In the present study, we had an opportunity to perform endodontic treatment under a surgical operating microscope after understanding that 4 roots and 5 separate root canals are present based on CBCT images before the treatment of maxillary left first molar. By CBCT, it is possible to evaluate up to three-dimensional conditions after root canal filling, which cannot be correctly judged by intraoral periapical radiography. These can be explanatory materials, which can be easily understood by the patients. The use of a surgical operating microscope and CBCT imaging helps the clinician to diagnose unusual anatomy of a tooth and facilitate successful endodontic treatment.

Recently, MHLW is expected to speedily and easily provide medical-treatment relative information for persons concerned in medical treatment and general requesters as a patient side. Medical device safety management is one of elements of the quality of medical services and patient safety in dental clinics. Dentists and dental staff have to be learned in various dental equipments. And furthermore, we must remember that we should obey the Pharmaceutical Affairs Law, the Medical Service Law and other laws about medical care.

Dentists use microscopes for diagnosis, and recovering transactions of teeth are often carried out using composite resins. Each processing uses a special dental machine. An important element of these machines is the physical characteristic of the light sources that they use. Typical dental lamps are halogen, xenon, and LED lamps, and each type of light source has its own characteristics. This report gives a comparison of the physical characteristics of each type of light source, and the practicality of each one.

Our hospital began paid dental treatments based on appointment in 2012. In this system, the patient pays the treatment and appointment fees at each visit. Appointment fees are not covered by health insurance. This was the first such system approved by the director of the Social Insurance Office of the Ministry of Health, Labour and Welfare in Japan. We investigated how many patients visited our hospital, where they were from, and the reasons why they needed microscopic endodontic therapy. Results showed that in 2012 and 2013, a total of 94 and 102 patients, respectively, visited our hospital after receiving a referral letter for microscopic endodontic treatment. The most common reason was root canal re-treatment. Endodontic treatment is very difficult if a microscope is not available because dentists must then use the naked eye. Many patients in Japan require accurate diagnosis and treatment using a microscope; therefore, it is desirable that every dental clinic in Japan be able to provide their patients with microscopic therapy, if necessary.

Rushton bodies, also known as hyaline bodies, are often observed in radicular cysts. The purpose of this study is to investigate the histopathological characteristics of Rushton bodies in radicular cysts and discuss the pathogenesis with a review of the literature. Histopathologically, Rushton bodies, which are localized in the cyst-lining epithelium, showed a linear, straight, curved or hairpin-like appearance, sometimes with calcification. The bodies were also associated with degenerated or apoptosis-like, cyst-lining epithelial cells, fibrin, erythrocytes, hemosiderin, and/or cholesterol crystals. In addition, lipid-like granules, CD68-positive foamy macrophages or siderophages were observed near Rushton bodies. These findings suggest that the pathogenesis of Rushton bodies is associated with both theories of hematogeneous and epithelial cell origin. The present study also supports the notion that these theories are also related to cholesterol crystals with accumulation of lipids and macrophages. Furthermore, based on the present study, oral surgeon and dental clinicians should completely remove the cyst-lining epithelium associated with Rushton bodies of microstructures in radicular cyst components.

Cholesterol crystals are a precipitated product of lipid degeneration. These crystals have also been observed in common jawbone lesions of radicular and residual cysts and radicular granulomas, but the pathogenesis and biological significance have yet to be fully clarified. The purpose of this study was to verify the morphological characteristics of cholesterol crystals in radicular cysts, residual cysts, and radicular granulomas under optical and polarization microscopy. Histopathologically, granulation tissues and fibrous tissues formed in these lesions involved various amounts of needle-shaped clefts surrounded by multinucleated giant cells. Accumulation of lipid-laden foamy macrophages was also observed around the clefts in some cases. In addition, cyst fluid aspirated from radicular cysts involved some shimmering, golden crystals. Imprint specimens of the fluid showed some rectangular crystals with notched corners. The crystals also emitted blue and yellow light under polarization microscopy. These findings suggest that the pathogenesis of cholesterol crystals is associated with precipitation of lipids, and accumulation of lipid-laden macrophages and multinucleated giant cells against a background of inflammation and foreign body reactions. Furthermore, since characteristic features of cholesterol crystals could be clarified using optic and polarization microscopy, we recommend microsurgery for useful technique for completely removing the lesions with cholesterol crystals.