Abstract : Root canal instruments are used in various handling methods depending on the location, shape, or conditions of the root canal dentists are treating. The instruments are considered to undergo various complicated deformations as a result of the dynamic differences involved in these actions.

 To prevent intracanal breakage of root canal instruments, dentists should know the physiochemical properties of the metals used for instruments. The dentists, then, can perform more efficient root canal therapy with less labor and strain.

 This article presents materials and manufacturing process of root canal instruments, the causes of the intracanal breakage of the instruments, and the terminology in material science metals.

Abstract : This experiment was designed to evaluate the relationship between the vertical force to the root, the instrumentation time and the operator’s EMG activities of forearm and hand muscles during root canal instrumentation.

 Acrylic resin root canal models (No. 35 size) were established on a force transducer. Seven dentists instrumented the root canal models using 2 methods (Group1 : instrumentation as gentle as possible, Group2 : instrumentation as quick as possible). The EMG from the flexor politics brevis muscle, the brachioradialis muscle and the interosseus dorsalis muscle I were recorded using bipolar surface electrodes, amplified and integrated.

 The vertical force to the root, the integrated EMG area, the maximum amplitude of EMG and the instrumentation time were measured and compared significantly.

 The results suggest that the instrumentation as gentle as possible reduced the maximum amplitude EMG of the operators as well as the vertical force. On the other hand, the integrated EMG area increased following an extension of the instrumentation time.

Abstract : Superoxol has been used for tooth whitening. Previously, we reported that superoxol resolved intertubular dentin and peritubular dentin, and hydroxyl radical was detected from superoxol by electron spin resonance method. However, we could not elucidate what effects mainly on whitening, i. e. hydroxyl radical or pH. In this experiment, the pH of HCl solution was adjusted equal to superoxol’s pH. We observed changes of canal walls using SEM, after applied those solution on root canal dentin surfaces. In the results, superoxol resolved the intertubular dentin and the peritubular dentin, but HCl solution did not. In addition, we observed Candida albicans in the case of HCl solution. It suggested that the generated hydroxyl radical from superoxol has both bactericidal effect and whitening effects.

Abstract : To appeal the importance of endodontic treatment, we surveyed a consciousness of general practitioners (3985) at Tohoku district on endodontic present condition and solution. The basic contents of this survey were office place, sex, age, opened years. Moreover this survey asked general practitioners that how to they asked and examined to endodontic patients, and did they agree with the health insurance valuation on electrical measuring root length, pulpectomy, infected root canal treatment and root canal filling.

 The response rate of this survey was 13.5% in Tohoku district. Almost of general practitioners asked and examined a patients by themselves. Three fourths of them didn’t agree with the health insurance valuation on endodontic treatments. To solve many problems, they suggested that our dentists should recognize the proper awareness to the importance of endodontic treatment.

Abstract : Root resorption is occurred by trauma, periapical periodontitis, replantation and orthodontic treatment. There are two types of resorption i.e. internal resorption and external resorption. Especially, external root resorption is brought by the traumatic force of unsuitable orthodontic treatment. In this case report, external root resorption with apical lesion followed by unsuitable orthodontic treatment is presented. After root canal treatment and root canal filling, healing of the tooth was satisfactory with disappear of the lesion, and with no progress of the root resorption.

Abstract : Longitudinal chronic origin of endodontic lesion, type Ⅰ endo-perio disease has been not clearly distinguishable from the type Ⅲ disease. Thus, it is difficult to decide to make a periodontal surgery for the type Ⅰ disease.

 In this report, we treated 3 patients of the type Ⅰ disease aged 20s to 30s without periodontal surgery. All case’s prognoses were good during 5 to 9 years.