We treated 217 cases (133 males and 84 females) for foreign bodies of dental origin in the airway and gastrointestinal tract in our hospital between 1986 and 2005. We found that 122 of the patients (56.2%) were over 50 years of age. Sixteen cases involved foreign bodies in the airway and 98 were in the gastrointestinal tract. The most common foreign objects were crown restorations followed by dental instruments. All but 6 of the 98 gastrointestinal foreign bodies were eliminated by defecation. When there was spontaneous elimination, it occurred within 4 days of swallowing in 67.3% of the patients. The accident occurred during dental treatment in 184 of the cases (84.8%) and while eating or sleeping in 33 cases (15.2%).
    We recommend that the dentist should make a model of the denture or crown that has been swallowed to aid the surgeon in its removal.

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Although sucrose-dependent plaque formation by oral streptococci in the oral cavity has been thoroughly studied, little is known about how the biofilm-forming capacity of sucrose-independent oral bacteria impacts their pathogenesis. We found a viscous material-producing, facultatively Gram-positive anaerobic rod in a stock culture collection that was isolated from an oral abscess. The aim of this study was to identify this strain (designated as K20), to determine its ability to form biofilms, and to clarify its potential for pathogenesis.
     Strain K20 was identified as Actinomyces viscosus based upon 16S rRNA sequencing. Scanning electron microscopy revealed that strain K20 had dense mesh-like structures on the cell surface, which is typical of biofilm-forming bacteria. Moreover, it was attached to abiotic material and stained with Calcofluor, a polysaccharide-binding dye, suggesting that it produces exopolysaccharide and has the potential to form a biofilm. Additionally, strain K20 induced persistent abscesses in mice at a concentration of 10^7-8 cells, as did exopolysaccharide-producing Prevotella intermedia/nigrescens. In conclusion, the ability of this Actinomyces viscosus strain to form a biofilm may contribute to its pathogenic potential to induce abscesses.

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In order to identify the gene(s) involved in promoting biofilm formation in Prevotella intermedia (P. intermedia), we designed a microarray using a whole genome sequence of P. intermedia strain 17, a biofilm-forming clinical isolate from our laboratory. Gene expression patterns of strain 17 were compared with those of strain 17-2, a variant of strain 17 that does not form biofilms. The virulence of strain 17 was also compared with that of strain 17-2 for its ability to induce abscesses in mice. Compared with strain 17-2, gene expression in strain 17 of heat shock proteins and of ABC transporter proteins were up-regulated two- to four-fold. Strain 17 induced greater abscess formation in mice than did strain 17-2. These results demonstrate that certain essential genes and the capacity to form biofilms may be important in the pathogenecity of P. intermedia.

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We used three-dimensional finite element analysis to investigate how the shape of the screw type temporary anchorage device (TAD) and the direction of traction affected stress distribution in the screw during loading with orthodontic force. Four different shapes of screws, all made of titanium, were tested. The simulated alveolar bone had 1mm of cortical bone, with the remainder being cancellous bone.
    Finite element models were prepared using a three-dimensional solid modeler. Stress was measured during loading of the TAD in five directions: directed upward 45 and 22.5 degrees relative to horizontal, 90 degrees to the long axis of the screw (perpendicular), and downward 22.5 and 45 degrees relative to horizontal. The data were subjected to linear static analysis using a universal structure analysis program.
     In all types of TAD tested, the maximum principal stress was found to be directed to the cortical bone on the side opposite the load. We found that internal stress was extremely high with the slender cylinder type TAD, and lowest with the conical type. There was no significant difference between the cylinder and short cylinder types. We also found that internal stress was lowest at a traction angle of 45 degrees upwards for each type of TAD.
     Our results suggest that the internal stress of the screw type TAD is affected by screw diameter, and that internal stress is lower when traction is applied upward on the screw.

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We treated a 53-year-old male who had acquired choanal atresia that was thought to be caused by extensive mucosal ulcers associated with Behcet's disease. The chief complaints were complete bilateral nasal obstruction, rhinolalia clausa, insufficient nasal respiration and conductive deaf ness. Since age 17, when the patient was certified as having Behcet's disease, he often suffered from intractable gingivostomatitis. Neurological Behcet's disease was diagnosed at age 45. Because he was able to open his mouth just 1 to 2mm as a result of temporomandibular joint disorders, extensive mucosal ulcers developed in the oral and pharyngeal mucus membrane. This caused ingestion problems and hospitalization. A feeling of nasal obstruction appeared and increased gradually during hospitalization.
    On intraoral examination, the entire soft palate had adhered to the posterior wall of the pharynx and could not be moved making nasal respiration impossible. Examination of the nasal passage revealed that the area between the nasal opening and postnaris was normal. As well, in the area where the auditory canal opened, the tubal tonsils and the rhinopharyngeal tectorium were essentially normal. However, there was no communication between the epipharynx and oropharynx.
     Opening surgery revealed that the occlusive tissues contained no osseous component and the thickness suggested that the occlusive tissues were from the soft palate. Although nasal respiration was possible after surgery, the patient complained of rhinolalia clausa and water reflux to the nasal cavity because the soft palate could not be adequately controlled. The risk of reocclusion was high because of mucosal ulcer formation associated with Behcet's disease. Longterm observation was recommended.

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We investigated the characteristics of the transverse mandibular shift in crossbite patients during growth by taking preoperative posteroanterior cephalograms and plaster models of 51 patients between the ages of 6 and 18, who were diagnosed with posterior crossbite. We measured indexes on cephalograms and models, and applied cluster and correlation analysis.
     We were able to classify the crossbite patients during growth into five clusters. Group 1 was that patients with the mandible rotated on its body axis (22%), group 2 had asymmetrical ramuses (22%), group 3 had a deformed temporal region (38%), and group 4 had no character which included two clusters (18%).
    The ratios for the above four groups show that the predominant cause of a mandibular shift during growth was deformation in the temporal region.
     Using cluster and correlation analysis, we found that patients with mandibular shift during growth could be categorized in a similar manner to adult cases. However, the characteristics of the cases differed with age.

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