Abstract : The oral and nasal cavities are the most important entrance for microorganisms, whether they are pathogenic or not. Some viruses such as herpes simplex, varicella-zoster and picorna viruses cause apparent lesions transiently in the oral area, but others such as hepatitis and human immunodeficiency viruses show no signs.

 In this chapter, outlines of the apparent of the apparent viral diseases, especially herpes group viruses, and HIV infections are discussed from the point of biosafety in the medical procedures.

Abstract : This paper reviews the root canal preparation and the apical seat.

 In my school, we have been teaching the standardized preparation technique using a reamer for these ten years. Although, various problems have been brought in clinical cases of the students ; such as overextension of the apical foramen, straightening of the canal, zipping, accidental perforation and others.

 To avoid these accidents, the causes for them and the new method for the root canal preparation have been considered.

 The results obtained were as follows :

 1. Even in straight canals, the method such as the step-back technique which can minimize the transportation of the canal should be applied.

 2. The minimum sized preparation should be performed in the vicinity of the apical foramen.

 3. In vital teeth, the termination point of the canal preparation should be located 0.5 mm more coronally of the minor foramen, and the tip of the guttapercha point should be positioned within the apical constriction. On the other hand, in non-vital teeth, the apical foramen should be penetrated with #15-20 files. Then, the canal should be prepared so that the tip of the guttapercha point is seated at the same place as in vital teeth.

 4. For the more accurate preparation near the apical formamen, the newly developed electronic apex locators (the Root ZX and the Apit) should be applied.

Abstract : The toxicology is study for research on toxic effect of chemicals, and the risk assessment of environmental chemicals is estimated by the basis of toxicological data. Animal experiments are especially important in toxicological research. In this report, methods of toxicology was first described in the case of study on o-phenylphenol, and the use of experimental animals was explained in following.Problems and future of toxicology were discussed in the last two paragraphs.

Abstract : Solubility of soft tissue and predentine remaining on the root canal wall by intracanal dressing of calcium hydroxide paste was investigated with a scanning electron microscope. Middle thirds of roots of extracted human teeth were split longitudinally into halves and the pulp tissues were removed, then the halves were divided into 3 groups. Specimens of control group were with no treatment. Specimens of 1 week-group were stored for 1 week in calcium hydroxide paste under the condition of 100% humidity and 37℃. Specimens of 4 week-group were stored for 4 weeks in the same manner, but washed and replaced into new paste every week. Root canal walls of these specimens were examined and compared with a scanning electron microscope. Remaining layer of odontoblasts was prominent in control group, but disappeared completely in 1 and 4 week-group. However, predentine remained almost intact in 1 week-group, and with slight surface erosion even in 4 week-group. It was found that calcium hydroxide paste dressing can dissolve remaining odontoblastic layer, but scarcely predentine.

Abstract : This case report describes the 12yr progress of replanted teeth for injured total luxation.

 The patient was a 25-yr-old female. She lived on a secluded island where there was no dentist.

 The history indicated that both of the upper central incisers and left lateral inciser were totally avulsed for during swimming in the sea when she was a 13-yr-old.

 Those teeth were replanted immediatly after endodontic treatment by the dentist who had volunteered on the island at the accident.

 A splint was made of a double strand of 0.1 mm stainless steel wire covered with acrylic resin.

 In this case, the replanted teeth have maintained normal function for a long period. After 12 years, she complained of slight pain and abscess formation on labial gingiva of left central incisor. Radiographic examination showed severe resorption of their roots and alveolar bone. We dicided that the teeth were extracted for severe resorption of their roots and alveolar bone, finally a temporary denture was applied.

Abstract : Hitherto, the panorama X-ray picture is thought to be unsuitable for the diagnosis of the soft tissue but one can guess the condition of the inner maxillary sinus to some extent when he observes carefully.

 The opinions which are revealed often on the clinical examples diagnosed as chronic odontogenic maxillary sinusitis are concerned with the opaque image like the gigantic columns of clouds which appears from the bottom of the sinus to the side wall of it. The example which decreases the X-ray transparency of the whole sinus is seldom and rather it is an unusual case. These diseased images which are seen in chronic odontogenic maxillary sinusitis disappear and decrease soon after the dental therapy.

 This suggests that a part of the sinus mucous membrane near the diseased tooth often swell by the chronic irritation of the tooth but the grater part is normal and retains vigorous healing ability.

 It suggests that the characteristic opinions on the panorama X-ray of chronic odontogenic maxillary sinusitis and change of its diseased image are able to be a sign of judging success or failure of endodontics.