Dental caries and its causes / an investigation into the influence of fungi in the destruction of the teeth

Front matter

3 0802 102296258 3

De^t/vl Caries

WITff

Contents

PAGE

Translator's Preface, 3

Authors' Preface, 5

II. Anatomical Alterations Of The Teeth During Caries

Caries, at least in a majority of cases, commences at the surface of the teeth ; it attacks first the enamel, which alone is exposed, while the dentine is covered entirely, either by the enamel itself or by the cementum ; this last is moreover protected by the gums.

Caries rarely attacks the exposed portions of the necks of teeth, and, when it does, naturally has its origin in the cementum. We shall dwell particularly upon the alterations undergone by the enamel and dentine when attacked by caries, as these are the most important tissues of the teeth, and shall speak of its eifects upon the cementum only as connected with these tissues.

Of Central Caries.

Many authors, Klencke among others, have asserted the existence of a caries which originates in the interior of the tooth and in the cavity of the pulp. Xowadays most dentists pronounce against the existence of a central caries. It is true that the process of destruction often begins in a minute crevice or furrow in the surface, and so penetrates the dentine even to the pulp-cavity, where it performs its ravages, while the enamel of the surface seems intact, at least to a superficial examination. This caries, although central, has yet its origin at the surface of the tooth. Therefore, in these latter days, the existence of a true central caries has been generally denied.

Although in most cases the caries called central is so only in appearance, there are cases, very rare it is true, where the destructive process has commenced in the dental pulp itself. In support of this opinion we will cite the following observation, the sole case which has presented itself during the long practice of one of us. Therefore it must be concluded that such cases are extremely rare.

A lady of 21 years of age presented herself and complained of three teeth, one inferior and two superior incisors which had an extraordinary bluish tinge. They were not painful, and one only caused any disagreeable sensation to the patient. She had consulted several dentists, who had told her that her teeth were dead, and there was no remedy. At the surface of these teeth no trace of caries was to be found. The blue color alone met the view and proved their death.

In piercing the posterior face of one of these teeth it was found completely softened, even to the enamel, and the tissues had a brownish color. The root itself was hollowed to a considerable extent. The same was found to be the case with one of the other teeth. The third, whose color was not so marked and which caused no unpleasant sensation, was let alone. As the cause, the patient referred to a blow from a fall which she had had in childhood, and which was followed by a swelling of the face. The pierced teeth were filled with gold. As for the inferior, there subsequently developed an abscess which was treated by puncturing the root.

It follows, from these observations, that the vessels and nerves of the pulp had been lacerated at the time, of the fall of the patient, which lesion was followed by the death of the pulp. But this might have taken place without the destruction of the dentine following. We cannot explain in this case the cause of the destruction of the dentine, for the teeth could not be examined by the microscope. Facts of this kind must never be confounded with those of ordinary dental caries, which is due essentially to the action of destructive agencies acting from the exterior.

We believe then that there exist cases where the dental tissues are attacked and destroyed from the cavity of the pulp ; but these cases are extremely rare, and the conditions of their

CARIES OF THE ENAMEL. 19

production are not yet well understood, except perhaps the previously necessary death of the tooth.

Caries of the Enamel.

Since caries hegins ordinarily at the crown of the teeth, the caries of the enamel constitutes the first stage of the process. The destruction reaches the dentine later, but the first pathological phenomena make their appearance in it, even before the enamel is destroyed in its whole thickness. Most frequently there is seen a black or brownish point in one of the furrows or folds of the crown. On examining a section of the diseased portion the dark color is seen to have its seat in the superficial layers of the enamel, and penetrates clear to the bottom of the furrow, where the thickness of the enamel is, in general, less than at other points.

If, on the contrary, the caries begins on a smooth surface, the approximal face of the tooth, for example, there appears an opaque spot of a yellowish or brownish shade. The points where anomalies of form, of thickness, of quality of dentine exist, are the preferred seats of caries. The dark color of the spots increases with the progress of the disease ; sometimes the centre is of a dark brown while the periphery has a yellowish or whitish tinge. The harder the enamel the darker is the color, for in a dense enamel the progress of the caries is slower and the intensity of the color increases more rapidly than the process, which is a long time in extending itself to the periphery, and to any depth.

The carious spots are easily distinguished, for in them the enamel has utterly lost its normal appearance ; it is transformed into a chalky mass, analogous to that which forms the congenital white spots of the enamel, which are also a frequent seat of dental caries At the carious points the enamel also possesses less hardness than in the normal condition ; but it is sometimes so resistant that it is almost impossible to detach fragments at the surface. Often the superficial seats seem to offer greater resistance than those which are deeper, which, the former once removed, permit themselves to be more easily excavated.

In other cases the consistency of the enamel is much feebler ; it is no more than a chalky mass, or even of no greater consistency than paper-pulp. These differences are explained partly by the stage of destruction, the density of the enamel diminishing with its progress ; but the pre-existing differences of the chemical composition, or consistency of the tooth, take an equal part, for the enamel is softened much more rapidly in some teeth than in others. At the beginning, the surface of the enamel is smooth and uniform ; the fine and parallel strise which are ordinarily noticed on its surface, are well defined ; there is, as yet, no loss of substance. This stage, in which the alterations may reach even to a considerable depth in the dentine, is generally described under the name of dry caries. The more the tooth resists the longer is the duration of this stage; but, in many cases, this stage has but a short life, and the disease rapidly passes on to the humid form.

Soon the portions of the enamel transformed by the caries are destroyed; there is a loss of substance sometimes spread over the surface, or forming a carious cavity, but, generally, this destruction has little extent before the dentine has been attacked in its turn. In this latter case the caries progresses rapidly, and extends itself in depth and laterally. The portions of the enamel situated at the borders of the cavity are undermined at their base, or greatly softened on their internal surface, and break in because they have no longer the natural support, the dentine.

AVe may distinguish two forms in the destruction of the enamel ; one jrrogrcssive, extending itself over the surface, the other penetrating. The former shows itself especially in cases where the caries has attacked a smooth surface of the enamel, the latter is found where the caries has commenced in a furrow. In the former case the caries has attacked, at the beginning, a considerable part of the surface, and the destruction will be quite extensive before it has penetrated as far as the dentine. In the latter case, on the contrary, the alteration of the enamel is limited by the sides of the furrow. The enamel is generally thin at this point, so that

HISTOLOGIC CHANGES IN CARIES OF THE ENAMEL. 21

the dentine rapidly becomes exposed, and its quick destruction causes the phenomena of the caries of the enamel to pass to the second form.

When a carious cavity is formed in the enamel, it is not unusual to see this tissue become carious, sooner or later in one or several other points ; these new points of disease progress by themselves, or add their forces to those already in existence. It is more rare to see the caries spread itself at once over a large surface ; there are, nevertheless, cases where the greater part of the enamel is attacked or destroyed by caries, and, at the same time, one or several carious cavities formed. In such cases there are generally faults of formation of the enamel, which presents, at several points, depressions, hollows, &c, or anomalies of structure. Each one of these points may then originate, either simultaneously or successively, the production of caries.

Histologic Changes in Caries of the Enamel.

Great importance has generally been attributed to the enamel cuticle, discovered by j^asmyth, in the production of caries, some regarding it as a protecting covering, others as the seat of the disease.

The cuticle of the enamel is, as is known, a very thin membrane, whose existence is easily shown by immersing a tooth for a short time in a weak solution of hydrochloric acid. We can thus readily detach the cuticle from the tooth's surface. This membrane, according to the investigations of M. Waldeyer, must be the vestige of the first formative strata of the enamel, and particularly of the intermediate layer and the external epithelium. After the development of the enamel has been completed the elements of these strata are transformed iuto a pavement-epithelium composed Of two or three layers of large polygonal cells, which cover the surface of the enamel. These cells become smooth, little by little, till their nuclei are difficult to be seen; and, during the dental evolution, they unite into a membrane of homogeneous appearance, in which is to be seen neither nucleus nor cell, and in which Mr. Waldeyer, by means of a solution of silver, has been able to render again visible the cell contours.

It is generally thought that the cuticle, on account of its great resistance to chemical agents, must protect the teeth. In fact, according to Ficiuus, neither maceration nor boiling in water affected it, and concentrated mineral acids did not dissolve it. Potassa and soda gave it a whitish appearance, and caused it to swell, but without making it lose its consistency. But it must be remembered that if this membrane cannot be attacked by acids, it permits itself to be penetrated by diffusion ; we must not then lay too much stress upon its role of protection. If the acids can reach the enamel by passing through it, as the method for the isolation of the membrane has already proved, it can at the most retard their action, but cannot hinder it completely. It may then be useful in cases where the acids act only in a transitory manner ; as, for example, when they have been introduced into the mouth with the food, or where they have come from the stomach, as happens in certain diseases, and are immediately removed from the mouth. But if a continuous acid reaction takes place in the mouth, as happens in the case of fermentation, then the protective office of the cuticle is nil.

In many cases we cannot even invoke the protective office of the cuticle, for it is often worn away on the masticating surface of the teeth, and may be wanting entirely to a greater or less extent. This cuticle is frequently wanting in the furrows or chinks of the masticating surface, which arc also the favorite seats of caries. It has been deduced from this fact that caries is developed on account of the absence of the cuticle, but this chosen seat is explained as well by the presence of the furrows which favor the development of fermentations and chemical decompositions.

It is astonishing to see authors defending the protective role of the cuticle, and at the same time admitting that it is the seat, the abiding-place of caries. Messrs. Ficinus and Klencke share this opinion. They admit with Erdl, that at

LEPTOTHRIX BUCCALIS. 23

the beginning of caries, the cuticle, at the surface of the brown spots, is covered with a deposit whose nature they do not agree upon. Ficinua says this deposit is formed of vibrios, and of the fibres called by Btihlmann filaments of the leptothrix. According to Klencke it consists of these elements sometimes, but, in other cases, there are found the cells of his pretended protococcus dentalis.

It is in fact easy to show that, at the point of the carious spots, the cuticle is almost always covered with the accumulated deposits of leptotkrix buccalis ; there is found there a substance finely granular, or bed of fungi, which is composed of very minute sporules. At the surface of this granular substance there are also to be found at times very delicate filaments which spring from it, and which are identical with the fibres of Biihlmann. As this fungus- plays a very important part in the production of caries, we will proceed to study it more in detail.

Leptothrix Buccalis.

There is almost always found in the mucus of the mouth, at the surface of the tongue, and in the interstices of the teeth, a whitish, cheesy substance, formed in great part by the leptothrix buccalis. Under the microscope we see a gray, finely granular mass, gangue or matrix, then filaments delicate and stiff, of various lengths, which erect themselves above the surface of this granular substance, so as to resemble an uneven turf. It is in the interstices of the teeth that this fungus attains its greatest size, when we do nothing to check its development ; its filaments there attain considerable length, and form bundles, sometimes parallel and undu-

* It may astonish some to see us designate the leptothrix buccalis b}r the name of fungus, and not by that of alga. Opinions are divided on this question which, for the rest, seems to have no great importance for our subject. We have simply used the name most common in Germany, without permitting ourselves to judge a question purely botanic. Yet, if it should come to be shown that the opinion of M. Hallier is correct, which is that the leptothrix is only a form of development of the fungus penicillium glaucum, it must be admitted as without doubi that the leptothrix is a fungus.

lous, at others firmly interlaced among one another. On the surface of the tongue we see cylindrical or club-shaped elements, which are epithelial prolongations of the filiform papilke of the tongue, as Kolliker has proved.

These prolongations are covered by a rather thick mass of granular substance of leptothrix. bristling at times with short filaments. In the fluids of the mouth, detached filaments are often met. The epithelial cells of the mouth are also frequently covered with numerous fine, oblong granulations, identical with those which compose the bed of the fungus. If we closely examine the grayish masses which the granulations form at the surface of the filiform papilla?, we see that they are composed of epithelial cells, detached in part, and dissociated, covered with thick masses of granulations which unite and make of them a compact mass. The club-shaped prolongations which result have often very well-marked contours, and the granulations are so intimately interwoven that the substance often appears homogeneous, but the addition of a little acidulated liquid permits the granular elements to be readily isolated. The cheesy matter which collects in the interstices of the teeth has an analogous structure, except that the granulations, instead of attaching themselves to the epithelial cells, are joined to the filaments of the fungus, cover and unite them.

It is easy to follow the formation of this substance. AVe observe, mider the microscope, filaments upon which granulations have fixed themselves ; some enveloped by a sheath of granulations, some united and intermingled with them. Frequently a great portion of the cheesy substance is exclusively composed of the granulations, fine, and generally a little drawn out, of which we have spoken.

These granulations are, according to M. Hallier,* only movable spores in repose, which wander during a certain period in the liquid, but finally attach themselves somewhere and increase by forming new articulations. If these observations are exact, as we are inclined to think, the

LEPTOTHRIX BUCCALIS. 25

movable spores resemble vibrios which are found in the mucus of the mouth, and possess the power of rapid movement. These organisms, called denticolce by M. Ficinus, belong then not to the animal but rather to the vegetable kingdom. Moreover, M. Ficinus compared them with the so called filaments of Biihlmann, or filaments of leptothrix. He had seen spores, which he considered infusoria, move for a time in the liquid among the filaments of the leptothrix and epithelial cells, and afterwards attach and fasten themselves to one of the filaments. Soon others were added, and thus was explained the formation of the filaments and epithelial cells covered with granulations of which we have just spoken M. Ficinus also believes that the filaments are due to the juxtaposition of the granulations, which is not correct. It appears, on the contrary, that the granulations push out prolongations, and that thus is formed successively an articulated chain. As M. Ficinus took the denticolce for infusoria, he could not have had a just idea of the nature of the fibres of Biihlmann. Later the vegetable nature of the filaments was recognized, but that of the granular substance could not be explained. M. Robin among others thought it was formed by the debris of alimentary substances. This supposition is false ; for, if this were so, the granular substance would not always present the same characteristic aspect. Composed, in fact, of granulations, fine, elongated, and shining, it has a peculiar matted appearance, by which it is easily recognizable.

According to M. Hallier, to whom we owe the opinions just given upon the spores of leptotlvix, this fungus may be only a form of development of the penicittium glaucum. If so this fungus should always be produced when the spores of penicittium are kept in a watery liquid. "We have not verified the truth of this opinion. However this may be, M. Hallier explains by his theory the formation of the granular substance, and teaches us the nature of the denticolce of M. Ficinus.

It remaius to explain why, in the mouth, the spores so quickly lose their movements ; in the cheesy substance, where the granulations are found closely packed, no movements are perceived. A portion of the elements which move about in the saliva as vibrios are larger than the little granulations of the leptothrix^ which can nevertheless change both form and volume.

In cultivating the leptotkrix in the saliva with the addition of sugar, or any other appropriate liquid, we ordinarily see developed movable spores in numberless quantities, and endowed with a power of very rapid motion. If the movements cease, which is observed on the edges of the preparation where it begins to dry, the spores resemble exactly the granular masses of the leptotkrix which are met with in the mouth. The cessation of movement in the mouth can be explained by the viscosity of the medium, and by the presence of the buccal mucus.*

We have already observed that it is always very easy to recognize the elements of the leptotkrix by their characteristic aspect ; but it is always desirable to have at hand a chemical reagent which will enable us to perceive the existence of the fungus when its external aspect is deceptive. This reagent we have found in iodine and the acids, which give to the

* The details which we have just given explain equally well the various opinions which have been expressed upon the composition of the tartar of the teeth, and upon the inferior orders of being which it contains. According to M. Mandl, the tartar maj' be composed of the calcareous carapaces of infusoria which live by millions in the mucus of the mouth. M. Ficinus had the same opinion, as his denticolce are evidently the equivalent of the infusoria of M. Mandl. Formerly the tartar was regarded as a deposit of salts dissolved in the saliva; its chemical composition, analogous to that of the inorganic products of the salivary liquids, still pleads in favor of this opinion. M. Robin found in the tartar filaments of leptothrix, and doubted the indications of M. Mandl. According to our researches there do exist in the tartar filaments and granulations of leptothrix. They are easily recognized .after treating the tartar with diluted acids. It is probable that it may contain at times more filaments, at others more granulations of leptothrix, so that there may occur cases where there can be found only granular masses, .which would very closely resemble the indications of M. Mandl. The infusoria with calcareous shells must be rejected. As for the salts of the tartar, they are precipitated very probably in the saliva, mixed with viscous mucus which incloses the filaments of leptothrix, and deposited graduall}' upon the surface of the teeth.

LEPTOTHKIX BUCCALIS. 27

elements of leptothrix a beautiful violet tinge. We obtained this reaction in trying the effect of that for cellulose (colored blue by iodine and sulphuric acid) upon our fungus, and we have noticed that MM. Leyden and Jaffe had already recommended the same reagent for the leptothrix which is found in putrid sputa, and in the lungs.* They are treating of fungi which are discovered in sputa which have become putrid in cases of gangrene of the lungs. '1 he sputa had a very acid reaction. The fungi were colored a beautiful violet by the simple addition of iodine. The fungi of the mouth which have undergone no change are colored, for the most part, yellow by iodine; generally we notice a violet color only after adding an acid. Sometimes we obtain a violet reaction by the aid of iodine alone, a fact which we must attribute to acidity of the buccal mucus. It is not necessary to make use of sulphuric acid, as in the case of the reaction of cellulose ; but any acid whose action is not too violent will render the same service. We have obtained excellent effects by the use of weak hydrochloric acid, by acetic, and by lactic acid. Sulphuric acid has with us less generally succeeded, because it occasions so rapidly other decompositions. The reaction which we have obtained is identical with that which MM. Leyden and Jaffe have described, for the color is likewise that of a beautiful violet (not blue as in the action with cellulose), and it is the contents of the filaments and not their envelope which is colored. We know this by the circumstance that the septa of the filaments remain inaccessible to all coloration. It results from this that the presence of an acid is indispensable to obtain the reaction. Nevertheless it will be useless to have recourse to any acid when the liquid which contains these fungi is acid enough, as is the case in putrid sputa, and even, at times, in the mucus of the mouth.

We almost always find, as we have already observed, at the surface of the carious points of the enamel, a coating of

* Vide Leyden and Jaffe. Sur les crachats putrides, la gangrene pulmonale et la bronchite putride. (Archives allemandes de clinique medicale. Tomes ii, iv, and v, 1866, p. 488.)

leptothriz, even when this surface seems still polished and intact. This coating adheres strongly, and is not so easily removed as the cheesy masses of leptothriz which cover other parts of the surface. When, by the aid of a weak acid, the enamel cuticle is removed, we find this coating thickened, composed most frequently of the accumulations of granular matters, and there is rarely to be recognized the presence of filaments of leptothriz. The fungi seem to have penetrated through the enamel cuticle, as they adhere to it strongly ; but. at this stage, it is not possible to prove their presence in the enamel itself.

'1 he filamentous and granular matters of leptothriz which are found accumulated on the cuticle of the tooth are not arranged in any regular manner ; we often see them under the form of rounded and irregularly disposed ma£ Neither are these masses well defined, but are joined one to another by delicate beds of granular matter. It is probable that these appearances have formed the base of the observations of MM. Erdl, Ficinus, and Klencke; but they have not giveu us exact descriptions of them. "We have never been able to perceive the presence of the cells described and pictured by M. Klencke in his Protococcus dentalis, and we think, after investigations made upon a great number of teeth which have all yielded us identical results, that his conclusions are founded in error. We are the more convinced of the correctness of our own results, in that no observer has succeeded in confirming the facts as stated by M. Klencke. Yet it is hard to say what could have given rise to this error, inasmuch as there exists absolutely nothing which offers any analogy to the facts as stated. M. Klencke describes cells of from Tin to oio'" m diameter, which would be collected, at the beginning of the caries, in simple beds crowded together upon the enamel cuticle, and. later, these same cells would form layers superposed, and capable of multiplying by division or by endogenous proliferation. The mode of propagation of these cells penetrating the dental substance is described and pictured with so great exactness that we

LEPTOTHRIX BUCCALIS. 29

may be permitted to wait, at least until the discovery again of some analogous elements.

We find, occasionally, after having removed, by the aid of a weak aeid, the cuticle which covers the tooth, minute elements, crowded against each other upon the denuded surface, which might be confounded with a sort of granular epithelium with ili-defiued contours. These are nothing but the extremities of the enamel prisms left adhering to the cuticle. It is impossible to confound them with the' cells of the fungus. It might with equal probability be supposed that such an error could spring from portions of vegetable or other alimentary substances which are found adhering to the teeth. It seems to us, from certain indications, that the round, granular masses of leptothrix which form upon the surface of the cuticle have given rise to this error, although a certain power of imagination is necessary to consider these irregular and badly defined masses as cells. In caries of the enamel these fungi, as we shall show, appear not to play a part as important as in that of the dentine. The action of acids and the decomposition of organic substances, which is its consequence, and which is recognized by a brown color, seem to us to demand more attention. Yet equal account should be made of the effect produced by the fungi.

The seat of leptothrix seems generally to be confined to the surface of the tooth as long as the dental substance remains intact. It may be otherwise when the teeth are covered with a greenish coating, and the lesion seems to have its seat in the very substance of the enamel.

We meet with this greenish coating in young people and upon the front teeth. It is generally attributed to the alteration of the enamel cuticle. The action is not bounded by the surface of the tooth, but penetrates even into the substance of the enamel. We have examined but a single case of this kind. We removed from the surface of the tooth small green and rather hard portions which resembled tartar, but which appeared to be rather minute fragments of enamel. Nevertheless it was impossible, after examining them under the microscope, to decide whether it was enamel or not. After having dissolved out the calcareous portions, we were convinced that the whole suhstance was strewn with granular matter of leptothrix. The greenish tinge was found only at the surface of the pieces ; the acids could not destroy it ; it had an appearance of shreds, delicate and plicated, or perhaps granular, and without other structure. It is important, therefore, to make new experiments to ascertain if, at the place of this green color, the fungi penetrate the substance of the enamel, or if we must attribute it to a particular kind of tartar, as appears much less probable. If the first supposition should be confirmed, we must seek to find why and how the fungi succeed in penetrating the enamel. It will not be less interesting to know the origin and the cause of this greenish color.

As regards the elements of the enamel, no particular change seems to precede its alteration. It can only be shown by the aid of the microscope that it is easier to recognize in minute fragments of diseased enamel the structure of this tissue, than in its fragments in a state of health, when the union of the prisms can with difficulty be perceived. This phenomenon can be explained by the disappearance of the calcareous salts consequent upon the work of caries. Carious enamel appears under the microscope like that which has been submitted to the action of acids, and differs only by a little more or less brownish color. The farther the work of caries has proceeded, the easier it is to prove this difference. There are found in minute cavities of the enamel delicate debris of this tissue. The extremities of the enamel prisms and their oblique stride have contours so fine that it is only by the shade of brown that we can recognize them. This occurs likewise when we employ acids. AVe find no more than a residue, very delicate and of a membranous nature, which reveals the composition of the enamel, whose total destruction is not slow in taking place.