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Biomedical subjects

K Soma

Publications and source records attributed to K Soma.

At least 37 records · Page 2Linked to original sources
PubMed2002

Bending properties of hollow super-elastic Ti-Ni alloy wires and compound wires with other wires inserted.

The purpose of this research was to investigate the possible orthodontic application of the hollow super-elastic Ti-Ni alloy wire, which was thought not only to deliver much lower and more continuous orthodontic force than conventional Ti-Ni wires, but also be able to be applied as a compound wire when combined with another wire. The examinations of bending properties were performed by the three-point bending test. The following results were obtained. 1. The hollow wire had lower load in the super-elastic range, smaller load-deflection rate and stress hysteresis in comparison with the conventional wire of the same diameter. 2. The load of the hollow wire was controllable by heat treatment. The stress hysteresis was further decreased by a two-step heat treatment. 3. The compound wire formed by inserting other types of wires into the hollow core exhibited changes in various bending properties such as increased load or load-deflection rate, according to the types and diameters of the inserted wire. The hollow wire delivers much lighter and more continuous orthodontic force, and, through heat treatment or deployment as a compound wire, it is possible to alter various bending properties. Therefore, this hollow wire was evaluated as a promising candidate for orthodontic application.

Journal Article↗
PubMed2002

Anisotropic orthodontic force from the hollow super-elastic Ti-Ni alloy wire by transforming the wire cross-section.

The purpose of this research was to devise a method for transforming the cross-section of the hollow super-elastic Ti-Ni alloy round wire and to examine the changes in its bending properties for clinical orthodontic application. The specimen wires were pressed with the use of heated pliers to transform the cross-sectional shape. As a result, transformation of the wire cross-section with super-elasticity was possible. As a verified by cantilever test and three-point bending test of the transformed specimens, a two-dimensional orthodontic force, which was different in each bending direction, was obtained. The hollow wire showed considerably high load level in the long axis along with markedly low load level in the short axis, which was mainly caused by the change in the moment of inertia by transforming the cross-section. It was revealed that, by transforming the wire cross-section of the hollow super-elastic Ti-Ni alloy round wires, anisotropic orthodontic force in bending properties could be obtained with super-elasticity.

Journal Article↗
PubMed2002

Relationship between the flow of bolus and occlusal condition during mastication--computer simulation based on the measurement of characteristics of the bolus.

The purpose of the present study was to clarify the relationship between the flow of a bolus and occlusal condition during mastication. First, the characteristics of a bolus under mastication was measured in subjects having different occlusal conditions. Secondly, the flow of a bolus between the upper and lower first molars under mastication was simulated using finite element non-linear dynamic analysis. Measurement of the elasticity of the bolus clarified the phenomenon of its communition. The measurement of the viscosity of the bolus clarified the phenomenon of its mixing with saliva. In addition, a relationship between the elasticity and the viscosity of the bolus at the point of just before swallowing was investigated. The flow of the bolus under mastication was revealed to vary according to the occlusal condition. These results suggest a close relationship between the occlusal condition, the flow of the bolus and its characteristics.

Adult↗
PubMed2002

Experimental tooth movement under light orthodontic forces: rates of tooth movement and changes of the periodontium.

AIM: To investigate light forces for experimental tooth movement. METHOD: Light orthodontic forces of 1.2, 3.6, 6.5, and 10 g force (gf) were applied for 14 days to move rat molars, and the effects of the forces on the rate of tooth movement and changes of the periodontium were examined. RESULTS: In the early period, despite the different levels of force used in each group, there were no significant differences in tooth displacement. From hour 56 to day 14, the tooth displacement in the 1.2 gf group was significantly smaller than that in the other groups and the rate was nearly constant. The rates of tooth displacement in the 3.6, 6.5, and 10 gf groups fluctuated repeatedly, while the orthodontic forces gradually decreased. CONCLUSION: Experimental tooth movement in rats, tipping without friction under light forces, were either constant or fluctuated in cycles of several days' duration. This is in contradiction to the three-phases-theory of tooth movement described in previous investigations using heavy forces.

Alveolar Process↗
PubMed2002

Neck motor unit activities induced by inputs from periodontal mechanoreceptors in rats.

Clinical evidence suggests that head movements may be coupled with oro-facial functions, which are predominantly controlled by somatosensory inputs from the oro-facial area. However, the effects of specific modalities of sensory inputs on the neck muscles' motor activity are still unclear. In the present study, natural pressure stimulation was applied to the rat's upper first molars, while motor unit electromyographic activity was recorded from the dorsal neck splenius muscle. During the hold phase of pressure stimulation, clear tonic discharges were elicited in the splenius muscles on both sides. Mean threshold values were 622.3 mN (+/- 19.6 SEM, n = 39) and 496.8 mN (+/- 26.4 SEM, n = 43) for ipsi- and contralateral sides, respectively (p < 0.001, Mann-Whitney U test). Analysis of our data suggests that periodontal inputs may play an important role in controlling the motor activity of neck muscles, in addition to its well-known coordination of the masticatory function.

Analysis of Variance↗
PubMed2001

Effect of neutral endopeptidase inhibitor on bradykinin-induced bronchoconstriction.

To evaluate whether neutral endopeptidase (NEP) inhibitors have adverse respiratory effects, the influence of a NEP inhibitor on bradykinin (BK)-induced bronchoconstriction was investigated. In anesthetized and artificially ventilated guinea pigs, changes in airway opening pressure (Pao) were measured as an index of bronchoconstriction. An infusion of phosphoramidon (3 mg kg(-1) h(-1)), a NEP inhibitor, significantly enhanced the bronchoconstriction induced by high-dose BK (30 nmol kg(-1), i.v.). Capsaicin (0.1 mg kg(-1), i.v.) and SR48968 (0.3 mg kg(-1), i.v.), an NK2 receptor antagonist, significantly inhibited the phosphoramidon-induced enhancement of BK-induced bronchoconstriction, although FK888 (3 mg kg(-1), i.v.), an NK1 receptor antagonist, did not. Both neurokinin A (NKA) (0.1-3 nmol kg(-1), i.v.) and substance P (SP) (0.1-3 nmol kg(-1), i.v.) induced dose-dependent bronchoconstriction which was enhanced by phosphoramidon infusion, although these enhancements were more prominent in the NKA series. Phosphoramidon partially inhibited BK degradation in lung homogenate, and both NKA and SP degradation in the lung homogenate were significantly suppressed by phosphoramidon. In bronchoalveolar lavage fluid (BALF), levels of NKA and SP were significantly elevated after a bolus of BK with a phosphoramidon infusion. These results suggest that NEP inhibitors may have adverse respiratory effects resulting from inhibition of the degradation of neurokinins, but mainly of NKA, when a large amount of BK is generated.

Animals↗
PubMed2001

Occlusal hypofunction causes changes of proteoglycan content in the rat periodontal ligament.

The biological functions of proteoglycans and glycosaminoglycans are closely associated with mechanical stress on the tissue. In order to reveal the relationship between proteoglycans in the periodontal ligament and mechanical stress such as occlusal stimuli, occlusal hypofunction of rat unilateral mandibular molars was induced by extraction of the opposing first, second and third maxillary molars. Immunohistochemical analyses were performed using antibodies for chondroitin sulfate, decorin, biglycan, heparan sulfate and keratan sulfate, and hyaluronic acid-binding protein. Chondroitin sulfate, observed more strongly in the cervical side than in the apical side of the periodontal ligament of the unextracted sides of mandible, and uniformly present in the extracellular matrix of the periodontal ligament, decreased significantly from 1 wk post-extraction of the antagonists, with a decrease in thickness and disarrangement in fibrous components. Decorin core protein, uniformly present in the periodontal ligament of the unextracted sides, decreased as early on as 2 d post-extraction. Heparan sulfate, mainly localized on the cell surface of vascular endothelial cells and osteoclastic cells as well as in the extracellular matrix of the unextracted sides, decreased significantly in association with the decreased number of blood vessels and osteoclastic cells as early on as 2 d post-extraction. Biglycan, keratan sulfate and hyaluronic acid, uniformly distributed in the periodontal ligament of the unextracted sides, showed little change after the extraction. These results demonstrate that occlusal hypofunction causes tissue remodeling of the periodontal ligament, with a significant decrease of chondroitin sulfate, decorin and heparan sulfate.

Animals↗
PubMed2001

Alkaline esophagitis evaluated by endoscopic ultrasound.

CASE REPORT: Two patients with corrosive esophagitis caused by alkaline household agents were examined with endoscopic ultrasound using a 20-MHz probe. In the first case, endoscopic ultrasound revealed circumferentially thickened mucosa and muscularis propria, and lack of differentiation between the mucosa and submucosa. However, esophageal stricture did not develop during 3 months of follow-up, suggesting that the deep lesion may have involved a narrow section of esophagus only. In the second case, a markedly thickened mucosa was seen, resulting in no sequelae. Endoscopic ultrasound offers a more accurate evaluation of the depth of the lesions in alkaline esophagitis compared to standard endoscopy or computed tomography. Longitudinal studies are needed to identify lesions at greatest risk for progression to stricture.

Adult↗
PubMed2001

Temporal and spatial mRNA expression of bone sialoprotein and type I collagen during rodent tooth movement.

To investigate the mechanism of bone formation during tooth movement, in situ hybridization was performed with digoxigenin-labelled RNA probes to detect bone sialoprotein (BSP) and type I collagen mRNAs in the dentoalveolar tissue of 72 Sprague-Dawley rats. An elastic band was inserted between the first and second right maxillary molars, and the teeth experimentally moved for 1, 3, and 7 days. The left first maxillary molar was used as the control. For the untreated molars, osteoblasts and osteocytes near the distal surface of the interradicular septum (IRS) expressed a high level of both BSP and type I collagen mRNAs, while cells on the mesial side of the IRS showed a low level of these mRNAs. For the first molars subjected to experimental tooth movement, a high level of type I collagen mRNA expression was found in the osteoblasts on the tension side of the IRS after 1 day of experimental tooth movement. A high level of BSP mRNA was detected after 3 days of experimental tooth movement. However, a negligible amount of both mRNAs was found in cells on the compression side. These results support the hypothesis that BSP may be involved in mineralization during physiological bone remodelling. On application of orthodontic force, osteoblasts were activated and induced to express BSP mRNA, which is involved in bone remodelling due to orthodontic force. In addition, response to the orthodontic force was observed in osteocytes.

Alveolar Process↗
PubMed2001

Acute mercuric chloride poisoning: effect of co-ingested milk on outcome and continued hyperamylasemia.

Thirty-six h after intentionally ingesting 25 g of mercuric chloride powder mixed with 5O mL of milk, an elderly woman presented to the emergency department with diffuse upper gastrointestinal erosions and acute renal failure. The patient was treated with dimercaprol and hemodialysis, and was discharged from the hospital without clinically apparent sequelae. However, elevated serum concentrations of amylase and proteases persisted for several months despite normal findings by computed tomography including contrast administration. Delayed absorption and weakened corrosive effect may have resulted from the binding of mercuric chloride to thiol-containing proteins in milk, improving the clinical outcome.

Administration, Oral↗
PubMed2000

The effect of a hemofilter during extracorporeal circulation on hemodynamics in patients with SIRS.

OBJECTIVE: To evaluate the hypothesis that extracorporeal hemopurification with a hemofilter contributes to the stabilization of hemodynamics in patients with systemic inflammatory response syndrome (SIRS) due to a mechanism other than the removal of cytokines. DESIGN: Prospective study. SETTING: Intensive care unit (ICU) in a university hospital. PATIENTS: Seven critically ill patients who met criteria for SIRS with unstable hemodynamics requiring vasopressors after emergency surgery. INTERVENTIONS: Before initiation of continuous hemofiltration (CHF) extracorporeal circulation through the hemofilter (ECC) with a hollow-fiber polyacrylonitrile hemofilter was performed for 6 h. MEASUREMENTS AND RESULTS: Vital signs were monitored continuously and hemodynamics were evaluated intermittently. The blood level of endotoxin and the plasma levels of cytokines were measured at 0 and 6 h. Changes in plasma levels of cytokines passing through the hemofilter were evaluated at 3 h. A significant decrease of body temperature (P < 0.05 at 3 and 6 h vs 0 h), a significant elevation of mean arterial pressure (P < 0.05 at 0.5 h, P < 0.01 at 3 and 6 h vs 0 h), and a significant increase of urinary flow rate (P < 0.05 at 0 to 3 h vs -3 to 0 h) were observed with ECC. Neither the blood level of endotoxin nor the plasma levels of cytokines decreased. A significant increase of plasma IL-6 as it passed through the hemofilter was noted. CONCLUSIONS: The beneficial effects of hemopurification with a hemofilter on SIRS patients are possibly due to mechanisms other than the elimination of cytokines with ultrafiltration, diffusion, or adsorption.

Aged↗
PubMed2000

The effect of phosphoric acid concentration on resin tag length and bond strength of a photo-cured resin to acid-etched enamel.

OBJECTIVES: To determine the relationship between depth of penetration and tensile bond strength of a photo-cured resin to phosphoric acid etched enamel, and the efficacy of enamel etchants that are less aggressive than a concentration of 10% H3PO4. METHODS: The tensile bond strength and length of tags produced by a photo-cured (20 s) resin consisting of pre-polymerized TMPT/silica in 3% HNPM-TEGDMA on acid-etched enamel was determined. The enamel etchants tested were various concentrations (3-65%) of phosphoric acid. The resin was applied to enamel samples that had been abraded with No. 600-grit SiC paper and acid etched (30 s) to create test specimens that were loaded to fracture on a testing device. The HCl-treated, then cut specimens, were examined under scanning electron microscopy and light microscopy. RESULTS: The tensile bond strength (10 MPa) of resin to enamel, pre-treated with various acid concentrations did not vary significantly. But resin tag length was found to decrease significantly from 22 microns for 35% H3PO4 to 12 microns for 20% H3PO4 to 9 microns for 5, 10 and 65% H3PO4 to 5 microns for 3% H3PO4. SIGNIFICANCE: These findings suggest that the length of the tags created by the tested photo-cured resin on phosphoric acid-etched enamel contributes little to the bond strength of the test specimens, and that the adhesive strength of the resin to H3PO4 etched enamel is mainly attributable to the resin's ability to penetrate between the enamel crystallites and rods. Further, enamel pre-treatment by phosphoric acid etchants of concentrations lower than 10% may be satisfactorily employed. The use of less aggressive acid concentrations might minimize any potential adverse effects to enamel substrates.

Acid Etching, Dental↗
PubMed2000

Development of a new device for recording condylar head movement.

Several excellent devices have recently been developed to precisely record mandibular movement. However, these devices are not always suitable for use under certain conditions, such as during sleep, because they incorporate a face bow unit. We report here a newly developed, easy and convenient recording device that does not require the use of an instrument within the mouth. Instead, a subminiature pressure transducer is inserted between the outer surface of a fixation device in the external auditory meatus and the anterior cutaneous surface of the external auditory meatus. The fixation device was made using silicone impression material in the shape of the inner external auditory meatus. Following moulding, the material was cut in half and the parts were reconnected using a coiled spring. This method is based on a routine clinical method for palpating the external auditory meatus to observe condylar head movement. By comparing the results obtained using this device with those obtained using CADIAX, we confirmed that it is useful for recording the movement of the condylar head in routine clinical examinations.

Adult↗
PubMed2000

Changes in jaw-jerk on different levels of jaw closure and teeth-clenching in humans.

We investigated how the jaw-jerk in the human masseter muscle is modulated in relation to the level of jaw closure (JC) and teeth clenching. Electromyographic (EMG) activity was recorded with surface electrodes. Background EMG activity of the masseter muscle was kept at three low teeth clenching levels with visual feedback. The level of JC was changed in six steps along the habitual path of closure relative to the mean maximal jaw opening during gum chewing by inserting a bite block between the upper and lower molars. The jaw-jerk was evoked by applying mechanical stimulation of about 20 N with a hammer to the bite-fork placed on the lower molars on one side in each condition of combination of a level of JC with a level of teeth-clenching. At the resting condition the excitability of the jaw-jerk increased with JC, while at weak voluntary teeth clenching it then decreased and increased again as the jaw was progressively closed. It is suggested that the excitability of the jaw-jerk would increase toward the occlusal position, which in turn would contribute to smooth masticatory movements. In addition, the mode of modulation of the jaw-jerk was studied in a subject with skeletal malocclusion.

Adult↗
PubMed2000

Decision analysis of prophylactic treatment for patients with high-risk esophageal varices.

BACKGROUND: Clinical decision analyses were conducted to quantify the uncertainty and to identify important factors in selection of prophylactic therapy for patients with esophageal varices. METHODS: A Markov model compared variceal ligation, beta-blockers, and "watchful waiting" strategies in terms of bleeding-free life years. Transition probabilities were obtained from meta-analyses of published data. A hypothetical 50-year-old white man with high-risk esophageal varices and cirrhosis served as the prototypical baseline case. Traditional n-way sensitivity analyses were applied to clarify the influence of each factor, and Monte Carlo probabilistic sensitivity analyses were used to investigate clinical uncertainty. RESULTS: Probabilistic sensitivity analyses demonstrated that 77.0% of hypothetical cases had more bleeding-free life years after variceal ligation, whereas 23% had more when treated with beta-blockers. On the basis of one-way sensitivity analyses, only 2 factors (variceal bleeding rates after ligation and treatment with beta-blockers) influenced the strategy choice. CONCLUSIONS: Variceal ligation is an effective prophylactic therapy in many cases, but nearly one quarter of patients with high-risk esophageal varices and cirrhosis may benefit more from prophylactic treatment with beta-blockers. Additional clinical studies identifying key variceal bleeding risk factors may lead to more effective clinical decision making for these patients.

Adrenergic beta-Antagonists↗
PubMed2000

Pulse steroid therapy in adult respiratory distress syndrome following petroleum naphtha ingestion.

CASE REPORT: A suicide attempt by a 23-year-old woman involved ingestion of 1000 mL of petroleum naphtha. Early chemical pneumonitis was complicated by life-threatening, diffuse interstitial lung consolidation with pneumatoceles. Pulse steroid therapy beginning on day 17 was associated with remarkable resolution of interstitial consolidation, although an enlarging secondarily infected pneumatocele ruptured to produce a bronchopleural fistula. Thoracic surgery and antibiotic therapy resulted in improvement of the patient's respiratory condition, and she was discharged with no residual respiratory symptoms. High-dose corticosteroid therapy appears to be a useful addition to aggressive supportive treatment in late adult respiratory distress syndrome following hydrocarbon ingestion.

Adult↗
PubMed2000

Time-related changes in periodontal mechanoreceptors in rat molars after the loss of occlusal stimuli.

The effect of a loss of occlusal stimuli upon the distribution and structure of the periodontal mechanoreceptors of the rat mandibular molar was examined after extracting opposing molars. The hypofunctional periodontal ligament narrowed significantly two weeks after tooth extraction, associated with an altered morphology of the Ruffini endings that showed typical dendritic profiles in normal controls. At four weeks and later periods after extraction, the Ruffini endings-including those without light microscopic changes demonstrated unusual ultrastructural features such as the eccentric localization of mitochondria along the axonal membrane and loss of other cell organelles, unusual elongation of axonal microprojections, or a deep invagination of the Schwann sheath into the axoplasm. Immunoreactivity for the growth-associated protein-43 (GAP-43) in the Ruffini endings was restricted to the Schwann element in both the normal and hypofunctional periodontal ligament, but the reaction was weaker and even negligible in some cases in the latter ligament. The present results suggest that occlusal stimuli are essential for maintaining the structural integrity of the periodontal ligament, including that of periodontal mechanoreceptors. A decreased immunoreactivity for GAP-43 in the Schwann sheaths supports the notion of a possible functional alteration in the Ruffini endings that showed no structural abnormality.

Acid Phosphatase↗