In 10 healthy subjects, isometric jaw-opening force and relations between the force and EMGs from the masseter and the anterior venter of the digastric muscles were studied. The opening force was actively exerted at various jaw positions; i. e. 0 mm (an intercuspal position), 10, 20, 30 and 40 mm opening position of the jaw. In each positions, successive five trials were repeated. Next results were obtained.
(1) Mean value of Maximum opening forces was 2.55± 0.35 kg.
(2) Jaw position had significant effect on the force (P<0.05); in 10 mm opening position the most forceful value of 3.19 kg and in 40 mm opening position the minimum of 1.07 kg were obtained on an average. An intertrial variation of opening force in the former position was smaller than that of the latter (P<0.05).
(3) In terms of time relationships between onsets or offsets of the opening force and EMGs, highly interindividual difference was found (P<0.0003).
(4) During isometric jaw opening, electromyographic activity of the masseter muscle was facilitated in 9 out of 10 subjects, although it differed with trials and/or jaw position.

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The purpose of this study was to compare and evaluate the relative reproducibility and equality as well as jaw relationships produced by four jaw guiding methods; the gothic arch tracing, the voluntary tapping, the myomonitor centric and to occlude warm wax bite rim by light habitual closure. Four patients were selected whose remaining teeth had already lost the maximum intercuspation. The intraoral tracer was fixed on upper complete denture base and lower removable partial denture in three cases. Only in one dentulous case needed complete occlusal rehabilitation, the appliance was fixed on transfer coping crowns.
The mandibular position guided by each methods was measured to the nearest 0.1mm in laterally and anteroposteriorly (x and y components). The accuracy of this experiment was estimated at 0.22mm (±2σ) or 0.34 mm (±3σ). This error was derive from width of tracing line, area of tapping point, mobility of denture base and mounting on articulator. Within the limits of this investigation, it is concluded that;
1. Each guiding methods determined different mandibular position in case 1, 2 and 4. But in case 3, they terminated in the same mandibular position.
2. The gothic arch tracing produced the least variable and the voluntary, tapping the most variable. The habitual closure tended toward eccentric position laterally. The myo-monitor centric produced more variable than the gothic arch tracing but less than the habitual closure.
3. The estimated region of apex point was 0.57mm in laterally and 0.45mm in anteroposteriorly, the myo-monitor centric showed 0.62mm in laterally and 0.76mm in anteroposteriorly, the habitual closure determined 0.97 mm in laterally and 0.96mm in anteroposteriorly and the voluntary tapping produced 0.95mm in laterally and 1.59 mm in anteroposteriorly in an average of rejection ellipse (α=0.05).
4. In an average of mandibular positon in anteroposteriorly, the gothic arch apex was the most retruded. The distance between apex point and the habitual closure was 0.4mm, the myo-centric was 0.7mm and the voluntary tapping was 0.9mm anterior.
5. An average distance between apex point and mean points of each methods produced more consistent mandibular position that ranged within 0.15mm in laterally.

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As a preliminary study for evaluating bony changes of the alveolar crest, 1, 115 sheets of intra-oral roentgenograms obtained from 130 dental patients with the bisecting-angle technique were observed.
In the age group lower than 30 years, the bone loss on the interalveolar and the interradicular septa were found in 72% and 16% of the samples. These values became higher with age. The former attained to a plateau level of 99% in the age group of the thirties and the latter the level of 51% in the age group the fifties.
It was suggested that the progressive bony loss with age was characterized by homologous change in the age group less than forty, while heteromorphous change was predominant in the age group higher than forty, resulting from an increase in the case of transformation H-type bony loss into V-type one.
Bony loss in the upper molars and the lower incisors might highly progressed than in others.
In the portions of the molars and the second premolar, V-type of bone loss was more frequently recognized than H-type on the mesial site of the tooth of the interalveolar septa, but inverted on the distal site of the tooth of the interalveolar septa.
In the portions of the incisors and the cuspid, frequency of bone loss with H-type was higher than that with V-type and wasnearly equal on both of the sites.

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The myothermal changes were investigated during clenching at centric occlusion in temporal and masseter muscles. Ten males (from 21 to 26 yrs.) volunteered as normal subjects.
At first, the deep temperature changes of the forehead area and the anterior temporal muscle were recorded at rest, during and after clenching. And then, changes of deep temperature in anterior temporal, posterior temporal, and masseter muscles were observed at rest, during and after clenching.
The results were obtained as followed:
1) At rest, the deep temperature of the temporal muscle was higher than that of the masseter muscle.
2) During clenching, the temperature rise of the masseter muscle was larger than that of the temporal muscle.
3) After clenching, no differences in temperature drop were found between muscles.
4) Concerning the selection of probe, PD-7 was suitable for the anterior temporal muscle, PD-1 for the posterior temporal and the masseter muscles.

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On studying the color of the natural tooth, as a means to record the tooth crown color objectively, color chart must be necessarily made so as to define the color range and plot it.
This time, concerning the color distribution of tooth crown color, in addition to the relations with Munsell color system taken up ever widely in the color study, color chart is made by using psychometric quantity highly relative to the psychophysical quantity based on psychoperceptive quantity presented by HUNT. R. W. G.
Color chart made and shade guides (VITA: Lumin Vacuum, DENTSPLY: Trubyte Bioform, SHOFU: Real crown, GC: Plastic Teeth) are spectro-measured JIS Z 8722 by using spectrophotometer, type M 307 of HITACHI. There expressed CIE L^* a^* b^* uniform color system, it becomes indisputable that with respect to the color-rending property of the color chart made at standard light source C with vision field two degree, the way of valuation for the vision varies at standard light source D₆₅and A in case of changing of the light source from one to the other.

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This experiment was attempted to make a new piezoelectric accelerometer of bender type for measurement of vibrations in the living bodies.
It was found that it had characteristics which output voltage was constant in the range of 0.2-110 Hz and vibrations particularly below 5 Hz could be detected.And further, the other characteristics obtained were as follows,
Sensitivity: 1V/1 G
Temperature range:-20-80°C,
Resonance frequency: 1.4 kHz
Size and weight: 22mm diameter, 14.5 mm height, 12 grams
Transverse sensitivity:-50 dB
Detecting direction:perpendicular to the disc.
With this new accelerometer, it was possible that Microvibration on each surface of forehead, menton, tempolomandibular joint, masseter muscle and anterior temporal muscle was detected.
From the visual inspection of the Microvibration records, it was found that the Microvibration waves were different between parts and between subjects.

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In this study, the regularity of masticatory movement and the phase of muscle activity in a dentate subject with disclusion in his 20s were recorded simultaneously with the Saphon Visi-Trainer CII, a device for analyses of jaw movement, and the polygraph, a multipurpose monitoring/recording device.
The following conclusions have been reached:(1)In the opening phase(I), the rhythm is just about the same in the early and middle periods.In the late period, the rhythm becomes signigcantly large.
(2)In the closing phase (II), the rhythm is significantly large in the early period and just about the same in the middle and late periods.
(3)In the occlusal phase(III), the rhythm is the smallest in the early period and it becomes significantly larger in the middle and late periods.
(4)In the cycle(C), just about the same level is shown in the early and middle periods and significantly the largest in the lane periods.
(5)I/C is just about the same in every period of the mastication.
(6)II/C is significantly the largest in the early period and becomes significantly smaller in the middle and late periods.
(7)III/Cis significantly the smallest in the early peri od, and becomes significantly larger in the middle and late period.
(8)The number of masticatory stroke is the largest for ham and about the same for peanuts and pickled raddish.
(9)Duration of muscular discharge in the closing phase (D1)is significantly the largest in the early period and it becomes smaller in the middle period and further smaller in the late period.
(10) The duration of the muscular discharge in the occlusal phase(D2), are significantly the smallest in the early period, and becomes larger in the middle period and further in the late period.
(11)D 1/D is significantly the largest in the early period and becomes smaller in the middle and periods.
(12)D2/D is significantly the smallest in the early period and becomes larger in the middle and late periods.

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In the present study, with the purpose of clarifying in detail the actual conditions of the SP that appear in the masticatory movements, the author selected normal dentate subjects who possessed the following different occlusal types:(1) Mutually Protected Occlusion (MPO), (2) Anterior Group Functioned Occlusion (AGO) and (3) Semi- Group Functioned Occlusion (SGO). Then, using the polygraph and the Saphon Visi-Trainer CII, the author conducted simultaneous recording of the electromyograph and mandibular movements to observe the frequency of SP (SP-F), the duration of SP (SP-D) and the mandibular positions at each time of occurrence of SP (VD and HD) in the mastication of three different kinds of food, viz., peanuts, ham and pickled raddish. As a result, the following conclusions were reached:
1. As for the SP-F, that of MPO tended to decrease from the early to the late periods, while that of AGO tended to decrease from the early to the middle periods and to increase in the late period. The SP-F of SGO showed the same tendency as that of AGO in peanuts and as that of MPO in ham and pickled raddish.
2. As for the SP-D, it was significantly long in the early period of peanuts and pickled raddish and about the same in the middle and late periods. In ham, the SP-D was significantly longer in the early period than in the late period of MPO and about the same for all periods of AGO, and significantly long in the early period of SGO.
3. As for the jaw positions, all occlusal types showed the largest VD and HD in the early period of peanuts and a significant decrease was seen from the middle to the late periods. In the early period of ham, VD was the largest and about the same in the middle and late periods. The HD was the smallest in the late period of MPO and AGO, and about the same for all periods of SGO.

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