This is wholly wrong. Phenol itself is an alcohol of the benzine group (C6H5OH) and may be completely evaporated by warm air almost as readily as ordinary or ethyl alcohol (C2H5-OH); and in the evaporating process water is not abstracted from the tooth structure as is the case with ethyl alcohol, which is a distinct advantage. Phenol Compound contains phenol, camphor and menthol; and it may be used advantageously for cavity desiccation in vital teeth –thus lessening pulp irritation. The camphor and menthol modified the escharotic action of phenol and at the same time enchances its disinfectant and analgesic power. It is for the latter properties largely that pheno is used in dental therapeutics. If, for any reason, we really want an escharotic effect, there are several agents that may be used to better advantage.

If in removing the decay the pulp is actually exposed it should be removed, unless the tooth is in the mouth of a child where the root is not fully developed. In such cases we are justified in taking a greater chance in attempting to save an exposed pulp than in the adult mouth. As a matter of fact we are not taking as great a chance as might be thought on first consideration. The roots of such teeth, having large apical foramen or being completely open, as the case may be, affords a much freer and better blood supply to the pulpal organ, which materially enchances the possibilities of saving an exposed pulp. Of course the cause and extent of the exposure are factors to be considered in any case. This is understood.

As a general rule in all such cases as are under consideration here we find deep seated cavities which, when the softened dentin is removed, are dangerously near the pulp. As the decay progressed the pulp may or may not have receded and protected itself by the formation of secondary dentin. If the decay has been slow and the pulp has functioned as it should, this has probably taken place. The X-ray may help to determine this, In any event it is in these cases that we need a material for pulp protection which can be applied as a plastic mass and which sets in a reasonable length of time into a hard and resistant substance. It must also be a non-conductor and, I think, should contain a strong but non-irritating antiseptic.

In the early days, I used and advocated Thymolized Calcium Phosphate. For the past fifteen years I have used a resinous mixture called Dentinoid. This latter product possesses every therapeutic requirement and has given splendid results, but its physical properties are such that its general use has been retarded. It is not as plastic when mixed with alcohol as a product of this kind should be for convenient use. Then, too, it sets slowly and the mass is not as hard as the requirements demand. There is a distinct advantage in the use of alcohol, over the essential oils or balsams, as the liquid for making the mix with prepared powders for such purposes. This will be explained later.

In recent months I have been spending a great deal of my time carrying on experiments along this line, for I have not been fully satisfied with any product offered the profession for this purpose or for use in filling root canals. I am not convinced that I have a mixture that meets every physical and therapeutic requirement. The powder consists of chemically pure calcined zinc oxide, finely pulverized resin (Colophony), thymol iodide and thymol, in the following proportions:

Zinc Oxide ……………….50
Resin ………………………..45
Thymol Iodide ………….3
Thymol ………………………2

For convenience I have named the product Zinc Compound. It has required much experimentation to compound this mixture so the product will work uniformly as to setting qualities. The difficulty seems to be caused by the variance in drugs on the market. We use selected drugs and follow a technique in its manufacture whereby a product is produced which sets quickly and uniformly.

Zinc Compound is a light yellowish gray powder, which is to be mixed with 95 per cent alcohol and oil of cloves at the time of using. The addition of oil of cloves to alcohol not only hastens the setting process but materially increases the adhesiveness and hardness of the mass when set, without detracting in any way from the many advantages possessed by alcohol as a liquid for this purpose. Zinc Compound may be used for temporary sealing purpose and for this use, it should also be mixed with the alcoholic solution of oil of cloves. For filling root canals alcohol is used alone. Here the setting of the mix should be delayed to give the operator time to check with the X-ray. The powder mixed with this liquid makes a plastic mass, readily adherent and easily applied, which sets firmly in a short period; yet giving plenty of time to complete the operation –whether used for protecting a pulp, temporary sealing, or filling a root canal. The mixed product is non-shrinkable and impervious to water-soluble stains and sets in the presence of moisture, which hastens the process. This is an advantage in cases of near or actual pulp exposure, in wide open canals of deciduous teeth and in the apical end of the canal in adult teeth. Let us analyze the formula for this product in the light of our knowledge of the drugs which enter into its composition.

Zinc Oxide is the forming substance. It gives bulk or form to the mass; and it is for this reason largely that it is used –plus the well-known fact that the white powder sets into a hard substance when mixed with certain liquids. The drug also has inherent medicinal properties which are of value. It is mildly antiseptic and sufficiently astringent for stimulating purposes.

Resin, in finely powdered form, is used, as it was in the Dentinoid, for the purpose of forming a varnish with the liquid, which gives the mixed product its adhesiveness when plastic and hardness when et.

Thymol iodide is used largely for a pharmacal reason. The dry bulky yellow powder tends to keep the mixture from becoming lumpy on standing and also give the yellowish tint. It no doubt adds also to the antiseptic properties of the product, though not used with this in mind.

Thymol is used for its recognized powerful antiseptic property. Chemically considered it is a phenol and may be classed as a true disinfectant. It possesses a peculiar but favorable action on animal tissue; and undoubtedly has a preservative action on dead animal tissue. The drug also has local analgesic properties and is feely soluble in alcohol, which, four our purpose here, is desirable.

Alcohol is used as the principal liquid for several reasons; In the first place it is always conveniently at hand in every dental office, which is also true of oil of cloves. It has an advantage over any of the essential oils alone, natural or synthetic balsams, or chloroform –all of which have been used for this purpose. The latter are physically incompatible with the moisture (water) of the tooth structure, which prevents the liquid in the mix from being carried into the tubuli. Alcohol, on the other hand, is miscible with water in all proportions. Then, too, it dissolves the resinous constituent of the powder, forming the varnish which gives the mixed product its plasticity and adhesiveness. As explained, thymol is freely soluble in alcohol and dissolves as the varnish if formed by spatulation.

The more thoroughly the mix is spatulated the more plastic and adhesive it becomes. This should be remembered. For pulp protection and temporary sealing, the mix should be made quite stiff, using equal parts of alcohol and oil of cloves, before applying it to the cavity. For root canal work it should be mixed rather thin, using alcohol alone, which retards the setting process. Because of the stickiness of the mass it is suggested that the mix be made on paper which can be thrown away. The proper size paper pad may be obtained from any stationery store. It should be highly glazed. The spatula may be cleaned with alcohol or acetone. The latter serves the purpose equally as well and is much less expensive.

As will be explained later, in the use of this product for either pulp protection or root canal filling, the tooth structure need not be thoroughly desiccated –removal of the surface moisture is all that is required. The moisture of the tooth has a great affinity for alcohol and when the mix is applied to either the cavity or canal, the germicidal resinous solutions is carried into the tubuli for some distance by this affinity; and, when the mix hardens, the tubuli are thus thoroughly sealed with this hard, medicated, highly resistant and compatible substance. This, it seems to me, approaches the ideal. Only enough of the resinous mass in any case should be used to accomplish our purpose. It should be remembered that it is easier to add more of the mixture if needed, than it is to try and remove any excess, because of the stickiness of the mixed product.

Pulp Protection

In pulp protection, it is well to fill the entire cavity with Zinc Compound and dismiss the patient for a day or so, when, if the tooth has remained quiet, the bulk of the protecting material may be removed and the cavity filled with a quick-setting cement. In all questionable cases, the patient should then be dismissed with proper instructions until the pulp has fully returned to normal and protected itself by the formation of secondary dentin. The, and only then, should the permanent filling be inserted.

If the pulp remains quiet after this treatment and gradually returns to normal, as proved by subsequent tests, all will be well. This is what will happen in every instance if our diagnosis has been correct and all essential details observed. Should the tooth ache after this careful treatment –I mean really ache, not simply be more or less responsive for a few days – then our diagnosis of the pulpal disease has been wrong and the sooner this pulp is removed, the better it will be for all concerned; especially the patient whose interest should always receive first consideration.

Sterilize Dentin

Let it be remembered that in all cases of deep-seated decay the intervening dentin between the floor of the cavity and the pulp is infected and must be sterilized. In questionable cases where the pulp is likely to die, I would much prefer to hasten the death of the pulp, by my efforts at sterilization and protection than to permit it to die a slow but certain death from subsequent shock or infection.

We will now take up the treatment of a pulp-involved tooth which has resulted in death of the organ. For thirty years or more, three rather general methods of treatment for dead and gangrenous pulp conditions were more or less closely followed by the profession: The sodium-potassium-ionization method of Rhein; the sulphuric acid method of Callahan; and my own Formocresol-Phenolsulphonic Acid method. About fifteen years ago, Howe introduced the silver-reduction method. Each of us, especially the first three named, practiced and taught our own technique. The younger men in the profession have selected and used from the various methods in vogue that which seems to meet the demands in their practice. Much credit is due these younger men for from them the profession has learned that no one method needs be followed in detail for success.

When the diagnosis confirms a dead pulp and resulting gangrenous contents of the root canal, the first or initial treatment, with me, is always an application of Formocresol, heremetically sealed in the pulp chamber or mouth of the canal with cement without pressure. While it may not be altogether modest for me to say it, having given the remedy to the profession about thirty-five years ago, I am going to say, nevertheless, that I know of no remedy as certain and positive in its action, where its used is indicated, as Formocresol. At the second sitting, with the rubber dam always in place, the initial dressing is removed and the canal or canals carefully explored, cleaned and sterilized to the apical end. This is accomplished by using properly selected broaches and a specially prepared Phenolsulphoric Acid, followed with a ten per cent solution of sodium bicarbonate for neutralizaiton –a chemico-mechanical process, as I term it.

I must recognize here that there are good root canal operators who object strenuously to the use of any caustic agent, whether acid or alkali, for the purpose of cleaning and sterilizing a root canal, depending on mechanics alone for cleaning and on supposedly non-irritating solutions for sterilization. The objection is based on the possible danger of destroying the tissue in the periapical area, should some of the caustic agent be worked through the end of the root. It must be admitted that there is this possibility, just as there is also the possibility of pushing infectious material through the root end in the attempt to clean the canal with mechanics alone. If either happens, I would much prefer to have a little of the Phenosulphonic Acid pass through than the highly infectious contents of a gangrenous root canal. If the latter happens an acute abscess is almost certain to develop with its painful and destructive sequellae; with the former, an aggravated case of acute apical pericemtitis may or may not follow. It is careless, of course, for either to happen. But I contend, in the hands of the average operator, it is far the safer practice to use in conjunction with the necessary mechanics some strong disinfectant. I prefer, as stated, this specially prepared Phenolsulphonic Acid, which is a thick syrupy liquid, easily handled and controlled.

“Surgical Asepsis”

This brings up the question of establishing and maintaining absolute asepsis in the performance of root canal operations. The insistence on this, together with continuing the treatment until the canal is proven negative by bacteriologic tests, I feel, has discouraged more sincere and earnest practitioners than any other thing relating to this work. Is absolute asepsis essential to success? While I fully realize it is dangerous doctrine to promulgate, I am going to answer, it is not. Now please do not misunderstand me here. I yield to no one in my recognition of the importance of cleanliness and asepsis in the performance of this or any other surgical operation; but if absolute asepsis in essential and depended upon, I want to be certain it is carried out in every detail and the aseptic chain kept unbroken at all stage. Too frequently those who think they are operating under these conditions fail to do so; yet the operation is a success.

Let us not deceive ourselves in this important matter, Dr. Alexis Carrel, of the Rockefeller Institute of Medical Research, is author of the statement that in surgical work “absolute asepsis” is neither necessary nor desirable. A degree of asepsis, which he calls “surgical asepsis.” is all that is required. Wounds heal and bone regenerates under these conditions. The presence of a germs in a part acts as a stimulus on the part of nature to arouse the phagocytes to a healthy activity. Somehow I have never been able to bring myself to the point where I feared the mere presence of a germ as some men seem to do. In the operation of treating and filling root canals, I have always felt it was much safer to work with and through antiseptics and disinfectants than to depend entirely on maintaining absolute asepsis, which, it must be admitted, in the dental operating room is difficult to do; and which, in fact, is not done by many who contend for its importance and who often deceive themselves by thinking they are working under these conditions. It is for these reasons that I answer negatively the question; Is absolute asepsis essential to success in root canal surgery? I trust I have made myself clear on this point, for, I repeat, I do not want to be misunderstood.

In exploring and cleaning the canal we should use care and judgment in not only preventing the contents of the canal or the chemical used to pass through the root end, but also in preserving the natural shape of the canal. We should remember that most root canals are choke-bored or constricted at the apical end; and if this natural obstruction is not destroyed or enlarged by pushing anything through –whether it be the contents of the canal, some medicament or the root filling itself –is materially lessened. The smaller the opening in the end of the root, the less hazardous will be the subsequent operation of filling the canal to and only to the apical end, no matter what material or method is used. This should be kept constantly in mind.

Secondary Cementum

When, in exploring a canal, we encounter live tissue which is highly sensitive and responsive, we should stop, sterilize and fill to this point only. Grove has shown how i many cases the pericementum dips down for a considerable distance into the canal proper and if this is left undisturbed, having observed surgical asepsis, the tissue will continue to function and ultimately close the apical end of the canal with normal cementum. It has also been demonstrated by the research department of the Chicago College of Dental Surgery that a pulp remnant left aseptically in the end of a tooth root will revert to the less highly organized pericemental tissue and function as such. We must be certain that the responsive comes from live tissue and not from pressure of confined air by our cotton-wrapped instruments.

We not come to the operation of filling the canal. In the past a great variety of materials have been suggested for this purpose, and the method employed depended largely on the material used. For a long period of years, gutta percha, modified and used in such a manner as to meet the demands of the individual operator, has been the material upon which most reliance was placed: and time and the radiogram have proved that gutta percha can be successfully employed. It has always seemed to me that the greatest hazard in using this material is the difficulty one encounters in firmly compressing it in the canal with the necessary solvents and heat required without forcing some of the softened material past the end of the root, which, in my judgment, should not be done.

I care not whether it has been scientifically proven that gutta percha, passed the end of the root under aseptic conditions, will be tolerated by the surrounding tissues, I don’t want any such in my own mouth or in the mouths of members of my family; and I maintain no higher standard for myself and family than I hold for those patients entrusted to my care. We are living in an age when such root canal fillings will not accepted by either medicine or dentistry. The sooner this fact is realized by the few in the profession who lean backward in their effort to save and who still follow the practice of over-filling root canals with plastic gutta percha, the better it will be for all concerned. Such practice only the proper placing of the lead point. It is desirable to have the setting delayed until we have time to check the operation with the X-ray. Using 95% alcohol to make the mix, takes care of this which only requires about ten minutes, if the machine is a part of the office equipment, which is almost essential for this work.

The importance of a perfect root filling in the apical third of the canal needs no emphasis. To deplete the dentin of its natural moisture in this area is as difficult as it is detrimental. With Zinc Compound mixed with alcohol it is unnecessary. This is one of the advantages the product has over others suggested to be used for this purpose. Then, too, if the lead point fits or binds at the place in the canal where we desire the root filling to stop, enough of the plastic mass will adhere to the point as it is placed in the canal to thoroughly and securely seal the apical end.

The product is also definitely radiopacic which helps the operator to know whether or not the canal is well filled. In these days the medical and dental professions have been trained to look for something definite in the radiogram of a tooth –the canal of which is supposed to have been treated and filled. Other than this the radiopacity of a root filling materials adds nothing to its value as such.

The Completed Filling

Many dentists today use both infiltration and conduction anesthesia, as indicated, for the painless removal of the dental pulp. In all such cases, where surgical asepsis has been observed in the operation, immediate root filling by the technique here described is indicated and advised. If all details are carried out no soreness of any kind will follow. IN these clean cases also, where no opening has been made through the end of the root by pathologic process or careless instrumentation, it is best as mentioned, to have the lead point stop as near the dento-cemental junction as possible with Zinc Compound just beyond. But where there is an opening of any size, how ever made, the point should fit or bind at the opening. Thus when it is finally introduced, the opening may be closed with the lead and very little, if any, of the Zinc Compound forced into the apical area.

Deciduous Teeth

For filling the canals of deciduous teeth Zinc Compound is the ideal material to use; and since there is no necessity of delaying the setting process in these cases, equal parts of alcohol and oil of cloves may be used as the liquid. Here the entire canal may be filled with the plastic mixture, which should be carried gently to the end of the root and firmly compressed. Only a small amount of pressure is required. The material is then covered with a quick setting cement and the cavity filled at this or a subsequent sitting. In these cases it is expected the filling material will be resorbed with the tooth root. With the former Dentinoid, this fact has been clinically demonstrated; and I know of no reason why it should not take place with this newer and far superior product.

In this paper, for the most part, I have endeavored to stress the fundamentals of the subject. I have only given in detail the formula for the new Zinc Compound. The formulas for the various other remedies suggested for use in the therapeutics of the conditions under consideration have been published in my text-book, in different dental journals and elsewhere. 104 Taft Bldg.

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