The Journal of Osaka University Dental School最新文献

Carbonic anhydrase (CA) was localized in osteoclasts of rat tibial metaphysis by light and electron microscopy using the histochemical method of Hansson. Ultrastructurally, positive staining was seen in the cytosol, mitochondrial cristae, Golgi apparatus, some nuclei and lysosomelike vesicles, and on the bone surface beneath the osteoclast. The presence of the enzyme within the Golgi ++apparatus, lysosomelike vesicles, and on the bone surface beneath the osteoclast suggests that some CA may be secreted into the resorbing zone. According to literature, the above localization of CA suggests that there may be three isozymes of CA in the rat osteoclast. These are ubiquitous cytosolic CA (CA-II), mitochondrial CA (CA-V) and secretory CA (CA-VI).

Three types of fluoridated hydroxyapatites were synthesized in the presence of low concentrations of gelatin solution. The crystallinity of gelatin-free fluoridated hydroxyapatites increased at high degree of fluoridation, after it showed complex behavior at lower fluoride content. However, increasing of gelatin concentration in the solution, the crystallinity decreased, especially at high fluoride content. Chemical analysis and a- and c-axis dimensions showed no significant difference among those series, and gelatin contents in the precipitates were negligible when compared with the supplied amounts. These results suggest that gelatin may inhibit the crystal growth of fluoridated apatites only as a surrounding factor, overcoming the promoting action of fluoride.

The purpose of the present study was to elucidate the nature of stress distributions in the PDL varied by different root lengths and alveolar bone heights. A three-dimensional model of the upper central incisor was constructed for the finite element method (FEM). The model was modified to produce various root lengths and alveolar bone heights. A lingually directed 100 g horizontal force was applied at a point on the labial crown surface. Stress distributions were determined in the center of the PDL for various apicogingival levels. Stress levels in the PDL gradually decreased with a longer root. Rates of changes in stress levels to those with an original root length were approximately 1.5 at maximum and 0.8 at minimum. Patterns of stress distributions were varied by different alveolar bone heights in both the qualitative and quantitative aspects; i.e., apicogingival level of stress transition shifted more apical, and stress levels also increased following a reduction of the alveolar bone in the apicogingival direction, approaching about eight times with a half alveolar bone height as the original. It is found that the root length and alveolar bone height affect stress distributions in the PDL. Thus, it is shown that an orthodontic force application should be determined on the basis of anatomical variations in root length and alveolar bone height to induce an optimal stress level in the PDL, which is a key to desirable tooth movement.

The purpose of this study was to investigate the relationship between jaw-opening muscle activity and craniofacial morphology in a sample of 64 adults with skeletal Class I malocclusions. EMG recordings from the inferior head of the right lateral pterygoid and the anterior belly of the right digastric muscle were analyzed together with mandibular displacement data sampled simultaneously with a kinesiograph. Incisor separation at the rest position and the threshold mandibular rotation position which corresponded to the onset of muscle activity in response to a graduated mandibular rotation were identified. Incisor separation was converted to a mandibular angle on lateral cephalograms. Anatomic points were digitized and sixteen traditional cephalometric variables were determined. The rest position angle did not correlate with the threshold angle for the anterior belly of the digastric muscle, but a significant correlation was identified with the inferior head of the lateral pterygoid muscle. One canonical correlation (r = 0.741; p less than 0.01) was identified between the mandibular rotation and dentoskeletal variables. Negative loadings with lateral pterygoid muscle threshold and rest position angles were obtained. The corresponding dentoskeletal variables had a positive loading with mandibular plane angle, total and lower anterior face height and gonial angle and a negative loading with lower posterior face height. The results suggest a possible relationship between lateral pterygoid muscle activity at two specific mandibular positions and the resultant form and posture of the mandible.

The accuracy of the three dimensional shape measurement of teeth was improved. The system was composed of a laser displacement meter and a computer controlled scanning machine. The compensation of errors which were observed when the reflected beam was shaded by the model teeth itself was attempted by connecting the data which were measured by rotating the model tooth at 180 degrees on the going stage. The accuracy of measurement was examined at the slope of 7 crown abutment tooth. When the model tooth were measured without tilting, the difference between the true value and the measured data was -240 microns (-2.8%). However, by tilting the model tooth at +/- 20 degrees on the going stage and connecting the two couples of data obtained, the difference considerably decreased into +/- 10 microns (+0.1%). In order to measure a complete crown abutment tooth with high accuracy and without error at the shaded portion, the model tooth was tilted +/- 30 degrees and rotated 180 degrees on the going stage and measured divisionally at four regions. The four partial data thus obtained were combined by using the software program. By the present procedure, the margin of the abutment tooth was recognized and the error data were eliminated. The overlapped data upon divisional measurements were excluded and the complete data of the single abutment tooth were saved into a file. They are possible to be the basic data for the future production of prostheses by means of CAM technique.