The Therapeutics of Hypersensitive Dentin

Desensitization of Dentin
Can be Produced
Several of the Author’s Original Agents are Discussed in

By J. P. Buckley, Ph. G., D.D.S.

                The problem of the desensitization of the dentin of teeth comes to the forefront from time to time. It has recently received much publicity in both the lay and professional press. This is evidence of the demand on the part of patients for a remedy or method by which that most dreaded operation of cavity preparation in vital teeth can be painlessly performed. It is also indicative of one of two other things: either dentists feel that there are no satisfactory methods or means available at the present time for this purpose, or else, in their indifference and haste, they are not using the remedies at their command. It is difficult to believe that this last inference is true, but it has been generally known for a long time that there are several ways by which this desired end can be accomplished safely and satisfactorily. We will now direct attention to some of these means.

The hypodermic injection of local anesthetic solutions for this specific purpose is not relished by many patients; and the results of the technique when used are not always satisfactory. If we had an immediate desensitizer which could be applied to the cavity of the tooth for a minute or two with perfect results, its advantages would be obvious. Various solutions for this purpose have been suggested.

In the author’s lectures to the senior classes of the Chicago College of Dental Surgery from 1904 to 1909, when the first edition of his book—Modern Dental Materia Medica, Pharmacology and Therapeutics—was published, the following remedies were given from year to year. After the publication of the book the formulas were mentioned therein.

One formula contained: zinc chloride, grains 20; alcohol, fluid drams 4; and chloroform, fluid cocaine (alkaloid), grains 20; chloroform, fluid drams 2; and ether, fluid drams 6. Under method, the discussion of which immediately followed, it was stated that this drug could be substituted for the cocaine in the above formula, thus obviating the necessity of using a narcotic blank, and with equally good results.

The theory of the action of these remedies mentioned for the immediate desensitization of dentin was based on a fundamental law in physics, viz., a solid in changing its form is to a liquid or a liquid in changing its form to a vapor or gas must abstract from the thing to which it is applied a certain amount of heat in order to affect the change. It was on this principle that ether or combination ether, and ethyl chloride, both used as sprays, have proved valuable in certain cases. To quote from the author’s book in connection with this class of remedies, he says. “In the use of these remedies advantage is taken of the physical law explained under Cold. As the highly volatile liquids, ether and chloroform, evaporate a certain amount of heat is abstracted from the tooth-structure, and a coating of the zinc chloride, alkaloidal cocaine, or menthol, driven to all remedies will not completely desensitize all dentin, but their use will be a material aid.”

Another similar formula is here given; metycaine (Lilly), grains 22; thymol, grains 9; alcohol, fluid drams 2; and ether, fluid drams 6. As will be observed later thymol is a constituent of the author’s Desensitizing Paste, as it is also of many other formulas mentioned in his textbook. The drug seems to have a peculiar and favorable action on animal tissue and for this reason the author has recommended its use for years, as have many others in the profession. In this particular formula the thymol and alcohol are used for disinfection, the metycaine and ether for desensitization.

All Remedies are Not Reliable

While it is true that such remedies as are mentioned above are helpful in many cases, their action is unreliable and the effect produced seems to be no better, if as good, than Phenol Compound, which contains menthol, camphor and phenol, in the proportion of 1-2-9, respectively; and which remedy has been used for desensitizing purposes for years. The remedy is also used for many other conditions in dental therapeutics.

In the treatment of hypersensitive dentin Phenol Compound is highly efficacious. Here it may be used in conjunction with hot air. the cavity should be carefully desiccated and the remedy applied on a pledget of cotton; after a few moments, evaporate with heated air until the cotton is dry. Care must be taken to protect the patient’s face from the fumes of the remedy as the process proceeds. This may be done with a napkin or the palm of the hand.

In cases where cavities have been prepared in vital teeth under conduction anesthesia, or for a jacket crown, the exposed dentin is generally hypersensitive after the anesthesia disappears. Here Phenol Compound is very useful. Simply apply the remedy with warm air, gently applied; after which it will be found the inlay or crown may be set without the irritating cement causing the slightest pain.

The mistake is often made by dentists in thinking of phenol as an oleagineous product and that its use on tooth-structure must be followed with alcohol in order to have cement adhere. This is wholly wrong. Phenol itself is an alcohol (C6H5 OH) and may be completely evaporated almost as readily as ordinary or ethyl alcohol (C2 H5 OH): and in the evaporation process water is not abstracted from the tooth-structure as is the case with ethyl alcohol, which is a distinct advantage here. Phenol Compound may be advantageously used for cavity desiccation in vital teeth—thus lessening pulp irritation.

Desensitizing Paste

Up to the present time neither local anesthesia nor topical solutions for the immediate desensitization of dentin have proven satisfactory. There is a demand for a remedy which will produce results in all cases. Such a remedy has been known and used continuously by dentists all over the world for over twenty-two years.

In 1914 the author announced to the dental profession that the perplexing problem of eliminating pain in cavity preparation had at last been solved. The announcement was first made at Brooklyn New York, in a paper read before the Second District Dental Society on “Desensitizing Paste; A New, Safe and Reliable Remedy for Hypersensitive Dentin.” The problem was solved then and has been since to all who use the suggested remedy, as any such potent remedy must of necessity be used, with judgment and care.

Experiments on Animals Not Dependable

It is well to mention here that laboratory experimentation on the desensitization of dentin in the United States, until recently at least, has not been extensive. More work along this particular line has been done in European countries. In this connection it should be remembered that there are certain factors to be taken into consideration in drawing conclusions in animal experimentation and working on human teeth. It is quite generally known among research workers that the dentin in the teeth of dogs, for instance, is much more permeable than in human teeth. Therefore, when cavities are made in dog’s teeth which are normal and sound in every respect, and remedies scaled therein, we should anticipate a greater reaction on the part of the pulp than when experimenting with sound human teeth. Then, too, in using remedies, like Desensitizing Paste in actual practice, we are not dealing with sound dentin, only in exceptional cases, but with teeth which are decayed and the dentin of which is hypersensitive. In this modern day of dentistry with our improved methods of bridge-work, we seldom recommend preparing a cavity in a perfectly sound tooth for anchorage purposes for either a fixed or a removable bridge; and if such recommendation is made, it usually meets with an objection on the part of the patient. In these exceptional cases when such practice is decided upon, it is generally found that the dentin is not hypersensitive and cavities may thus be prepared with very little pain. When this cannot be accomplished, it may be best to use periapical or conduction anesthesia; and this method must also be used with judgment so as not to encroach too near the pulp or trouble will surely follow.

Knowledge of Tooth Structure Essential

In the desensitization of dentin one should not only understand the histologic and physiologic make-up of the pulpal organ, but of the dentin as well. A knowledge of the departure from normal of these structures is also of vital importance. In other words a knowledge of the histo-pathology of the structures involved must be understood and utilized or trouble is likely to follow. It is not the intent here to deal in any detail with this phase of the subject. A point of interest, however, which has been observed by every careful clinician, is that the most sensitive area of a cavity is found at the dentoenamel junction, where the tubules ramify to form the so-called marginal plexus; and it is in this immediate area where most of the drilling or grinding must be done to parallel the walls, flatten the base and for anchorage purposes in cavity preparation. With a little forethought and care, it is possible in using a remedy for desensitizing purposes, which requires sealing in the tooth, to so place it in the cavity that only these areas are affected thereby.

The dental pulp is a delicate and highly susceptible organ, and it must, therefore, be handled with intelligence and care. Most patients who repose confidence in the operator are sensible and are willing to endure some pain in the preparation of cavities in their teeth. With confidence, a true running engine, a sharp but, a dry field, a steady hand, and a knowledge of what ought to be done in a given case, it is not necessary to use any absolute and positive means of desensitizing the dentin in every case which presents. Yet, it must not be forgotten that the preparation of cavities in vital teeth without some means of obtunding the dentin more effectively than has been done in the past, is generally a painful operation which is dreaded by most patients.

The use of Desensitizing Paste in the hands of careful operators is absolutely safe and its action is always reliable. In the hands of careless operators no effective remedy for desensitizing dentin is safe. With these preliminary considerations attention will now be directed in detail to the use of this preparation.

ANALYSIS OF FORMULA—Desensitizing Paste contains metycaine, thymol and trioxymethylene, in the proportion of 11, 12 and 77 parts, respectively; all combined with a petroleum base, and incorporated in a fibrous vehicle and colored with an insoluble pigment. One grain of the preparation is sufficient for about fifteen applications. On this basis the amount necessary for one application contains metycaine 1/300 grain, thymol 1/270 grain, and trioxymethylene 1/43 is the chief constituent of the remedy. This drug could be employed in lesser strength in this preparation, but it would only mean that a larger amount would be shallow cavities this would be an objection.

PHARMACOLOGY—it is highly essential that we understand how desensitization Paste is brought about when Desensitizing Paste is applied to the dentin. The metycaine applied directly to the exposed sensitive dentinal fribrillae acts quickly thereon and temporarily paralyzes the ends thus exposed. The thymol permeates the softened dentin. The heat of the body gradually liberates formaldehyde from the trioxymethylene, which gas diffuses through the decayed dentin, combining chemically with the aminegroup of the protein constituent constituent of the dentinal fribrillae. The formaldehyde also acts upon maintain intermediate and end products that may be present in the carious tooth-structure as a result of albuminous decomposition, and this aged, together with the thymol brings about complete sterilization. Thus the dentin affected by the remedy is not only desensitized, but sterilized as well, which is an all-important factor. The vitality of the fribrillae is temporarily destroyed in the area affected, but the remedy will not affect sound dentin to any dangerous depth. In the preparation of a cavity, in the average case, the dentin affected by the remedy is practically all removed. If it is not, it is known from experience with the preparation that the vitality of the fibers is subsequently restored, for after a few weeks sensation returns. While this regeneration is being brought about, the tooth may develop slight thermal sensitiveness which lasts for about a week. This occurs only in a small percentage of cases. It is mentioned here simply that the operator may know the cause, and that should such sensitiveness develop, it will be of short duration.

INDICATIONS—Desensitizing Paste may be used with perfect safety in all cases of hypersensitive dentin where the pulp of the tooth is not diseased to the extent of necessitating the removal of the organ because of its pathology. As has previously been mentioned, it is not necessary to employ the remedy in every case of cavity preparation. Where the pain is not great, and where the patient is willing to endure the small amount, no therapeutic remedy is needed; but every dentist has cases in which it is impossible to do satisfactory work because of the hypersensitiveness of the dentin. In such cases Desensitizing Paste has proven its worth to both patient and dentist. As has been elsewhere mentioned the remedy is not intended to take the place of conduction anesthesia or other pain-relieving methods where extensive cutting of tooth-structure is necessary. There is a place in dentistry for every method which will aid in accomplishing our purpose.

The bite-wing method of detecting cavities in teeth, while by no means accurate in showing the depth of the decay, is nevertheless a great aid; and by this means also we should be able to determine whether or not the pulp has protected itself from the carious process. Where the picture shows a deep cavity with little or no secondary dentin formation, Desensitizing Paste or any other positive means of desensitization, is either contraindicated or must be used with extreme care; for such a pulp is probably infected and doomed to die no matter what treatment is given. Fortunately this condition is not generally found, for pulps as a rule react to external stimuli. When we do find extensive decay with practically no defensive secondary dentin it means one of two things: either the decay has been so rapid that the pulp was overwhelmed before it had time to protect itself, or else we have one of those exceptional pulps which reacts sluggishly if at all.

Best Results in Shallow Cavities

The ideal place for Desensitizing Paste, and where its proper use is not only safe but advantageous in every way, is in shallow cavities wherever located, whether gingival or proximal. As a rule these are the cavities which are most sensitive for the reason the pulp has not as yet had time to protect itself, and here the remedy will do two things besides that of desensitizing—the primary purpose for which it is used: First, it will thoroughly disinfect the dentin; and, secondly, it stimulates the deposition of secondary dentin. The remedy will also be found useful in sensitive areas, due to exposure about the necks of teeth.

DIRECTIONS FOR USING—In employing Desensitizing Paste, it is not necessary to remove any of the carious dentin that is at all sensitive. To attempt this often causes pain, and the remedy, if used at all, is intended to, and will, absolutely eliminate all pain in cavity preparation. The cavity and immediate tooth-structure should be dried with alcohol and a small amount of the Paste sealed therein with a good cement. Perfect results will be obtained if the remedy is thinly spread over the cavity surface, leaving a little thicker coating over such areas as are generally known to be more sensitive. This can be accomplished with a ball of cotton held in the pliers. In gingival cavities it is often necessary to flow the cement over the enamel surface, depending entirely on its adhesiveness to hold the Paste on the softened tooth-structure.

Desensitizing Paste Completely Effective

Twenty-four to forty-eight hours is sufficiently long to bring about complete desensitization, and this is the proper length of time to leave Desensitizing Paste sealed in a tooth. However, no harm will follow if the remedy should remain in the tooth for a longer period. The small amount employed will soon exert its full influence, after which no further action follows. An effort should be made to hermetically seal all the margins of the cavity—thus confining the action of the remedy to the dentin. This is sometimes difficult to do with gingival cavities. If it is not accomplished, a certain amount of the formaldehyde gas may escape as it is liberated, in which case the dentin would not be profoundly affected.

When it becomes necessary to prepare a cavity in sound dentin, as in the case in superficial cavities and occasionally for bridgework, it may be necessary to make a second application of the Paste in order to prevent any pain. In all cases where there is considerable decay, one application will be sufficient to desensitize the entire cavity. The depth to which the dentin is affected by the remedy will depend upon the condition of the dentin.

In using Desensitizing Paste it will be found that in about five to ten percent of all cases the teeth to which it has been applied will grumble or have a tendency to ache. If the remedy has been properly used where indicated, no alarm need be felt because of this, for it will subside in a few hours. Whenever the Paste is used itis well to advise the patient that a “grumbling” effect from the action of the remedy anticipated. If, however, the tooth should really ache severely it indicates a possible mistaken diagnosis; in which case the remedy should be removed forthwith and its action checked by applying aromatic spirits of ammonia to the cavity on a pledget of cotton for a few seconds, when an anodyne remedy, like Phenol Compound should be sealed in. such a tooth should be kept under surveillance for a period of time before the final filling is inserted.

Only Small Dosage is Necessary

In the original article on Desensitizing Paste emphasis was given to the fact that only a “small amount” of the Paste is required for successful results. It was realized then, and now, that this does not say much, and perhaps, means less; but it should be remembered that the “dosage” is governed by conditions which present in a given case, and this in turn requires knowledge and experience. Common sense is thoroughly compatible with most things in life; and this is certainly true here. In dental practice the object in using Desensitizing Paste is to so affect the dentin that the cavity in the tooth may be painlessly prepared; and, personally, the author is always pleased when he finds that just as the preparation is about complete it is beginning to hurt a little. Then it is known that the dentin affected by the remedy is practically removed. Let it be repeated here what has been said before, viz., most patients who repose confidence in the operator are sensible and are perfectly willing to endure a little pain in order to have good work done. It is the severe or excruciating pain, which is wholly unnecessary today, that they fear and to which they have every right to object. Cavities in teeth with hypersensitive dentin need no longer be prepared on a compromise basis because of the factor of pain. This means not only better dentistry, but more satisfied patients as well. In this modern days it is possible to meet every demand of these sensible patients.

It is the safest practice not to use the remedy in cases of extensive decay whether the pulp is supposedly normal or not. The condition of the pulp is always questionable in such case; and fortunately the dentin, as a rule, is not hypersensitive. Should it be found necessary to use the Paste at all, it should not be applied to the entire cavity surface. Here one of the immediate desensitizers may first be-used, which should permit the painless removal of most of the decay, when the operator can be more or less certain of the depth of the cavity, the condition of the pulp, and the sensitive areas involved. Desensitizing Paste may then be applied in small doses to those areas only, and an anodyne remedy, like Phenol Compound placed immediately over the pulp. It was never intended that Desensitizing Paste should be used in cases of extensive decay, unless used with the idea of removal of the pulp should it be found to be diseased.

The experience and intelligent dentist knows the location of pulp in a tooth; he should also know whether or not the organ is diseased as a result of a carious process; and, if so, that any remedy containing formaldehyde is contraindicated as a desensitizing agent. On the other hand, if the decision is to remove the pulp because of its pathologic condition, then formaldehyde remedies may be used to hasten the death of the pulp and facilitate its subsequent removal. The use of Desensitizing Paste for such purposes is secondary only; the primary use of the remedy is to desensitize hypersensitive dentin where the pulp of the tooth is not yet involved.

Paste is Safe and Efficient

In the treatment of sensitive areas about the necks of teeth, Desensitizing Paste is highly efficacious. Here the area involved may be covered with the Paste and held in position with a good sticky cement for a period of twenty-four hours. If the gum is not inflamed, the remedy, if necessary to cover the sensitive spot, may be placed in contact with the normal gum tissue with no evil results. There may result just a superficial slough which helps to get the soft tissue away from the cavity margin, like in shallow gingival cavities. This is not true, however, where the tissue is inflamed or pyorrhetic. Formaldehyde will attack diseased tissue, whether hard or soft, with energy and vigor. It will not affect to any appreciable depth sound dentin or normal gum tissue. Herein lies the safety and value of the drug as a desensitizing agent. The sensation of these exposed areas, thus treated, will gradually return, and in five or six weeks a second application of the remedy may be necessary; after which the pulp in most cases will have protected itself by secondary dentin formation. Oftentimes when these sensitive areas are etched with but a slight tendency to decay, the area may be highly polished after desensitization, which, in many cases, permanently prevents further decay.

CAUTION IN REALTION TO DISEASED PULPS—In this connection it should be remembered that dental pulps, like human being at times, just simply die for no known or discernable reason. The cause of many an obscure case of trigeminal neuralgia has finally been located in a perfectly sound tooth, the pulp of which was either dead or in a dying condition. For many years it has been known that formaldehyde preparations would hasten the death of a diseased pulp. In former days when the use of arsenic trioxide was in vogue for pulp devitalization, the author advocated sealing the arsenical preparation in the tooth for a period of twenty-four hours only. This was long enough to poison the pulp and permit its liberal exposure with a bur without pain, when the devitalization could more safely be completed by sealing Formocresol in contact with the poisoned tissue for a few days. This remedy contains equal parts of formalin and colorless cresol.

CONCLUSION—In detailing the use of Desensitizing Paste, we desire to specifically call attention to the fact that every dentist has had cases in his practice where vital teeth have ached after permanent fillings have been inserted, and that pulps occasionally die following these operations. Unless the dentist is well posted on pulp pathology and is cautious in his diagnosis similar experiences will follow the use of this valuable remedy. If such should be the case, however, it will be through no fault of the remedy; it will be the fault of misuse or a mistaken diagnosis. It is easy to understand how much harm may follow the use of any remedy or method by which cavities can be painlessly prepared. In the hands of careless operators pulps may be left in teeth which should have been removed. In the hands of the great army of conscientious practitioners, which constitutes the vast majority, Desensitizing Paste will lighten their burdens and prove its worth.

We will repeat, then, that Desensitizing Paste is a definite and positive remedy for hypersensitive dentin. Satisfactory results may be had in every case where its use is indicated. This can be said of few remedies. Perhaps its one and only disadvantage is that it requires sealing in the sensitive cavity. With a little head-work and planning this can be done with no loss of time to either patient or dentist; and, when done, both time and nervous energy are saved; besides we have the added advantage of sterilization as well as desensitization of the dentin.

In the absence of an effective immediate desensitizer, the dentist who has not learned to use Desensitizing Paste in his practice has failed to meet the demands of a long-suffering and appreciative public; he has also been unfair to himself. Painless methods in dentistry are the best practice builders one can legitimately use. Desensitizing Paste will safely eliminate all pain in one of the most dreaded operations the dentist is called upon to perform.


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