The inner enamel of human permanent teeth has been reported to be divided into three zones : I, II, and III. In this study, we observed the inner enamel in the lingual side of deciduous incisor teeth with a scanning electron microscope. All transverse ground sections were treated with chromium sulfate. The about 10-μm-thick innermost enamel consisting of prism-like structures was deeply and almost entirely etched. This zone, which was similar to Zone I in permanent teeth, was suggested to contain a smaller amount of organic material and to show a lower calcification. The inner enamel except for the innermost zone may be divided into Zone II and III, because the prisms in the inner enamel adjacent to the innermost zone, about 30 to 40 μm in thickness, contained a larger amount of organic material than the outer-side inner enamel. However, the inner enamel can not be divided into two zones, when the outer-side inner enamel showing an arrangement of Pattern 3 prisms is contained in the middle enamel. Abnormal-shaped prisms were observed in the middle enamel as well as in the inner enamel. The lamella-like stalks of enamel tufts, insoluble with chromium sulfate, ran through the prism bodies surrounded by chromium sulfate-insoluble sheaths for a short or a longer distance towards the enamel surface and then ran together with the prism sheath regions. Many of the tuft stalks appeared discontinuously in the prisms, and some of them had fine branches within prisms. Discontinuous structures of the tuft stalks suggest that the lamella shows a fenestrated membrane.

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The purpose of this study was to examine the collagen fibril arrangement organizing the bone matrix of the upper jaw with a high-resolution scanning electron microscope to clarify the relationship between the collagen fibril arrangement of bone and the direction of strength inside bone.
Materials were maxillae and zygomatic bones of 3 year-old male crab-eating macaques. Specimens were dissected free of fibrous layers under a stereoscope and incubated in 1% trypsin solution to digest osteoblasts and amorphous organic matrix. These steps were followed by conductive-staining, dehydration, critical point drying, ion-sputter coating with platinum-palladium, and examination with a field emission type scanning electron microscope.
The surfaces of the maxillae and the zygomatic bones were composed of collagen fibril bundles. At the alveolar crest of the maxillae, collagen fibril bundles ran in parallel along the border. Bundles were arranged perpendicularly at the surface of the alveolar process of the maxillae. Bundles organizing the surface of the anterior alveolar process were arranged upward outside the piriform aperture and transferred to the surface of the frontal process of the maxillae. Bundles on the surface of the central and posterior alveolar process ran forward to the zygomatic bone at the body of the maxillae. At the infraorbital border, bundles were running in parallel along the border. Bundles surrounded the infraorbital foramen. Collagen fibril bundles crossed in front of, behind, and under the infraorbital foramen. Bundles running horizontally on the surface of the body of the maxillae divided into the surfaces of the frontal process and the temporal process of zygomatic bone.

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A light microscopy investigation was performed on the orientation, configuration, and aging changes of the elastic fibers that manifested themselves and were distributed in the lamina propria of the mucous membrane and inferior muscle layer of the dorsal tongue of the rat. The materials were the tongues of Sprague-Dawley rats that had been raised from 0 days to 500 days after birth. The totally extracted tongues were cut along the frontal plane into three sections ; anterior, intermediate, and posterior sections. After preparing celloidin specimens, Weigert's resorcin fuchsion straining was performed to clarify the elastic fibers. Some of the materials (50 days after birth and 600 days after birth) were made into specimens for TEM and SEM usage.
As a result of this, the manifestation of elastic fibers within the lamina propria of the mucous membrane of the dorsal tongue 0 days after birth was observed and some of the fibers were found to have invaded the muscle layer. The amount of elastic fiber manifestation was average in both the anterior and intermediate sections in 0 days and 5 days after birth, and their configurations for fine elastic fibers were in the form of straight lines, curved lines, branched lines, or meandering lines, while some formed a net like structure. In the lamina propria of the posterior section of the dorsal tongue a large amount of fine elastic fibers manifested themselves, and their configuration was similar to that of the anterior section and intermediate section, but at 5 days after birth, some elastic fibers were in the form of waste threads. Furthermore some elastic fibers that had invaded the muscle layer to somewhat deeper depths were observed.
A large amount of elastic fibers were found in the lamina propria of the mucous membrane of the dorsal tongue by 10 days to 500 days after birth and both in the anterior and intermediate sections of the dorsal tongue a rather large amount of manifestation was observed, while in the posterior section of the dorsal tongue the elastic fibers showed a further increase resulting in a very large amount of manifestation. As the age increased, the thickness of the elastic fibers showed a tendency to increase. The number of elastic fibers invading the muscle layer also increased, and with the lapse of time they were found to invade further deeper into the muscle layer.
Observations of OTE stained vallate papillae 50 days after birth with TEM suggested that the elastic fibers were composed of constituents with a high electron density (elastic fiber) and microfibrils.
Compared with the elastic fibers that manifest themselves in the anterior and intermediate sections of the dorsal tongue, the posterior section always shows a large manifestation of elastic fibers. Especially in the vallate papillae a large amount of elastic fibers is observed. This may be attributed to the following cause ; when swallowing lumps of food, this section has to move most intensely, which causes a large pressure (swallowing pressure) to be applied to the lower layer of the epithelium. It becomes necessary to relieve pressure, and thus causes physiologically a large amount of elastic fibers to be created.

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To examine the three-dimensional arrangement of bone matrix fibrils at their attachment with Sharpey's fibers or muscle tendons, we observed the surface of the body of the mandible, the angle of the mandible, and the coronoid process with a scanning electron microscope. Materials were three male crab-eating macaques (three years old). The fibrous layers of the ectoperiosteum were dissected free. Specimens were incubated in 1% trypsin solution for 72 hours at 37°C to digest both osteoblasts and amorphous organic matrix. At the external and internal surfaces of the body of the mandible, collagen fibril bundles ran horizontally. Spindle-shaped openings were observed between collagen fibril bundles, and we believe that the Sharpey's fibers entered the spindle-shaped openings. At the uneven area of the body of the mandible, collagen fibril bundles crossed each other. Many openings into which tendons of the masseter muscle entered were observed at the external surface of the angle of the mandible. The collagen fibril bundles organizing the surface matrix surrounded the places where the tendons entered. At the external surface of the coronoid process, collagen fibril bundles ran up and down in parallel. Tendons of the temporal muscle entered between collagen fibril bundles.

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Conventional steel burs for the root canal preparations were not available for resin composites core materials that became popular in clinic nowadays. In this study, diamond points for the contra-angle micromoter handpiece with low speed were experimentally developed using an electro forming method on the stainless steel rods. Grinding efficiency of the diamond points on resin composites core materials was evaluated at rotary speed, ranges between 600 rpm and 20,000 rpm. The developed points were available for the post preparation on resin composites and had enough grinding efficiency and durability at rotary speed above 10,000 rpm. However, SEM observation appeared the ground surface of the composites suffered degradation because of heating, vibration, poor exhaust of ground chips and dropped particles. These findings suggested that we need further development of the points with internal holes and external grooves for coolant and exhaust of chips.

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For use with titanium, which is difficult to grind with conventional dental tools, four kinds of diamond sintered wheels (A through D) with the different binders and particle sizes were experimentally prepared. The grinding efficiency of diamond wheels and a commercial green carborundum (GC) wheel was evaluated with titanium plates. The amount of grinding with diamond wheels was equivalent or inferior to that with GC. However, the amount of wear with diamond wheels was far less than that with GC. Therefore, diamond wheels showed a high grinding ratio, the C wheel, which is bonded with copper containing coarse diamond abrasives, was best for grinding titanium. The thermal behavior of titanium specimens during grinding and the reactivity between the wheels and specimens were also evaluated. The temperature of titanium during grinding was influenced by both the wheels and the grinding load. The values with the C wheel under each grinding load were smaller than those of the GC wheel. Furthermore, an energy dispersive X-ray (EDX) analysis of the surface of titanium after grinding with the experimental wheels showed little contamination by elements of the wheels. These findings suggest that sintered diamond wheels are effective mechanical tools to grind titanium.

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The relationship between occlusal elevation with a mouthguard and whole body muscle strength during exercise was evaluated with an Ariel machine, which allows measurement of muscle strength during multiarticular exercise. Also, physiologic changes in masticatory muscles during clenching with and without mouthguard were evaluated by measuring the skin surface temperature and blood flow with a thermograph and a laser Doopler flowmeter.
Muscle strengh at maximum output tended to be increased in subjects who clenched the mouthguard during exertion and but was unchanged or slightly decreased in those who did not clench the mouthguard during exertion.
Significant differences were observed during bench press (up) (increased in 1 and de-creased in 1), bench press (down) (increased in 2 and decreased in 1), and squat (increased in 1 and decreased in 1).
Without the mouthguard, the width of changes in blood flow increased in 2 and showed no change or decreased in the other 2 immediately after clenching. It decreased in all subjects 0 to 30 seconds after clenching but increased and approached the resting position after 60 seconds. With the mouthguard, the width of changes in blood flow increased in all patients immediately after clenching (0 seconds) but decreased after 30 seconds. Skin temperature without the mouthguard changed in one of two patterns. In one pattern, the temperature decreased 0 to 30 seconds after maximum clenching but increased thereafter. In the other pattern, the temperature increased immediately after maximum clenching, decreased after 30 to 60 seconds, and increased again after 60 to 120 seconds.
With the mouthguard, the temperature tended to decrease in 1 subject but increased in the other 3 as compared with the resting level although the degree of increase varied among the three subjects.

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Electrolyzed water is obtained at the cathode by electrolyzing tap water to which a small amount of NaCl has been added. To apply this electrolyzed water to the dental region, we studied its basic characteristics.
To study the bactericidal effect, we used 31 species of bacteria (410 strains), and 5 species of eumycetes (63 strains). From the result of bactericidal tests, all the Gram-positive bacteria, except B. subtilis were killed in 10 seconds.
Of the eumycetes, A. benhamiae was killed in 30 seconds, but other eumycetes were killed in 10 seconds. Environmental isolates were almost completely killed in 60 seconds. Acid electrolyzed water had stronger bectericidal effect than did NaOCl, which was used as a positive control. For storage the best results were obtained by shutting the container tightly and storing in complete darkness at -20°C.
The survival ratio with human epithelial keratinocytes was less with electrolyzed water than with physiological saline or distilled water.
When dental alloys were exposed to acid electrolyzed water, gold alloy showed a rapid decrease of gloss, but Au-Ag-Pd alloy and Co-Cr alloy showed a slight decrease of gloss and Ti alloy showed no decrease of gloss.
For hand washing and sterilizing, we found that the most effective method was to wash hands with acid electrolyzed water after washing with soap with gloves.

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The oral movement trajectories have been studied in a patient with cleft palate to evaluate masticatory capability by monitoring the patient's orofacial movements during mastication of a color-developing chewing gum. In designing a prosthesis for this patient, who presented an overclosure and a retruded maxillary dental arch, oral-movement trajectories at different stages of treatment were tested and compared, i.e., at stage A, before prosthetic treatment ; at stage B, while using a temporary overdenture ; at stage C, using the final prosthesis ; and at stage D, one month after insertion of the final prosthesis.
To monitor orofacial movements, a light-emitting marker that recorded as a shining point with a clear outline when illuminated by a cold spotlight provided trajectory data for the following reference points : the modiolus (Mo), the menton (Me), and the incisal point (IP), which was represented by a point on a wire extending from the lower incisors teeth to the outside of the mouth. Use of an image processor enabled the recording and auto-tracking of multiple reference points.
During 250 strokes of chewing, the subject's face markers were recorded on videotape by two high-speed TV cameras from two different perspectives, i.e., frontally and laterally. After every 50 strokes, the color of the chewing gum was assessed by a Chroma Meter (CR-300, Minolta Co.) with respect to the degree of redness or a* value, one of the coordinates of the L*a*b* color evaluating system. Thus, the same chewing gum was continuously chewed for a total of 250 strokes, with the a* value measured at the end of every 50 strokes.
The videotape recordings of the start of the first period (1F) and the end of each period (1L-4L) were then reproduced on high-speed video and fed into an image processor (Image Data ID-8000, nac) that automatically tracked the movements of each marker, after which the resulting data of the three-dimensional (3-D) coordinates were fed into a computer.
Then, the trajectory of each monitored point for each 16-second period was computed with a 3-D analyzer (Movias 3D) with reference to the following parameters : the total length from start to finish of the trajectory (TL); the distance between the start and finish of the trajectory (SL); the ratio of the TL to the SL (T/S); the volume of the rectangular solid encompassing the entire trajectory (the cubical range); and the mean of the 3-D angles that were created by differences in the direction of the preceding and following trajectories for each measured time point (TH).
Our results have revealed that the time needed for one chewing cycle during the stages decreased gradually from 1F to 4L and at stage D the time needed were significantly shorter (p<0.01) than at stage A. Similarly, the TLs and the THs of the IP, Me, and Mo during the closing phases were significantly smaller (p<0.01) at stage D than at stage A. These findings indicate that as occlusion improves, the range of mouth movements becomes narrower and the trajectories become smoother and more converged.

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The purpose of this study was to evaluate the clinical effectiveness and usefulness of the recently developed Alumina Jet KCP 2001J (Kuroda Seikou Co., Tokyo, Japan) for cavity preparation. For this study, 30 teeth of 30 patients, including teeth with caries, cervical WSD, and teeth with cervical hypersensitive dentine, were used. Al₂O₃ powder 27 and 50μm in diameter was used for cavity preparation. The following results were obtained : 1. Class V and I cavities were prepared in 28 of 30 teeth (93.3%) withoutpain. Slight and moderate pain were each produced in one tooth. There was a statistically significant difference between the groups with no pain and slight or moderate pain (p<0.01).2. No patients experienced unpleasant feelings or tenderness during cavity preparation withe Alumina Jet KCP 2001J. 3. There were no side effects, such allergic reactions. 4. Follow-up found no clinical symptoms at 7days or 30 days after the procedure. Prepared cavities were fillled with composite resin. These results suggest that cavity preparation by the Alumina Jet KCP 2001J is clinically useful and safe.

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