[in Japanese]

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Accuracy in observation of opening and closing movement by clinical researchers depends very much on the recorder's observational abilities. The purpose of this research is to improve the quality and accuracy of such observation.
To this end the opening and closing movements of the mouth of the same subject were recorded in the following three ways and compared :
1. by Gnathohexagraph JM 1000^® (manufactured by Ono Sokki Co.) . We called this ME Group.
2. 16 dentists with no previous experience of using an ME machine for measurement : A Group.
3.4 dentists who had previously used an ME machine : B Group.
There was only a small divergence between B Group's and ME Group's average figures. However, there was a big difference between A Group's average figure and those of ME Group and B Group. Therefore, in order to observe loci of movement with observational accuracy comparable to that of an ME machine, we suggest it is necessary to have a high degree of competence with ME machines, and that this can only be achieved through practice.

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The purpose of this study was to investigate the susceptibility to the pain in the preparations of vital teeth for abutments using of a high-speed mechanical contra-angles. The susceptibility to the pain was evaluated by visual analogue scale (VAS) values. The VAS data were obtained from 574 vital teeth from 313 patients ; 152 for male, age 14-73 and 161 for female, age 12-72. The VAS values were increased with age in male and female subjects and higher in males than females. The rate of infiltration anesthesia showed a tendency to be higher in males than females.
This study showed that in general males had higher VAS values and underwent anesthesia more often than coeval females. The only exception was females in the fifties who felt pain equally to or more than males in the fifties. Significant difference between males and females was observed in the sixties (p<0.05) . Females in the thirty had the lowest VAS values and males over sixties had the highest VAS values.I conclude that pain sensation during abutment preparation tends to differ depending on age as well as sex.

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Implant placement in narrowed residual ridges was conventionally difficult, which often caused functional or aesthetic problems in the superstructure.
However, at present, the buccolingual width of the narrowed residual ridge can be restored by the guided bone regeneration method (GBR method), bone grafting, residual ridge enlargement using an osteotome, or the split crest technique using a bone chisel, and predictable bone growth is possible.
Implants can be placed at the optimal site by these methods used alone or in combination. These methods are widely used in clinical practice.
We present 3 cases treated by the split crest technique and discuss this technique and its effects.

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