Shika Kiso Igakkai zasshi = Japanese journal of oral biology最新文献

The present study was carried out to investigate the morphological changes in the alveolar bone in rats fed a low calcium diet, in order to establish an experimental model of alveolar bone resorption. Male Wistar rats (70-85 g in body weight) were either fed a low calcium diet (0.05% Ca, 0.35% P) or a control diet (0.5% Ca, 0.35% P) by using a pair feeding technique. The rats were sacrificed at intervals of 3, 6, 9 and 20 days. No difference was found in the growth rate between the control and the low calcium group. In the low calcium group, the bone area significantly reduced at day 3 and progressively decreased to 46% of that of the controls by the end of the experiment. The bone resorption was obvious in the cancellous bone during the early period of the experiment and then the cortical bone was seen to resorb. However, the contour of bone and the rate of bone apposition did not change. At day 20, bone still remained in three regions: the alveolar bone proper that surrounds the tooth sockets, a few cancellous bones and a thin wall-like cortical bone. These results suggest that the process of alveolar bone resorption is related to the mechanical forces induced by the occlusal function of the tooth and, further, that this experimental model might be useful for investigating the mechanism of alveolar bone resorption and disorders of the alveolar bone.

Morphological changes of the T cell immune system compartments (thymus and spleen) and the steroid hormone producing glands (adrenal and testis) in the submandibular-ectomized (SMx) male mice of CBA/H strain were analyzed. Thymus, spleen, testis and adrenal gland were weighed and processed for the morphological examination by light- and electron-microscopy. The serum level of testosterone was evaluated by radioimmunoassay. No weight and morphological changes were observed in the testis and adrenal gland, and the testosterone level in sera was not changed after SMx. These results indicate that any relationship between the submandibular salivary glands and the immune system was not mediated through them. The epithelial hormone-producing cells located in thymus medulla showed the most prominent changes after SMx evaluated by the neuron specific enolase immunostainings and by the ultrastructural analysis. After SMx, the number of very active epithelial hormone-producing cells in both cortex and medulla of the thymus was markedly increased.

Phenolic compounds are widely used in dental clinics especially for the treatment of inflammatory responses of the dental pulp. However, the role of these agents in the repair of pulpal connective tissue is unclear. In the present study, an effect has been identified in several phenolic compounds that can stimulate active proliferation of pulpal fibroblasts. Human pulpal fibroblasts (HPF) were obtained from subcultures of between 5 and 15 passages. HPF in tissue culture plates were incubated in serum-free medium with several phenolic compounds at concentrations of 10(-8) M to 10(-4) M for 4 days. After incubation, cells were fixed, stained in culture plates and the number of nuclei counted. Phenol (10(-8) M to 10(-4) M) stimulated proliferation in a quiescent population of HPF, and the number of cells increased 27-41% compared with unstimulated cells. When HPF were incubated with p-chlorophenol, guaiacol, thymol or eugenol, there was a significant activation of cell proliferation (5 to 22%). Moreover, cell viability of the HPF was not influenced at all, except in the cases of p-chlorophenol and eugenol at concentrations of 10(-4) M. These observations may contribute to an understanding of the relationship between the stimulative effects of phenolic compounds and pulpal tissue repair.

We succeeded in separating and the cultivating stable monolayer cultures of dental pulp fibroblast strains derived from permanent and deciduous human teeth. Human permanent (n = 67) and deciduous teeth (n = 26) were extracted under acupuncture anaesthesia for the correction of malocclusion. After splitting the teeth, the pulp tissues were carefully removed, placed in tissue culture flasks, and grown in Dulbecco's modified Eagle medium supplemented with 10% fetal calf serum (FCS). The human pulpal fibroblasts (HPF) of permanent teeth and deciduous teeth (DHPF) were subcultured. Both the HPF and DHPF appeared to migrate from adherent tissues within 24 to 48 hr after explanation. They proliferated in the pulp explants, and lined up in parallel rows of cells closest to the explant tissue within 7 to 10 days in all of the experimental cases. The outgrowing cells were subcultured at 1.3 x 10(4) cells/cm2 in tissue culture flasks every 4-11 days. They showed vigorous proliferation. The average number of cells in the 6-7 day cultures of HPF were 5.6 x 10(4) cells/cm2 from 3 to 16 passages. It was 4.7 x 10(4) cells/cm2 from 3 to 10 passages with DHPF. However, no difference was observed between HPF and DHPF in the amount of synthesized protein in culture flasks. Furthermore, the growth rate of DHPF was more sensitive than that of HPF to the FCS percentages of the culture media.

A study on the number of anomalous teeth was made by using gross and radiographic examinations on 179 skulls (male: 68, female: 53, unknown: 58) of raccoon dogs (Nyctereutes Procynoides Viverrinus T.) captured in the northern part of Kyushu. Results were as follows: 1. 8 skulls had 15 supernumerary teeth. They were in the upper incisor, the upper third premolar and the upper and lower first premolar regions. 2. 35 skulls had 58 congenitally missing teeth. Most of them were upper and lower first premolars or lower third molars. 3. One skull had one supernumerary tooth in the upper second incisor region and one congenitally missing tooth, a lower third molar. 4. The anomalous teeth were about 25%, the supernumerary teeth and congenitally missing teeth were about 4.5% and 20% respectively.

Development, growth, maturation and aging processes of secretory cells of rat salivary glands progress mainly after birth. Nuclear non-histone proteins, phosphorylated actively and reversively, have an important role as regulatory molecules of gene activity and have a possibility to bring about specific changes in these cellular processes. We examined in the present study the age-dependent changes in the phosphorylation of non-histone proteins of rat salivary glands. Nuclei purified from submandibular and parotid glands of 8-week-old rats rapidly incorporated 32P from gamma-32P-ATP into the nuclear phosphoproteins and reached equilibrium within 9 min. A preponderant amount of the 32P was present in non-histone proteins. The levels of phosphorylation of non-histone proteins in salivary gland nuclei increased rapidly after birth, reaching a maximum in both gland nuclei of 4-week-old rats and then decreasing to the levels observed in submandibular and parotid gland nuclei from 20 and 16-week-old rats, respectively. These levels were still maintained in nuclei from aged rats. Moreover, age-dependent changes in the protein kinase activity of submandibular and parotid gland nuclei were linked up with the changes in the phosphorylation of non-histone proteins. However, changes were not observed in the phosphorylation of histone proteins after birth. These results suggest that protein kinase activity in salivary gland nuclei may have an important role on age-dependent changes in cell function, mediated through the control of the phosphorylation of non-histone proteins.

Maximum biting force and chewing performance were measured in adult subjects before and after four-weeks training by newly devised "Chewing Ability Enhancing Substances (CAES)". The CAES is made of glucomannan. The number of chewing strokes and chewing time until the last swallowing action are much larger when chewing CAES than those of other usual eating materials. By four weeks training using CAES, the maximum biting force and chewing performance of the subject were clearly increased. However, this increased chewing ability began to return to the control level gradually 2 weeks after the cessation of the training.

Self-setting apatite cement was investigated to evaluate its use as a possible bone substitute in the rat femur. The implant sites were recovered at intervals up 12 weeks postoperatively and investigated by the use of x-ray diffraction, contact microradiography, light and electron microscopy. By x-ray diffraction analysis, the cement placed for at least one day in the medullary canal of rats was found to be completely converted to a set phase of hydroxyapatite resembling the main inorganic phase of bone. In any specimens prepared at 1, 4, 12 weeks after implantation, no appreciable foreign body response was observed in the tissue around the set cement. At four weeks after implantation the set cement was in tight contact with the newly formed bone which appeared to involve osteocytes in lacunae and osteoblastic cells on its surface. At twelve weeks after implantation, the newly formed bone tended to grow into the interior of the set cement. With scanning electron microscopy, the newly formed bone was found to be directly deposited on the set cement. The newly formed bone consisted of fine needle-like crystals. These results strongly suggest that this cement is well tolerated by bone tissue and osteogenesis when used as a bone substitute. The advantage of the present material as a promising bone substitute is that it can be filled in surgical or traumatic bone defect as a slurry or paste.