It has been reported that enterococci cause significantly persistent root canal infection, especially after Ca(OH)₂ intracanal dressing, and that they often show tolerance to certain antibacterial drugs. We aimed to evaluate the susceptibility of enterococci to a combination of antibacterial drugs, i.e. ciprofloxacin, metronidazole and minocycline (3Mix), which is used for Lesion Sterilization and Tissue Repair (LSTR) therapy. The minimum inhibitory concentrations (MICs) of ciprofloxacin and minocycline on E. faecalis (6 strains) and E. faecium (1 strain) were 5-20μg/mL, respectively, and no inhibitory effect was observed with metronidazole. However, 3Mix (100μg each/mL), as a mixture, inhibited the growth of every strain completely. In addition, 3Mix also inhibited all bacterial growth in faeces (16 samples). The present result strongly indicates that 3Mix is sufficiently able to inhibit enterococcal growth, and may be useful for endodontic treatment, even in cases where enterococci are suspected to cause endodontic disorders.

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Remodelling of alveolar bone is a crucial factor determining tooth movement against orthodontic forces. Occlusion is the most influential stimulus causing physiological remodelling of alveolar bone. A removable metal appliance was devised, which can sequentially induce hypofunctional occlusion at molar teeth and reestablish normal occlusion. Using this appliance, remodelling of the alveolar bone was examined by histological morphometric analyses, with particular attention to localized regions of bone resorption by identifying the receptor activator of NF-κB ligand (RANKL), a growth factor inducing osteoclastogenesis, and osteoclasts. In the occlusal hypofunction period, the number of TRAP-positive cells increased at the margin of marrow spaces, and the marrow space enlarged. RANKL-positive osteoblasts also increased, especially around the blood vessels. In bone morphometric parameters, BV/TV, Tb. Th and Tb. N decreased, and Tb. Sp and Oc. N increased. These results are consistent with active bone remodelling consisting of active resorption at the inner alveolar bone and bone formation on the outer alveolar bone surface. In the 3 days recovery group, many TRAP-positive cells were observed at the inner alveolar bone and around the bone surface. RANKL-positive osteoblasts were observed at the margin of the marrow space in alveolar bone. However, BV/TV, Tb. Th, and Tb. Sp returned to the control level in the 7 days recovery group, with decreased TRAP-positive cells and RANKL-positive osteoblasts. These findings suggest that occlusal stimuli play important roles in the maintenance of functional alveolar structure and the regulation of alveolar bone in rats.

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Coronal cementum is generally noted in herbivorous animal teeth. Cementum is occasionally formed in the cervical area and the impacted tooth occlusal surface in humans.
Therefore, it is suggested that coronal cementum is formed under certain conditions. In this study, using cattle premolar tooth germs, the relationship between the movement of cementoblasts and the initiation site of cementogenesis was observed, and the following results were obtained:
1. Cementogenesis was initiated in the bottom area of occlusal surface grooves, and gradually progressed toward the cuspal crest area.
2. When reduced enamel epithelial cells migrating from the enamel surface toward the dental sac were at a distance of 20-30 μm from the enamel surface, cementoblasts appeared and cementogenesis was initiated.
These findings demonstrated that after the degeneration of reduced epithelium, coronal cementum was gradually formed, showing a relationship between the formation area and progression process of coronal cementum and tooth development, since the completion period for enamel formation differs between areas.

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The volume of masticatory muscle and volume of the mandibular region corresponding to the denture base (V. M. D. B.) of edentulous Japanese cadavers were measured using Spiral X-ray CT to assess the correlation between masticatory muscles and V. M. D. B.. For the results, the average volume was the highest for the masseter (15.06±7.12 cm³, n=32), followed by the medial pterygoid (6.72±2.94 cm³, n=32) and lateral pterygoid (5.74±2.76 cm³, n=32). The average volume of the mandible of the male cadavers was 52.69±10.01 cm³ (n=18), and that of female cadavers was 36.11±6.22 cm³ (n=14). The average volume of the V. M. D. B. of male cadavers was 6.58±2.79 cm³ (n=18), and that of female cadavers was 3.51±1.36 cm³ (n=14). The relationship of the masticatory muscles with the volume of the mandible and V. M. D. B. was assessed statistically, and the results showed that the volume of the mandible and V. M. D. B. correlated with the volumes of the medial and lateral pterygoids, but not with the volume of the masseter. The results suggest that various factors may be involved in the relationship between muscle and mandible volumes, and poor denture fit or misuse may play a major role. And if prosthetical factors play a major role in anatomical structure, the volumes of the medial and lateral pterygoids are unlikely to be affected by the use of dentures, but the volume of the masseter can be affected by denture use.

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