Biomedical subjects

Shinya Yano

Publications and source records attributed to Shinya Yano.

4 recordsLinked to original sources

PubMed2006

Tapered orthodontic miniscrews induce bone-screw cohesion following immediate loading.

The aim of this study was to investigate the initial stability of tapered orthodontic miniscrews (T-type screws) after placement, the necessity of a healing period, and the propriety of immediate loading. Twenty male Wistar rats with a mean age of 20 weeks were divided into two groups. In the immediate-loading groups, straight orthodontic miniscrews (S-type screws) and T-type screws (five rats each) underwent experimental traction force for 2 weeks (W) immediately after placement. In the healing groups (S- and T-type, five rats each), force was applied for 2 W after a 6-W healing period. The right tibia in each rat was identified as the test limb, while the left tibia in each rat was used as the control group, and underwent no experimental force during the experimental period. The screw-to-bone contact was observed histologically and the bone-screw contact ratio was calculated. Scheffe's test was performed to compare the bone-screw contact ratio in each group using statistical software package (SPSS 8.0 for Windows). In the control group, the bone-screw contact ratio improved from 34.8 +/- 16.0 to 74.8 +/- 12.0 per cent with S-type screws in proportion to the experimental period (2 to 8 W, respectively). With the T-type screws in the test group, there was no significant difference between the immediate-loading and healing groups. In the immediate-loading group, the bone-screw contact ratio with T-type screws was significantly greater (82.3 +/- 15.0 per cent) than with the S-type screws (33.3 +/- 11.8 per cent; P < 0.05), suggesting that T-type screws can be used for orthodontic anchorage immediately after placement.

Animals↗

PubMed2005

Permissible limit for mandibular expansion.

In recent years, mandibular expansion has been increasingly performed in conjunction with orthodontic treatment. Lateral tipping of the molars associated with mandibular expansion should, however, be considered, because excessive expansion may result in excessive buccal tooth inclination, which may disturb the occlusal relationship. This study was conducted to quantitatively clarify molar movement during mandibular expansion using the Schwarz appliance to determine the permissible limit of mandibular expansion as a clinical index for inclination movement. Inclinations in the masticatory surface of the first molar and intermolar width were measured before expansion (T1), after expansion (T2), and before edgewise treatment (T3). Lower plaster models from 29 subjects treated with expansion plates were used and compared with models from 11 control subjects with normal occlusion. The average treatment change (T1-T2) in intermolar width was 5.42 mm (standard deviation 1.98), and the average angle of buccal tooth inclination was 10.16 degrees (standard deviation 3.83). No significant correlation was found between age prior to treatment and the treatment period when they were compared with the intermolar width increments and inclination angles. There was a significant positive correlation between retention duration and the amount of expansion. The regression coefficient of the angle of buccal tooth inclination during expansion to the increment of the intermolar width was approximately 0.2. This means that 1 mm of expansion is accompanied by 5 degrees of molar lateral tipping. This coefficient is clinically useful for estimating the permissible limit for mandibular expansion.

Analysis of Variance↗

PubMed2005

Biomechanical effect of abutment on stability of orthodontic mini-implant. A finite element analysis.

The biomechanical influences of primary factors on titanium mini-implant, which is used as an anchorage for orthodontic tooth movement, were quantified using the three-dimensional finite element method. Six types of finite element models were designed to show various thread pitches from 0.5 to 1.5 mm. Three models were designed with abutment and three other models without abutment. A traction force of 2 N was applied to the head of the mini-implant or abutment to be at 45 degrees to the bone surface. No remarkable differences were observed in the stress distribution patterns regardless of thread pitch variance. However, the stress distribution was remarkably different between models with abutment and without abutment. The maximum stress of the model with abutment and thread pitch 0.5 mm was the least as compared with the other models. Areas of high-level stress were obviously smaller than in the models without abutment. The plots of the displacement distributions of the models with abutment also presented significant pattern differences as compared with the models without abutment. The high-level area was localized to the head of the implant and the abutment in models with abutment. Therefore, the existence of the abutment is significantly useful in decreasing the stress concentration on the bone, while the effect of thread pitch was uncertain.

Biomechanical Phenomena↗

PubMed2002

Comparative studies of a humanized anti-glycoprotein IIb/IIIa monoclonal antibody, YM337, and abciximab on in vitro antiplatelet effect and binding properties.

The effects of YM337, the Fab fragment of a humanized anti-glycoprotein IIb/IIIa (GPIIb/IIIa) monoclonal antibody C4G1, on in vitro platelet function and binding properties were compared with those of abciximab, the Fab fragment of the human/murine chimeric anti-GPIIb/IIIa monoclonal antibody 7E3. Both agents completely inhibited platelet aggregation caused by all agonists tested except ristocetin. Further, both inhibited human platelet adhesion to von Willebrand factor, fibrinogen, fibronectin and subendothelial matrix with similar potency. Fibrinogen binding to washed platelets was dose-dependently inhibited by both agents. In binding assay using 125I-YM337 and 125I-abciximab, Kd values determined with platelet-rich plasma were 6.74 +/- 0.56 nM for YM337 and 6.65 +/- 1.45 nM for abciximab, and the number of binding sites were 42,700 +/- 3,000 for YM337 and 76,000 +/- 5,400 for abciximab. GPIIb/IIIa was precipitated from the solubilized fraction of platelets by both agents. In contrast, integrin alphavbeta3 was precipitated from the solubilized fraction of human umbilical vein endothelial cells by abciximab but not by YM337. Fibrinogen binding to purified GPIIb/IIIa was dose-dependently inhibited by both agents. In contrast, vitronectin binding to purified integrin alphavbeta3 was dose-dependently inhibited by abciximab but not by YM337, supporting the idea that abciximab reacts to integrin alphavbeta3. Therefore, YM337 was suggested to bind to a different epitope of GPIIb/IIIa from abciximab. These results suggest that YM337 specifically acts on platelet GPIIb/IIIa receptors and has similar inhibitory properties on platelet aggregation and platelet adhesion to abciximab.

Abciximab↗