The mandible took the tensile of muscle and the masticatory pressure. So it has been thought that the bone lamellae forming the adult mandible have the arrangement suitable for the tensile of the masticatory muscle and the masticatory pressure. On the purpose to study the relationship between collagen fibrils forming the bone lamellae of the compact bone in mandible and the stress on the mandible, I examined the arrangement of matrix fibrils of mandibles with all teeth dissected from young adult men's bodies for the anatomical laboratory.
The surface of the external basic lamellae in young adult mandible was formed by matrix fibril bundles of collagen fibrils in all areas. Matrix fibril bundles arranged suitable for the stress on the each part of mandible. At the alveolar crest, dense matrix fibril bundles ran backward. At the alveolar part, matrix fibril bundles ran downward or diagonal backward. Both matrix fibril bundles of the alveolar crest and the alveolar part transferred each other. At the mandibular body and the base of mandible, matrix fibril bundles ran in parallel to the under edge of the mandible. At the internal surface of the mandibular body, matrix fibril bundles on the surface over the mylohyoid line ran diagonal backward, and these bundles transferred to the fibril bundles running backward on the mylohyoid line. At the surface of Tuberositas masseterica, many tendons of masseter muscle entered between matrix fibril bundles.
In the external basic lamella, the surface layer was formed by the lamella of about 2.5μm thick composed of matrix fibril bundles which ran backward. The adjacent lamella was about 1μm thick, and matrix fibril bundles ran downward. Lamellae composed of matrix fibril bundles which ran in different direction piled up alternately.
In osteons forming the Haversian lamellae, the lamellae of about 4μm thick and about 1μm thick arranged alternately. Matrix fibril bundles in the lamellae of about 4μm thick ran along the long axis of the bone, and the bundles in the lamellae of about 1μm thick ran concentrically. In the each lamella of osteon, matrix fibril bundles ran parallel, and matrix fibril bundles crossed diagonally between adjacent lamellae.

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To obtain guidelines for the application of dental implant in patients with postmenopausal osteoporosis, bone reactions after placementimplants in ovariectomized osteopenicrat model were examined. Female Wistar rats, aged 12 weeks, were subjected to bilateral ovariectomy or sham surgery. At 168 days after surgery, titanium screw implants were installed in the proximal part of the tibia. The animals were killed seven, 14, 28, or 56 days after implantation. Undecalcified section were prepared and examined by routine microscopy and microradiography. Histomorphometric measurements were obtained with a computer-based image analyzer to quantify the percentage of implant-bone contact and trabecular bone around the implant. In the cortical bone area, only a slight difference in bone contact was noted between ovariectomized and sham-operated rats until 28 days after implantation. However, ovariectomy significantly affected bone contact with the implant 56 days after implantation. In the medullary cavity, ovariectomy significantly affected contact between new bone and the implant and the density of peripheral trabecular bone. These results suggest that bone substance, especially the reduced density of peripheral bone supporting the dental implant, should be considered when dental implant is placed in patients with postmenopausal osteoporosis.

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Jaw reflexes are evoked bilaterally even when stimulated unilaterally. This bilateral cooperation is one of the characteristics of jaw reflexes. The periodontal masseteric reflex also has this bilateral cooperation. The mechanism underlying bilateral cooperation in the periodontal masseteric reflex, however, still remains unclear. The present study was designed to clarify this mechanism. Experiments were performed on male Wistar albino rats weighing 250-320 g. Electrical stimulation was applied to either the left masseteric nerve or the left maxillary molar periodontal ligament. Recordings were made from the trigeminal mesencephalic nucleus and its vicinity. When the periodontal ligament was stimulated, evoked potentials were obtained from the caudal part of the trigeminal mesencephalic nucleus and the reticular formation in the recording region ipsilateral to the site of the stimulation. The latency of evoked potential was in the range of 1.05-1.73 ms, indicating the conduction velocity of Group II and III afferent fibers. In the recording region contralateral to the site of electrical stimulation, evoked potentials were recorded from the rostral and the caudal parts of the trigeminal mesencephalic nucleus and the reticular formation. These evoked potentials were abolished by both local anesthesia around the stimulating electrodes and repetitive stimulation at a high frequency (300 Hz). The latency was in the range of 1.16-1.85 ms which was longer than that of the evoked potential ipsilateral to the site of stimulation. These results suggest that synaptic transmission in the brainstem is involved in the bilateral cooperation of the periodontal masseteric reflex.

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The purpose of this study was to establish an objective method to evaluate pain, which occurs during the movement of experimental tooth using the presence of c-Fos, intranuclear protein of proto-oncogene c-fos, in central nervous cells due to irritation involving the periphery as a marker.
The distribution of c-Fos-immunoreactive cells which would appear following the proximal movement of the upper left first molar in rats was studied immunohistochemically. Furthermore, the effects of different orthodontic forces (0, 10, 30 and 90g) on the number of immunoreactive cells at Sp 5 C (layer I & II) which is the pain receptor neuron in the area of the jaw and face were studied. The effects of indomethacin on the number of immunoreactive cells that would appear were also studied.
Under the 10 g orthodontic force, immunoreactive cells were observed in Sp5C and the nuclei concerned with descending system for the modulation of pain at LRt, PGi, Arc, DR and CG. No immunoreactive cells were detected in Sp5I and Sp50. When the animals were pretreated with indomethacin, no immunoreactive cells were detected in Sp5C and the nuclei concerned with descending system for the modulation of pain described just above. When the molars were moved proximally, immunoreactive cells in Sp5C were detected in the dorsolateral and lateral areas on the tooth movement side. They were detected only in the dorsolateral area on the contralateral side. Appearance of immunoreactive cells in the above various nuclei is probably because prostaglandin was produced in the periodontal tissues due to orthodontic irritation.
The number of immunoreactive cells in Sp5C increased as orthodontic force increased. These result suggest that this method could become a tool for objective evaluation of pain that occurs during experimental tooth movement.

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A lot of powdered products (for drinking and eating) of the Japanese green tea has been on the market as a kind of health food. However, direct eating of powdered tea leaves increases the fluoride (F) intake levels, and there is a possibility that the acidlabile F in the tea leaves release ionic F by gastric and intestinal juices in the digestive organ. Therefore, it is important to examine the ratio of the releasing ionic F and estimate the increase of F absorption.
The objective of this research was to determine the level of the releasing ionic F from the powdered tea leaves treated by artificial gastric and intestinal juices. The fluoride levels in the tinned tea drinks on the market in Japan were also measured.
The results were as follows :
1) In the case of an artificial gastric juice, a different F releasing curve was observed between the drinking and the eating tea leaves. The maximum ratios of F releasing from the drinking tea leaves were about 40% of non-ionic F in them both at the room temperature and 37°C.
2) The eating tea leaves showed different F releasing curves between at room temperature and at 37°C. In room temperature, ionic F was released slowly from non-ionic F compared to the case of drinking ones. In the case of 37°C, ionic F was released faster than the cases of room temperature. These observations indicate that a considerable amount of ionic F is released from powdered tea leaves and the F-releasing patterns vary according to the different manufacturing processes.
3) In the case of an artificial intestinal juice, the different ionic fluorine releasing curves were observed among the products. The maximum ratio of F releasing from the edible tea leaves No.1 was about 12 and 25% of non-ionic F in them at room temperature and 37°C, respectively. The case of the edible tea No.2 released lower ionic F than the case of No.1 both at room temperature and 37°C.
4) The maximum ratio of F releasing from the edible teas were about 40% of non-ionic F in them at 37°C. In the room temperature, however, ionic F was released lower than the case of 37°C.
5) One case in the tinned tea drinks in Japan was found to have a high concentration of ionic fluorine.

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This study was done to establish the methodology for analyzing synchronously the acoustic signals of temporomandibular joint sound with the jaw movement. The analyzing system consisted of the computerized acoustic analyzer and Sirognathograph analyzing system.
Eight asymptmatic adults were served as the subjects. Three detecting methods for acquiring temporomandibular joint sounds using an electret condenser microphone were evaluated. Three types of detecting method were as follows.
Method 1 : An electret condenser microphone was fixed in the external auditory canal using adhesive tapes. The external auditory canal was partially open in this method.
Method 2 : An electret condenser microphone was fixed in the external auditory canal using impression material. The external auditory canal was tightly closed in this method.
Method 3 : An electret condenser microphone was fixed using impression material with an air vent tube. The external auditory canal was tightly closed but keeping air vent in this method.
Method 3 was evaluated to be the most suitable method for detecting the temporomandibular joint sounds because this method showed the greatest signal to noise ratio.
Using this method, the acoustic characteristics of the temporomandibular joint sounds were evaluated.
The results were as follows.
Coefficient variance of the duration between the beginning of jaw movement and the point of the maximal amplitude of temporomandibular joint sound was smaller than that between the beginning of the jaw movement and the beginning point of the temporomandibular sound in both closing and opening phases of jaw movement. In the one octave band analyses, the frequency bands with the maximal magnitude were different among the subjects.
However, the frequency bands with the maximal magnitude were nearly constant in both closing and opening phases of jaw movement in each subject.

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Previously, we reported a moderate correlation between the Vickers hardness number (Hv) and the P concentration, but no correlation with the Ca concentration in sound human enamel. From such a previous study and other studies of sound human dentin on Hv and mineral content, the correlation may not be estimated. In this study, we investigated the correlation by using Vickers microhardness tests and energy-dispersive X-ray microanalysis, and found a relatively high correlation between the Hv and the Ca concentration (r=0.872), and also a relatively high correlation with the P concentration (r=0.876) in the dentin including the outer and middle layers. These data may be based on the dentin matrix possessing higher amounts of organic substance than the hypercalcified enamel. In addition, the relative variances of the Ca and P concentrations between the outer and the middle dentin layer were larger than their concentrations between the inner and the outer enamel layer reported previously, and were similar to the Hv variance in the dentin compared with that in the enamel. Thus, the Hv will reflect a relative mineral content in the sound dentin.

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Recently, autologous blood transfusion has been utilized in order to avoid the risk of infection such as HIV, hepatitis and GVHD. We made a retrospective study of autologous blood transfusion in 107 cases from January of 1996 to April of 1997 in Showa University Dental Hospital. The patients consisted of 95 cases of saggital split ramus osteotomy, 5 cases of simultaneous repositioning of the maxilla and mandible, and 7 cases of malignant tumors. In sagittal split ramus osteotomy, the mean blood loss was 671 ml and the volume of autologous blood was 400-800 ml. In simultaneous repositioning of maxilla and mandible, the mean blood loss was 1461 ml and the volume of autologous blood was 1200-1600 ml. We could avoid homologous blood transfusion during surgery in almost cases of maxillofacial deformity operation. But one case of operation needed homologous blood transfusion because of severe blood loss. In malignant tumor, 4 cases needed homologous blood transfusion, but we could refuse volume of homologous blood transfusion. In consequense, autologous blood transfusion is useful technique for the case of oral and maxillofacial surgery.

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The reduction of the second maxillary molar of Chinese was analyzed from a metrical perspective. Materials used were plaster casts obtained from 100 male Chinese living in Jinan (Shandong province). Dimensions of the crown were measured with a digital caliper (0.01 mm). The dimensions of the crown included mesiodistal and buccolingual crown diameters, the distances to the direction of the diagonal line, the cusp sizes, and intercusp distances. The molar size sequences and reduction indices were calculated in order to compare first and second molars (Ml, M2). Ml was larger in the mesiodistal diameter (P<0.01). M2 had slightly larger buccolingual diameter than Ml did, but the difference between them was not significant. The diagonal sizes were significantly larger in Ml than in M2 (P<0.01). The intercusp distances were also significantly larger in Ml (P<0.01). The distal two cusps were more developed in M1 than in M2, while the mesial two cusps were nearly the same sizes in Ml and M2. M2 was more variable in size, with the exception of the intercusp distances. Linear discriminant function analysis was performed for the crown dimensions in order to investigate the difference between M1 and M2. The hypocone size and buccolingual diameter was the most effective measurements for the discrimination between Ml and M2. The paracone which was formed early in the developmental stage, hardly contributed to the discrimination.

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This study was investigated whether bone regeneration is improved in the healing of experimental osseous defects with subperiosteal membranes. Muscle/periosteal flaps were raised, and 4.5-mm osseous defects were created bilaterally in the tibiae of ten rabbits. On the test side, a silicone membrane was placed over the defect, and the flaps were sutured outside the membrane. The defect on the contralateral side served as a control (no membrane). After healing periods of 1, 2, 4 and 8 weeks the animals were killed, and 15μm hematoxylin-eosin-stained, undecalcified sections were prepared and examined histologically. The results suggest that the subperiosteal membrane keeps the osteogenic tissue structurally stable so that osteogenesis remains functionally stable during the early stages of healing.

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