Identification and characterization of clinically isolated biofilm-forming gram-positive rods from teeth associated with persistent apical periodontitis.

We isolated spore-forming gram-positive aerobic rods from three patients with persistent periapical periodontitis. These cells possessed unique phenotypic characteristics by exhibiting dense meshwork-like structures on their cell surfaces that could be found in a number of biofilm-forming bacteria. We identified these strains as Bacillus subtilis by the API system and 16S ribosomal RNA gene (rRNA) sequencing. Treatment of the meshwork-like structures with protease K and staining with calcofluor for polysaccharides indicated that these structures were polysaccharides in nature and could be essential for biofilm formation by these isolates. Our findings suggest that B. subtilis could form biofilms in periapical periodontitis lesions, and this might contribute to the resistance to treatment resulting in the development of persistent periapical periodontitis observed in these patients. The particular mechanisms for B. subtilis biofilms to develop periapical periodontitis are still unknown. Further studies are needed to clarify the role of biofilms in persistent infections.

A novel method of removing artifacts because of metallic dental restorations in 3-D CT images of jaw bone.

CT images, especially in a three-dimensional (3-D) mode, give valuable information for oral implant surgery. However, image quality is often severely compromised by artifacts originating from metallic dental restorations, and an effective solution for artifacts is being sought. This study attempts to substitute the damaged areas of the jaw bone images with dental cast model images obtained by CT. The position of the dental cast images was registered to that of the jaw bone images using a devised interface that is composed of an occlusal bite made of self-curing acrylic resin and a marker plate made of gypsum. The patient adapted this interface, and CT images of the stomatognathic system were filmed. On the other hand, this interface was placed between the upper and lower cast models and filmed by CT together with the cast models. The position of the marker plate imaged with the dental casts was registered to those adapted by the patient. The error of registration was examined to be 0.25 mm, which was satisfactory for clinical application. The damaged region in the cranial bone images as an obstacle for implant surgery was removed and substituted with the trimmed images of the dental cast. In the method developed here, the images around the metallic compounds severely damaged by artifacts were successfully reconstructed, and the stomatognathic system images became clear, and this is useful for implant surgery.