The purpose of this study was to evaluate the role of the receptors connected with oral thickness perception. Twenty dentate volunteers participated in this study. The right second premolars were selected as test teeth. The thickness perception test was performed using aluminum foil.
The experimental conditions were : 1) two types of occlusal contact positions; intercuspal position and teeth contact position of a single pair, 2) two types of closing velocities ; “slow closure”and“fast closure”which were synchronized with 50 and 150/min metronome, and 3) application of local anesthesia to test teeth. The number of incorrect assessments for all trials and the proportion of correct assessments for actual trials were used for analysis. There were significant increases of incorrect assessments below 200μm in“slow closure”at teeth contact posision of a single pair. The minimum thickness of 80% of correct assessment was 100μm both with and without anesthesia in“fast closure”at teeth contact posision of a single pair. There were significantly fewer incorrect assessments in“fast closure”than in“slow closure”with anesthesia at teeth contact position of a single pair.
These findings suggest that the closing velocity may influence oral thickness perception.

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The influence of wearing complete dentures on body balance of edentulous elderly was examined in this study. Eight edentulous volunteers (5 females and 3 males) who were satisfied with their new dentures participated in the study. Static and dynamic balance were compared between subjects with and without dentures. To evaluate static balance, path length of spontaneous postural sway with eyes closed was measured for 60 seconds using a stabilometer. To evaluate dynamic balance, gait cycle, gait velocity, and stride length during 15 meters of free gait were measured using a newly-developed gait-cycle-analyzing device and gait-speedometer. The data analysis showed that path lengths of subjects when wearing complete dentures significantly decreased compared to subjects without dentures (p<0.05) .
Subjects when wearing complete dentures performed significantly faster and more stable gait compared to subjects without dentures (p<0.05) . Significant increases were concurrently observed in frequency of gait cycle and stride length (p<0.05) .
The results suggested that the presence of an established occlusal vertical dimension had an influence not only on static balance but also on dynamic balance of the subjects. It was concluded that for edentulous elderly, wearing complete dentures may enhance body balance rather than not wearing a complete denture.

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A retrospective study was made on 1, 000 outpatients visiting the Clinic for Oral Implant, University Hospital, Faculty of Dentistry, Tokyo Medical and Dental University between April 1995 and June 1998. The following findings were obtained according to sex, age group, reason for visit, classification of edentulous area, indication and contraindication for implant therapy, and pre-implant surgical treatment.
Forty percent of the outpatients were male and 60% were female. The largest number was in the 50-59-year-old group. The reason for visit of 822 patients was request for implant therapy. 123 patients with discomfortable implants done at other clinics, 12 patients undergoing maintenance of implants at other clinics and 43 other patients.
There were 505 upper jaw cases and 529 lower jaw cases. Most anterior edentulous cases were in the upper jaw group. Most of the posterior edentulous cases were unilateral cases and many of them were freeend saddle cases.
Indication patients were 447 of the 822 outpatients. The main contraindication was insufficient volume of bone. Two hundred twenty-one of the 477 indication patients did not need the pretreatment which consisted of extraction, bone graft, free gingival graft, provisional prosthetics, sinus lift, and so on.

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The purpose of this study was to clarify the influence of tooth contacts during mandibular retrusion on terminal jaw relations (TJR) and the surface EMG activity during habitual opening and closing movements. The age of five healthy subjects were 25 to 28 years.
The maxillary stabilization splints with steep retrusive contacts (S-SP) and with flat retrusive contacts (F-SP) were prepared for each subject who was instructed to wear S-SP for one week and then to wear F-SP for one week after an interval of two weeks without S-SP. The EMG activity of the masseter and temporal muscles and the TJR during habitual opening and closing movements using a device for recording jaw movements in 6 degrees of freedom were simultaneously measured by an intraoral central bearing device.
The results were as follows:
1. The TJR recorded after wearing F-SP shifted more posteriorly than that of wearing S-SP.
2. The posterior temporal muscle activity after wearing F-SP, compared with that of wearing S-SP, resulted in a significant increase.
In conclusion, the elimination of the retrusive guidance caused the predominance of posterior temporal muscle activity, and posterior displacement of the mandible.

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Quail-chick chimera experiments have shown a contribution of carnial neural crest cells to the craniofacial skeletal elements. Moreover, tissue interactions between epithelial-mesenchymal interaction during early facial process development are required for both skeletal differentiation and morphogenesis. In this study, it was observed that Msx homeobox containing genes expressed in the facial process were important molecules of cartilage morphogenesis. Rat cDNAs were isolated and encoded by Msx-1 and -2, and then the expression patterns using in situ hybridization were investigated during early rat face development. These genes were correlatively expressed in the cranial neural crest forming area (E 9.5 dpc) and the facial process (E 12.5 dpc) . Antisence inhibition of Msx genes in the E12.5 mandibular process exhibited the alteration of their gene expression and cartilage patterns. Antisence inhibition of Msx-1 induced lack of the medial portion of cartilage, and antisence inhibition of Msx-2 enhanced chondrogenesis of mandibular process under the organ culture condition. Thus it was concluded that expression of Msx genes during mandibular process development comprises important signals of chondrogenesis.

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The purpose of this study was to estimate the usefulness of plasma GST-π in diagnosis of oral SCC and to confirm the expression and localization of GST-π in human oral SCC. Plasma GST-π levels of 109 untreated oral SCC cases, 47 recurrent oral SCC cases and 36 healthy controls were measured by the sandwich enzyme-immunoassay (ETA) system. Human oral SCC and human oral SCC cell lines (HSC-3, HSC-4) were examined immunohistochemically and by the immunoelectron microscopic technique. The results were as follows:
1. The cut off level was 30.0 ng/ml (mean+2S.D.) . There was a statistically significant difference between the mean plasma GST-π levels in oral SCC (both untreated and recurrent cases) and controls (p<0.001) .
2. The positive rate of GST-π was 63.3% in untreated cases and 68.1% in recurrent cases.
3. There was no significant correlation between plasma GST-π levels and each clinical factor.
4. The positive rates of plasma GST-π were compared with those of serum SCC antigen in oral SCC. Plasma GST-π was 62.9%, while serum SCC antigen 22.2%.
5. From immunohistochemical observation, GST-π positive staining was evident in the cytoplasm and nucleus of oral SCC.
6. By immunoelectron microscopy, GST-π was confirmed to be in the mitochondria and the inter-chromatinic regions of the nucleus.

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A measuring system to record three-dimensional displacement of removable partial dentures (RPDs) in six degrees of freedom has been developed. The system employed three pairs of photodiode and LED that were set up in a triangle. This system was capable of recording the in vivo RPD displacement with a recording sensitivity of 0.1 mm. In vivo displacement of upper RPDs with unilateral distal extension saddle was investigated using this measuring system to determine the effect of artificial cusp inclination of molar teeth on denture mobility. Two groups of different artificial dentition were switched to be attached to each of three experimental RPDs. The artificial teeth with cusp inclinations were calibrated to contact with opposing natural dentition during lateral grinding of the mandible, while the other artificial teeth were prepared to disclude with the mandibular teeth (flat-cusp group) . Displacement range and average position of a reference point at the first molar of the RPDs during mastication were measured and analyzed as a function of the cusp inclination and the test food. As a result, the average displacement of the RPDs toward the edentulous ridge was smaller in the cusp group than that in the flat-cusp group, while the range of horizontal displacement in the buccal-palatal direction was greater in the former group than the latter. The denture wearers demonstrated typical grinding strokes at the end of the closing phase of the mandiblar movements when they chewed a peanut, which was attributed to a wide range of horizontal displacement of the dentures.

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The purpose of this study was to elucidate the influence on masticatory function when the mandibular unilateral distal extension removable partial denture changed the Interocclusal distance. The experiments, crushability, the sense of mastication, and the masticatory strokes until swallowing, were conducted, on four subjects, using the denture with the apparatus that enabled to change the interocclusal distance. The results were as follows : The particle size distribution showed that the ratio of small particle (diameter 2.5-4.5 mm) decreased, while that of large particle (more than 5.0mm) increased, on three of four subjects, and the value of crushability diminished. A reduction of the value of crushability when the interocclusal distance was extended more than 800μm was found. As for the other subject, no change was recognized on the particle size distribution under experimental condition, and the value of crushability showed no significant change.

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Nocturnal tooth contact such as bruxism has been considered to be one of the major factors of temporomandibular disorders (TMD) . However, little information has been reported regarding mandibular movements during bruxing, because of the limitation of the measuring method. The purpose of this study was to investigate the influence of bruxism on the stomatognathic system. A new device for measuring nocturnal mandibular movements was developed using a PIN photodiode sensor, which was integrated with the polysomnography including both masseter and anterior temporal EMG. The maximum error of the system was revealed to be less than 0.2mm. One episode was defined depending upon EMG activities above 5% MVC, and mandibular movement for each episode was classified into 3 patterns (Clenching, Grinding, and Mixed) .Nine subjects were selected for the study. Two of them reported bruxing habits and one subject had some symptoms of TMD. Mandibular movement was analyzed only for these three subjects. Frequency and duration of the episode were 3.8-10.9 and 47.8-174.9 sec per hour, respectively. The values of two bruxism patients was high, comparing to the other seven subjects. Clenching pattern during“Mixed movement”was most frequently observed for all three subjects, and EMG activities during clenching were stronger than those during grinding. These findings suggested that tooth clenching during sleep may be harmful to the stomatognathic system, rather than other mandibular movements.

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Rhythmical sucking-like activity (RSA) is known to be induced in the hypoglossal nerve (XII n) in an isolated brainstem-spinal cord preparation from newborn rats with bath application ofN-methyl-v-aspartate (NMDA) . Since natural sucking consists of well-coordinated rhythmical activities of the tongue, face, and jaw muscles, it is assumed that the trigeminal (V) and facial (VII) motoneurons would show rhythmical activities during the RSA. The purpose of this study was (1) to induce rhythmical activities in the V and VII ns in addition to XII n during bath application of NMDA, and (2) if they are induced, to locate the structures essential for generation of NMDA-induced rhythmical V, VII, and XII n activities using sectioning tech-niques. Experiments were performed on brainstem-spinal cord preparations isolated from newborn mice with or without the orofacial structure. Neural activities were recorded from the V, VII, and XII ns with suction electrodes. Movements of the tongue and jaw were recorded with a CCD camera system. It was found that (1) bath application of NMDA (5-20μM) induced RSA in the V, VII, and XII ns, (2) it also induced rhythmical sucking-like movements of the jaw and tongue, and (3) after complete transections of the brainstem between the V and VII ns as well as at the pontomedullary junction, NMDA still induced the RSA in the V, VII, and XII ns. These results demonstrate that separate rhythm generators for rhythmical NMDAinduced activities in the V, VII, and XII motoneurons are located at the respective levels in the brainstem.

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Recent progress in ultrasonography has enabled to provide high-resolution images of superfical regions. In this study, the usefulness of ultrasonography using a high frequency probe for squamous cell carcinoma of the tongue was evaluated.
Thirty normal adult subjects were examined to study ultrasonographic findings of normal tongue. The pattern of the normal tongue showed clearly three different zones, corresponding to three layers; mucosal epithelium, proper lamina and tongue muscle. The mean and standard deviation of epithelium thickness was 2.1±0.6mm.
The ultrasonographic findings for tongue carcinoma in 104 patients were evaluated. The ultrasonographic pattern of tongue carcinoma showed a hypoechoic structure as compared with surrounding tongue muscle. Depth of invasion defined as the distance between normal mucosal surface and the deepest point in 59 patients was measured. The mean and standard deviation of depth of invasion measured by ultrasonography was 8.1±4.0mm. The depth of invasion increased with T-stage. The difference of tumor depth between T1 and T2, or T1 and T3 was statistically significant (p<0.001) . A significant correlation (p<0.001) was obtained between depth of invasion measured by ultrasonography and that measured by histological sections. In the group of patients with the tumor depth exceeding 8mm (mean depth), the lymph node metastasis rate was 75.0% (15/20) . In the group of patients with the depth of less than 8mm, the incidence of metastasis was 29.8% (14/47) . The difference betweem the two groups was statistically singificant (p<0.001) . The 5-year survival rate calculated by the Kaplan-Meier method was 45.7% in patients with the depth exceeding 8mm and was 87.5% in patients with the depth of less than 8 mm. The difference was statistically significant (p<0.001) .
In conclusion, ultrasonography using a high-resolution probe was very useful for evaluation of squamous cell carcinoma of the tongue, and depth of invasion measured by ultrasonography could be a predictive factor for cervical lymph node metastasis and patient survival rate.

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The effect of gene-transduction of a co-stimulatory molecule, CD80, on generation of cytotoxic T lymphocytes (CTL) against oral squamous cell carcinoma (SCC) was investigated. Long-term or primarilyestablished short-term cultured oral SCC cell lines were transfected with the human CD80 gene using a replication-deficient recombinant adenovirus (Ad) . High levels of CD80 expression were obtained in most tumor cell lines examined. Allogeneic peripheral blood mononuclear cells (PBMC) co-cultured with CD80transduced tumor cells for 7 days elicited high cytotoxicity against melanoma (526me1) and neuroblastoma (IMR32) cells, but not against oral SCCs (HSC3 and Ca9-22) . Addition of either IL-2 or IL-12 failed to induce specific cytotoxicity against oral SCC cell lines.
The combined effect of CD80-transduced tumor cells and cytokines, IL-2 and IL-12, on generation of CTL in allogeneic and autologous system was investigated. PBMC from three SCC patients elicited MHC-restricted and TCR-dependent cytotoxicity against autologous SCC, although the level of induced cytotoxicity varied. In contrast, allogeneic PBMC obtained from healthy donors exihibited non-specific cytotoxicity alone.
These results suggested that CD80-transduction may be effective in oral SCC for generating tumor specific CTL in an autologous system.

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In this study, the effects of bFGF and OP-1 on rat bone marrow cells and bone formation by the cultured bone marrow cells in porous hydroxyapatite (HA) in subcutaneous sites of syngeneic rats were investigated.
The effects of bFGF and OP-1 on the proliferation and the differentiation of rat bone marrow cells were investigated by means of measurement of [³H] thymidine incorporation into DNA, ALP activity and bone nodule formation.
Thisin vitrostudy showed that both bFGF and OP-1 increased [³H] thymidine incorporation, especially bFGF which stimulated it 3.5-fold at a dose of 30ng/ml. OP-1 stimulated ALP activity and bone nodule formation, whereas bFGF suppressed them. These data suggested that bFGF stimulates proliferation of rat bone marrow cells and OP-1 accelerates their differentiation. These growth factors were used to fabricate cell hybrid artificial bone, which consisted of the bone marrow cells. The ectopic bone formation was induced by the bone marrow cells cultured in HA, regardless of the treatment of these growth factors. However, the histological analysis revealed that the treatment with bFGF and/or OP-1 increased the area of new bone formation and accelerated the maturation of bone compared with the controls. The results suggested that the bone marrow cells cultured in HA three-dimensionally could be used clinically as a biomaterial. Furthermore, the use of bFGF and OP-1 to produce this cell hybrid artificial bone increases its bone forming activity.

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