Kazuki Morinaga

Hypoxic condition promotes differentiation and mineralization of dental pulp cells in vivo.

AIM To investigate the behaviour of dental pulp cells under hypoxic conditions in vivo using an experimental animal model. METHODOLOGY A mini-screw was inserted into the inferior dental nerve canal of rats to arrest the blood supply, which resulted in a reduced oxygen level in the dental pulps of molar teeth used for the experimental group. The decrease in blood supply was evaluated by injected India ink in transparent specimens. The hypoxia marker hypoxyprobe-1 was investigated by immunohistochemical staining. The mRNA expressions of ATP-binding cassette transporter (ABC) G2 (ABCG2) which is a marker for the capacity to excrete metabolites and for stem-like cells as well as dentine sialophosphoprotein (DSPP) and osteocalcin (OCN) which are markers for mineralization were evaluated by RT-PCR. Protein was evaluated by immunohistochemical staining using ABCG2, dentine sialoprotein (DSP) and OCN. RESULTS The evaluation of India ink indicated a decreased blood supply in the transparent specimens, and hypoxyprobe-1 immunohistochemical staining showed positive expression. ABCG2, DSPP and OCN mRNA expressions increased at 7 and 14 days. Immunohistochemically, ABCG2, DSP and OCN-positive cells were localized in the odontoblastic layer. CONCLUSIONS Hypoxic conditions promoted mineralization and differentiation of dental pulp cells of the odontoblastic layer.

Analysis of Needlestick and Similar Injuries over 10 Years from April 2004 at Tokyo Dental College Chiba Hospital

Here we investigated needlestick and similar injuries reported over a 10-year period between April 2004 and March 2014. The purpose of this study was to prevent recurrence and reduce the incidence of such injuries at Tokyo Dental College Chiba Hospital. The Division of Medical Risk Management at Chiba Hospital anonymized the data to protect personal information prior to analysis. A total of 213 injuries occurred over the 10-year period investigated, but the number of cases decreased yearly. Many cases involved dental undergraduate students and dentists, followed by trainee dentists, students at the school of dental hygiene, nurses, dental hygienists, and cleaners. Suture needles, followed by injection needles, were the top two most common injury-causing instruments, contributing to approximately 50% of the total number of such cases. Many injection needle injuries occurred during tidying up, while those caused by suture needles occurred during dental treatment. Taken together, these findings suggest the importance of strict adherence to guidelines provided in safety manuals on error-free procedures and handling of instruments. Improvement in the ability to sense potential risk is essential if such injuries are to be avoided.

CBCT-based Diagnosis of Periapical Lesion of Maxillary First Premolar Mimicking That of Second Premolar.

Apical periodontitis is usually diagnosed based on clinical findings and dental X-rays. Recently, however, dental cone beam computed tomography (CBCT), which provides 3-D images of the maxillofacial region, has enabled dentists to examine patients undergoing endodontic therapy more effectively, improving diagnostic accuracy. Here, we describe a positive treatment outcome achieved using CBCT to diagnose apical periodontitis of the maxillary premolars, which had proven difficult to diagnose based on clinical findings and dental radiography alone. The patient was a 42-year-old Japanese man who presented with the chief complaint of gingival swelling in the maxillary right premolar region. Our initial diagnosis, based on clinical findings and dental X-ray, was apical periodontitis of the maxillary right second premolar, and treatment was started. However, after the patient failed to respond to the treatment, CBCT was performed. Based on these new findings, the diagnosis was changed to one of apical periodontitis of the upper right first premolar, and the patient was treated accordingly. Previous studies have described the complex anatomical morphology of the upper premolars, noting multiple roots and variation in the morphology of the root canals. The 3-D images provided by dental CBCT allow better assessment of oral conditions than the traditional 2-D images provided by dental X-rays, which in turn enables the dentist to better select the most appropriate treatment. Here, the patient showed no symptoms and was progressing well at a 6-month follow-up visit. The present results indicate that when clinical findings and dental X-rays alone are insufficient to allow a secure diagnosis, CBCT offers an effective alternative which will enable the appropriate treatment to be selected more reliably.