In the present work, we examined histologically the effects on enamel and dentin formation of rat upper incisors, as well as on growth and modeling of maxillary and craniofacial bones, by modulation of incisor eruption. Male SD-rats (200g b. w.) were used. The animals were divided into three experimental groups: (1) unimpeded or accelerated eruption by cutting the incisor edge twice a week throughout the experimental period; (2) pinning the incisors to completely prevent eruption: and (3) impeded eruption as control. Fluorescent labelings were given two or three times at 7-day intervals prior to sacrifice of the animals. At the end of the 4-week experimental period, resin-embedded cross-sectional ground sections were prepared from the individual incisors and from three regions of the skull corresponding to premaxillarynasal, frontal-maxillary and parietal-squamosal planes. On the basis of macroscopic and histologic examination, histomorphometric analysis, and elemental analysis, it was found that: (i) kinetic aspects of enamel and dentin formation were markedly affected by either acceleration or prevention of tooth eruption, but there were no marked changes in either the quantity or mineralization of the mature enamel; (ii) the alveolar bone surfaces facing the unimpeded or pinned incisors continued active modeling and remodeling in a comparative manner as observed in the control group; (iii) pinning the incisor gave rise to an upward dislocation of the pinned tooth in the alveolar socket and a distorted appearance of premaxillary bones, but no further effects by the disturbed incisor eruption were ascertained on the contour and structure of bones in the craniofacial regions.

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Local anesthetic potency is markedly modified by the chemical properties of the local anesthetic solution. However, there are no experimental reports distinguishing among local anesthetic solutions of varying osmotic pressures and pH values. Therefore, in this study, in order to increase local anesthetic potency and reduce the local irritation of prilocaine-HCl, we investigated the effects of varying the pH and osmotic pressure of this solution in: (1) the infiltration potency in guinea-pig gingiva, and (2) the inhibition effects of prilocaine-HCl on tibialis contraction induced by electrical stimulation of the sciatic nerve.
An osmotic pressure of 308 mOSM was optimal for maintaining a higher local anesthetic potency, compared with pressures of 280 mOSM and 380 mOSM. At pH 7.4, the depth of anesthesia was increased approximately 1.6 times, and the duration of anesthesia by 1.7 times, compared with at pH 5.0.
When the effect of sodium bicarbonate was tested in infiltration anesthesia in guinea-pig gingiva at pH 7.0 and 7.4, no significant difference was found between the solutions to which sodium bicarbonate was added and those without it. Overall, there were significant differences when the solutions of pH 5.0 and 7.4 were compared with the control solution of pH 6.6, when inhibition effects on sciatic-nerve stimulation were tested. The same tendencies were also observed for the infiltration anesthesia of prilocaine-HCl. The irritation of this anesthetic on porcine cornea was marked at a low pH and decreased with increasing pH.
These results suggest that prilocaine-HCl has a maximum potency and minimum irritation at pH 7.4 and 308 mOSM. Moreover, the addition of sodium bicarbonate is not essential for enhancing the potency of prilocaine-HCl.

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In the present study, the dithiothreitol methylation activity in submandibular gland microsomeswas characterized. The reaction did not require a divalent cation, and was sulfhydryl group-specific and Sadenosyl-L-homocysteine susceptible. The activity preferred alkyl thiol compounds such as 1, 4-butanedithiol and 2-mercaptoethanol to biological thiol compounds such as L-cysteine and glutathione. These findings suggest that methylation is performed by the action of thiol S-methyltransferase. Thiol S-methyltransferase in the submandibular gland microsomes showed high activity for dithiothreitol and formed dimethyldithiothreitol in addition to monomethyldithiothreitol. The activity was also enhanced by the addition of non-ionic detergent. These findings suggest that the membrane structure embedding thiol S-methyltransferase affects the conformation of the substrate binding-site and/or catalytic site in the enzyme protein. We speculated that the microsomal thiol S-methyltransferase found in salivary glands detoxifies the extracellular thiol compounds and/or the intracellular hydrogen sulfide to protect the secretory functions from the toxic thiol compounds. In addition, the enzymes in the submandibular gland may regulate the thiol-activatable Tkininogenase-T-kinin system via metabolism of thiol compounds.

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The ERPs in paradigms with transient, sustaining, step-down, and step-up clenching tasks was investigated using the conventional EEG recording method. The clenchings were performed at the incisor teeth along with corresponding sound signals, and the potentials were the mean of 15 time repetitions. Positive potentials were generated approximately 300 msec after the clenchings predominantly at the frontal region and these were similar to the so-called P 3 (00). The results indicated that the P 3-like potential occurs on the complete release of activities of jaw closing muscles, but not on the intermediate changes of the clenching movement. We speculated that the potential observed might reflect the activities of the neurons that reset the potential level of motor neurons relating to jaw closing at the cortex.

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The characteristics of jaw movement patterns during water drinking and pellet and bread chewing were investigated using an artificial neural network. The network consisted of three perceptrontype layers and was constructed using the back-propagation method by analyzing the discharge patterns of masticatory muscles during chewing in unanesthetized and unrestrained rabbits. Differences in jaw movement patterns during the above-mentioned three trials were detected by the conventional analysis of masseter muscle activities, but were not detected by the activities of digastric muscles. Using the artificial network method, the jaw movement patterns could also be detected by digastric muscle activities. Therefore, the present method was useful to quantitatively analyze and estimate jaw movement patterns.

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The aim of the present study was to determine the anchorage potential of Branemark titanium implants for orthodontic mesio-distal tooth movement in four adult male Beagle dogs. Two implants were surgically placed bilaterally in healed mandibular extraction sites of the second and third premolars on each side. After 18 weeks, full-casted metal crowns were fitted to the pair of implants and the fourth premolar (P4). Arch wires with a T-loop or an L-loop were placed between the implants and P4. The arch wire was calibrated to produce 200g of lateral force on P4 (loaded side) or none (unloaded side). Tetracycline was injected subcutaneously biweekly. The animals were killed at weeks 24, 28, 28, and 32, and dissected mandibles were prepared for backscattered electron images and fluorescence microscopic observation. Trimmed mandibula with implants were sagittally-sectioned, and then cross-sectioned in half. The percentages of calcified area (Cal Area) and tetracycline-labeled area (TC Area) were calculated from the region between the cross-sectioned implant surface and a line 0.5mm from the surface on the mesial or distal side. P4 on the loaded side moved 3 to 10mm mesially, while that on the unloaded side did not move. The back scattered electron image from the sagittal section on the loaded side was similar to that on the unloaded side. No significant differences in either Cal Area (ave. 80%) or TC Area (ave. 35%) were noted between the control and experimental sides. These results indicate that endosseous titanium implants connected to a metal crown can function as anchors for orthodontic tooth movement.

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The purpose of this study was to investigate the bactericidal effect against several genera of bacteria and fungi of the newly developed super reductive water (SRW) and its cytotoxicity. SRW has -310mV oxidation reduction potential when the pH is 12.0. We used 14 strains of 11 genera of bacteria and 1 strain of fungi. Each genus of bacteria (initial concentration of 10² cells/ml) was incubated with SRW for one and ten min. at room temperature. Then the survival rate was determined by colony formation. For the genus E. coli, P. aeruginosa, A. actinomycetemcomitans, F. nucleatum, and P. gingivalis, the number of cells that survived less than 1010² cells/ml, but for the genus S. aureus, S. epidermidis, S. mutans, S. salivarius, S. sanguis, E. faecalis, L. acidophilus, B. subutilis and C. albicans, cell survival was more than 10² cells/ml. The bactericidal activity against E. coli was not reduced in the presence of serum or thiourea. The cytotoxicity of SRW was tested by alamar blue assay with L 929 cell lines established from subcutaneous tissue in C 3 H mice. The cytotoxicity (LD 50) of SRW determined by alamar blue assay was 33w/w%. These results suggested that newly developed SRW has an excellent bactericidal effect against only gram-negative bacteria and lower cytotoxicity, and that the application of SRW is restricted to the disinfection of gramnegative bacteria.

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This study using Fourier transform infrared spectroscopy (FTIR) and atomic force microscopy (AFM) was undertaken to further elucidate the sequential alterations of amelogenin conformation and morphology in the process of protein aggregation. Porcine 148-residue amelogenin (called hereafter the 20 kDa amelogenin), which is the major matrix constituent in pig secretory enamel, was used as a model molecule. The results verified that the protein molecules in a monomeric state at 0°C have multiple conformational elements, whereas most of the structural elements become indiscernible in the progression of protein aggregation, except for the β-strand presumed to exist at the N-terminal region. The observations by AFM confirmed that the self-assembly process of the protein in aqueous milieu generates semispherical structures of around 20-30nm in diameter. The overall results support the theory that the programmed extracellular processing of amelogenins is directly mediated by the conserved primary structure and the resulting supramolecular aggregates.

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