[Osaka Daigaku shigaku zasshi] The journal of Osaka University Dental Society最新文献

The purpose of the present study was to analyse the quantitative relationship between the property of food and the jaw-closing muscle activities as well as how the periodontal afferents participated to establish such a relationship. The following experiments were performed in the urethane anesthetized rabbits: 1) EMG activities of the masseter muscle during the cortically-induced rhythmical jaw movements (CRJMs) before and during chewing rubber strips with different hardness were compared each other. 2) Effects of combined sections of the maxillary and the inferior alveolar nerves on the masseteric EMG responses during chewing a strip were analysed. 3) Effects of the transection of the trigeminal spinal tract on the above masseteric responses were also analysed. The results were as follows: 1) The masseteric activities during the CRJMs differed depending on the site of the cortical stimulation. According to the level of the masseteric activity, CRJMs were divided into two types; one was the opening-dominant jaw movement (ODJM) with small masseteric activity, and the other was the closing-dominant jaw movement (CDJM) with large masseteric activity. In any CRJMs, the masseteric activity became larger during the insertion of a strip, but the increment was more prominent for the ODJM. The rate of increment of the masseteric activity became larger with the hardness of the strip. 2) After the periodontal deafferentation, the rate of increment of the masseteric activity during chewing a strip was remarkably reduced, especially in the ODJM. On the contrary, deafferentation was less effective to that in the CDJM. 3) The effects of the transection of the trigeminal spinal tract were similar to those of the trigeminal deafferentation. From these results, the following conclusions were obtained: 1) The masseteric activity was facilitated with the hardness of the strip. Furthermore, the rate of increment of the masseteric activity during chewing a strip differed depending on the masseteric activity induced before the strip insertion. 2) Periodontal afferents played an important role in the above facilitatory effect, especially when the masseteric activity was small. 3) The contribution of the periodontal afferents which descended through the trigeminal spinal tract was suggested to be involved in the facilitatory response of the masseter muscle during chewing a strip.

Occlusal plane is one of the important and fundamental factors that establish the mandibular position and the form of dental arch and prosthesis. The aim of this study is to investigate the morphological and functional importance of occlusal plane in relation with orofacial morphology and stomatognathic function. Cephalograms were taken and electromyograms of masseter, anterior and posterior temporal muscles were recorded during clenching, tapping and chewing movements in 30 normal young adult subjects. Mandibular movements were simultaneously recorded using Sirognathograph (Siemens, West Germany). A correlation analysis was performed to study the relationship between the occlusal plane and morphological and functional parameters. As a result, the occlusal plane angle showed; 1) close correlations with the mandibular plane angle, Camper's plane angle and palatal plane angle, 2) correlations with the duration of activity of anterior temporal muscles and the sagittal angle of chewing pathway. The results suggest that there is a close relationship between the occlusal plane and orofacial morphology. Furthermore, the morphological parameters closely related to the occlusal plane were found to affect stomatognathic function. It is concluded that the occlusal plane is the important factor which harmonizes morphology and function of the stomatognathic system.

Normal human gingival fibroblasts stimulated in vitro by lipopolysaccharide (LPS) from black pigmented oral Bacteroides species produced cell-free (CF) and cell-associated (CA) thymocyte activating factors (TAF). The LPS from other bacteria, including Escherichia coli and Salmonella species, induced minimum levels of TAF in the cultures. The CF-TAF was partially inhibited by anti-human interleukin (HuIL)-1 beta or HuIL-6 antibody, but not by anti-HuIL-1 alpha antibody. However, complete inhibition of the CF-TAF was not observed upon addition of both anti-HuIL-1 beta and HuIL-6 antibodies. Fibroblasts stimulated with Bacteroides LPS released high levels of CF-IL-6 activity. Recombinant (r) HuIL-6 negligibly exhibited TAF activity even in high doses up to 500 U/ml, although it augmented the TAF activity of rHuIL-1 beta. These findings indicated that the CF-TAF consisted mainly of IL-1 beta, and that IL-6 enhanced TAF activity of IL-1 beta. However, other TAF factor (s) may be present in CF specimens. In contrast to CF-TAF, the CA-TAF was inhibited with anti-HuIL-1 alpha. Recombinant human tumor necrosis factor (rHuTNF) directly stimulated fibroblasts to produce CA-TAF, and it also primed them to enhance CA-TAF induction in response to Bacteroides LPS. On the other hand, natural human interferons (nHuIFN) alpha, beta, and gamma did not induce CF- or CA-TAF in fibroblasts. When fibroblasts were primed with nHuIFN beta or gamma, the CA-TAF production by the cells in response to LPS, but not rHuTNF, was markedly enhanced.(ABSTRACT TRUNCATED AT 250 WORDS)

The distance of distal movement of the lower canine was measured, using metal tooth with metal bracket and three types of ceramic bracket (polycrystal alumina x 2, zirconia x 1). Sizes of the wires used in this experiment were 0.018" round, 0.016" x 0.022" and 0.17" x 0.022". The bracket slot and the wire surface employed in the experiment were observed by use of stereoscopic microscope and S.E.M. The following results were obtained. 1. The distance of tooth movement with three types of ceramic bracket was significantly less than that with the metal bracket. 2. Rate of decrease in tooth movement with three types of ceramic bracket ranged from 30% to 60% in comparison with the metal bracket. 3. The wire surface was obviously scratched by the ceramic brackets, whereas slight scratch was observed on the wire with the metal bracket. 4. The distance of tooth movement decreased associated with an increase of wire size. 5. The distance retracted from the cuspal position was less than that from the cervical point. It was shown that efficiency of tooth movement was significantly reduced by the use of ceramic brackets in comparison with the metal bracket. This result seems to be caused by the frictional resistance between the wire and ceramic bracket. It is suggested that refinement of ceramic brackets, slot edge and surface in particular, would produce more efficient and desirable tooth movements in clinical orthodontics.

The gene coding for a dextranase activity of Arthrobacter CB-8, named dex gene, was isolated and cloned into Escherichia coli and into Streptococcus sanguis. The gene library was screened by transparent halo formation around the colonies grown on agar medium containing blue dextran. DNA fragment consisting of about 3,200 base pairs was prepared for further cloning procedures. Dextranase activity was detected in the periplasmic space of E. coli clones, using pUC19, pVA 838 and their derivatives. Dex gene was also introduced into S. sanguis Challis using pVA 838, a plasmid that is able to replicate in both E. coli and S. sanguis. But the clones did not express the dex gene. For the expression of dex gene in S. sanguis, a new shuttle vector was constructed, which contained the promoter region of a glucosyltransferase gene from S. mutans as well as the terminator region of ribosomal RNA from E. coli. The plasmid was designated pMNK. Using pMNK as vector, dex gene was expressed in S. sanguis. Dextranase activity was detected in the cellular fraction of the clones.

The present study was conducted to investigate mechanical properties of the nickel-titanium (Ni-Ti) alloy wire developed by the diffusion method, in comparison with the previous Ni-Ti wires. Two types of the wire, work hardening and super elastic wires, were used for three experiments; three-point bending test, tension test and torque test. The following findings were obtained. 1. A newly developed work hardening wire exhibited lower force level with a generous reduction of force at various wire deflections, in comparison with the previous work hardening Ni-Ti wires. It was also found that tension strength and extension ratio of this wire were greater, and its modulus of longitudinal elasticity was smaller than those of the previous wires, indicating high resistibility to breakage. 2. A super elastic wire, developed by the diffusion method, showed similar pattern of force reduction associated with varying wire deflections, although magnitude of force was slightly larger than those of the previous super elastic wires. 3. An interesting finding was that force and its reduction with various deflections were varied by controlling how the wire was ligated onto a bracket, which was more obvious in the work hardening type of the present Ni-Ti wire. 4. Magnitudes of force exerted by Ni-Ti wires were around 200 gf at a deflection of 2 mm with an interbracket distance of 7 mm, and seemed to be beyond an optimal orthodontic force for anterior teeth. A further refinement is expected in terms of improving mechanical properties and/or developing finer wires.

We encountered a case where a 30 gauge disposable dental needle was accidentally broken and inoculated into pterygomandibular space by a dentist during a block anesthesia for the inferior alveolar nerve. Several approaches including use of a guide needle and roentgenograms were made but all were unsuccessful. Eleven days later, further operation was attempted monitoring the needle on X-ray TV, resulting in that the broken needle was successfully removed. This technique may be useful for removal of mandibular broken needles.

The effect of biomechanical factors on tooth movement has not been clarified in a quantitative manner. This study was designed to investigate the stresses affecting tooth movement, using a numerical simulation. The influence of decrease in Young's modulus of the periodontal membrane on canine retraction was also examined through the simulation. A two-dimensional finite element model was constructed based on the average anatomic morphology of Japanese canine. A numerical simulation program based on the finite element method was developed for the orthodontic tooth movement. The stresses in the periodontal membrane were evaluated. The principal stress of which absolute is larger was selected as a reference stress. Each nodal point at the alveolar bone-periodontal membrane interface was repositioned in the direction of reference stresses, in response to discrepancy between assumed thresholds and the reference stresses. Moment to force (M/F) ratios at the bracket position of this model were examined for evaluating force conditions. Simulation of tooth movement were executed under three force conditions with different M/F ratios for distal movements and two force conditions for vertical movements. Three types of canine retraction, tipping movement, bodily movement and root movement, were displayed with the numerical simulation. Extrusion and intrusion were also displayed. Analytic movements of the canine were close to the actual tooth movements that have been reported, utilizing the principal stresses with the thresholds of the maximum and minimum principal stresses being about +0.4 gf/mm2 and -0.4 gf/mm2. The decrease in the Young's modulus of the periodontal membrane changed bodily movement to tipping movement under the same force conditions. These results indicate that the value and the direction of the principal stress in the periodontal membrane are key determinants of tooth movement and this numerical simulation is useful for investigating the influence of the biomechanical factors on tooth movement.

Analyzing occlusal contacts is significant for establishing the occlusal scheme as well as for the diagnosis on dysfunction of stomatognathic system. We tested a new occlusal contact analyzing device (T-Scan: Tekscan Inc. Boston, U.S.A.) for its sensitivity and reproducibility in relation to its clinical application. Following results were obtained. 1) As the modeling of dental arch of this system was not always correct, much care should be needed for identifying the contact location. 2) The minimum amount of load needed for displaying each five step occlusal force increased linear fashion (step 1: 250 g and step 5: 1750 g) when the sensor was vertically pressed on the intersection of force sensitive line. The minimum amount of force changed with the loading condition such as area and direction. Distortion of the sensor could lead the measurement error. 3) Since the time measurement data by this system were shorter than actual length of time and were measured over about 250 g load, light and early occlusal contacts could not be detected.

In designing removable partial dentures (R.P.D.) for edentulous patients, variety of designs are selected with considering the condition of residual teeth, alveolar ridge, occlusion and other factors. We have been trying to develop the computer consultation system for designing R.P.D. (so called "expert system") to rationalize the processes of R.P.D. design. In developing and expanding this system, the construction and enlargement of the rulebase and database are indispensable. In this report, we analyzed R.P.D. designs in student's clinic ('83-'85), in order to find the logic for design (rulebase) and to construct databases. Following results were obtained. 1) Wire clasps were most frequently used in Kennedy classification I, II in maxilla. Double clasps were mostly used in Kennedy class I, II in mandible. Akers' clasps were mostly used in class III. 2) Canine, first and second premolar were more frequently selected for abutment than other teeth.