I studied the variations in human habitual mandibular movement without tooth contact using the Mandibular Kinesiograph (Myo-tronnics, K-6) when pressure was applied to the right or left maxillary canine from the lingual or labial direction. Twenty-one normal subjects were examined 25 times each while opening and closing between two experimental opening distances. The first was maximum opening (MAX) and the second was one half that distance (MID). The average path for the 15〜23 opening was calculated by signal processor (NEC San-ei, 7T17) and statistically analyzed with a personal computer (NEC, PC-9801RX).
     Applying heavy pressure (700〜800gf) to the canine caused significant ipsilateral and anterior displacement of the jaw from the control path during movement. This reflex varied significantly with changes in the opening distance and with tooth contact condition.
     Application of light pressure (0〜500gf) caused significant displacement of the mandible in the contralateral direction and this displacement was proportional to the magnitude of the load.
     These results indicate that the periodontal mechanoreceptors have a significant effect on coordination of cranio-mandibular muscle activities during madibular movement.

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     We investigated age-related changes in glycosaminoglycans (GAGs) in the rat temporomandibular joint (TMJ). The TMJ were removed from Sprague Dawley rats 3, 5, 10, 15, 30 and 50 weeks of age. Immunohistochemically, paraffin sections were treated with Mab 2B6, 3B3, 6B6 or 5D4 antibodies, and stained by the indirect immunoperoxidase technique. Biochemically, thd GAG composition was determined by electrophoresis on cellulose acetate strip, and the total amount of GAGs was measured as uroric acid.
     Immunohistochemical analysis revealed an intense reaction in the hypertrophic zone and mature cell zone of cartilage for chondroitin sulfate, in the condylar disc and articular zone for dermatan sulfate, and in the hypertrophic zone, mature cell zone and condylar disc for keratan sulfate. Although the relative amount of chondroitin sulfate decreased with age, dermatan sulfate and keratan sulfate increased.
     Biochemical analysis revealed that the GAGs were 14.3〜22.6% hyaluronic acid, 53.2〜66.8% chondroitin sulfate, 6.4〜14.4% dermatan sulfate, and 4.1〜18.1% keratan sulfate. Although the relative amount of hyaluronic acid and chondroitin sulfate decreased with age, dermatan sulfate and keratan sulfate increased. The total amount of the GAGs in the TMJ tended to decrease with age.

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     We investigated how human chewing path movements change from the deciduous through the mixed and into the permanent dentitions. We analyzed the changes from the deciduous dentition to the mixed dentition having four completely erupted permanent first molars. The chewing paths of children in the above two dentitions were then compared with those of adults.
     Ten children with normal deciduous dentition were tested. Six of them were later tested during the mixed dentition phase, and ten adults were used as controls. Japanese fish cake (“kamaboko”) was used as the test food and the chewing movements were recorded on a modified MKG-K6 system.
     The results were as follows:
1.  Between the deciduous and mixed dentitions, as the value of the opening time increased, the values of both the closing time and cycle time increased. Although the maximum opening displacement, maximum anteroposterior displacement, maximum opening velocity, and maximum closing velocity tended to increase slightly, the maximum lateral displacement decreased.
2.  Compared with that of normal adults, the chewing paths of children with both deciduous and mixed dentitions tended to have lower values for maximum opening displacement, maximum anteroposterior displacement, and maximum opening and closing velocities. However, the maximum lateral displacement in children with deciduous dentition was greater than that in adults, although these values were similar for children with mixed dentition and adults.
     These results indicate that the chewing path of children approaches that of adults as the children develop from deciduous to mixed dentition. In particular, the values for maximum lateral displacement were similar for adults and children in mixed dentition.

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     The mechanical behavior of crowns made of calcium phosphate crystalline ceramic (castable ceramic) was studied by the finite element method. Bond strength between the calcium phosphate crystalline ceramic and metal or composite resin core materials was established by cementation with adhesive resin cement.
     The finite element model employed in this investigation was that of a mandibular second premolar restored with a calcium phosphate crystalline ceramic crown. Two-dimensional stress analysis of the crown was carried out under vertical and horizontal loading at the buccal cusp. We investigated the effects of the loading point, crown margin width, post core material and cement. Bond strength was evaluated by measuring the compressive shear strength between the calcium phosphate crystalline ceramic and the two core materials, with and without primer treatment.
1.  Stresses induced in the crown under horizontal loading were higher than those induced under vertical loading. Tensile stresses were induced on the loading side of the inner surface of the crown.
2.  As the width of crown margin increased, stresses induced in the crown decreased, and displacement of the abutment tooth increaced.
3.  Stresses induced in the crown differed with the post core material. When the abutment was a natural tooth, stresses were likely to concentrate largely toward the buccal and lingual axial walls. When the abutment included a metal core, stresses were mainly concentrated in the crown under the loading point. However with a metal post and composite resin core abutment, stresses were mainly concentrated in the metal Post.
4.  Tensile stresses generated in the crown cemented with temporary soft cement were mainly concentrated on the inner surface of the crown under the loading point, as well as on the buccal and lingual outer surfaces of the crown.
5.  Compressive shear bond strength between the calcium phosphate crystalline ceramic and metal core material was significantly higher with primer treatment than without.
     A rigid core and optimal bonding with the calcium phosphate crystalline ceramic are necessary for adequate long-term prognosis.

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We investigated the physical properties and tissue response to canal sealer pastes prepared of an equimolar mixture of tetracalcium phosphate and dicalcium phosphate dihydrate in McIlvaine's buffer solution containing 2.5 or 5.0% chondroitin sulfate A sodium salt. The pastes had a pH of about 8.5 immediately after kneading, their solubilities were 1.9 and 1.2%, respectively, and they displayed good sealing ability. Histologic examination revealed encapsulation and few inflammatory cells around the subcutaneously implanted pastes. Commercially available apatite sealer and zinc oxide eugenol sealer were encapsulated by thick fibrous tissue with many inflammatory cells. The prepared pastes promoted remineralization of alveolar bone in the periapical lesion better than commercially available sealers.

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We evaluated β-lactamase activity in β-lactam antibiotic-resistant strains of Prevotella intermedia by microiodometric assay of β-lactamase. β-Lactamase activity of ten oral strains was 0.004〜0.0074U/ml against ampicillin, and 0.0035〜0.0046U/ml against cefazolin. Although these enzymes resolved cephalo-ridine and cefuroxime, their resolution of imipenem, latamoxef and aztreonam was different for each strain. Penicillin G and cephalexin induced production of β-lactamase in one strain tested, but not in two others. We concluded that constitutive β-lactamase produced by β-lactam antibiotic-resistant strains of P. intermedia plays an important role in this resistance mechanism, and that these enzymes are oxyiminocephalo-sporinase.

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We examined scanning electron micrographs using Prevotella intermedia cells isolated from infectious oral diseases. Cell fringes were observed after staining with uranyl acetate. Scales on the cell surface could be clearly observed on samples fixed with glutaraldehyde and OsO_4. Fluffy structures were rarely observed on the surface of the various strains. Bacterial cells adhered to the surface of aluminum foil by string like structures. However, bacterial cells that adhered to red blood cells did not have these structures. The number of scales on the cell surface in freeze substitution samples was less than that for the double fixation samples. Freeze substituted cells were covered with viscous material and secretions during incubation, but fluffy structures were not observed. We found the freeze substitution method better than other techniques for observing cell surfaces that are very close to fresh cells.

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Monoclonal antibodies against human oral squamous cell carcinoma transplanted into nude mice were produced and a λ gt11 cDNA library was constructed from its mRNA extracts. Carcinoma homogenate was used as immunogen and electrofusion was carried out with pulses of 1.0-3.5 kV/cm. Antibody production was immunohistochemically screened by treating sections of transplanted tumor with a complex mixture consisting of three components; hybridoma supernatant, biotin-labeled anti-mouse Igs, and normal mouse serum. Extracted mRNA was used to prepare an oligo dT primed cDNA library. One hundred percent hybridoma formation was observed at certain pulse amplitudes and 2.3% of the hybridoma immunoreacted with the transplanted tumor. A total of 1.2×10^7 independent clones were obtained in the library and the insert sizes were 0.6-1.6 kbp. These techniques may provide pathologists with new methods of obtaining valuable diagnostic markers.

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Surface electromyographic (EMG) patterns for the masseter, temporal and digastric muscles were investigated during gum chewing. In order to reduce inter- and intra-individual variability, time averaging of each rectified EMG over each chewing stroke was accomplished by normalizing stroke period (maximum opening to maximum opening) to 100% and then averaging the selected stroke at 0.3% intervals. Each muscle had a longer duration of EMG activity during the early stage of gum chewing. The duration shortened as chewing progressed. A wide range of peak amplitude was seen for the EMG profile from the masseter during contralateral chewing. These profiles can be developed for use in diagnosis of temporomandibular disorders.

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The present study was designed to evaluate postoperative dysfunction following glossectomy in 21 cases of tongue cancer. 1. Speech intelligibility of 100 Japanese monosylables was significantly decreased in the patients with hemiglossectomy. There were significant articulatory disorders in alveolar, palatal and velar sounds. 2. Patients with hemiglossectomy could not touch the tip of the tongue to the hard palate. There were significant disorders in tongue movement to the intact side, and considerable difficulties with speech, mastication and swallowing. Regardless of how reconstruction surgery was carried out, it was clear that glossectomy of more than one half of the tongue created significant functional problems.

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