Recently, the chewing plastic device was created as a new brushing method. The objective of this paper was to determine whether the plastic device is useful for elimination of plaque and for improvement of gingivitis. The results obtained from this study with OHI (Oral Hygiene Index), OPI (Occlusal Plaque Index) in 10 university students, and with salivary occult bleeding index in 13 adults were as follows.

  1. After 5 minuts brushing, OHI and OPI were significantly decreased (p<0.01). And the average of removed plaque was about 56%. But it was difficult to remove the pits' and fissures' plaque on the occlusal surfaces of molars and premolars. So it was suggested that it is better to use the former toothbrush together.

  2. After 2 weeks brushing (10～20 minuts per day), salivary occult bleeding index was also decreased (p<0.05). It was concluded that treatment of gingivitis needs brushing for over 2 weeks.

  In endodontic therapy it is supposed that success in the obturation of root canals depends on how well the root canal is dried just prior to obturation. There are various ways which are commonly used in daily clinics to dry the root canal-wiping or absorbing moisture with paper points, aspirating with instruments, using drying agents together with aspirators, etc.

  Its difficult, however, to ascertain the effects of each of these methods. So experiments were performed on these drying methods using root canal models and extracted teeth and discussed.

  From the results of the study it was concluded it was impossible to dry the root canals completely using only the paper points but the following method was very effective : First drying agents are applied and then absorbed with paper points or something similar, and finally an aspirator is used to remove residual drying agent.

  Bilateral upper second incisors of 20 years old woman showing the recurrence of the periapical lesion after the long period of healing process. Both teeth were clinically diagnosed as cysts. Large periapical rarefaction areas caused by previous maltreatments were shown on the pictures. Usual non-surgical endodontic treatments were performed and several smear slides of the exudates from the canals were made to know the pathological changes of the periapical tissues. Chloramphenicol was dressed into the canals as a disinfectant. Both canals were obturated with canals (Grossman's sealer) and guttapercha points using lateral condensation method.

  X-ray pictures taken 3 years after the initial treatments showed remarkable improvement of the periapical lesions. Recurrences of the periapical lesions were found on the pictures taken 7 years after the treatments. Surgical curretage was tried on the right second incisor and the histopathological slides of the periapical tissue showed the re-establishment of the cyst.

  The proliferation of the microorganisms remaining at the apical area of the tooth was considered as a main cause of the recurrence.