We attempted to clearify the primary factors in timing of the intial electromyographic discharges of the jaw depressor muscles (EMG onset). We measured the changes of EMG onset of the inferior head of lateral pterygoid (Lpt) and anterior belly of the digastric muscles (Dig) by varying duration of the open-close movement or occlusal force during the open-close-clench cycle (OCC). We also considered the effect of tooth contacts and mechanoreceptors in the periodontal tissues.
      In both normal dentate and edentulous subjects, EMG onset tended to precede the beginning of opening movement during OCC. In normal subjects, duration of the open-close phase and duration of the occluding phase had no significant correlation with the time lag between EMG onset and the beginning of mandibular movement during jaw opening (onset time), however mean masseter muscle (Mm) activity, which is related to occlusal force, had significant correlation with onset time. In edentulous subjects, mean Mm activity had no significant correlation with onset time in any of the subjects. During open-close movement without tooth contact, EMG onset tended to delay the beginning of opening movement.
      It therefore appears that occlusal force is a major in EMG onset in jaw depressor muscles. However, mechanoreceptors in the periodontal tissues had little effect on changes in EMG onset.

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Prevotella intermedia strain E18 possesses non-fimbriated hemagglutinin that is closely related to pathogenicity. We found several strains subcultured from Prevotella intermedia strain E18 (1801, 1802 and 1803) that lost the ability to produce black pigment on blood agar plates. We examined the pheno- and geno-typic characteristics of these strains.
      The non-black pigmented strains had phenotypic characteristics similar to Prevotella intermedia strain E18. These included production of alkaline and acid phosphatase, phosphoamidase and α-glucosidase in an API ZYM system, and production of hydrolytic enzymes such as β-lactamase, DNase, lecithinase and lipase. As well, they had hemagglutinating activity. Fimbriae-like structures on the cell surfaces were not observed in either non-black pigmented strains or Prevotella intermedia strain E18 cells. Cell suspensions of each of these strains reacted with antisera against vesicles (Fractions B and C) and a purified hemagglutinin (derived from Fraction A) from Prevotella intermedia strain E18. SDS-PAGE and pulse-fielded gel electrophoresis revealed that the protein and chromosomal DNA patterns of all strains tested were quite similar. Bacteriophage similar in morphology and size were induced in these strains after irradiation with ultraviolet light. No plasmid bands were detected in any of the strains tested.
      These results indicate that strains 1801, 1802 and 1803 are mutants of Prevotella intermedia strain E18.

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Previous studies have shown that partially purified hemagglutinin isolated from non-fimbriated Prevotella intermedia strain E18 can be further purified by arginine agarose and gel filtration. We characterized a purified hemagglutinin and examined the range of genera and species that possesses a common antigen for anti-purified hemagglutinin antiserum.
      Hemagglutination activity was sensitive to heat and enzymes such as trypsin, chymotrypsin, protease, hyaluronidase, lysozyme, β-galactosidase and β-glucosidase. Hemagglutination activity of the hemagglutinin was eliminated by antihemagglutinin antiserum. Residual activity of the hemagglutinin was 50% by addition of galactose and melibiose. Addition of L-arginine and lactose caused hemagglutination inhibition. These results suggest that a common component in the above sugars and amino acid may be associated with receptors for hemagglutinin. Lowering the pH of the hemagglutinin decreased the activity, which reached a residual level of 6.3% at pH2.0.
      Many Prevotella intermedia and a few Prevotella nigrescens strains tested possessed antigen specific to anti-Prevotella intermedia strain E18 hemagglutinin antiserum. In particular, Prevotella intermedia strain 17 cells reacted with the antiserum, indicating that this strain has fimbrial and non-fimbrial hemagglutinins. However, no common antigen was recognized for other species of black-pigmented bacteria. Protein A-gold labeling of Prevotella intermedia strain E18 cells with anti-hemagglutinin IgG revealed that the IgG bound specifically to hemagglutinin present on the Prevotella intermedia strain E18 cell surface, but not on cells that did not react with anti-Prevotella intermedia strain E18 hemagglutinin antiserum.
      These results indicate that the non-fimbriated hemagglutinin in this study is glycoprotein in nature and species-specific.

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We measured the cell envelope structures of Prevotella intermedia ATCC 25611, ATCC 33563 and Porphyromonas gingivalis 381 after shade processing and threshold setting using the LUZEX-FS image processor. The periodical structure of the bacterial cell surface was studied to detect the high frequency element of the power spectrum after Fourier transform. The width of each aspect of the 25611 strain cell envelope by GA-OsO₄ fixation was 13.0nm for the cell membrane, 4.6nm for the inner leaflet, 2.7nm between the inner and the outer leaflets, 3.6nm for the outer leaflet, 2.1nm for the periplasmic space near the cell membrane, 6.2nm for the peptidoglycan layer (PG), 17.2nm for the periplasmic space near the outer membrane, 9.2nm for the outer membrane, 2.7nm for the inner leaflet, 3.1nm between the inner and the outer leaflets, and 3.1nm for the outer leaflet. PG could not be observed in the sample fixed by freeze substitution (FS). The width of periplasmic space (between the outer leaflet of the cell membrane and the inner leaflet of the outer membrane) of bacteria by GA-OsO₄ or Kellenberger-Ryter fixation was larger than that of bacteria by FS. The high-frequency element of the power spectrum after fast Fourier transform was detected in the periplasmic space in transmission electron micrographs, and in particles on the cell surface in scanning electron micrographs. Some twists in the image of the periplasmic space could be detected after inverse fast Fourier transform.
      We found that the image processing system could be used to measure aspects and periodical structure of the bacterial cell envelope.

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We studied the ultrastructure of bacteria in host cells to understand the appearance of oral infectious diseases using the LUZEX-FS image processor. Electron microscopic samples were taken of pus from patients with abscesses. Gram positive and negative bacteria were detected in almost all the abscesses used after anaerobic culture and electron microscopic observation. The area-ratio of bacteria to phagosomes was 33.0% for Gram negative, and 43.8% for Gram positive bacteria. A bacterial capsule was often observed on the surface of both Gram negative and Gram positive bacteria. The area-ratio of the capsule to bacteria was 33.0% for Gram negative and 26.7% for Gram positive bacteria. Vesicles originating from the outer membrane of Gram negative bacteria were about 26.0±3.2nm in diameter and had an area of 541.0±133.4nm². The total lysosome area was about 20.5% of the host cell cross sectional area, while this area was 21.1% for the phagosome.
      We confirmed that the degree of resistant and pathogenic factors could be expressed quantitatively using the digital image processor.

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Human papilloma virus (HPV) infection has been implicated in the etiology of oral cancer. The frequency of detection of HPV in oral cancer tissues ranges from 0 to 100%. Some of this variability can be attributed to the various methods of detection. Therefore, we developed a highly sensitive HPV detection system using the in situ polymerase chain reaction (PCR). It makes use of the extreme sensitivity of PCR and the localizing ability of in situ hybridization. The HPV primers (MY 09 and MY 11) used in this study target the highly conserved L1 gene coding for the major component of viral capsid protein, and amplify 450 base-pair product from more than 50 HPV types. A number of control experiments were performed to prevent false positive reactions and to find the optimal conditions. In situ PCR appears to be an effective technique for examining HPV in oral lesions.

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We assessed the ability of chloroform, eucalyptol and D-Limonene to dissolve 4 different #140 gutta-percha cones and 5 different thermoplasticized gutta-percha filling materials (Obtura II, Thermafil, Ultrafil Regular Set, Ultrafil Firm Set and Endo Set). The 8 gutta-percha samples were immersed in the solvents for 5, 10, 15 and 30 minutes, and dried at 37℃. The decrease in weight was then calculated. Chloroform was the most effective of the solvents used in this study. D-Limonene and eucalyptol were not as effective, and there was no significant difference between the two in solubility. Thermoplasticized gutta-percha dissolved more rapidly than standardized gutta-percha cones. Ultrafil in particular dissolved more rapidly than Obtura II or Thermafil.

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We developed a subminiature three-dimensional load transducer, and constructed a system for simultaneously recording masticatory forces, mandibular movements and electromyograms. The data was recorded as an analog signal, which was converted for digital processing. The data were calibrated, corrected, and saved in a computer. The data could then be displayed in one of two modes. The sweep mode was used to show recorded data as a function of time. The vector mode was used to plot one parameter against another, for example forces in two different directions. This system was very valuable for analyzing occlusal forces.

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