The intercuspal position (IP) is the most important jaw position associated withstomatognathic function. Since this position is determined by the upper and lower teeth, it is changeable according to the occlusal states of the teeth. Three-dimensional areas of IP useful for occlusal diagnosis and occlusal reconstructionwas discussed.
In such cases, IP should be the position where the condyle isstable in the TMJ fossa and the jaw muscles function without any hindrance. The area of IP was considered to be rather great vertically because of adaptability of the muscles and the range of the rest position of the mandible.
The habitual opening-closing jaw movements terminated in the area of approximately 0.3mm in diameter in normal subjects. Activities of the muscles on both sides showed imbalance when IP was displaced approximately 0.5mm laterally. Therefore, the area of IP was considered to be narrow horizontally.
Clinically, it is comparatively easy to restore and maintain IP stability by the fixed prosthodontic technique. However, in case of an occlusion supported by removable free-end partial dentures, how to keep IP stable longitudinally is a big problem.

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The color change in samples of unpigmented self-curing resins prepared with a new initiator using barbituric acid derivatives (Ba-CI-Cu) was found to be less than specimens prepared with conventional Benzoylperoxide-tert Amine initiator (BPO-tert Amine). One cause of the perceivable color change for BPOtert Amine was the increase in the values of |Δa*| and |Δb*| during storage periods. ANOVA showed statistical significance in that the higher the storage temperatureand the longer the periods of sunlight exposure, the higher the value of ΔE*ab for BP0-tert Amine became. On the other hand, in the case of pigmented resins, the values of ΔE*ab for ivory shade (Ba-Cl-Cu/I) except 60°C-dry and for pink shade (Ba-Cl-Cu/P) were less than 1 during storage for 56 days. Therefore, no color differences could be perceive either before or after storage and exposure to the various conditions. In the case of 37°C-wet, i.e., oral environment, the values of ΔE*ab for Ba-Cl-Cu/I and Ba-Cl-Cu/P were approximately 1/6 to 1/2 and 1/15 to 1/4, respectively, compared with the values of a commercially available product.

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The correlation between movements of the mandible and hand in response to auditory signals were studied to compare motor skills in the orofacial structures and upper extremities.
Ten dentulous young adults and 2 geriatric edentulous patients (one, who was not adapted: A, another, who was well adapted to complete denture wearing: B) were asked to make tapping movements of the mandible or hand in synchronization with auditory signals generated at regular intervals of 1.3 time/sec. While tapping, the markers on the menton (Me) and fingertip (Ft) were recorded on videotape using 2 high-speed video cameras from frontal and lateral perspectives. The movements of each marker were automatically tracked, and the resulting data of the 3-dimensional coordinates was constructed. Then, the trajectory of each monitored point was computed using a 3-dimensional analyzer (Movias 3D) with reference to the following parameters: total length from start to finishof the trajectory (TL); distance between start and finish of the trajectory (SL); TL to SL ratio (T/S); volume of the rectangular solid encompassing the entire trajectory (Cub); the 3-dimensional angles created by the difference in the direction of the preceding and subsequent trajectories at each measured time (TH); and velocity (V).
The following results were observed: The time-lag between the auditory signal and Ft movement in the edentulous subjects (A, B) was greaterthan that of the dentulous subjects (N). Although the time-lag between the signal and Me movement in B was similar to that of N, the time-lag in A was greater than in N and B.
In both A and B, during the down phases of Ft, Cub, TL, SL and V were smaller and TH was greater than that in N. During the closing phases of Me in A, Cub, TL, SL and V were remarkably greater than that in N, however, in B, only T/S was smaller than in N and the others were almost within the range of1 SD of N.

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This study was conducted to evaluate edentulous mandibular bone sections by tomography. Tomography provided more useful information regarding the three-dimensional shape of sections and additional information can be gained from mesiodistal images of the mandible by rotational panoramic radiography and buccolingual images by tomography. Dry human mandibles, in which a metal index had been calculated, were examined by rotational panoramic radiography and tomography, and the accuracy of measurements was calculated at five sites and compared on each image. The center of gravity of mandibular bone sections was measured, and morphologicalmeasurements were investigated.
It was possible to determine the mandibular corpus height and width using the metal index of tomography. Furthermore, that index was useful for deciding the site and direction of tomography. The accuracy of measurements of the mandibular corpus height by rotational panoramic radiography and tomography were similar. By using the center of gravity of mandibular bone sections, it seemed possible to obtain highly accurate and effective measurements for evaluating the shape of sections.

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There are many types of stress in dental treatment, for example, pain or uncomfort due to denture. However, it is too difficult to judge the stress objectively. Therefore, it is attempted to judge them with the Clinical Electroencephalogram (SYNAFIT 2100). By clenching, some changes in the EEG rate were observed. These results suggested that it was effective to use the EEG to indicate mental stressdue to dental treatment.

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To simplify the conventional porcelain application procedure, Bonding Porcelainand Opaque Porcelain of Super Porcelain TITAN (Noritake) were blended in this study. Powder of Bonding Porcelain and Opaque Porcelain were blended in weight ratios of 1: 1, 1: 2, and 2: 1, and then applied to titanium (KS50, Kobe Steel) and fired at one time. The bond strength of each compound was measured using the pull-out method. Measurement of color stability was performed in specimens, at variousthicknesses of the porcelain compounds and Body Porcelain, and differences from the standard color were calculated. Values for bond strength were significantlyhigher in compound specimens than “Opaque Porcelain only” specimens. Color stability varied depending on the blending ratio, but no color difference was observed only in monolayer specimens with the blending ratio of 1: 2 and thicknesses of 0.2 mm and 0.3 mm. From these findings, it was considerd that blending ratios hardly make any difference in color stability and that differencce inthe thickness of compound porcelain and Body porcelain affect color stability.

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The purpose of this study was to investigate the effect of coronal and gingival contours in the contact with the food bolus on the cervical area of the crown atdifferent heights during mastication. A bridge containing a load cell with two sensitive areas within the pontic and having adjustable coronal and gingival buccal contours was constructed for the missing lower first molar. The buccal surface of the crown was contoured normally or 0.5 mm excessively, and the gingival crest was contoured with 0.5 mm thick or 1.0 mm thick.
Forces in the cervix direction were observed during the closing phases, and forces in the cusp directionwere observed during the opening phase. The former forces were more frequent andintense, and the following results were obtained therefrom.
The contact forces were less frequent in the lower sensitive area than in the upper one, and wereless intense and frequent with the overly contoured crown and gingiva. The contact force decreased greatly in the upper sensitive area because the buccal surface of the crown was overly contoured, and in the lower one because the thickness of the marginal gingiva was increased.
These findings suggested that the friction caused by food bolus on the tooth surface close to gingival crest could be difficult to control by altering only the coronal contour.

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Conditions of repetitive jaw tapping movements in time to acoustic signals with 1.3 Hz fixed cycle (fixed cycle tapping), in time to acoustic signals with random interval (observation on 1.3Hz parts: random interval tapping), ad lib tappingwere observed. The subjects were 16 healthy dentulous young adults, and their mean age was 25.0 years. They were instructed to make tooth contact close to the signals. Observation was made on the relation among Mm EMG, MKG, and acoustic signal. The results were as follows:
1. In random interval tapping, it was found that the subjects began jaw tapping after they recognized acoustic signals.
2. Though in random interval tapping they could not anticipate time relation, there was proficiency in the movement control by experience in trials. It was considered that the proficiency depended on spatial anticipation of the task.
3.These characteristics in random interval tapping were similar to those in 0.3 Hzfixed cycle jaw tapping. It was confirmed that both tasks hardly depend on anticipation and depended greatly on “an instant performance control”.
4. It was suggested that to remove many influences by anticipation was one of characteristics of 0.3 Hz fixed cycle tapping and that when it was used it had some advantages of diagnosis of movement control of the jaw.

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Hybrid ceramics “Estenia” has appropriate mechanical strength and natural color appearance for posterior prosthesis. The purpose of this study was to evaluate the fitness of posterior jacket crowns fabricated by Estenia under different experimental conditions.
Two types of epoxy abutments, normal and wide shoulder, of upper first molar were used in this study. In addition, five different conditions of die-spacer layering were used. The crowns and abutments wereembedded and sectioned buccolingually to measure the internal and marginal gaps between the crown and abutment.
The marginal gaps ranged from 18.4 to 66.6 pmfor normal abutment and from 15.8 to 59.0 um for wide shoulder abutment. When the internal and marginal gaps of the normal abutments were compared with those ofwide shoulder abutments, no significant difference was found among the two typesof abutments.
Under the conditions of this study and from the results, the following conclusions were reached:
1. Estenia demonstrated clinical acceptability in fitness of posterior crowns.
2. Marginal and internal fitness was not influenced by the types of abutment.
3. Die-spacer application to internal line-angle of shoulder preparation was an effective method for decreasing marginaldiscrepancy.

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Between April 1, 1987 and August 7, 1997, a total of 128 abutment teeth associated with 34 telescope removable partial dentures in 28 patients (22 females and 6males) who had a mean age of 57.4±9.3 years was observed. The survival time (with extraction being the endpoint) for each abutment tooth was calculated using Kaplan-Meier analysis. Significance levels were determined using 8 prognostic factors for 4 statistical tests, i. e., the generalized Wilcoxon, the Cox-Mantel, the Logrank, and the Mantel-Haenszel tests. Furthermore, survival estimates and relative risks were calculated by Cox hazard regression.
The results conclusively indicated a higher survival for vital as compared to endodontically-treated teeth. The relative risk of an abutment tooth adjacent to a free-end saddle was 5.81. The risk increased by 2.79 for each group from molar to cuspid, to premolar, and to incisor. The survival estimate was 89.8% at 9-10 years after placement of the denture.

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The purpose of this study was to clarify how different components of biomaterials affect cell activities of osteoblasts. In this experiment, osteoblasts were cultured on titanium and bioactive glass, and the intracellular free calcium ([Ca²⁺] ₁) that plays an important role in the intracellular signalling system was measured. In the early stages of the culture, the osteoblaststended to increase [Ca²⁺], when cultured on bioactive glass more than on titanium. This indicated that direct contact of osteoblasts to bioactive glass was essential to generate theobserved effect on [Ca²⁺] ₁. Furthermore, elevation of [Ca²⁺] ₁ did not occur whenextracellular calcium was supplied. These results suggested that bioactive glassaffects the intracellular signalling system of the osteoblasts when in contact with bioactive glass

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Involuntary clenching is common during physical exercise; therefore, the purposeof this study was to elucidate the relationship between stomatognathic function and physical exercise as well as role and mechanism of involuntary teeth clenching during physical exercise.
In 15 healthy, fully dentate males (mean age 26.5±2.1), electromyographic activities from jaw closing (JM), sternocleidomastoid, biceps brachial (BB), and rectus femoral (RF) muscles; mandibular positions; and muscle strength during both isometric elbow flexion and knee extensionexercises were recorded and analyzed.
From the analysis of electromyographic activities and mandibular position, the subjects were divided into two groups, Clenching group (n=9) and Non-clenching group (n=6). The subjects in the Clenching group showed involuntary clenching during the exercise and their mandibular positions were located at the inter-cuspal position. The onset of electromyographic activity of JM was earlier than that of the agonist (BB, RF) in the 7 subjectsof the Clenching group. In the Clenching group, both elbow flexion and knee extension strength with involuntary clenching were lowered when voluntary mouth opening was directed during the exercise.
These results suggested that stomatognathic function and physical exercise had an interdependent relationship and involuntary clenching during physical exercise could be explained by a so-called feedforward mechanism.

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An experiment using a gloss meter and a spectrophotometer was performed to elucidate the effects of surface texture on the glossiness and color stability of porcelains. Opaque porcelain (opaque), body porcelain (body), incisal porcelain (incisal) were used, and the effects of surface texture obtained by finishing with #150, #600, #2000 waterproof abrasive paper and by puff polishing with colloidalsilica having a particle size of 0.06 μm on glossiness and color stability were determined. The following conclusions were reached.
1. The golssiness of the porcelain varied among opaque, body, and incisal, and increased as the surface texture became finer.
2. As to the color stability of porcelains with surface texture obtained by various methods, L* and b* were the highest in opaque, followed by body, and then incisal, but no significant differences were noted for a*.
3. As for the color stability of porcelain, L* decreased and b* increasedas the surface texture became finer in opaque, body, and incisal, but no significant differences were observed for a*.

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The purpose of this investigation was to elucidate the fatigue characteristics of the masticatory muscles. In five healthy, fully dentate male subjects, maximalvoluntary isometric bite force and elbow flexion and knee extension isometric strength were registered with the Dental Prescale System and a load cell. Simultaneously, the electromyographic activity from the masseter, temporal, biceps brachial and rectus femoral muscles was recorded using the Multi-Telemeter System. A protocol involving three 5-second and three 30-second isometric contractions with 10-second rest periods in between was designed to induce fatigue. The 5-secondisometric contractions were compared to a control with the initial duration of 5seconds that was recorded at the beginning of the protocol. The integrated EMG and their peak frequency of power spectrum was calculated.
The results were asfollows:
1. In the masticatory muscles the integrated EMG decreased with muscle fatigue.
2. In all the muscles, a shift in the peak frequency of the EMG power spectrum was observed according to the state of the muscle, lower values inthe fatigue phase, and higher values in the recovery stage.
3. The muscle force/integrated EMG ratio of the masseter and temporal muscles showed higher values than the biceps brachial and rectus femoral muscles.

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To clarify stress reducing effect of informed consent on experimental dental treatment, psychological test, pain threshold, hemodynamics and plasma catecholamine were used as indication of stress during heat stimulation to the gingiva, impression taking and infiltration anesthesia. The subjects were divided into two groups, one group was informed about the procedure in detail before the experiment (I.C. group), while the other group was not informed at all (n-I.C. group).
1.In the n-I.C. group, state anxiety before the experiment increased significantly compared with that in the normal resting stage.
2.In the experiment of heatstimulation, fingertip blood flow decreased significantly in both groups when the probe made contact in the first trial, and that in the n-I.C. group showed a significant decrease compared with that in the I.C. group in the second trial.
3.During taking impression, systolic blood pressure in the I.C. group decreasedsignificantly 15 minutes after taking impression compared with that in the resting condition, and showed a significant difference between the two groups.
4.During infiltration anesthesia fingertip blood flow decreased significantly in the n-I.C. group. The present data suggested that informed consent is useful for reducing stress during experimental dental treatment as indicated by the sympathetic activity.

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To clarify the differences in fracture mechanism when different modes of load were applied, two types of dental adhesives were used in various tests-for tensilestrength, compressive shear strength, flexural strength and cleavage strength-and fractographical analyses of the bonding surface after breakage were perfomed by SEM. Furthermore, the distribution of stress in the adhesive layer subjected to tensile, compressive shear and torsion loads was examined by three-dimensionalphotoelastic analysis. The results were as follows:
1. The kind of fracture occurring in two types of adhesive was cohesive fracture due to a force induced in the adhesive layer.
2. Fractographical analysis of Panavia EX by SEM revealed the occurrence of a brittle fracture characterized by a river-like pattern inall but one of the tests for tensile strength.
3. Super Bond C & B presented a ductile fracture featuring elongated dimples in tests for tensile strength, 4-point flexural strength, and compressive shear strength. In cleavage strength and 3-point flexural strength test, the ductile fracture had tear dimples.
4. The compressive shear strength test revealed that the amount of stress was the smallest in the central area of the bonding surface and tended to increase toward the upper and lower margins.
5. In the torsion test, stress gradually increased from the center outward.

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The purpose of the present study was to investigate mastication of steamed rice as the end point for evaluation of masticatory function. Tongue motion was simultaneously recorded with the mandibular movement and EMGs of anterior and posterior temporal and masseter muscles. Observations of masticatory function were the recording of tongue motion with B-mode ultrasonographic image in the median sagittal plane of the mandible, the relationship between tongue and mandible motionsand the cooperation of tongue and mandible motions and EMGs of masticatory muscles.
Traces showed two phases, the sorting out (SO) and bolus formation (BF) phases, observed during mastication. Efficient masticatory function corresponded with the change of food texture in the progress of mastication. Their motion andthe EMGs were changed according to the patterns and rhythms and automatically regulated. The function enabled evaluation by recognition of SO and BF phases during mastication of steamed rice.

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