Recent studies have indicated that bacteria possessing biofilm phenotype cause persistent infections. However, the exact distribution of biofilm-forming bacteria in periodontitis lesions remains poorly understood because of difficulties with isolation procedures and because repetitive subcultures can disrupt the biofilm organization. We isolated and identified viscous material-producing bacteria with biofilm-like structures from subgingival plaque in periodontal pockets. Samples were collected from four patients at Osaka Dental University Hospital, and incubated anaerobically for 48 hrs on blood agar plate. The isolates achieved were transferred into enriched-trypticase soy broth for measurement of viscosity. Cell-surface structures were observed by scanning electron microscopy.
Forty bacterial strains having viscosity and meshwork-like structures were isolated. Identification of these isolates revealed three anaerobic rods (Eubacterium sp., Fusobacterium sp. and Prevotella sp.), one anaerobic coccus (Veillonella spp.), three facultative anaerobic rods (Actinomyces spp., Capnocytophaga sp. and Eikenella sp.), one facultative anaerobic coccus (Streptococcus spp.), and one aerobic/microaerophilic rod (Kingella sp.). The results indicate that a far larger number than expected of bacterial genera in periodontal pockets have the ability to produce viscous materials and form biofilm-like structures. This may suggest that this screening method is useful for grasping the distribution of biofilm-forming bacteria in a periodontal pocket.

View full abstract

Scaffolds for bone regeneration need a porous structure with appropriate bioabsorbability and the capacity to guide vascular invasion. We investigated the use of collagen microspheres as a scaffold, focusing on a novel bone formation material that is used in combination with human mesenchymal stem cells. When human osteoblast-like cells that had been induced for 7 days to differentiate into bone were transplanted under the periosteum of the skull of nude rats, marked new bone formation was noted after 4 weeks. When human mesenchymal stem cells were cultured on collagen microspheres under bone differentiation-inducing conditions, marked calcium deposition occurred, confirming that collagen microspheres have good ability to deposit bone matrix. Collagen microspheres may exhibit this marked osteogenic ability not only by maintaining the differentiation character of osteoblast-like cells at a high level and promoting bone matrix deposition, but also by forming a porous structure in which blood vessels can invade spaces between the microspheres. Bone formation materials that combine collagen microspheres as a scaffold with human mesenchymal stem cells have good osteogenic ability, and should be studied for clinical application.

View full abstract

We evaluated differences in CNS electrical activity immediately before and during convulsions in animals receiving intravenous administration of lidocaine, pentylenetetrazole (PTZ), and picrotoxin. Based on typical electroencephalogram (EEG) changes, this study characterized the relationship between electrical activity and regional cerebral blood flow (r-CBF) immediately before and during convulsions among animals receiving lidocaine and the two CNS stimulants.
Thirty-six Japanese white rabbits were anesthetized and mean arterial pressure (MAP) was monitored. They were randomly allocated to three groups of 12 each : Iidocaine 4.0 mg/kg/min, PTZ 5.0 mg/kg/min, or picrotoxin 0.5 mg/kg/min. Test drugs were administered intravenously until EEG seizure activity developed. In experiment 1, cortical r-CBF was monitored using laser Doppler flowmetry, and cisterna magna pressure (CMP) and EEG were monitored. Experiment 2 was performed based on typical EEG changes observed in the first experiment to determine r-CBF in five regions of the brain using colored microspheres and to observe changes in partial oxygen pressure (PtO₂) before and during convulsions.
In experiment 1, tetraphasic changes were observed in the EEG before and during convulsions in the lidocaine group, while in the PTZ and picrotoxin groups triphasic changes were observed. In the PTZ and picrotoxin groups, MAP during convulsions was significantly increased to at least 1.5 times the baseline value. In the PTZ and picrotoxin groups, CMP and cortical r-CBF were increased substantially during convulsions, while in the lidocaine group CMP alone was increased compared with the baseline. In experiment 2, r-CBF increased during wave discharges in all five regions in the PTZ group, but only in the right hemisphere in the lidocaine and picrotoxin groups. PtO₂ increased during reoccurrence of slow waves in the lidocaine group, but not in the PTZ or picrotoxin groups.
We concluded that CNS electrical activity before and during convulsions differed between the lidocaine and CNS stimulants. During drug-induced convulsions, r-CBF differed between the two drug classes, although homeostasis of PtO₂ was maintained in all groups.

View full abstract

We investigated the relationship between occlusal force, mandibular morphology and facial morphology in 60 adults with normal occlusion. We prepared the subjects' three-dimensional (3D) facial models using a non-contact 3D laser scanner, and measured facial distances and angles with a program for analyzing 3D shapes. Occlusal force was evaluated using pressure sensitive occlusal sheets. Mandibular morphology was assessed by measuring the Frankfort mandibular plane angle (FMA) on a lateral cephalogram.
We found a significant correlation between occlusal force and FMA in both males and females. Occlusal force and FMA also correlated with facial width, vertical position of the chin, and anteroposterior position of the chin. These results suggest that occlusal force and mandibular morphology influence facial morphology in normal occlusion.

View full abstract

We used electroencephalography (EEG) to determine whether the frequency of flinching in phase 2 of the formalin test using rat neuropathic pain models is appropriate as a parameter of pain. The partial sciatic nerve ligation model rats (PSL group) showed a significant increase in the frequency of flinching in phase 2, a change to rapid EEG waves, and a significant increase in the fast Fourier transform (FFT) power for β waves compared with the controls. The flinching and EEG results suggest hyperalgesia to inflammatory stimulation in the PSL group. The chronic constriction injury model rats (CCI group) showed a significant decrease in the frequency of flinching compared with the control group. These flinching results suggest hypoalgesia to inflammatory stimulation in the CCI group. However, the EEG results suggested pain in the CCI group, as in the controls. Thus, in the CCI group, there was dissociation between the interpretation of the flinching results and that of the EEG results. We concluded that the use of flinching in phase 2 of the formalin test based on the rat neuropathic pain model may be inappropriate as a parameter of pain.

View full abstract

Inflammatory cytokines, interleukin-1 β (IL-1 β), interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α), are considered to be involved in the expression and activation cascade of matrix metalloproteinases (MMPs). Increased expression of these inflammatory cytokines in gingival tissue and gingival sulcus exudates in periodontal disease patients has been confirmed. Cytokines are also related to the development and progression of inflammation, and are classified into those promoting and inhibiting alveolar bone resorption. In this study, we measured the plasma levels of IL-1 β, IL-6 and TNF-α in rats with spontaneous periodontal disease (ODUS/Odu), an animal model of periodontal disease developed by our laboratory, which has reached the 104th generation as an inbred strain. We used an enzyme-linked immunosorbent assay (ELISA) kit to measure the plasma cytokine levels at the initiation of the experiment and at 1, 3, 6, 9, and 12 months, in ODUS/Odu and in plaque-resistant rats (Res). The IL-1 β and TNF-α levels were significantly greater in ODUS/Odu than in Res at all experimental periods (p<0.001). The IL-6 level was significantly greater in ODUS/Odu than in Res at 6, 9, and 12 months (p<0.05). These findings were similar to those in patients with periodontal disease, suggesting that ODUS/Odu serve as a useful animal model.

View full abstract

Patients with jaw deformities generally have lower occlusal force and unstable occlusion. It is important to understand the relation among occlusion, maxillofacial morphology and muscle morphology before carrying out an operation. We examined how occlusal force, maxillofacial morphology and muscle morphology were related in 14 men with mandibular prognathism. Maximum occlusal force was measured using Dental Prescale, and parameters relating to mandibular morphology were measured using lateral cephalography. The mean volume and inclination of the bilateral masseter muscles were calculated using magnetic resonance imaging, and multiple correlation analysis was applied to the obtained data.
We found that occlusal force had a negative correlation with gonial angle and a positive correlation with inclination of the mandible, volume of masseter muscle, and posterior facial height (p<0.05). These results suggest that occlusal force is influenced by morphology of the mandible and the masseter muscle.

View full abstract

When treating skeletal mandibular prognathism in pediatric patients in the period of active growth, appropriate consideration must be given to the amount and direction of development. However, because the exact prediction of structural changes in a growing patient is difficult, no standardized treatment modality is now available. The subjects of this study were children with comparatively prognathic mandibles chosen among schoolchildren who had not received orthodontic treatment. The subjects were further subdivided into two groups according to the magnitude of the anteroposterior discrepancy between the maxilla and mandible. Longitudinal observation of changes in the occlusal plane were made and the two groups were compared.
Lateral cephalograms of 60 boys and 60 girls who were in Hellman's developmental stages IIC through IMC and who had never received orthodontic treatment were studied. Seventeen children of each gender who showed skeletal mandibular prognathism with an ANB angle of 5.5 degrees or more were chosen as subjects for this study. Among these subjects, one boy and 4 girls, who had negative ANB angles were chosen as subjects for Group 2. Angular and linear measurements were performed on all subjects for longitudinal analysis of the degree of change. Alveolar changes were also monitored in the group with negative ANB angles.
Over four years the mean of the angle formed between the occlusal and mandibular planes, decreased 4.9 degrees in the boys in Group 1, increased 0.9 degrees in the girls in Group 1, and increased 2.6 degrees in Group 2. These results show the diversity of development and the changes in the occlusal plane among children with skeletal mandibular prognathism, and indicate the importance of longitudinal monitoring of these changes and consideration of the maxillary relationship compensation mechanism of the occlusal plane when treating children with skeletal mandibular prognathism.

View full abstract

We classified and analyzed statistically 192 odontogenic tumors from the files of the First Department of Oral and Maxillofacial Surgery in Osaka Dental University Hospital from April 1994 to March 2006 according to the new WHO histological classification revised in 2005. None of the tumors were malignant. There was no statistical sex predilection ; the male-female ratio of the tumors was 1.04:1. The average age of the patients was 40 years, with a range from 7 to 87 years. One hundred twenty-five cases (65.1%) were found between the second and fifth decade of life, with a peak in the third decade (22%). The keratocystic odontogenic tumor (54 cases, 28%) was the most frequent type, followed by ameloblastomas (44 cases, 23%), odontomas (31 cases, 16%), osseous dysplasias (25 cases, 13%) and ossifying fibromas (10 cases, 5%). The maxilla-mandible ratio was 1:3.9. The most frequent area of odontogenic tumors was the posterior mandible (40%) followed by the anterior to posterior mandible (17%). Swelling was the most frequent chief complaint (39%), followed by pain (22%). However, 18% of the cases were symptomless. Among 171 surgically treated odontogenic tumors, enucleation with or without curettage was performed in 125 cases (65.1%). At least 5 ameloblastoma cases and 4 cases of keratocystic odontogenic tumors recurred.

View full abstract

To confirm the effectiveness of the use of an enamel matrix derivative (EMD) for periodontal tissue regeneration, we clinically compared a flap operations done with EMD application (EMD group) and without (control group). At each observation point, gingival recession, pocket depth, and the clinical attachment level were lower in the EMD group than in the controls, and significant differences were observed in all parameters at all observation times except for gingival recession 3 months after the operation. In particular, the clinical attachment level as a parameter of periodontal tissue destruction most markedly differed between the two groups at each observation point, confirming the effectiveness of EMD for periodontal tissue regeneration.

View full abstract

We attempted to clarify how the mandibular rest position is affected by psychological stress and by relaxation brought about by auditory stimulation. The jaw movements of ten subjects were recorded with a mandibular kinesiograph together with electromyograms of the bilateral anterior temporalis and masseter muscles, and electroencephalograms at Cz. White noise and relaxation sounds at 90 dB were used as auditory stimulation. When the subjects were exposed to the white noise, the interocclusal rest space significantly decreased, and jaw-closing muscle activity and beta waves significantly increased, compared to the periods of silence or exposure to relaxation sound. In addition, synergistic effects between the restraint stress and sound stimulation were expressed in jaw-closing muscle activity. The effect of white noise exposure on interocclusal rest space and jaw-closing muscle activity diminished as the experiment was repeated. Thus, it was shown that unpleasant stress, such as white noise, affected the mandibular rest position. These results indicate special care is required for patients with stress when recording the interocclusal record determined from mandibular rest position when there is no occlusal vertical support. For this purpose, relaxation music might help the patient relax during registration of the interocclusal relationship.

View full abstract

In order to study the optimum conditions for immunohistochemical stainability, we immersed rat maxillae and intestines in the following six decalcifying solutions : K-CX, 10% ethylenediamine tetra-acetic acid (EDTA), Plank-Rychlo (P-R), 10% formic-5% citrate acid (Cit), 5% hydrochloric acid (HCI), and 5% nitric acid (NA). Rat maxillae were used to measure the time required for complete decalcification. Rat intestines were immersed in various decalcifying solutions, to determine the appropriate decalcifying solution for ideal immunohistochemical stainability. The ideal decalcifying solution should maintain good immunohistochemical stainability of the intestines for the full decalcifying period. Decalcification of the maxillae required one day for K-CX and P-R, 7 days for Cit, HCI, and NA, and 10 days for EDTA. Good stainability of the intestines for both HE and immunohistochemical staining could be attained in one day for K-CX and P-R, and over 28 days for EDTA and Cit. Our previous data showed that K-CX and HCI are good for the reticular silver impregnation technique, while K-CX and 10% EDTA are good for rapid in situ hybridization. K-CX has wide application for certain stainings, such as HE, immunohistochemical staining, the reticular silver impregnation technique, and rapid in situ hybridization.

View full abstract

We investigated the change in retentive force of electroformed telescope crowns over the long term by analyzing the retentive force curve during 10,000 cycles of vertical insertion and dislodgement of ten outer crowns using a tensile and compression testing machine. The peak retentive force, the peak pushing force and the duration of retentive force were measured. No significant differences were found during 10,000 cycles in the peak retentive force, the peak pushing force or the duration of retentive force. The retentive characteristics of electroformed telescope crowns did not change after the 10,000 cycles. Our results clarified that the electroformed telescope crown could be used as an effective retainer over the long term.

View full abstract