Biomedical subjects

S Minagi

Publications and source records attributed to S Minagi.

At least 19 recordsLinked to original sources

PubMed1999

The effect of diabetes mellitus on histopathological changes in the denture-supporting tissues under continuous mechanical pressure in rat.

The histopathological changes in denture-supporting tissues of streptozotocin-induced diabetes mellitus rat were studied in relation to continuous mechanical pressure exerted through an experimental denture base. The experimental dentures were designed to load continuous mechanical pressures (3.4, 1.5 or 0.5 kPa) to the hard palate of the molar region of a rat. From the results of this study, the following conclusions were drawn: the streptozotocin-induced diabetic condition (1) tended to prolong the appearance period of a shortened epithelial ridge, and weakened the phenomenon, (2) reduced the appearance period and severity of the compression of epithelium, (3) delayed the time of manifestation of the proliferative change in the recovery process of the shortened epithelial ridge, and weakened the phenomenon, (4) prolonged the appearance period of the compressed lamina propria mucosae, and enhanced the phenomenon, (5) reduced the number of osteoclasts, (6) lowered the threshold for induction of the osteoclastic bone resorption to between 1.5 and 0.5 kPa, (7) inhibited the appearance of osteoblast which follows the disappearance of osteoclasts, (8) did not induce any inflammatory change, and (9) tended to enhance the longitudinal change of the continuous mechanical pressure. The histopathological changes in the denture-supporting tissues of the streptozotocin-induced diabetes mellitus rat related highly to the longitudinal change of the continuous mechanical pressure exerted through the denture base. From the results of this study, it was suggested that the streptozotocin-induced diabetic condition lowers the tolerance of the denture-supporting tissues to continuous mechanical pressure.

Animals↗

PubMed1998

Double-casting method for fixed prosthodontics with functionally generated path.

STATEMENT OF PROBLEM: The construction of precise fixed prostheses that are harmonious within the stomatognathic function has been regarded as a critical requirement for successful oral rehabilitation. However, techniques for construction have been unsuccessful in producing a prosthesis that can be inserted without intraoral occlusal adjustment. PURPOSE: In this study, a new method of constructing a precise prosthesis that requires limited occlusal adjustment at the final seating is described. MATERIAL AND METHODS: The precision of this method was compared with a conventional method. Fourteen artificial crowns were fabricated on an experimental abutment by using both double-casting and conventional methods. The distances between the cusp tips and occlusal surfaces of the abutments, which were measured on wax/resin patterns and resultant crowns, were recorded to estimate clinical error for each method. RESULTS: Error for the double-casting method was markedly less than the conventional method. This study demonstrated that a new double-casting method was precise and sufficiently reliable for clinical application.

Analysis of Variance↗

PubMed1998

Efficacy of tray adhesives for the adhesion of elastomer rubber impression materials to impression modeling plastics for border molding.

STATEMENT OF PROBLEM: Tray adhesive, which is used for the adhesion of elastomer rubber impression materials to a custom resin tray, lowers the retention of the impression materials to the impression modeling plastics, as some ingredients of tray adhesive make the impression modeling plastic soft and tacky. PURPOSE: The efficacy of tray adhesive, which is used for the adhesion of elastomer rubber impression materials to a custom resin tray, on the adhesion between elastomer rubber impression material and impression modeling plastic was investigated. MATERIAL AND METHODS: Four silicone rubber impression materials (two addition reaction types and two condensation reaction types), two polysulfide rubber impression materials, and one impression modeling plastic were used in this study. Tensile strength between elastomer rubber impression material and impression modeling plastic with or without the application of tray adhesive was evaluated. RESULTS: Although tray adhesives for both addition reaction type and both condensation reaction type of silicone impression materials and one tray adhesive for polysulfide rubber impression material increased the tensile strength between the impression material and impression modeling plastic, one tray adhesive for polysulfide rubber impression material decreased the tensile strength when sufficient drying time was not applied.

Adhesiveness↗

PubMed1998

The effect of diabetes mellitus on histopathological changes in the tissues under denture base and without mechanical pressure.

Histopathological changes in the tissues under a denture base were studied with respect to the difference between diabetic and normal rats. Diabetes mellitus was induced in Wistar rats by streptozotocin. The experimental denture base was designed to make contact with the palatal mucosa without any continuous nor masticatory pressure. Histopathological observation periods were 1, 2, 4, 8, 12 and 20 weeks after the insertion of the denture base. Histopathological examination revealed that only the transient slight proliferative reaction observed in mucosal epithelium under a denture base in normal non-diabetic rats, was lessened by induced diabetes mellitus. Moreover, covering the palatal mucosa with a denture base without any continuous nor masticatory pressure and with the maintenance of mucosal cleanliness under it and of the denture itself, did not cause any inflammatory change or bone resorption in the tissues under the base.

Acrylic Resins↗

PubMed1998

Relationship between mandibular position and the coordination of masseter muscle activity during sleep in humans.

Although bruxism has been regarded as having a possibly important role in the aetiology of craniomandibular disorders, the activity of masticatory muscles relative to mandibular position during sleep grinding as recorded by electromyography (EMG) has not yet been clarified. Surface EMGs of the bilateral superficial masseter muscles were recorded simultaneously with mandibular position during sleep from 12 volunteers for three consecutive nights. The incidence of two mandibular positions were recorded with magnetic sensors for both left- and right-sided mandibular grinding. One of the mandibular positions was the canine edge-to-edge position, and the other was the midpoint between the intercuspal position and the canine edge-to-edge position. The mode of the working/ balancing activity ratio ranged from 1/10 to 2/10, showing the marked predominance of balancing side masseter muscle activity during sleep grinding. During sleep grinding, EMG bursts of masseter muscle were observed mainly with mediotrusive mandibular movement from the canine edge-to-edge position. From the results of the present study, it is suggested that muscular dynamics during sleep are unique compared to that during voluntary clenching, and exert a greater mechanical load to the balancing side temporomandibular joint.

Adult↗

PubMed1998

An appliance for management of TMJ pain as a complication of Parkinson's disease.

This is a case report of a 71-year-old female with pain in the right TMJ, who was also suffering from Parkinson's Disease and was treated using a new intraoral occlusal appliance. The new appliance was designed to limit excessive mandibular excursion of the right side by restricting the mediotrusive movement of the left coronoid process. The appliance significantly suppressed involuntary mandibular excursion.

Aged↗

PubMed1998

Threshold for bone resorption induced by continuous and intermittent pressure in the rat hard palate.

Osteoclastic bone resorption under the denture base has been considered to be influenced by mechanical force exerted through the denture base. However, no scientific evidence has been shown concerning whether osteoclastic bone resorption is a pressure-threshold-regulated phenomenon or merely a proportionally pressure-dependent phenomenon. In this study, a clear statistical criterion as an objective standard for the evaluation of histopathological bone resorption was established, and the relationship between the amount of continuous or intermittent compressive pressure exerted on the rat hard palate and induced osteoclastic bone resorption was studied based on this criterion. Eighty-five male rats of the Wistar strain, 15 weeks of age, were fitted with experimental dentures which were designed to exert a defined amount of continuous or intermittent compressive pressure on the intermolar region of the hard palate. No bone resorption was observed when continuous compressive pressure was < or = 1.96 kPa or when intermittent compressive pressure was < or = 9.8 kPa. In contrast, continuous compressive pressure > or = 6.86 kPa or intermittent compressive pressure > or = 19.6 kPa caused significant bone resorption in all rats studied. From these results, it was revealed that osteoclastic bone resorption under the denture base was a pressure-threshold-regulated phenomenon, and that the thresholds exist for the induction of bone resorption under the denture base by both continuous and intermittent compressive pressure, respectively. It was also clearly revealed from the results that the threshold for continuous compressive pressure is lower than that for intermittent compressive pressure.

Animals↗

PubMed1997

Effect of balancing-side occlusion on the ipsilateral TMJ dynamics under clenching.

The effect of balancing-side occlusal contact patterns on ipsilateral TMJ dynamics was evaluated in this study. Vertical displacement of the balancing-side lower second molar during clenching at canine edge-to-edge position, with 0 and 1 mm of inter-canine distance, was measured for 42 normal subjects in relation to their balancing-side occlusal contact. Balancing-side occlusal contact was classified into four following patterns; (1) simultaneous balancing-side and working-side contact (without clenching); (2) balancing-side contact (with clenching only); (3) no balancing-side contact (with or without clenching); and (4) exclusive balancing-side contact (no working-side contact). The vertical displacement of the balancing-side condyle, calculated from the displacement of the balancing-side second molar, showed three different types of displacement pattern. These three types showed distinctive incidence in relation to the pattern of balancing-side occlusal contact. It was revealed that balancing-side occlusal contact can affect the ipsilateral TMJ dynamics.

Adult↗

PubMed1997

Effect of continuous pressure on histopathological changes in denture-supporting tissues.

The histopathological changes in denture-supporting tissues were studied in relation to continuous pressure exerted through an experimental denture base. The experimental dentures were designed to load continuous pressures (1.5, 3.4 or 4.9 kPa) to the palate of molar region of rat. Histopathological changes caused by the continuous pressure were observed, and the intensity of the pressure was also estimated. A high correlation was observed between the histopathological changes under the denture base and the intensity of the continuous pressure. In groups exposed to 4.9 and 3.4 kPa, the continuous mechanical pressure caused bone resorption; in 1.5 kPa group, no evidence of bone resorption was observed. The epithelium and lamina propria mucosa under the denture base, which were compressed by the continuous pressure, recovered histopathologically depending on the decrease of the pressure caused by bone resorption; no quantitative recovery of the absorbed bone tissue was observed. No inflammatory change was induced by the continuous pressure. From the histopathological results observed in this study, the possibility of the existence of a threshold for bone resorption induced by continuous pressure was suggested.

Acrylic Resins↗

PubMed1997

Relationship between size of denture foundation area and resorption of alveolar ridge in the edentulous mandible.

The relationship between the size of the denture foundation area and the resorption of the alveolar ridge was investigated in 55 edentulous subjects. The denture foundation area was recorded using a modelling compound impression technique with border moulding. Both sides of each edentulous mandible were examined separately, making a total of 110 experimental sides in the study. On a stone cast made from each impression, the size of of the superficial denture foundation area and of the projected denture foundation area on the tentative plane of occlusion of each anatomical zone were measured. The vertical height of the alveolar ridge at the lateral incisor and first molar region was also evaluated. The size of the superficial denture foundation area in the antero-lingual and postero-lingual zones showed no significant correlation with the degree of alveolar ridge resorption. The size of the projected denture foundation area on the tentative plane of occlusion in the anterior section showed negative significant correlation with the degree of alveolar ridge resorption. The size of the projected denture foundation area on the tentative plane of occlusion in the posterior section showed no significant correlation with the degree of alveolar ridge resorption.

Aged↗

PubMed1996

Adenosquamous carcinoma of the stomach associated with separate early gastric cancer (type IIc).

Adenosquamous carcinoma originating in the stomach is a relatively rare entity. It comprises less than 0.5% of all gastric cancers. Recently, we encountered a patient with gastric adenosquamous carcinoma associated with separate early gastric cancer (type IIc). The patient was a 72-year-old man who was diagnosed as having gastric cancer in a multiphasic health screening examination conducted in May 1992. The patient subsequently underwent pylorogastrectomy. Examination of the resected specimen revealed two lesions, advanced cancer (Borrmann 2) and early cancer (type IIc). The lesions were histopathologically diagnosed as adenosquamous carcinoma and adenocarcinoma, respectively. The majority of gastric adenosquamous carcinomas are stage III or IV advanced cancers, and are treated according to the therapeutic protocol for adenocarcinomas. Their prognosis is generally poor. Continuous follow up is required for patients with these adenosquamous cancers, even after curative resection has been performed, because of the advanced nature of these lesions.

Adenocarcinoma↗

PubMed1996

Effect of occlusal pressure on the histopathological changes in denture supporting tissues.

Histopathological changes in the denture supporting tissues in relation to the occlusal pressure exerted through an experimental denture base were studied. An experimental denture, which prescribed the occlusal pressure by the amount of subsidence of the denture base (100, 50 and 13 microns), was constructed for the palate of the molar region of rat. Histopathological changes caused by the occlusal pressure were observed, and the intensity of the pressure was also estimated. In the 100 microns subsidence group, compression of epithelium and lamina propria mucosae, inflammatory change and bone resorption were caused by the occlusal pressure. In the 50 microns subsidence group, compression of epithelium and lamina propria mucosae and bone resorption were observed, while in the 13 microns subsidence group, no evidence of inflammatory change and bone resorption were observed. The epithelium and lamina propria mucosae recovered histopathologically depending on the gradual decrease of the occlusal pressure resulting from bone resorption, whereas no quantitative recovery of the resorbed bone tissue was observed in the 100 and 50 microns subsidence groups. From the results observed in this study, a high correlation was observed between the histopathological changes under a denture base and the intensity of the occlusal pressure, and the possibility of the existence of the threshold for bone resorption induced by occlusal pressure was suggested.

Acrylic Resins↗

PubMed1996

A new method for recording mandibular position during nocturnal bruxism.

Experimental equipment for recording mandibular excursive position during nocturnal bruxism has been devised. The equipment consists of chromium-cobalt alloy cast frameworks for each upper and lower dental arch and two pairs of tiny magnetic sensors and magnets, capable of electromyographic (EMG) recordings of the bilateral masseter muscles and simultaneously recording mandibular position. The two subjects tested were confirmed to be bruxing during sleeping. Although EMG records for the two subjects showed a common EMG pattern as a bruxer, the sensor records revealed that one subject was a bilateral bruxer and the other bruxed almost unilaterally. The present study demonstrated that this newly devised equipment is practical for studying mandibular position during nocturnal bruxism.

Adult↗

PubMed1995

The effect of the slope inclination of buccal polished surface of mandibular denture base on food retention.

The accumulation of food debris in the buccal vestibule can inhibit normal mastication and appears to be a factor that can cause patient discomfort. This study focused on the effect of the slope inclination of the buccal polished surface of the mandibular denture base on the ability to expel test-food particles from the buccal vestibule. It was revealed that an inclination of the slope steeper than 80 degrees markedly inhibits the normal ability to expel foods from the vestibule. It was revealed that the most appropriate inclination of the buccal slope is approximately 60 degrees or 70 degrees. These results could be utilized for constructing a denture prosthesis.

Adult↗

PubMed1994

An experimental study on histopathological changes in the tissue covered with denture base without occlusal pressure.

In order to clarify the basic histopathological effect of a denture prosthesis on the denture supporting tissues, a new experimental appliance was developed. The denture base was designed to make contact with palatal mucosa of the experimental animal without any mechanical pressure and transmit no occlusal force to the mucosa. The objectives were: (i) non-pressure contact of denture base with palatal mucosa; and (ii) lack of physiological stimulation for palatal tissue by tongue and/or food. The results of the study revealed that covering the palatal mucosa with a denture base without any mechanical pressure and with the maintenance of a clean palate and denture base, did not cause any inflammatory change and bone resorption in the denture supporting tissues, except for a slight transient proliferative reaction in the epithelial ridges.

Animals↗

PubMed1992

Effect of mechanical pressure on the blood flow in human palatal mucosa measured by temperature controlled thermoelectrical method.

Mucosal blood flow in the human palate was measured by a temperature controlled thermoelectrical method based on the thermal conductivity of mucosal tissue using a blood flow monitor and a non-invasive surface probe. The effect of mechanical pressure on the palatal mucosal tissue was studied. Mechanical pressure (2.5, 5.0, 7.5, 10.0 or 15.0 g mm-2) to the mucosal surface was exerted circumferentially around the surface probe. In five out of seven subjects, the blood flow showed a tendency to be almost constant under the mechanical pressures which are 10.0 g mm-2 or higher. The effect of the duration of the pressure (10.0 g mm-2) exertion on the blood flow was also investigated and it was revealed that the blood flow tended to be constant after 60s in every subject. In the present study, it was also demonstrated that the temperature controlled thermoelectrical method is appropriate for studying the blood flow dynamics in oral mucosa.

Adult↗

PubMed1991

A manipulation technique for treatment of anterior disk displacement without reduction.

Anterior disk displacement without reduction, called "closed locking," is a serious stage of the internal derangement of the temporomandibular joint. Many types of conservative and surgical treatments have been applied to this problem. A new manipulation technique to release "closed locking" of the temporomandibular joint and the clinical results on 35 patients are reported in this study. Voluntary maximal mouth opening of the patients were measured as interincisal distance before and after the application of the manipulation technique. The voluntary maximal mouth opening of 14 of 17 patients (82%) who were younger than 30 years was improved to more than 40 mm after the application of the manipulation technique. Contrariwise, the voluntary maximal mouth opening of only 5 of 18 patients (28%) who were older than 30 years was improved to more than 40 mm.

Adolescent↗

PubMed1990

Antifungal drugs affect adherence of Candida albicans to acrylic surfaces by changing the zeta-potential of fungal cells.

The effect of sub-inhibitory concentrations of antifungal drugs on the adherence of Candida albicans to acrylic surfaces was investigated. Among five antifungals tested, azalomycin F and aculeacin A significantly enhanced the adherence. The zeta-potential of fungal cells was affected by antifungal drugs, whereas no significant change in cell surface hydrophobicity was observed. The relationship obtained between the change in the adherence and that in zeta-potential suggests that the enhanced adherence was caused by decreased electric repulsive forces.

Acrylates↗