Measurements of gingival thickness with dental probe have been clinically applied. An ultrasound thickness gage would be simple and less invasive compared to gingival piercing technique. However, neither relation between probe pressure and tissue displacement amount nor precise sound velocity in oral mucosa is clear. The purpose of the present study was to clarify these points.
The mucosa of alveolar ridge at porcine lower premolar region was trimmed at 10mm square and approximately 2mm thickness and then it was placed in the box cavity mold of the same size, which was made of plaster. Sound velocity of the ultrasound thickness gage was set to 1,540m/s, which has been reported as the mean sound velocity in a soft tissue. The probe, 5mm diameter, was connected to the micro material testing machine and it was touched to the surface of the mucosa perpendicularly. Then, the pressure was increased up to 2N with 0.25N stepwise for 2 minutes. Amount of the tissue displacement and thickness, which was obtained with the ultrasound thickness gage, and the thickness of the gingival mucosa were recorded. The sound velocity in the gingival mucosa was calculated based on these data.
The amount of tissue displacement was not constant from the first touch to 0.5N whereas this value was constant from 0.75N to 2N. The sound velocity at 0.75N was 1,567.8m/s.
Although the porcine gingival mucosa was used in the present study, these results indicate that precise measurement of gingival mucosa thickness is possible when the sound velocity is set to 1,567.8m/s. These results suggest that can be applied to the oral tissue regeneration technique.

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The purpose of this study was to clarify the immunological characteristics of human periodontal ligament (PDL) cells in culture after exposure to a static magnetic field. Changes in the intercellular manganase-superoxide dismutase (Mn-SOD) induction and interleukin-1β (IL-1β) production were examined. Mn-SOD induction was measured by electron spin resonance spin trapping and radical enzyme immunoassay methods. As a consequence, exposure of PDL cells to a magnetic field increased the intercellular Mn-SOD formation depending on the magnetic field intensity. When the cells were previously exposed to a magnetic field in order to elevate the intercellular Mn-SOD level, subsequent exposure to lipopolysaccharide (LPS) resulted in reduced intercellular IL-1β production. These results suggested that exposure to a static magnetic field promotes the induction of Mn-SOD in PDL cells as a mechanism of defense of the cells against stimulation with LPS.

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Apatite formation on titanium or partially stabilized zirconia disks in simulated body fluid was investigated in order to clear the influence of ultraviolet irradiation to both substrates on the enhancement of bone formation. The structural analysis of deposited crystals was performed by x-ray diffraction and Fourier-transform infrared measurements, and the deposition behavior of crystals was observed by the scanning microscope.
The deposited crystals on each substrate in simulated body fluid were carbonate apatite. The deposition amounts of apatite on each substrate were not influenced by ultraviolet irradiation, but apatite deposition was progressed at the early stage of the immersion by ultraviolet irradiation. The adhesiveness between apatite crystals and titanium or partially stabilized zirconia tended to be improved by ultraviolet irradiation. The bonding ability of apatite crystals to titanium was better than that to partially stabilized zirconia.

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In this study, we used the supragingival dental calculus of males and females between 10 and 80 years old to examine the morphology and composition changes respect to gender and age. The calculus samples of male and female aged 10 to 50 were whitish or gray. Samples from those in the 60's were blackish brown. In polished samples from females, the lamella structures were clear under fluorescence microscopy, polarization microscopy, and SEM. On the calculi of both males and females, the small spherical structures were frequently observed; on that of the older samples, the irregular structure was frequently observed by SEM. EPMA analysis revealed calculus composition to be, in decreasing amounts, Ca, P, Mg and Na. HA was detected by X-ray diffraction method in younger samples, and both OCP and whitlockite were detected in older samples. It is possible that the difference in crystal type and composition of supragingival dental calculi is due to gender and age.

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