Biofilm formation is an important virulence factor contributing to the chronicity and persistency of oral infections. Biofilms are formed by microbial cells embedded in exopolysac­ charides (EPS), which are a component of biofilm. We previously isolated EPS­producing Rothia mucilaginosa (strain DY­18) from a persistent apical periodontitis lesion. The aim of the present study was to identify genes relating to biofilm formation. High viscosity of spent culture medium obtained from static culture indicated that strain DY­18 produces large amounts of EPS and forms biofilms. In contrast, the low viscosity shown in shake culture was correlated with the planktonic mode of growth of this strain. Gene expression of strain DY­18 in the biofilm mode (static culture condition) was compared to that in the planktonic mode (shake culture condition) using microarray analysis. The results suggest that the genes encoding DNA polymerase Ⅲsubunit beta (gene tag :RMDY18_00020), signal transduction histidine kinase (RMDY18_00350), and molecular chaper­ one (RMDY18_16800) were significantly up­regulated in the biofilm mode. Bioinformatic analysis showed that RMDY18_16800 has domains relating to stress response, which has been shown to be a regulator of biofilm formation in other bacteria. The results suggest that these genes might contribute to EPS production and biofilm formation of strain DY­18.

Bisphenol A (BPA) is a well­known environmental endocrine disrupter and is re­ leased from widely used polycarbonate plastics and some dental sealants. In vitro studies have shown that BPA exerts estrogenic and anti­androgenic effects at the receptor level. Previously,we reported the low­dose effects of BPA on sexually dimorphic behavior in rats. In this study,we focused on the impact of BPA on emotional behavior. With the forced swimming test, there was an increase in the immobility time of BPA rats. It was found that a depression­like response was clearly enhanced by BPA exposure. In addition, we evaluated the effect of prenatal BPA on the behavioral response to fox odor by using a novel cross­form apparatus consisting of four plastic chambers. The odor­avoidance response was significant only in the BPA rats. The BPA­ exposed rats were obviously sensitive to odor. We feel that this susceptibility to predator odor stress may be associated with enhancement of the depression­like response.

A single­unit crown placed in the mouth was checked to observe dynamic changes in interproximal distance one month after cementation. The subjects were 4 males and 3 females with an average age of 57 years for whom a total of 6 anterior teeth and 7 molars received crown prostheses. The prostheses were fabricated following conventional procedures, and placed in the mouth with an 80 μm interproximal distance. The pocket depth, tooth mobility, oc­ clusal contact areas and points, and interproximal distance between the proximal teeth were measured. Periotest was used to measure clinical tooth mobility. An occlusal checker and a tooth contact analyzing device were used to measure the occlusal contact points and area. Measurements of the crown were made immediately after placement and one month later. The Wilcoxon rank­sum test was performed (p＜0.05). There was no significant difference observed in any of the measurement factors. The initial interproximal distance of the crown prostheses was 80 μm, and there was no marked change in the interproximal distance mesially or distally one month after placement. We considered that a longer period of observation is needed to elu­ cidate dynamic changes in the interproximal distance.

Comparison of gene expression profiles between static and shake culture in Rothia mucilaginosa Tadashi Furumori, Kazuyoshi Yamane and Pao­Li Wang（Dept. Bacteriology, Osaka Dental Univ.） Biofilm formation is an important virulence factor contributing to the chronicity of oral infections. Biofilms are formed by microbial cells embedded in exopolysaccharides（EPS）. We isolated EPS­producing Rothia mucilaginosa（strain DY­18）from a persistent apical periodontitis lesion. In this study, gene expression of strain DY­18 in the biofilm mode of growth was compared to that in the planktonic mode using microarray analysis. The results suggest that the genes encoding DNA polymerase III subunit beta,signal transduction histidine kinase, and molecular chaperone DnaK were significantly up­regulated in the biofilm mode. These genes might contribute to the biofilm formation of strain DY­18.

Reliability of distance measurements in dental CBCT imagesYurie Mori, Yoritaka Yotsui*, Korenori Arai**, Kimishige Shimizutani* and Shunsuke Baba**（Graduate Sch. Dentistry（Dept. Oral Implantology）, *Dept. Oral Radiology and **Dept. Oral Implantology, Osaka Dental Univ.）We evaluated the reliability of distance measurements in dental CBCT images by determining the distortion at each site in the field of view（FOV）. The phantom we used in this study was 30 stacked commercially available CDR blocks. The phantom was scanned with two CBCTs（Uni3D Multi OS and Morita 3D Accuitomo F17）and measured with digital calipers and the digital measuring application Osirix.We found that the characteristics of the distortion were different for each CBCT device. However, there was similar distortion in the edge portion of the FOV at 90 kV. The distortion in the upper and lower regions of the FOV tended to be slightly larger than in the central region. When using CBCT images, it is important to understand that the reliability of the distance measurements may depend on the site in the FOV.