We examined the inhibitory effects of morphine administration on the nociceptive neurons in the thalamic relay nuclei of the medial pain pathway in cats anesthetized with urethane and chloralose. Single unit activities were recorded from the thalamus using glass capillary microelectrodes filled with 2% pontamine sky blue in 0.5M sodium acetate. The greater splanchnic nerve (SPL), greater occipital nerve (C2), bilateral maxillary and mandibular canine dental pulps, and midbrain reticular formation (MRF) were prepared for electrical stimulation.
     We electrically stimulated the peripheral nerve and MRF and recorded the response in the nucleus centralis lateralis and nucleus parafascicularis of the thalamic intralaminar nuclei. We also investigated the effects of intravenous administration of morphine on the responses obtained from these neurons. Morphine inhibited the late responses elicited by electrical stimulation of the peripheral nerve. As well, it inhibited the early responses elicited by electrical stimulation of the MRF. Administration of naloxone and cholecystokinin partially reversed these inhibitory effects of morphine.
     These data suggest that morphine acts on the medial pain pathway at the supraspinal level.

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     A living free bone graft is the most effective treatment for reconstruction of bone defects. However, it is limited by anatomical factors, such as the length of the pedicle and the blood supply to the donor bone. I attempted to demonstrate the possibility of creating a new donor site for secondary living bone grafts free from anatomical constraints, and to apply this technique to mandibular reconstruction.
     I investigated histological and microvascular changes in a vascular bundle transplanted into the tibia of a rabbit (Group 1) and during the healing process of a mandibular defect in the same animal packed with a secondary living free bone graft from the tibia (Group 2).
     Three weeks after transplantation in Group l the transplanted vascular bundles communicated with the pre-existing medullary vessels via the newly-formed capillaries. In Group 2 establishment of circulation in the pre-existing vessels of the donor was observed five days after transplantation, and the donor material was completely fused with the mandible by four weeks.
     The secondary living free bone graft seems a clinically effective treatment for mandibular defects.

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     We investigated the adherence of S. mutans to pit and fissure sealants containing the powdered semiconductor TiO₂, which exhibits a photocatalytic reaction. TiO₂ (0.5, 1.0 and 5.0%) was dispersed in the sealant which was then polymerized and illuminated with a fluorescent Iamb (peak wavelength at 578 nm, band width 202 nm) at 2,000 lux for 120 min in saline solution. Three strains of S. mutans (Ingbritt, NCTC 10449 and GS-5) were incubated at 37℃ for 48 hr in an aerobic growth chamber. The viability of S. mutans on the TiO₂-containing sealant varied with the bacterial strain. Scanning electron microscopy showed that TiO₂ had an anti-bacterial effect. This effect, especially the surface adherence to the sealant containing TiO₂, was different for the various strains. Ingbritt and NCTC 10449 demonstrated polysaccharide-like substances, while GS-5 showed aggregation of the bacterial cells. Brinell hardness number slightly increased, but flextural strength decreased with addition of TiO₂ in the sealant.
     It seems that the photocatalytic reaction of TiO₂ in the sealant inhibits S. mutans adherence.

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     In order to evaluate functional aspects of complete dentures, I compared 10 adults having complete dentures and good function with 10 young adults and 10 older adults, all with healthy dentition. Japanese fish cake (“kamaboko”) was used as the test food and recordings were made on an mandibular kinesiograph K6 system of mean mandibular displacement and standard deviation in the frontal and sagittal planes for each 1 mm of vertical jaw opening.
     The results were as follows:
1) Young adults with normal dentition had a greater maximum opening than the other two groups.
2) Complete denture wearers had the highest standard deviation of antero-posterior displacement.
3) Older adults with normal dentition had a greater mean lateral displacement than young adults.
4) Young adults had the lowest standard deviation of lateral displacement.
     These results suggest that aging influences maximum opening and standard deviation of lateral displacement, and that wearing dentures influences the standard deviation of antero-posterior displacement.

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     We studied the relation between the resistance to β-lactam antibiotics and β-lactamase activity, and the role of the outer membrane permeability of β-lactam antibiotic resistant Prevotella in the saliva of four elementary school children (case A, B, C and D). Strains which had a higher antibiotic minimum inhibitory concentration (MIC) also had high β-lactamase activity. The number of strains was calculated that had both a MIC of 50 μg/ml or greater and β-lactamase activity of 30 mU/mg or more. The percentage of these strains was 17-57% for penicillin G (PCG), 0-61% for ampicillin (ABPC), 50-83% for cefaclor (CCL), 0-57% for cefazolin (CEZ) and 0-50% for aztreonam. However, the percentages for cefmetazole, latamoxef and cefteram-pivoxil (CFTM-PI) were low, and the value for imipenem was zero. In about 20% of the strains tested, the MIC for PCG, ABPC, CER, CCL, CFTM-PI with EDTA was one fourth or less than the MIC without EDTA.
     These results suggest that β-lactamase plays on important role in the mechanism of β-lactam antibiotic resistance in the Prevotella tested, and that outer membrane permeability is related to this mechanism in some of the strains.

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     In order to investigate the spread of methicillin-resistant staphylococci (MRS) in Osaka Dental University Hospital, we examined 65 locations in the hospital wards and tested the antimicrobial susceptibility of the isolates. MRS were isolated from 55 hospital ward locations. About half the MRS strains were isolated from locations in contact with the medical staff or inpatients, and the others from non-contact locations. MRS were classified into various types according to antibiotic sensitivity. All strains tested were susceptible to vancomycin.
     These results suggest that nosocomial infections were occurring in the hospital wards.

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We studied the rearrangement and amplification of the myc gene family in rat ascites tumor (TS)cells at the 2,918 th passage after successive transplantation in Spraque-Dawley rats. Southern-blotting analysis showed that TS cells presented a different pattern from normal rat spleen cells in c-myc probe hybridization, indicating that the molecular weight of c-myc fragments in TS cells differed from that in normal cells. This implies that the c-myc in TS cells had been rearranged. Slot-blotting analysis showed that the myc genes in TS cells had the same intensity as those in the control, indicating an absence of amplification of the myc gene family in TS cells. These observations may contribute to our understanding of the characteristics of gene expression in TS cells.

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We investigated age-related changes in the cranial bone collagen of senescence-accelerated mice (SAMP8) using SAMR1 mice as controls. Both the extractability of soluble collagen by neutral salt solvent and the hydroxylation of lysine decreased with age. This effect was especially marked in the experimental group. The pyridinoline content increased with age in both groups and was greater in the experimental group than in age-matched controls at 7, 27 and 37 weeks. The above findings relating to collagen suggest that these changes are characteristic of the acceleration of normal maturation and aging.

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We investigated the bactericidal effects of antiseptics against methicillin-resistant staphylococci (MRS)isolated from Osaka Dental University Hospital, and examined the minimum inhibitory concentrations of 5 germicidal hand wash agents to 16 MRS strains. Ethanol with benzalkonium chloride was the most potent, while povidone-iodine also had good antibacterial effect. However, chlorhexidine gluconate had poor activity against all MRS strains tested. Because ethanol with benzalkonium chloride and povidone-iodine were the most effective of the antiseptics tested, they are considered appropriate for preventing nosocomial MRS infections in Osaka Dental University Hospital.

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In order to investigate the dynamic response of the cervical vertebrae during occlusion, we electrically stimulated both masseter muscles of anesthetized adult monkeys, and measured the resulting strains in the lamina arcus vertebrae on both sides of each vertebrae when the monkeys were made to occlude on objects of 3, 7 or 10mm thickness at either the canine or first molar on one side. The cervical vertebrae were subjected to both compression and tension as a result of the occlusal forces. The strain wave form patterns observed resulting from distortion of the cervical vertebrae indicated that these vertebrae, according to their position and morphology, ingeniously dispersed the stresses arising from occlusion.

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We electrically stimulated the peripheral nerve and midbrain reticular formation (MRF) in the cat and recorded the response of the nociceptive neurons in the intralaminar nuclei of the thalamus. We also investigated the effects of intravenous administration of morphine on the responses obtained from these neurons. Morphine inhibited the late responses elicited by electrical stimulation of the peripheral nerve. As well, it inhibited the early responses elicited by electrical stimulation of the MRF. Administration of naloxone and cholecystokinin partially reversed these inhibitory effects of morphine. These date suggest that morphine acts at the supraspinal level.

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Many of the artificial teeth developed for simulation training of cavity preparation do not reproduce the same sensations the operator experiences when preparing natural teeth with an air turbine hand-piece. We investigated the sensations produced with several artificicial teeth and evaluated a new ceramic for use as an artificial tooth material. We measured the three-dimensional cutting forces during cavity preparation and the speed required to cut the test pieces with a constant cutting force. The new ceramic tooth was found suitable for simulation training.

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