Eberhart's Manual of High Frequency Currents
Noble M. Eberhart
Chapter Twelve
High Frequency in Dentistry.
    General Field of Usefulness. High frequency currents are coming daily into more and more frequent use by dentists. They are employed in pyorrhea, in drying cavities, in devitalizing teeth, in sterilizing root-canals, in bleaching teeth, in abscesses, in locating devitalized teeth, and for the relief of pain. The author is not a dentist, but has tried to give in this chapter a resume of current dental opinion and technique as gathered from various sources. Several dental electrodes are illustrated in fig. 68.
    Pyorrhea. Pyorrhea early manifests itself by a light reddening of the gums at the margins and a tendency to bleed on slight provocation. A large majority of patients having pyorrhea are anemic, and in these the gums, instead of being red, may have a yellow and discolored appearance and are apt to be flabby or receding instead of puffy. In the second stage of the disease, pus appears, attacking first the peri-dental membrane. Later the bony socket of the tooth may be slowly eaten away or destroyed. The gums gradually recede and the tooth becomes loose in its socket and painful to the touch.
    From this we can see at once indications for the employment of high frequency currents.
    A french authority says that it is necessary "to destroy the microbic and suppurative state of the gums, correct the depleted nutrition in the tissue and produce an over-active phagocytosis and increase the index of leucocytic destruction. For this result one uses high frequency currents with the greatest success in the two forms, the effleuve (spray) and the spark."
    Gremeaux and Arnal (l'Est Dentaire, Sept., 1913) use the high frequency as follows; "One introduces the metallic fulguration electrode as far as possible between the loosened gum and the tooth, in order that the spark may reach all the recesses and purulent foci. During the operation, which lasts an average of a minute for each tooth, one sees the margin of the gum blanch and the pus bubble out at the neck of the tooth. When all of the recesses have been penetrated, the fulguration point is replaced by a small vacuum electrode, which is passes over the external and internal surface of the gums for about ten minutes."
    They wait three or four weeks to note results before giving a second treatment, employing a rigorous antiseptic regime in the meantime, consisting in brushing with an alkaline powder night and morning, and numerous rinsings with boiled water, etc. About a week after the treatment the patient massages the gums with the finger twice a day. In three or four weeks, if pressure on the gum shows presence of pus, the treatment is repeated; otherwise the case is dismissed, with instructions to keep up the massage of the gums an antiseptic care of the mouth. One to three treatments were required in the cases treated.
Fig. 66 - D'Arsonval Outfit for Diathermy.

    Dr RF. Morel (Bulletin du Syndicat des Chirurgiens-Dentistes de France, Sept.-Oct., 1910, Jan.-Feb., 1911) makes use of medicaments in connection with the high frequency. He claims that the high frequency effleuve renders mucous membranes porous and facilitates the penetration of medicaments, and that the simultaneous application of the solution and the current produces an electro-chemic effect. He decomposes by the currents a solution of potassium bi-chromate, claiming that the base will be taken up by the diseased tissues.
    After thoroughly removing the tartar from the teeth, he carefully irrigates with peroxide and evacuates all of the pus. Then he paints the teeth and gums with the following solution, using a spatula to get it up as far as possible around the roots:

R -   Fluoride of Ammonia.........1 gramme
        Chloride of Ammonia.........1 gramme
        Chloride of Potash.............1.5 gramme
        Salicylate of Theobromine. 1 gramme
        Methyl alcohol...................50 centigrammes
        Distilled Water...................20 grammes
M. - Filter.

    This solution favors ionization and lessens the resistance of the tissues to porosity.
    A pad is then soaked in a ten per cent aqueous solution of bichromate of potash and held over four teeth and a vacuum electrode held over this for about fifteen minutes, with close contact. He only treats four teeth at a time. In advanced cases he uses a metal point and carries a few sparks up into the infected canals.
    The vacuum tube application is for cataphoric purposes, and one of the electrodes illustrated herewith having a cup to hold the saturated cotton may be used for this purpose.
    He repeats this treatment every second day, sometimes giving three five-minute seances with eight minutes' rest between. Usually four treatments produce a cure, occasionally six, seven or eight have been required. During the whole course of treatment the patient washes the mouth six times a day with the following solution, using half a glass each time:

    Sodium salicylate.............10 grammes
    Sodium fluorosilicate........2 grammes
    Distilled water..................1 Litre

    Dr. Irwin Jirka applies methyl salicylate in these cases, driving it in with the vacuum electrode. He treats for eight minutes every other day. Reports a number of cases cured in three to fifteen treatments. Hubbel uses the cataphoresis electrode first and then the ball pointed pyorrhea electrode to massage the gums for five or six minutes each, treating daily until improvement takes place.
    Dessication, Metallic Ionization and Phoresis. I have been furnished with a translation of a paper by Dr. A. A. Nouel of Venezuela. This paper, read at the Dental Section of the Medical Congress at Caracas in 1911, is entitled, "Dessication, Metallic Ionization, and Phoresis of the Canals in One Sitting with High Frequency Currents." The author's methods seem to be distinctly original. He speaks of using at first a coil and resonator and with this and iodide of potash because this chemical absorbed the ozone when the current was introduced into infected root canals. After four years of experimenting he found a method and a machine that enabled him to get simultaneously metallic ionization and thermopenetration.
    He says: "I have used the *** high frequency coil but even though the machine is just as efficient as other more powerful coils for fulguration; with vacuum electrodes and with the ozone inhaler, in the dessication of the canals, the current is found to be of too pronounced faradic character.
    "I have also used several other types of high frequency machines, and found the one most suitable giving a smooth, high frequency current without any faradic sensation, such as is used in diathermy. In this case there will be felt by the patient nothing
but a progressive increase of warmth, if there is no continuity of solution. If there is one, no matter how small, beside the progressive thermic increase, there will result an ionization of the canal in which a small arc will be established. This arc is formed between the walls of the canal and extends the full length of the electrode.

Fig. 68 - Dental Electrodes.

    "The electrode is connected by means of a flexible and well-insulated metallic conductor to the right hand 'auto-condensation' terminal. The electrode handle may be about ten centimeters long, and made of either fine wood or ivory, with a metallic point similar to that of the broach holders employed in dentistry. Small pieces of either copper or zinc wire, as required in each case, will be fitted to the handle. In some cases, where no abscess is formed, I believe the copper is superior to the zinc electrode. To substantiate this statement, I have observed that after a diseased spot has been treated with a copper electrode no pain is felt if that spot is touched.
    "Before the current is turned on, it is better to thoroughly dry the cavity leading to the canal in order that the sparks may not be diverted, but will confine themselves to the length of the wire and walls of the canal throughout its length.
    "I firmly believe that the metal, during its ionization, is cataphorically introduced into the dental canals through the apex, and that once in the presence of the salts that form the composition of the blood, a chloride is formed, this being the reason why the peridontium and adjacent parts are irritated when zinc is employed. A zinc electrode is beneficial in case of an abscess on account of the chemical composition formed by the zinc.
    "The ionized and ozonized copper is also introduced into the dental canals by means of the cataphoric action of the current, thus forming a deposit of oxide or bi-oxide of copper, which will permanently act as a disinfectant. I shall later on explain the method through which its action is brought about.
    "Although a tooth may be profoundly infected (it is understood that I refer to a tooth without pulp), with inflammation of the peridontium, with an abscess or fistula, it can be 'stopped' in one sitting, fearing no ulterior difficulties, if this novel method is employed.
    "The technique is very simple; After the pulp chamber is open it is to be moistened with a small quantity of trikresol and iodoform or trikresol and formalin, after which the electrode is applied, being held at a distance of half to one millimeter and moving it over the surface until the cavity is dry. A broach is now employed, being operated into one-half the length of the canal, drying with cotton and compressed air, not too warm; then the copper wire is introduced and the current turned on for five minutes. The broach is now used again, this time reaching to the apex. The canal now being perfectly freed from the bits of pulp and other foreign bodies, is now thoroughly dried with cotton inserts. The copper electrode treatment is then repeated for five minutes, and after this time has elapsed the tooth may be 'stopped.'
    "The great efficacy of this modality is supported by the fact that the dental canals constantly maintain a certain humidity, which serves as an easy conductor for the introduction of the ionized metal, and permits the easy access of the flowing-in process of the ozone while being dried by the thermopenetration, which goes to complete the oxidation and the consequent coating of copper, leaving it permanently deposited in a state of oxide or bi-oxide of copper."
    Abscesses. The dental technique advised by some operators consists in ten or fifteen minute applications of a mild current in contact with the cheek, followed by the use of one of the cataphoresis electrodes containing cotton saturated with iodine and aconite solution. Duration of this application about eight or ten minutes. Jirka uses methyl salicylate, and also speaks of formo-cresol, which I infer is used with the cataphoresis electrode.
    Drs. Barber and Van Valkenburg have reported a case where the copper wire was employed in treating an abscess.
    Post-operative Pains. For the pains and soreness existing after extraction or after setting bridges or crown, the use of the cataphoric electrode with any suitable solution has been recommended, followed by application of mild current with the ball-pointed pyorrhea electrode.
    Sterilizing Root Canals. Another method of sterilizing root canals is the touching of the pointed dental electrode (carrying current enough for a half-inch spark), to a broach which has previously been inserted in the canal. The broach carries the current into the canal. The direct D'Arsonval current may be used the same way.

Fig. 69 - Portable Outfit for Dentists.

    Bleaching the Teeth. Hubbel says: "Place your bleaching solution on a fibre of asbestos or cotton, placing it in the cavity of the tooth and applying the point of the electrode directly against this fibre, the cataphoric action of the current driving the solution into the dentine, getting results much quicker than from ordinary measures. Care must be taken that the apex of the tooth is first stopped with gutta-percha so that there is no danger of the solution being forced through the apical foramen."
    Diagnosing Live from Dead Pulp. The pointed dental electrode is used with a mild current, and the point applied to the cusp of the tooth. If the pulp is alive the patient will feel the current; if he does not, the tooth is devitalized.
    Obtunding Sensitive Dentine and Devitalizing Teeth. "In obtunding sensitive dentine, a small crystal of carbolic acid is placed in the cavity and the pointed electrode is used in the generator, the current being toned down as mildly as possible. The point of this electrode is then placed against the cavity, and if still sensitive, use the current for a half minute longer. You may now start to excavate, and if the one application of the carbolic acid does not last sufficiently long to complete the operation, place another tiny crystal in the cavity and apply as before. In the majority of cases, operations have been rendered entirely painless by this method of treatment.
    "In devitalizing the teeth a small crystal of novocain is placed in the cavity, or, if no cavity is apparent, cut into the enamel with a very small stone, placing a crystal of novocain therein and dipping the tip of the electrode in adrenalin. Apply the high frequency current to this with a very mild flow of current the same as in obtaining sensitive dentine, using the current for about one minute. Drill into the teeth until as close to the pulp cavity as possible without unnecessary pain, and again apply a crystal of novocain and use the current for about a minute to a minute and a half, and in most cases it is then possible to cut into the pulp cavity. If the nerve is then sensitive, pressure anesthesia is advisable. The greatest trouble that we find in getting success from this treatment is the inability of the operator to successfully control his current, as it takes considerable practice in order to get the proper amount of stimulation. But, after some experimenting, it is possible to get results in the majority of cases." - Hubbel.