Hisanori Komatsu

HPLC analysis of dental resin composites components

Five uncured commercial dental resin composites (two bis-glycidyl methacrylate based products and three non-bis-glycidyl methacrylate based products) were examined for contamination with bisphenol A, which is a known xenobiotic. After the samples were processed with acetonitrile for extraction of their components, high performance liquid chromatography analysis was performed and the eluted peaks were fractionated for comparison using UV spectra. The results suggested that all the resin composites tested were contaminated with bisphenol A or its derivatives. Theoretically, bisphenol A is not a component of dental resin composite, but it could remain as an impurity of the composite during the synthesis of Bis-GMA. The results suggest that it is necessary to investigate the ability of this impurity and its derivatives in dental resin composites to cause estrogenic effects, as well as to evaluate the release of the impurity from cured resin composites.

Antibiotic Susceptibility of Bacteria Detected from the Root Canal Exudate of Persistent Apical Periodontitis

Intracanal exudates in persistent endodontic cases were sampled for detecting bacteria using a preculture method, and the antibiotic susceptibility of the bacteria identified was examined. Twelve species were recovered from 15 cases. The species most commonly detected were alpha-Streptococcus and Enterococcus. The results of the antibiotic susceptibility tests revealed that Enterococcus was highly resistant to antibiotics tested, especially to cephalosporin products. Enterococcus is known as one of the bacteria that show multidrug resistance. In cases of prolonged endodontic treatment, a specific antibiotic prescription would play an important role for efficient treatment. Collecting data about antibiotic susceptibility could be helpful. Identification, however, take approximately 2 wk and a further study to develop the method that rapidly informs us about the antibiotic susceptibility that might be needed.

Aluminum ions in analysis of released fluoride from glass ionomers

OBJECTIVES Aluminum ions interfere with fluoride determination when an ion-selective electrode (ISE) method is used. This study examined the effect of the presence of aluminum ions on the determination of fluoride ions released from glass ionomers. METHODS Disk-shaped specimens of five different commercial glass ionomers were immersed in deionized distilled water at 37 degrees C for one day or up to seven weeks. The amounts of released aluminum were determined by atomic absorption spectrophotometry, whereas the released fluoride was quantitated using a fluoride ISE with TISAB plus two different decomplexing agents for aluminum (CDTA or sodium citrate-potassium nitrate) or TISAB only. RESULTS Released amounts of aluminum and fluoride ions were found to be significantly different among the five different glass ionomers tested. Based on preliminary examination of the effect of the amount of aluminum ions on the measured value of fluoride, it was found at the end of one day for some of the glass ionomers that the fluoride concentrations measured without decomplexing agents were significantly lower than those measured with decomplexing agents, depending on the amounts of aluminum in the solution. However, since all the glass ionomers tested leached out most the aluminum ions by seven days, the measured fluoride concentrations were not affected by a small amount of released aluminum from the glass ionomers immersed longer than seven days. CONCLUSIONS When fluoride release from the glass ionomer is determined using ISE, care must be taken with the experimental design and analytical procedures to eliminate the interference by aluminum ions.

A new technique for analyzing trace element uptake by human enamel

Fluorine (F) and strontium (Sr) are key elements in the de- and remineralization of teeth. To quantitatively analyze the distribution of F and Sr, micro-particle-induced gamma/X-ray emission (PIGE/PIXE) technique was used. The cavities were prepared and filled with the fluoride- and Sr-containing restorative materials (FSCMs) in extracted human molars. The single-section enamel specimens were prepared by slicing from the buccal to lingual surface including the FSCMs. After 5 weeks of automatic pH cycling, the demineralization was calculated by integrated mineral loss (ΔIML) from transverse-microradiography. The distributions of F and Sr were analyzed by the PIGE/PIXE technique. The micro-PIGE/PIXE technique indicated a fluorine uptake difference between the enamel surface and enamel cavity wall. ΔIML of FSCMs were significantly lower than intact enamel. The micro-PIGE/PIXE technique enables measurement of F and Sr uptake from FSCMs into enamel, which would be beneficial for research on caries development and prevention.

FLUORIDE UPTAKE INTO HUMAN TEETH FROM A FLUORIDE-RELEASING THIN LAYER AFTER A LONG PERIOD OF FILLING

Fluoride (F) distribution in human teeth was measured using an in-air micro-PIGE and micro-PIXE system. Class V cavities in the extracted teeth were prepared with Fluoro-Bond Shake One to provide a thin layer of an F-releasing material (FRM). The cavities were then filled with Beautifil Flow F10 (FRM, Group I) or LITE FIL IIP (non-FRM, Group II). Following a four-year period, specimens were cut longitudinally perpendicular to the cavity floor. The F distribution was measured at the floor of the cut surface. The position including 90% of the intact Ca level was defined as the wall surface. Based on this demarcation, indices of F distribution (surface F concentration and F penetration depth) were determined. Thickness of FRM thin layers varied (≈339 μm) and did not affect F distribution. Both values of F distribution indices in Group I [821–8763 (mean 3797) ppm, 34–668 (mean 241) μm] were significantly larger than those in Group II [0–7064 (mean 1865) ppm, 0–143 (mean 21) μm]. The F distribution in Group I was affected more by the filling material than by the FRM thin layer during the four-year exposure. Methodologies using this system may give insightful information for the development of new dental materials.

A comparison of methods for detecting bacteria in root canal exudate

This study compared the ability of bacterial detection from intracanal exudate by two different methods. One is a conventional method (i.e. the samples were transported into anaerobic chambers immediately after sampling and then moved to an outside laboratory for identification of bacteria). Another is a preculture method (i.e. the samples were inoculated into semisolid medium immediately after sampling, incubated for 24 h under anaerobic conditions, and then moved to the laboratory for bacterial identification). In 22 cases, the preculture method detected bacteria in 18 of 22 cases, whereas the conventional method detected bacteria in 6 of 22 cases. The preculture method showed significantly higher frequency of bacterial detection (p = 0.0003). Gram-positive cocci (alpha-Streptococcus, Enterococcus, etc.) were detected in many cases. These results suggested that the preculture method could be helpful in detecting root canal bacteria and enhance antibiotic treatment of endodontic disease.