The purpose of this study is to find out the analytical accuracy and the detection limit of the EPMA, which are the important factors when analyzing the changes in the surface condition or the composition of the dental metals used in an oral environment. The results were as follows: 1) The EPMA used in the analysis had an excellent detection limit which was less than 0.005% for Fe, Cr, Si, Cu and Mo. 2) The X-ray detection limit measured for the elements in the alloys were close to that of the pure elements. 3) The results of the quantitative analysis for the standard samples using the EPMA were close to the results of the chemical analysis for each of the samples, with their differences within 1%. 4) When the quantitative results between the mirror polished surfaces and the surfaces treated with different grits of Emery papers were compared, the error was within 1% for the major component elements even when treated with the rough #80 Emery paper. 5) The effects of the inclination of the sample surfaces on the results of the analysis were small for the non-precious metals. Even with the precious metals, it was within 1% of the measurement error when the inclination was less than 2°.
There have been many reports recognizing vascular changes on pressure side of periodontal tissues during orthodontic tooth movement. The vascular changes cause local hypoxia which seems to affect the phenotypes of periodontal tissue cells. In order to clarify the effect of hypoxia on proliferation and function of periodontal tissue cells, DNA content, alkaline phospha-tase (ALP) activity and prostaglandin E2 (PGE2) production under a hypoxic condition in both periodontal ligament fibroblasts (PLF) and osteoblastic cells (MC3T3-El cells) were examined in vitro. PLF were cultured from human periodontium and identified by both morphologic cha-racterization and presence of ALP. The results obtained were as follows: 1. Under 10% O2 condition, the activity of proliferation in PLF did not change but that of osteoblasts was inhibited. 2. ALP activity in PLF was stimulated but that of osteoblasts was inhibited under the hypoxic condition. 3. Production of PGE2 in osteoblasts increased after 7 days of hypoxia though that in PLF decreased. In addition, the enhancement of PGE2 production in osteoblasts was due to activation of both phospholipase A2 and PGE2-synthesizing enzymes. 4. From the orthodontic point of view, hypoxia on the pressure side may induce bone resorption by inhibiting mineralization activity of osteoblasts and enhancing production of PGE2 in osteoblasts.
The purpose of this study was to investigate the neuronal mechanisms of the clinical symptoms of unusual muscle stiffness and/or pain in the neck and shoulder sometimes observed in patients suffering from chronic pulpal or periodontal diseases. Physiological properties of the neurons responding to the inferior alveolar nerve stimulation (inferior alveolar nerve drivenneurons : IANDNs) were studied by recording single unit activities in the upper cervical cord in cats anesthetized with α-chloralose. The results were as follows: (1) IANDNs were widely distributed from the dorsal horn to the ventral horn in the gray matter of the cervical cord (C2 and C3) . (2) IANDNs were subdivided into two types of neurons based on the latencies of the spike responses: fast-type (F-type) (n=60) and slow-type (S-type) (n=101) . (3) Two possible pathways from the inferior alveolar nerve to the cervical spinal cord participating in these spike responses were assumed: one was through the trigeminal spinal nucleus and the other through Probst's tract by way of the trigeminal mesencephalic nucleus. These results suggest that the impulses originating from dental inflammatory loci might drive IANDNs in C2 or C3 and that their activities may evoke contraction of the neck muscles, resulting in their stiffness and cervical back pain.
Actinobacillus actinomycetemcomitans (A.a.) has been implicated in the etiology of juvenile periodontitis and also of advanced destructive periodontitis (ADP) . It has been reported that the levels of the IgG antibody against the A.a. in the peripheral blood sera of the ADP patients were often high as well as those against the Bacteroides gingivalis. To clone the genes of antigen reactive to the sera of the ADP patients, we constructed a phage library of the A.a. strain Y4 DNA in lambda L47, which was then screened by the immunochemical detection method using a serum from the ADP patient. Of about 1, 000 phage clones six were positive with the serum and also the sera of the other patients, and were named 3, 4, 6, 7, 8 and 9 respectively. Restriction enzyme and Southern blot analyses indicated that clones 8 and 9 were identical and that these clones, 3 to 8 were overlapping since they shared in common the 4 kbp and 5kbp Hinc II DNA fragments of the A.a. The cloned DNA fragment hybridized to the DNAs of the two other strains of the A.a. but did not to those of the Bacteroides intermedius, Bacteroides fragilis, Bacteroides melaninogenicus, Bacteroides gigivalis, Capnocytophaga ochracea and Fusobacterium nucleatum. These results suggest that the DNA sequence encoding an A.a. Y4 antigen strongly reactive to the sera of the ADP patients was present specifically in the A.a. but not in the other bacteria isolated from the periodontal patients. Thus, the DNA could serve also as a DNA probe for the diagnosis of periodontitis.
Evaluating masticatory ability is a fundamental subject in dentistry. However there is no sufficient clinical method for it. The purpose of this study was to evaluate compressive ability in mastication from compressive energy in mastication. To measure compressive energy from compressive transformation of a material before crushing, a new artificial material, CHEWING GUM CONTAINING POLYCARBONATE MICROCAPSULES, was originated. And by the material, a method for evaluation of compressive ability was made. The method was tested on 11 persons in the twenties (6 males, 5 females) . The results were as follows: 1) The coefficient of variations of values that were measured 5 times on one male subject was 4.24%. 2) The distribution of values that were measured on 11 subjects ranged widely. The ratio of the minimum value to the maximum value on 9 adults of normal occlusion was 1 : 3.0. Compressive energy and occlusal contact area in mastication were calculated from these values. The results show that the method for evaluation of compressive ability is one of the new clinical methods for evaluation of masticatory function.
The purpose of this study was to examine the response patterns of single sensory units innervating the human temporomandibular joint to the displacements of the mandibular head. 13 single sensory units were recorded from the auriculotemporal nerves of five adult subjects by the method of microneurography and the response patterns were analyzed. The results obtained were as follows : (1) The response patterns of the same unit to the directions of the mandibular movements were classified as Slowly Adapting Type and Fast Adapting Type according to the characteristics of their adaptation. (2) The threshold value of the Fast Adapting Type was higher than that of the Slowly Adapting Type. (3) Increasing the rate of the mandibular opening movements in the initial stage, the firing frequency of the units increased in the response pattern of the Slowly Adapting Type. It was concluded that the sensation in the directions of the displacements of the mandibular head can be induced by the response patterns of the impulses in the nerve fibers innervating the temporomandibular joint.
A human dental pulp tissue was explanted in culture and the outgrowing cells were transf ected with the plasmid, pMT1-neo, which included the early region of SV40 DNA and the neomycin-resistant gene. The transf ected cells were cloned and cultured beyond the period of senescence for the non-transfected HOP cells, over 170 passages (360 population doubling levels and 730 days) . The characteristics of the transf ected LSC cells and the non-transfected HOP cells were investigated during in vitro aging. The results were as follows: 1. The alkaline phosphatase (ALPase) activity of the HOP cells decreased as the culture passages increased. In contrast, the ALPase activity of the LSC cells did not change during the entire serial culture period. 2. The ALPase inhibitory test indicated that the ALPase in the LSC cells was the bone/liver/kidney type. 3. The addition of 250μg/ml of L-ascorbic acid resulted in an increased collagen synthesis compared with that of 50μg/ml. 4. The growth rate and the ALPase activity of the LSC cells were affected by lα, 25-dihy-droxyvitamin D3, L-ascorbic acid, β-sodium glycerophosphate, epidermal growth factor or transforming growth factor-β even after the serial culture. These results suggest that the LSC cells preserve some properties of the dental pulp and may be useful in the future research for exploring the mechanisms of the dental hard tissue formation and for testing the biocompatibility of the dental restorative materials.