The dental treatment, free from pain and anxiety to the patient, is made possible by combining special techniques with acurate knowledge of treatment countermeasures of dental pain, if these steps are taken during daily dental procedures.

  In order to describe in detail the above theme, Treatment countermeasures of dental pain, special attention was given to pain following periapical diseases and endodontic procedures.

  First of all, the classification of dental pain in the endodontic field was described. Following the localization of enamel, dentin and periapical pathosis, they were first classified into two large groups and each group was then divided into subgroups. When we diagnose these sophisticated diseases, the classifications are very important. Among them, the therapy about pulpal and periapical diseases are very interesting and important. The adequate procedures of painful pulpitis and acute periodontitis are essential for endodontic specialists.

  Thus, for this purpose, knowledge of the tooth and periapical tissue structure, diseases and techniques based on this information are required of all of us. For this reason, a detailed explantion of the toothache and special therapy of acute diseases were referred to.

  GP-solvent is a newly developed root canal filling material solvent that contains d-limonene as its principal component.

  In the preliminary and clinical studies GP-solvent demonstrated less side effects than chloroform, so we recommend it as an effective, safe root canal filling material solvent for clinical application.

  It is an undoubted fact that an occasional breakage of root canal instruments during clinical practice has bothered and frustrated endodontists for a long time. Such an accident has occurred even in the most experienced operator.

  Various methods and instruments have been discussed and suggested for the settlement of this problem. However, in spite of such development, the intracanal breakage still remains an unsolved problem, which seems to have been more complicated.

  This paper describes a method which I have recommended, together with other approaches which have been suggested.

  Accurate measurement of the root canal length in essential for successful endodontic treatment. In the ideal case, endodontic treatment should be performed without causing damage to the apical tissue to clean and shape the root canal. It should be remembered that the steric felling of the root canal must terminate at the location of the physiological apical foramen (that is, 0.5～0.7mm anteriorly of the apical foramen). To achieve this, it is thus essential to determine the exact location of the apical foramen.

  In the past, a variety of methods have been tried by using X-ray photography. The shortcoming of the X-ray methods is their inability to provide accurate results. Since the anatomical root apex and apical foramen are not necessarily identical, it follows that the real length of the root canal cannot be measure with accuracy by X-ray techniques, even though it may be possible to measure the actual length of the tooth. In recent years, attention has therefore been focused on electrical measuring techniques to determine the root canal length. The electrical measurement technique was developed by Suzuki and Sunada et al. as a result of their revolutionary research work. It has gradually come into use over the last twenty years because of its greater simplicity as compared with the X-ray techniques and its superiority in terms of providing accruate measurement results even when the root apex and the apical foramen are not identical. In 1978, the electrical measurement technique also became available under the National Health Insurance Scheme, thereby opening the way to the general use of this method. The technique does, however, present some problems in connection with the accuracy of the measurement results, so that basic research is being continued to shed light on the problems.

  As a completely separate approach to the problem, the authors developed from a clinical viewpoint a root canal length measuring device in 1971. This method uses sound generated by low-frequency oscillation. So far, clinical experiments with this method have been conducted, in an extensive scale, principally in Europe and the United States.

  The clinical results have been utilized to improve and perfect the device to achieve a very satisfactory level of precision that meets present-day clinical requirements. The authors intend to develop this method for the accurate measurement of the root canal length further by taking into consideration the procedure and the difference between the two techniques.

  The purpose of this study is to investigate some surfactants as root canal irrigants instead of sodium hypochlorite solution which cause the caustic action to periodontal tissue or oral mucosa. Test surfactants were cationic surfactants (CPC, CAB, benzalkonium chloride, benzethonium chloride), amphoteric surfactants (C₁₄HSB), and non-ionic surfactants (E. 710, E. 715).

  The minimum inhibitory concentration (MIC) of the surfactants against 20 anaerobic bacteria isolated from human infected root canals and 5 facultative bacteria and dissolving activity for type Ⅰ collagen gel were examined.

  The results obtained were as follows :

  The antibacterial effects of cationic and amphoteric surfactants were stronger than nonionic surfactants. And growth of all bacteria tested were completely inhibited by 10^-1% of cationic and amphoteric surfactants as same as 5% sodium hypochlorite solution.

  The dissolving activities of cationic surfactants such as 10^-1% cetyl trimethyl ammonium Bromide and 10^-1% benzalkonium chloride were found as well as 5% NaOCl solution, however activities of amphoteric and non-ionic surfactants were less than half of 5% sodium hypochlorite solution.

  FDI, ISO and ADA have reported lately the method of valuation attaching importance to biological valuation of the safety standard of the dental materials in which the subcutaneously implanting test is imposed and the reaction which is in direct contact with the tissue of the living body is required in a different way than the conventional test in vitro.

  Especially, the endodontic materials applied to are imposed the use test besides the ordinary tests.

  Then, the irritation test of the tissue was performed by the method mentioned bellow.

  1. The subcutaneously implanting test was performed using male Wistar rat.

  2. The test materials were made by filling in the tube of poly-ethylenetetrafluoride.

  3. The difference was recognized among the test materials.

  Furthermore, the results of 8 weeks and 12 weeks after in the subcutaneously implanting test will be reported in the next number.