The pressure exerted on the buccal and lingual polished surfaces of the lower denture from the surrounding soft tissues during various functions of the mouth was investigated to compare the standard denture (St-D) with the flange technique denture (Fl-D) .
Five subjects who were missing their right and left first lower molars or more teeth participated in this study.
The pressure was recorded by four miniature pressure sensors placed on the buccal and lingual polished surfaces of each side during the following movements.
1. Directed movements (jaw opening, tongue protrusion, upper and lower lips protrusion)
2. Swallowing (empty, water)
3. Chewing (right side, left side)
The results were as follows:
1. The same tendency was observed in the case of the pressure between the St-D and the Fl-D during the various functional movements.
2. The Fl-D generally exerted more pressure than the St-D.

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Inhibitory premotor neurons projecting to the jaw closer motoneurons (IM neurons) and excitatory premotor neurons projecting to the jaw opener motoneurons (ED neurons) in the bulbar reticular formation were shown to be involved in the inhibition of the jaw closer motoneurons and the excitation of the jaw opener motoneurons during the jaw-opening phase of the cortically induced masticatory rhythm in the immobilized cats. The present study analyzed the role of these bulbar reticular neurons in the control of the natural masticatory jaw movements during food ingestion in the chronically prepared unanesthetized cats.
The single unit activity was recorded from 40 bulbar reticular neurons which modulated the firing frequency in the same rhythm as the masticatory jaw movement. Thirty-four neurons showed a burst during the jaw-opening phase (opening type), while the remaining 6 neurons showed a burst during the jaw-closing phase (closing type) . By averaging the full-rectified EMG of the masticatory muscle by the spikes of the reticular neurons, 4 neurons were found to be the IM neurons and the other 4 neurons the ED neurons. All these premotor neurons belonged to the opening type.
A posi tive correlation was found between 1) the instantaneous firing frequency (IFF) and the velocity of the jaw movements in 4 of 6 opening type neurons (2 of 3 IM neurons and 2 of 3 ED neurons) and in 3 of the 6 closing type neurons, 2) the IFF and the jaw displacement in 3 of the 6 opening type neurons (2 of 3 IM neurons and 1 of 3 ED neurons) and in 2 of the 6 closing type neurons, 3) the number of spikes in a burst and the duration of the jaw-opening phase or the jawclosing phase as well as the maximum displacement and/or velocity of the jaw movement in 16 tested neurons and 4) the maximum firing frequency and the maximum displacement and/or velocity of jaw movement in the 16 tested neurons.
It was concluded that the bulbar reticular neurons were involved in the control of the velocity and displacement of ja movement during mastication by modulating the firing frequency and the number of spikes in a burst.

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The purpose of this study is to evaluate the generally accepted enamel etching procedure for the composite resin restoration and to develop a more useful one.
The flat ground enamel surfaces of human teeth were treated with varying exposure period to various etchants and different washing pressures.
The tensile bond strength of the adhesive resin applied to the enamel was determined. After testing, the enamel surface and the interfacial resin structure were observed by SEM.
The bond strength would greatly depended upon the microfine irregularity resulting from the individual enamel crystal rather than much greater irregularity due to the preferential loss of prism periphery. The bond strength was remarkably reduced when the dissolution products deposited on the etched enamel surface. These products were generated by long etching with orthophosphoric acid solution or citric acid containing FeCl₃. Compared with the acid solution, the gel-like liquid generally required a longer etching to produce such a microfine irregularity contributing to bonding.
A new etching technique with two applications of the gel-like liquid for 5 seconds each succeeded in efficiently producing the microfine irregularity resulting in the marked increase of the bond strength. This double etching technique was found very practical for clinical use.

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The present study is concerned with the tooth movement during loading in natural dentition to clarify the relationship between the movement of the teeth and the functional situation. The mobility of each tooth from the upper central incisor to the first molar was measured on six subjects in the bucco-lingal and axial direction with a non-contact sensor system utilizing the eddy current. The diphasic curves were obtained with and without the load and they differed in the pathway, and the difference was generally remarkable when loaded in the axial direction on the molar. The mobility was generally large in the upper teeth when the force was applied in the buccal direction. Every tooth showed a characteristic mobility path and they did not always coincide with the direction of the load. The unique path gathering in a certain direction was observed within the mobility path, in spite of the change in the direction of the force.

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The purpose of this study was to investigate the permeability of formocresol into the root dentin and its effects on the periodontium in beagle dogs. The fourth upper and lower premolar pulp of 9 dogs were removed and formocresol containing ³H-formaldehyde or ³H-cresol was dressed in the root canal. After a given period, the amount of tritium radioactivity permeating into the blood was measured by a liquid scintillation counter. The periapical periodontium and lateral periodontium were evaluated histologically and autoradiographically.
The results obtained were as follows:
1) Both ³H-formaldehyde and ³H-cresol were present in the blood within half an hour postoperatively. There was more ³H- cresol than ³H-formaldehyde in the blood within 4 hours but after 24 hours more ³H-formaldehyde than ³H-cresol.
2) In the periapical periodontium, the inflammatory cell infiltration was observed in 12 (50%) of 24 roots and hyperemia and dilatation of the vessels were observed in 16 (66.7%) of 24 roots after 3 days. In the lateral periodontium, several specimens showed inflammatory cell infiltration and more than half of the whole specimens showed hyperemia and dilatation of the vessels after 3 and 7 days.
3) Grains of ³H-formaldehyde and ³H-cresol were found distributed from the pulpal side of the dentin to the cemento-dentinal junction after 3 and 7 days. There were more grains of ³H-formaldehyde than those of ³H-cresol throughout the root dentin.

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In order to clarify that marsupialization is effective in the treatment of cystic ameloblastoma, 35 cases of mandible ameloblastoma treated by means of marsupialization were examined clinically, radiologically and histopathologically.
The age of the patients ranged from 4 to 80 years (average 24 years) . In 31 cases (88.6%), a reduction of lesion was found clinically and radiologically between 2 months and 2 years 4 months after marsupialization and in 4 cases no reduction was found.
As for the relation between the macroscopic findings and treatment result, most of the lesions with smooth cyst wall reduced soon after the operation. About half of the lesions with smooth and rough cyst wall reduced wholly, but the other half reduced only partially. All four lesions with a rough cyst wall (granular type) didn't reduce but grew into the lumen of the cyst.
The lesions of the squamous cell type and large follicular type reduced distinctly. As for the lesions of the plexiform type, some lesions reduced but the others grew.
When some tretment has been necessary after marsupialization, minimal resection of mandible was satisfactory in most cases.
From these results, it is suggested that marsupialization is effective in the treatment of cystic ameloblastoma.

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The response of the dental pulp to calcium hydroxide or zinc oxide and eugenol cement was investigated histopathologically, using the germ-free and conventional rats. The upper first molar pulp was exposed with a p1/2 round bur through the mesial surface of the teeth and covered with the capping agents. The observation period was 1, 2, 4, 7, 10, 14 and 28 days postoperatively. The results obtained were as follows:
1) In the conventional rats, severe inflammation of the pulp was observed as the result of bacterial contamination throughout the observation period. The response of the pulp itself to the capping agents could not be assessed exactly.
2) In the germ-free rat pulp covered with calcium hydroxide, the inflammation was slight and a higher calcified tubular dentin bridge was observed 28 days postoperatively.
3) In the germ-free rat pulp covered with zinc oxide and eugenol cement, the inflammation was moderate and a relatively poorly calcified dentin bridge without the dentinal tubules was observed 28 days postoperatively.
4) In the germ-free rat whose pulp was left open to the oral environment, the response of the pulp was the mildest of all the experimental groups. The calcification of the dentin bridge of this group was slightly higher than that of the pulp capped with zinc oxide and eugenol cement 28 days postoperatively.
5) The presence of the dentin chips weakened the response of the pulp tissue to the agent, but the formation of the dentin bridge was delayed.

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