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Biomedical subjects

M Sakuda

Publications and source records attributed to M Sakuda.

At least 73 records · Page 4Linked to original sources
PubMed1995

Biomechanical behavior of the periodontium before and after orthodontic tooth movement.

This study was designed to investigate the biomechanical behavior of the periodontium including the periodontal ligament (PDL) in terms of tooth mobility. Tooth mobility was measured in the canines of 10 adolescent patients before and after distal movement. Distal movement of the canines was carried out by use of a calibrated sectional archwire exerting an initial retraction force of 200 g. Tooth mobility was measured immediately before and after canine retraction by use of a noncontact displacement sensor when varying distal forces of 0 to 500 g were applied to the mesial of the canine. Before tooth movement, tooth mobility exhibited a substantial increase in loading with forces ranging from 50 to 150 g. The rate of increase gradually decreased up to 500 g. A nonlinear change in tooth mobility was similarly observed at the end of tooth movement or 24 days after the initiation of movement. Tooth mobility, however, was significantly greater when forces above 200 g were loaded. The periodontal tissues--the PDL and alveolar bone in particular--become more flexible at the end of tooth movement, indicating reduced support by the periodontal tissues. These findings suggest that the elastic nature of the PDL and alveolar bone may decrease substantially at the end of tooth movement.

Adolescent↗
PubMed1995

Location of the centre of resistance for the nasomaxillary complex studied in a three-dimensional finite element model.

The purpose of this study was to investigate the location of the centre of resistance (CRe) for the nasomaxillary complex by the use of finite element analysis. A three-dimensional finite element model of the craniofacial complex, consisting of 2918 nodes and 1776 elements, was used for displacement analyses. Anteriorly and inferiorly directed forces of 9.8 N were applied at five different levels, parallel and perpendicular to the functional occlusal plane, respectively. For each loading condition, horizontal and vertical displacements of eight anatomic points in the complex and on the maxillary dentition were analysed. The complex exhibited an almost translatory displacement of approximately 1.0 microns in the forward direction when the horizontal force was applied at a point on the horizontal plane, passing through the superior ridge of the pterygomaxillary fissure, whereas the complex experienced clockwise or counter clockwise rotation when the forces were applied at the remaining levels. Furthermore, the downward forces produced anteriorly upward, or posteriorly upward rotation. However, the force applied at a point on the vertical plane passing through the posterior wall of the pterygomaxillary fissure, produced almost equal displacements of approximately 6.0 microns in an inferior direction for all the anatomic points. It is suggested that CRe of the nasomaxillary complex is located on the posterosuperior ridge of the pterygomaxillary fissure, registered on the median sagittal plane.

Biomechanical Phenomena↗
PubMed1995

Stress distributions in the TMJ during clenching in patients with vertical discrepancies of the craniofacial complex.

This study was designed to investigate stresses in the TMJ during clenching in patients with skeletal discrepancies in the vertical direction. A three-dimensional model of the mandible including the TMJ was used for finite element analysis for the stresses. The model, referred to as a standard model, consists of 2,088 nodes and 1,105 solid elements, comprising the cortical and cancellous bones, articular disc and cartilage layer, and periodontal ligament. The standard model was modified by varying the gonial and mandibular plane angles to simulate vertical discrepancies between the maxilla and mandible observed in open and deep bites. Stresses were analyzed on the surfaces of the condyle, the glenoid fossa, and the articular disc, and the values were compared to those found with the standard model. Stresses increased substantially for the condyle, the glenoid fossa, and the articular disc with greater gonial and mandibular plane angles, and those changes were more obvious in association with the divergent mandibular plane. Thus, the nature of stress distributions in the TMJ was substantially affected by vertical discrepancies of the craniofacial skeleton. It is also suggested that these changes in stresses produce a lack of biomechanical equilibrium in the TMJ, which may have some association with temporomandibular disorders.

Cartilage, Articular↗
PubMed1995

Malignant transformation of leukoplakia three times in period of 11-years--case report.

Leukoplakia is a commonly occurring precancerous lesion. The following case report describes a patient who had multiple leukoplakia in this mouth. He had three sites of leukoplakia, the left hard palate, the gum of the right maxilla and the gum of the left mandible, all of which underwent malignant transformation during the period of 11-years after diagnosis.

Adult↗
PubMed1995

Effects of salvia miltiorrhiza bunge (SMB) on MC3T3-E1 cells.

In previous research, we found that the Salvia Miltiorrhiza Bunge (SMB), a traditional Chinese medicinal herb, accelerates orthodontic tooth movement. In the present study, to characterize the actions of SMB on bone remodeling, we investigated the effect of SMB on DNA synthesis and alkaline phosphatase activity of murine osteoblast like cell-clone, MC3T3-E1 cells in vitro. Treatment of the cells with SMB for 72 hours caused significant increase in ALPase activity. It was found that SMB increased ALPase activity in a dose-dependent manner, and up to maximum at the concentration of 5.0 mg/ml. At that concentration, ALPase activity was about 135% greater than that of control. SMB at 5.0 mg/ml significantly stimulated ALPase activity of the cells in multilayer on day 8 or calcification stage on day 16, but inhibited it in the sparse stage on day 2 or subconfluency stage on day 4. SMB had no effect on DNA synthesis in any stage of culture. ALPase activity significantly increased at 48 hours and was up to 300% greater than that of control activity at 96 hours. These findings suggest that SMB directly stimulates ALPase activity of MC3T3-E1 cells in multilayer stage or calcification stage without any effect on proliferation. Locally administrated SMB may affect the differentiation of osteoblasts in vivo.

3T3 Cells↗
PubMed1995

A method of three-dimensional measurement and evaluation of external nasal forms.

An accurate, quantitative method of measuring external nasal forms was described to evaluate the results of rhinoplasty, in which facial plaster models were measured with a highly accurate contact-type three-dimensional coordinate measurement apparatus. Furthermore, two original programs to identify facial landmarks objectively and to measure the curved surface of the external nasal form in order to evaluate cleft lip nasal deformities were described. These provided accurate and objective data for the facial landmarks and the curvature of nasal alae.

Anatomy, Cross-Sectional↗
PubMed1994

A three-dimensional finite element model of the mandible including the TMJ and its application to stress analysis in the TMJ during clenching.

The purpose of this study was to develop a three-dimensional finite element model of the mandible including the temporomandibular joint (TMJ) and further to investigate stress distributions in the TMJ during clenching. The model consisted of 2088 nodes and 1105 elements, comprising cortical and cancellous bones, articular disc, articular cartilage layer and periodontal ligament. For loading condition, a resultant force of 500 N derived from the cross-sectional areas of the muscles was applied to the model. Compressive stresses were induced in the anterior, middle and lateral areas of the TMJ during clenching, whereas the tensile stresses were induced in the posterior and medial areas. The mean principal stresses on the surface of condyle were -1.642, -0.543, 0.664, -1.017, 0.521 MPa in the anterior, middle, posterior, lateral and medial areas, respectively. The mean stresses on the surface of glenoid fossa were approximately 1/5 to 4/5 those on the surface of condyle, although the patterns of stress distributions were almost similar. In both the articular disc and cartilage layer, the stress distributions were very approximate in qualitative and quantitative aspects. Thus, it is shown that stresses during clenching vary substantially in different structures and areas of the TMJ and that the stresses are reduced by the articular disc and cartilage layer in comparison with actual biting forces exerted by the masticatory muscles, if anatomic relation between various TMJ components is well maintained.

Biomechanical Phenomena↗
PubMed1994

Frictional forces and surface topography of a new ceramic bracket.

The present study was designed to measure the frictional forces between orthodontic wires and a new ceramic bracket and to investigate the differences in the frictional forces with the new and two previously available ceramic brackets. Frictional forces were measured during the sliding of 0.016 x 0.022-inch and 0.017 x 0.022-inch cobalt-chromium alloy wire through three brackets bonded to a simulated tooth. The wires were not ligated into the brackets, so as to eliminate the influences of ligation on the bracket-wire friction. Further, slot surfaces of the three brackets were examined by scanning electron microscope (SEM). The magnitude of frictional forces produced by the new ceramic bracket was significantly less for both the wires than that produced by the two ceramic brackets at 1% level of confidence. The frictional forces with all the brackets exhibited a slight increase as the wire size became larger. The magnitude of frictional forces decreased substantially as the retraction point shifted more cervically. Slot surfaces of the new ceramic bracket were substantially smoother than those surfaces of the two other ceramic brackets. It is shown that refinements of slot surfaces of the ceramic bracket may be effective to reduce friction, although the bracket-wire frictions in this in vitro study were somewhat underestimated because of the lack of ligation of the wire into the bracket.

Aluminum Oxide↗
PubMed1994

Orthodontic forces exerted by activators with varying construction bite heights.

The present study was conducted to investigate the nature of forces induced with activators by measuring strains, electromyogram (EMG) and electroencephalogram (EEG) during a 2-hour sleep period. Fifteen adolescent patients with Class II and Class III malocclusions, (30 subjects) were used. Four types of activators were made for each patient with construction bites taken at incisal edge clearances of 2, 4, 6, and 8 mm vertically. The magnitude of forces generated by passive tension of soft tissues increased significantly (p < 0.01) from approximately 80 to 160 gf in the Class II group and from approximately 130 to 200 gf in the Class III group with varying construction bite heights from 2 to 8 mm. Higher construction bites also significantly changed (p < 0.01) the direction of forces by passive tension from vertical to posterior and from vertical to anterior in relation to the reference plane in the Class II and Class III groups, respectively. Duration of forces generated by passive tension was most significantly longer than that of active contraction of the jaw closing muscles, irrespective of the construction bite heights. It is concluded that passive tension, derived from viscoelasticity of soft tissues, plays a more important role in inducing changes that phasic stretch reflex during jaw orthopedic therapy with activators.

Activator Appliances↗
PubMed1994

The prevalence of cardinal TMJ dysfunction symptoms and its relationship to occlusal factors in Japanese female adolescents.

Cross-sectional data were obtained from 1182 Japanese high school girls of 12 and 15 years old. The data were analysed for the prevalence of specific occlusal features and the prevalence of cardinal Temporomandibular Joint Dysfunction (TMJD) symptoms in different occlusion groups. The associations between occlusal features and TMJD symptoms were analysed by the Z-analysis. The results were as follows: the prevalence of TMJD symptoms (total) was about 23% in both age groups examined. Noise had the highest prevalence of the specific TMJD symptoms in both age groups (16% and 11%). With age and for different occlusion groups, there was a significant increase in deviation on opening (P < 0.001) and a decrease in pain and noise (P < 0.05). No significant associations were found between the occurrence of TMJD symptoms (total) and occlusal features in all the examined occlusion groups. With respect to specific TMJD symptoms, however, the investigation of the different groups revealed a significant association (P < 0.05) of intra-arch occlusal (crowding) features with the occurrence of deviation on opening and with the occurrence of the combined TMJD symptoms which include deviation on opening. This indicates that crowding may be an important sign for predisposing TMJD. For the other single disorder symptoms (except pain), we did not find a significant relationship (P < 0.05) with aspects of occlusion, which may confirm a multifactorial TMJD problem wherein occlusal features can have a contribution to TMJD.

Adolescent↗
PubMed1994

Adenoid cystic carcinoma with morphological diversities--report of a case and discussion of the morphologic and immunohistochemical features.

A case of adenoid cystic carcinoma (ACC) with polymorphous features and an unknown differential diagnosis was presented. It appeared, without any pain, in the right maxillary sinus of a 47 year-old man. A variety of histopathological patterns were found, including glandular, cribriform, tubular and solid ones. However, the typical features of ACC, such as cribriform pattern associated with pseudocyst and tubular formations were rather scarce. A single cell strand appearance, so-called "Indian file arrangement", and papillary cystic formation were also noted, which are often associated with polymorphous low-grade adenocarcinoma (PLGA). Immunohistochemistries of EMA, CEA and musclespecific actin showed also similar staining patterns to those of PLGA in some areas. Our case could not be regarded as PLGA; but this case with features of PLGA as well as those of ACC might suggest an entity of transitional type between ACC and PLGA.

Adenocarcinoma↗
PubMed1993

Effect of prolonged administration of clonidine on [3H]PN 200-110 and [125I]omega-conotoxin binding in mouse brain.

The effect of chronic exposure to clonidine or morphine on clonidine- and morphine-induced analgesia in mice was examined. Binding of L- or N-type calcium channel antagonist to cortical membrane fractions was also compared between these groups of mice. A decrease in the analgesic effect of clonidine and morphine was observed following prolonged administration of clonidine or morphine. Binding of [3H]PN 200-110, an L-type calcium channel antagonist, decreased following prolonged administration of clonidine whereas it increased after morphine treatment. On the other hand, a significant increase of [125I]omega-conotoxin, an N-type calcium channel antagonist, binding was observed after chronic clonidine or morphine treatment. These results will be discussed in relation with the possible development of cross-tolerance between clonidine and morphine through the change in calcium channels, more specifically in N-type channels.

Animals↗
PubMed1993

Suppression of tumorigenicity in temperature-sensitive mutants of embryonal carcinoma cells by induction of cell differentiation at non-permissive temperature.

The temperature-sensitive (ts) mutants of cell differentiation derived from the mouse teratocarcinoma cell line F9, when exposed to non-permissive temperature, undergo stem-cell differentiation concomitant with a transient retardation of cell-cycle progression. By incubating these mutant strains at non-permissive temperature, we were able to study the relationship between cell differentiation and tumorigenicity. Upon exposure to non-permissive temperature, the mutant cells undergo extensive differentiation and lose their ability to initiate tumors in vivo, but retain their in vitro proliferative potential. Our data suggest that the loss of tumorigenicity is not caused by altered proliferative potential, but rather by cell differentiation. We therefore suggest that the loss of proliferative potential and the onset of cell differentiation in teratocarcinoma F9 cells are 2 independent events which can be genetically dissected, and that there is (a) crucial step(s) in the differentiation pathway at which these ts mutant cells lose their tumorigenicity.

Alkaline Phosphatase↗