Experimental Study on the Pulp and Root Canal Treatment by Means of High Frequency Current

Abstract

In order to improve technics on the root canal treatment in applying a high frequency current, the author used three different length of the waves ; short waves, middle short waves and diathermy current, and searched the passage of the current heat distribution of the root of the tooth and the tolerant thermal limit of the periodontal tissue etc. by em-ploying human teeth in situ and extracted ones in models. And the following results were obtained.
1. When a needle shaped electrode is inserted in a root canal and a high frequency is sent to the outer side of the root, the current can easily pass through the root wall.
In this case, the diathermy passes mainly as conduction current and the short waves act mainly as displacement current. And it was observed, on the contrary of the previous theory, that the current which passed through an apical foramen was extremely little.
2. When the electrode is inserted in the root canal and the high frequent current is supplied as discribed above, the strongest heating takes place at the end of the electrode and the heating spreads over the canal contents, canal wall and the outer surface of the root by turns.
3. The elevation of the temperature of the canal wall by the short waves is mainly originated in the thermal conduction from the interior of the canal and it is considerable, in the case of the diathermy, that Joule's heat effect produced by the conduction current is also added.
4. As to the burning of the near gingival margin which has been reported repeatedly, it is discussed that a considerable amount of heat derived from the convection of the intra canal liquid accumulates at the upper portion of the root canal and then comes through the tooth snbstance to the periodontal tissue. In the case of the diathermy, by addition of Joule's heat effect, the burning is accelerated.
5. The tolerant thermal limit of the periodontal tissue is considered to be 45°C or so, from the result of the examination of the gingival pocket in situ.
6. When the heating in the root canal is stopped at the tolerant thermal limit of the periodontal tissue, an average temperature of the intra canal liquid, in the case of the short waves, is 56°C and in the diathermy, 50°C.
7. In order to maintain the intra canal temperature to be high and the heating of the periodontal tissue to be under the tolerant thermal limit at the same time, it is recommendable that at first 30-40 mA of the current is to be supplied until the temperature of the root surface reaches to its tolerant thermal limit and then the current is to be supplied intermittently with 5-10 seconds' interval.
8. It is desirable, in pulp coagulation, that the electrode should be inserted to the near region of the would-be coagulation. And it is effective that electrode is inserted to the apical portion of the root canal to elevate equally the temperature of the intra canal medicament.
9. In the root treatment, it is effective to use the short waves which can maintain the intra canal temperature to be high.