Bridge bone grafting of fresh autogenous rib, with or without three or four small holes using a dental reamer, was performed on the bilateral lower margin of the mandible of 30 Wister’s male rats. The results were observed to compare with the histological findings on 7, 14, 30, 60 and 90 days of the experiment.

1)The degeneration in bone marrow and the bone resorption of the graft on 7 days after grafting were observed more rapidly in the group without small holes than in the group with small holes. The granulation tissue invading through the small holes from the host site took place when coming in contact with the graft at that time.

2)The invasion and proliferation of granulation tissue was active from the small holes on 14 and 30 days after grafting. Therefore, the new bone formation, the bone remodeling of graft, and the bony bridge between bilateral recipient parts of the mandible and the graft were more superior in the group with small holes than in the group without small holes at these times.

No differential findings of the bone remodeling of grafts were observed in two groups on 60 and 90days after grafting.

3)In this experimental study, it appears that the holes formed in the grafted ribs promoted to invade the granulation tissue from the host site. Therefore, it was possible for the bone remodeling of the graft.

4)Sixty days after grafting, the connective and cartilaginous tissues were observed in parts of some holes, and these findings probably indicated the healing process of the fracture occurring in the same parts. For the prevention of such fractures, the holes should be made as small as possible and attention should be given to the appropriate number of holes on the grafted bone.

Deoxyribonuclease of Staphylococcus aureus, Staphylococcus pyogenes, Serratia marcescens has been known.

However, the production of DNase by oral streptococci, hitherto have not been reported.

In this report the production of extracellular DNase by oral streptococci, S. sanguis, S. mutans, S. mitis and S. salivarius was examined, and the following results were obteined.

1. Only S. sanguis produced when incubated under anaerobic condition, but not under aerobic condition, in CO₂ incubater or candle jar. On the other hand, S. mutans, S. mitis and S. salivarius did not produced any condition.

2. Crude enzyme fraction of S. sanguis I Challis strain was obteined from supernatant of culture broth, and its DNase activity was determinated.

From these results it was concluded that the crude enzyme fraction isolated culture of S. sanguis I was extracellular DNase.

DNase was separated from culture fluid of Streptococcus sanguis I and another biochemical properties of DNase were examined.

The enzymatic activity was purified about 6 fold by DEAE-Sephadex A-50 ion exchange chromatography and further Gelfiltration on a Sephadex G-100 column. Two DNase which designated fr. a and fr. b were fractionated. Molecular weights of these enzyme were determined by Sephadex G-50 gelchromatography, fr. a is 24,000 apporoximately and fr. b is 8,000.

Optimal pH range is 7.0~9.0, there are double peak. This enzyme was activated by the addition of Mg ion, but illhibited by Ca ion.

On the other hand, the enzyme has not activity for RNA (Yeast) and has specific activity for native DNA. The thermally denatured DNA is poor substrate, 30% of activity decreased.

The pathological analysis on 52 cases of benign fibrous and fibro-osseous lesions of the j aws were performed. These cases classified according to WHO’s classification, i. e. 23 cases of cementoma and its related lesion, 17 cases of fibrous lesion, 5 cases of osseous lesion, 3 cases of giant cell lesion, and 4 cases of others which could not be classified as any other diagnosable diseases. Majority of clinical symptom in these cases was swelling of affected regions. The significant difference of mean age was found in cementoma, osteoma, fibrous and giant cell lesions. In its location, fibrous and fibro-sseous lesions were found more frequent in premolar and molar regions.

Our report was based on a rare case found in the upper right lateral incisor with a double root of a 50-year old female patient.

Labiolingual dimension and the mesiodistal dimension of the upper lateral incisor which the root was separated into the labial and the lingual side by a deep fissure, was greater than the average measurements reported by Professor Kamijo of Tokyo Dental College in the case which have studied.

In the mesial surface and distal surface of the root the fissures originated from the cervical line to the apex.

Therefore the root separated completly into the labiolingual side from the apical one-third.

According from the observation it may be presume that this case is of the ontogenical type.

Our report was based on the anomalous case of an upper canine with an abnormal tubercle of a 20-year old male.

The development of the crowns of the remaining teeth is normal.

However, the upper right canine is abnormal.

It seems to be fact that this tubercle would be originated from the cingulum.

Some of patients who are too much afraid of dental treatments, and physically handicapped persons are unable to be treated in the same manner as usual patients.

For such patients, general anesthesia has been employed to enable various dental treatments.

In this paper, we report the present status of general anesthesia for dental outpatients in three establishments in detail, and add our opinion about its.