Occurrence and healing process of artificially induced gingival inflammation associated with local irritation was investigated using cats.
To find the most suitable irritating material, steel wire, cotton thread, silk thread, vinyl tube and wood piece were investigated in a preliminary experiment using six cats, and #80 cotton thread was selected from them.
In the main study, #80 cotton thread was ligated around tooth neck from 0 to 96 hours in seven adult mongrel cats.
Macroscopically and microscopically, inflammatoric response of gingival tissue was advanced with time.
Plaque and calculus deposits circumscribing cotton thread was clearly demonstrated in all animals experimented over 48 hours.
Bacteriological factor may has a severe irritating role for the initiation of gingival inflammation.

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The purpose of this experiment was to clarify the role of the gingivitis on Dilantin gingival hyperplasia.
As the experimental animals, 18 adult cats were used. They were divided in two groups, 14 cats' group and 4 cats' one. The former was used as the experimental group which had been administered Dilantin for 1 day, 2 days, 4 days, 7 days, 14 days. and 28 days respectively, and the latter was used as the control.
To compare the difference of response to Dilantin between inflammatry gingivae and normal gingivae in the same oral cavity, the following procedures were employed.
In all cats, the left side teeth were ligated with thread #80 so as to make chronic inflammatry changes of gingivae with its continuous irritation, and on the other hand, the right side were kept free.
These experimental animals were examined macroscopically and histologically.
The results were as follows:-
1) In 5 of 14 cats of experimental group, gingival response to Dilantin was observed.
2) The response was limited on gingival margin.
3) In almost every animals, severe response was much observed in inflammatry part as compared with normal part.
4) Gingival inflammation may be one of the causative factors of Dilantin gingival hyperplasia.
5) Dilantin gingival hyperplasia was seemed to be accelerated by gingival inflammation.

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A study of the gingival injury associated with hand scaling has been reported. Following the former study, we would like to report a histopathological study of gingival injuries caused by ultrasonic scaling.
Gingival biopsies were obtained 24 hours after hand or ultrasonic scaling, and they were compared each other histopathologically.
The results are as follows;
1) Injury and tear of pocket epithelium were relatively slighter in ultrasonic scaling than those of hand scaling.
2) In the group of ultrasonic scaling, hemorrhagic changes has never been observed in the gingival tissue.
Contraversely to hand scaling specimens, no hemorrhagic change around the base of pocket was found in ultrasonic specimens.
3) Comparative study of healing proscess of the gingival tissue following hand or ultrasonic scaling is on progress.

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After finishing hand or ultrasonic scaling, structures and roughness of the root surface were investigated using SUMP technique.
The results were as follows;
1) Without any scaling, procedures, the roughness of unexposed root was smoother than exposed ones.
2) In case of hand scaling, remarkable injury scraped by instrument edge was found on the root surface, and it was a little smoother than those caused by file.
3) The exposed surface of root was smoothed by repeated use of ultrasonic scaler and the roughness of it resembled to unexposed root surface.

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As part of Study of splinting, for mobile teeth associating with alveolar pyorrhoea, tooth mobility was investigated experimentally. For the convenience of experiment, real tooth was not used but four types of glass piece were employed. The shapes of glass were cylinder, cone, cuboid and trapezoid and the root of these pieces were implanted within plaster model. The surface of root was circumscribed with rubber tube or rubber impression material to imitate the periodontal membrane. In order to represent various grade of bone destruction, many kind of plaster model was prepared. Square wave of 700kc was given to stroke a model tooth and resulting vibration was recorded using an osciloscope kit. Vibration of model tooth was rapidly increased according with the degree of bone destruction, especially it was remarkable when root was corn-shaped. Even in case of minor bone destruction, thickening of periodontal membrane and vertical bone resorption were extreme accerelating factors to increase the mobility of tooth.

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