Multifunctional flexible magnetic drive gripper for target manipulation in complex constrained environments.

Soft actuators capable of remote-controlled guidance and manipulation within complex constrained spaces hold great promise in various fields, especially in medical fields such as minimally invasive surgery. However, most current magnetic drive soft actuators only have the functions of position control and guidance, and it is still challenging to achieve more flexible operations on different targets within constrained spaces. Herein, we propose a multifunctional flexible magnetic drive gripper that can be steered within complex constrained spaces and operate on targets of various shapes. On the one hand, changing the internal pressure of the magnetic gripper can achieve functions such as suction or injection of liquid and transportation of targets with smooth surfaces. On the other hand, with the help of slit structures in the constrained environment, by simply changing the position and orientation of the permanent magnet in the external environment, the magnetic gripper can be controlled to clamp and release targets of linear, flaked, and polyhedral shapes. The full flexibility and multifunctionality of the magnetic gripper suggest new possibilities for precise remote control and object transportation in constrained spaces, so it could serve as a direct contact operation tool for hazardous drugs in enclosed spaces or a surgical tool in human body cavities.

Spider Web-Inspired Lightweight Membrane-Type Acoustic Metamaterials for Broadband Low-Frequency Sound Isolation.

Membrane-type acoustic metamaterial (MAM) has exhibited superior sound isolation properties, as well as thin and light characteristics. However, the anti-resonance modes of traditional MAMs are generated intermittently in a wide frequency range causing discontinuities in the anti-resonance modes. Achieving broadband low-frequency sound attenuation with lightweight MAM design is still a pivotal research aspect. Here, we present a strategy to realize wide sound-attenuation bands in low frequency range by introducing the design concept of bionic configuration philosophy into the MAM structures. Built by a polymeric membrane and a set of resonators, two kinds of MAM models are proposed based on the insight of a spider web topology. The sound attenuation performance and physical mechanisms are numerically and experimentally investigated. Multi-state anti-resonance modes, induced by the coupling of the bio-inspired arrangement and the host polymer film, are systematically explored. Significant sound attenuation is numerically and experimentally observed in both the lightweight bio-inspired designs. Remarkably, compared with a traditional MAM configuration, a prominent enhancement in both attenuation bandwidth and weight-reduction performance is verified. In particular, the bio-inspired MAM Model I exhibits a similar isolation performance as the reference model, but the weight is reduced by nearly half. The bio-inspired Model II broadens the sound attenuation bandwidth greatly; meanwhile, it retains a lighter weight design. The proposed bio-inspired strategies provide potential ways for designing sound isolation devices with both high functional and lightweight performance.

Flexible Microswimmer Manipulation in Multiple Microfluidic Systems Utilizing Thermal Buoyancy-Capillary Convection.

Flexible and accurate control of microswimmers is significant for lots of applications. Herein, we present a method for effective microswimmer manipulation in multiple microfluidic systems by thermal buoyancy-capillary convection. In the microdevice, four strips of microheaters arranged at the bottom of the microchannel are used to unevenly heat microfluids, and the convection flow forms under the influence of gravity and interfacial tension gradient. By adjusting the DC signals applied on these four heating elements, the intensity and direction of convection flow can be flexibly adjusted. Accordingly, granular samples dispersed in liquid buffer can be controllably driven to the target position by the Stokes drag. The swimming behavior of polystyrene (PS) microspheres at the solid-liquid interface of the device is first investigated. It shows that the PS microswimmers can migrate along various geometrical patterns by powering the microheaters with designed voltage combinations, and the migration velocity is positively affected by the increased voltage. Then, the butyl acrylate (BA) microswimmers are manipulated at the gas-liquid interface of the microchip. It turns out that the BA microswimmers migrate oppositely compared with PS swimmers under the same energization strategy. Additionally, the translation direction of BA swimmers can be changed over a 360° range by different voltage combinations. The multifunctionality of our approach is further demonstrated by conveniently driving the trimethylolpropane triacrylate microswimmers at the liquid-liquid interface of the microplatform along different directions and pathlines. Therefore, this technique can be promising for many cases needing granular sample control, such as cargo delivery and sensing.

The long-non-coding RNA NEAT1 is a novel target for Alzheimer's disease progression via miR-124/BACE1 axis.

OBJECTIVES: Long-non-coding RNAs (lncRNAs) have been involved in central nervous system recently. A number of studies have reported that lncRNA NEAT1 exerts critical roles in neurodegenerative disorder. Beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) has been reported to exert function in the accumulation of amyloid-ß (Aß). Moreover, BACE1 acts as a target of miR-124 in the progression of AD. So far, the biological role and underlying mechanisms of NEAT1 and miR-124 in AD remains elusive. METHODS: The relative NEAT1 and miR-124 expression was examined by qRT-PCR in the tissues and cells line of AD. Cell apoptosis was examined by FACS. Luciferase reporter assay was performed to verify that miR-124 is a direct target of NEAT1, and BACE1 is a downstream target of miR-124. qRT-PCR and western blot analysis were also performed to determinate the BACE1 and the phosphorylation of tau protein. RESULTS: NEAT1 was notably up-regulated and miR-124 was remarkably down-regulated in AD mouse model. Knockdown of NEAT1 or overexpression of miR-124 showed the protective effects on cellular AD model induced by Aß. Moreover, miR-124 expression could be up- and down-regulated by suppression or overexpression of NEAT1, respectively. In addition, the expression of BACE1 was the potential functional target of miR-124. These findings suggested that NEAT1 might play a vital role in the development of AD by regulating miR-124/BACE1 axis. DISCUSSION: The present study showed that NEAT1 worked as a regulating factor to promote the development of AD via modulating miR-124/BACE1 axis, which might be considered as a novel target in AD treatment.

Comparison of convective heat transfer for Kagome and tetrahedral truss-cored lattice sandwich panels.

The aim of this paper is to make a thorough comparison between Kagome and tetrahedral truss-cored lattices both experimentally and numerically. Two titanium sandwich panels -one cored with the Kagome lattice and the other with the tetrahedral lattice -are manufactured by 3D printing technology. Comparisons of the thermal insulation, the inner flow pattern and the heat transfer between the two sandwich panels are completed subsequently according to the results from forced convective experiments and numerical simulation. Within the Reynolds number range of interest for this study, the Kagome lattice exhibits excellent heat dissipation compared with the tetrahedral lattice. In particular, when the cooling air flows in the direction OB of the two sandwich panels, the Kagome lattice provides an 8~37% higher overall Nusselt number for the sandwich panel compared to the tetrahedral lattice. The superiority of the Kagome lattice comes from a unique configuration in which the centre vertex acting as the vortex generator not only disturbs the primary flow but also induces more serious flow stagnation and separation. The complex fluid flow behaviours enhance heat transfer on both the endwalls and the trusses while causing a pressure drop that is almost two times higher than that of the tetrahedral lattice in the flow direction OB.

Micromechanical Modeling of Fiber-Reinforced Composites with Statistically Equivalent Random Fiber Distribution.

Modeling the random fiber distribution of a fiber-reinforced composite is of great importance for studying the progressive failure behavior of the material on the micro scale. In this paper, we develop a new algorithm for generating random representative volume elements (RVEs) with statistical equivalent fiber distribution against the actual material microstructure. The realistic statistical data is utilized as inputs of the new method, which is archived through implementation of the probability equations. Extensive statistical analysis is conducted to examine the capability of the proposed method and to compare it with existing methods. It is found that the proposed method presents a good match with experimental results in all aspects including the nearest neighbor distance, nearest neighbor orientation, Ripley's K function, and the radial distribution function. Finite element analysis is presented to predict the effective elastic properties of a carbon/epoxy composite, to validate the generated random representative volume elements, and to provide insights of the effect of fiber distribution on the elastic properties. The present algorithm is shown to be highly accurate and can be used to generate statistically equivalent RVEs for not only fiber-reinforced composites but also other materials such as foam materials and particle-reinforced composites.

Effect of lysosomal and ubiquitin-proteasome system dysfunction on the abnormal aggregation of α-synuclein in PC12 cells.

The aim of this study was to investigate the effect of lysosomal and ubiquitin-proteasome system dysfunction on the abnormal aggregation of α-synuclein, and to analyze its role in the pathogenesis of Parkinson's disease (PD). PC12 cells subjected to nerve growth factor-induced differentiation were used as the cell model to study the dopaminergic neurons, and the lysosomal and proteasomal inhibitors trans-epoxysuccinyl-L-leucylamido-(4-guanidino) butane (E64) and, respectively, were used exclusively and in combination to treat the PC12 cells. The viability and metabolic state of the cells was assessed using the MTT assay; flow cytometry was used to measure the rate of cell apoptosis; and the double immunofluorescence method was applied to observe the formation of thioflavin S- and α-synuclein protein-positive aggregates and inclusion bodies in the PC12 cells. In addition, the Hoechst 33258 staining method was used to observe the apoptosis of the α-synuclein protein and thioflavin-S double-labeled cells. Following the administration of the lysosomal and proteasomal pathway inhibitors, the cell viability decreased in a concentration-dependent manner and the cell apoptosis rate increased. The proportion of PC12 cells with α-synuclein protein-positive aggregates and inclusion bodies in the E64 group was 7.94%, compared with 20.33 and 36.77% in the lactacystin and combination treatment groups, respectively. Statistical analysis indicated that the number of inclusion body-positive cells in the treatment groups was significantly higher than that in the control group (3.78%) (P<0.05). Apoptosis was evident in the double-positive cells with α-synuclein protein-positive inclusion bodies (17.29±1.54%). In conclusion, lysosomal and proteasomal dysfunction may play an important role in the pathogenesis of PD through the induction of abnormal α-synuclein protein aggregation in dopaminergic neurons.

[Cephalometric analysis of the relationship between occlusal plane and sagittal position of the mandible].

OBJECTIVE: To investigate the relationship between occlusal plane and sagittal position of the mandible by examining dental and skeletal morphologies of average angle patients for better understanding of etiologies and definitive clinical guidelines of mandibular malpositions. METHODS: The lateral cephalograms of 114 female average angle patients with neutral maxillary positions were selected and divided into three groups according to sagittal mandibular positions (ANB angle). Twenty-five skeletal and dental measurements were compared. The correlations between skeletal and dental measurements were analyzed by rectilinear correlation. RESULTS: Cant of posterior occlusal plane (OP-P) and height of the upper second molar were significantly related to sagittal position of the mandible (P < 0.05). Height of the upper second molar was relatively inadequate and OP-P was sloped when the mandible was positioned posteriorly; conversely, height of the upper second molar was excessive and OP-P tended to be flat when the mandible was positioned anteriorly. Tooth axial inclinations were affected by sagittal position of the mandible. Maxillary teeth proclined distally and mandibular ones mesially for patients with retrognathia. On the other hand, maxillary teeth proclined mesially while mandibular ones distally for patients with prognathia. CONCLUSION: There was a definite relationship between cant of posterior occlusal plane and sagittal position of the mandible in average angle patients, consistent with the dental morphologies of different skeletal configurations. In treating malocclusions of sagittal discrepancy of mandible, the height of posterior teeth and cant of OP-P might be a primary concern.

[Differences in maxillary growth vector of skeletal class I with various vertical growth types before and after growth spurts].

OBJECTIVE: To identify the differences in maxillary growth vector with different vertical skeletal patterns of skeletal class I before and after growth spurts. METHODS: One hundred and ninety four cases with different vertical skeletal patterns of skeletal class I were selected and categorized into six groups according to their vertical skeletal patterns and cervical vertebral stages: cervical vertebral maturation stage (CVMS)1,2-horizontal pattern (n=30); CVMS1,2-average pattern (n=32); CVMS1, 2-vertical pattern (n=33); CVMS5, 6-horizontal pattern (n=34); CVMS5, 6-average pattern (n=29); and CVMS5, 6-vertical pattern (n=36). Lateral cephalograms were taken on all of the cases. The angle SN-C axis (theta) and angel PP-C axis (alpha) were measured. RESULTS: (1) The skeletal class I with a vertical growth pattern had larger angle SN-C axis than those with a horizontal or average growth pattern before growth spurts (P(average-vertical) < 0.05, P(horizontal-vertical) < 0.001). (2) The skeletal class I with a vertical growth pattern had the largest angle SN-C axis after growth spurts, followed by those with an average growth pattern. Those with a horizontal growth pattern had the smallest angle SN-C axis. The differences were statistically significant (P(horizontal-average) < 0.05, P(horizontal-vertical) < 0.001, P(average-vertical) < 0.001). (3) The skeletal class I with the same vertical growth pattern had slightly larger angle SN-C axis after growth spurts than before growth spurts, but without statistical significance. (4) The skeletal class I had relatively stable angle PP-C axis and no significant differences were found before and after growth spurts or among those with various vertical skeletal facial types. CONCLUSION: The magnitude of angle SN-C axis is closely associated with vertical growth patterns and is weakly influenced by maxillofacial growth and development.

[Study on the posterior teeth mesiodistal tipping degree of normal occlusion subjects among different facial growth patterns].

OBJECTIVE: To study the relationship between the mesiodistal tipping degree of maxillary and mandible posterior teeth and different vertical facial skeletal types of subjects with normal occlusion. METHODS: 163 subjects with normal occlusion were selected, lateral cephalograms were taken and divided into three different facial skeletal types. The difference of the mesiodistal tipping degrees and intersection angles of upper and lower posterior teeth between the three different facial skeletal types were analyzed. RESULTS: Among 163 subjects, vertical growth pattern, average growth pattern and horizontal growth pattern were 24, 96 and 43 respectively. There were statistic differences of mesiodistal tipping degrees of the first and second maxillary and mandible premolar and the first permanent molar between vertical growth and horizontal growth pattern, horizontal growth and average growth pattern (P < 0.05). But there were no statistically significant differences between vertical growth and average growth pattern (P > 0.05). The differences of the maxillary and mandible posterior teeth's intersection angle among three vertical facial skeletal types had no statistic significance (P > 0.05). CONCLUSION: Different vertical facial skeletal type has its own normal and coordinated posterior teeth mesiodistal tipping degrees.

[Morphological characteristics of mandibular symphysis in adult skeletal class II and class III malocclusions with abnormal vertical skeletal patterns].

OBJECTIVE: To figure out the differences of the morphological characteristics of mandibular symphysis between Class II and Class III adult skeletal malocclusions with different abnormal vertical skeletal patterns. METHODS: 109 Chinese female adults of skeletal Class II and Class III were chosen and divided into four groups according to vertical and sagittal skeletal pattern: Class II--vertical-growth-pattern group (n=30), Class III--vertical-growth-pattern group (n=25), Class II--horizontal-growth-pattern group (n=29), Class III--horizontal-growth-pattern (n=25). Lateral cephalograms were taken. The symphyseal widths and heights, along with lower incisor positions were evaluated. Observation and statistics analysis were done to clarify the morphological characteristics of the symphyseal region of different skeletal patterns. RESULTS: There were morphological differences of symphyseal region between Class II and Class III skeletal malocclusions, but not significant in width and total height. With a vertical-growth-pattern, Class II malocclusions had higher alveolus than Class III, but smaller chin prominence and lower basal bone (P < 0.01). With a horizontal-growth-pattern, Class II malocclusions had higher alveolus (P < 0.05) and larger alveolar top width (P < 0.001). With a same sagittal skeletal pattern, vertical-growth-pattern group had thinner but higher symphyseal region and bigger chin prominence (P < 0.001 in Class II while P < 0.05 in Class III). Besides, a vertical-growth-pattern malocclusion was prone to have a cucurbit-morph chin, of which Id width was larger than basal width (P < 0.01). CONCLUSION: There are morphological differences in symphyseal region between Class II and Class III skeletal malocclusions with different abnormal vertical skeletal patterns. The influence of abnormal vertical skeletal pattern to symphyseal morphological characteristics is greater than that of abnormal sagittal skeletal pattern. There is a risk of orthodontic movement of low incisors in vertical-growth-pattern skeletal malocclusion.

Static magnetic field combined with functional appliances: a new approach to enhance mandibular growth in Class II malocclusion.

Class II malocclusion is one of the most common orthodontic problems. The main aetiology of Class II malocclusion is mandibular retrognathia. A variety of functional appliances have been used to stimulate mandibular growth in adolescence, however, the effects remain unsatisfactory. Therefore, new approaches are in need to strengthen the effects of functional appliances. Static magnetic field (SMF), created by permanent magnets, has long been proven to be clinically safe and is well accepted as a practical and non-invasive therapy. Numerous experimental and clinical data suggest that exogenous SMF can make profound effects on a large variety of biological systems. There has been increasing interest in curing bone injuries with SMF. More recently, literatures shed light on the chondrogenic and osteogenic effects of SMF. SMF and functional appliances may well have a synergistic effect in mandibular growth promotion. Based on experimental results and theoretical analysis, it is hypothesized that SMF combined with functional appliances can enhance mandibular growth in Class II malocclusion. A practical clinical design is also put forward.

[Clinical characteristics and long-term prognosis of patients with ischemic and hemorrhagic stroke].

OBJECTIVE: To investigate the risk factors, pathogenesis, cause of death, and outcome of different stroke subtypes. METHODS: The relevant data, including demographics, baseline risk factors, cause of death, and 1-year case fatality, were analyzed among 1913 consecutive hospitalized patients with ischemic and hemorrhagic stroke, 599 (31.3%) with intracerebral hemorrhage (ICH) and 1314 with ischemic stroke (68.7%), including 209 cases (15.9%) of total anterior circulation infarction (TACI), 417 cases (31.7%) of partial anterior circulation infarction (PACI), and 186 cases (14.2%) of posterior circulation infarctions (POCI), and 502 cases (38.2%) of lacunar infarctions (LACI), 1098 males and 815 females, aged 64 +/- 13 (14-98). RESULTS: Multivariate analysis showed that when age and sex were adjusted, atrial fibrillation was the independent predictive factor of TACI [odds ratio (OR) = 1.42, 95% CI = 1.25-2.31), hypertension and alcohol intake were the independent predictive factor LACI (OR = 1.24, 95% CI = 1.02-2.18; 0R = 1.12, 95% CI = 1.03-3.04) and ICH (OR = 1.84, 95% CI = 1.31-3.02; OR = 1.04, 95% CI = 1.01-4.13). A negative association was observed between hypertension and TACI (OR = 0.62, 95% CI = 0.34-0.72), atrial fibrillation and LACI (OR = 0.46, 95% CI = 0.26-0.82), and ICH and diabetes (OR = 0.56, 95% CI = 0.42-0.76). As compared to LACI, TACI and ICH significantly increased the risk of 1-year mortality (OR = 6.21, 95% CI = 2.86-8.42; OR = 5.86; 95% CI = 2.46-8.52). CONCLUSIONS: Stroke subtypes have different risk factor profile, causes and outcome. Information on determinants of the clinical syndromes may impact on the prevention and acute phase interventions.

[Cephalometric comparisons of the craniofacial characteristics of Class II 1 malocclusions with different vertical types in adolescences].

PURPOSE: To compare the craniofacial characteristics in Class II(1) malocclusions with different vertical types in adolescence. METHODS: The sample, including 60 males and 60 females, was divided into three groups equally based on their FMA degrees (high-angle group, average-angle group, low-angle group and normal occlusion group). Cephalograms were traced for all the subjects. Data were obtained to perform analysis of variance and LSD multiple range test. RESULTS: 1. The vertical growth of the anterior part of maxilla was greater than the posterior part in the three groups with Class II(1) malocclusion. The vertical dimension of the composite ramus-cranial floor was deficient relative to that of anterior maxilla in the high-angle and average-angle groups, the mandible rotated backward, especially in the high-angle group. In the low-angle group, the vertical dimension of the composite ramus-cranial floor grew excessively relative to that of posterior maxilla. The palatal plane and mandible plane rotated forward and upward. 2. The dentoalveolar characteristics of Class II(1) malocclusion group showed that: U6 tipped distally, the dentoalveolar height of L6 decreased, the functional occlusal plane (FOP) of average-angle group deviated away from the neutral occlusal axis (NOA), and rotated downward. In the high- angle group, the FOP deviated away from the NOA severely. The vertical dentoalveolar heights of U6 were normal. In the low-angle group, the vertical dentoalveolar heights of U6, the dentoalveolar height of L6 decreased, the angle of FOP between NOA showed no significantly difference from normal-occlusion group. CONCLUSION: There were different craniofacial vertical characteristics of Class II(1) malocclusion with different vertical types in adolescences. Different methods should be used to control the vertical dimensions in different types.

Cytogenetic analysis of nasal mucosa cells and lymphocytes from high-level long-term formaldehyde exposed workers and low-level short-term exposed waiters.

The evidence for genotoxic potential of formaldehyde (FA) in humans is insufficient and conflicting. We previously reported a higher frequency of micronuclei in nasal and oral exfoliative cells from students exposed to formaldehyde vapor for short-term. To further evaluate the genetic effects of long-term occupational exposure to FA and short-term exposure to FA of indoor sources, the frequencies of micronuclei (MN) in nasal mucosa cells, sister chromatid exchanges (SCEs) of peripheral lymphocytes, and the lymphocyte subsets were evaluated in 18 non-smoking workers (mean exposure duration was 8.6 years) in an FA factory and 16 non-smoking waiters exposed to FA for 12 weeks in a ballroom. A non-smoking student group without occupational exposure (n=23) to FA was used as control. The 8h time-weighted average (TWA) concentrations of formaldehyde was 0.985+/-0.286 mg/m3 with the ceiling exposure concentration of 1.694 mg/m3 in the workshop, and 0.107+/-0.067 mg/m3 in the ballroom (5 h TWA). Higher frequencies of micronuclei per thousand cells in nasal mucosa cells of workers versus control (2.70+/-1.50 versus 1.25+/-0.65, p<0.05) and higher frequency of SCEs in peripheral lymphocytes of workers group (8.24+/-0.89 versus 6.38+/-0.41, p<0.05) were observed. Increased frequency of micronuclei in nasal mucosa cells or SCE in peripheral lymphocytes was not found among waiters group. The results suggest that the genotoxic potential of high level FA exposure may have occupational risks in long-term exposure groups.

[K-mean cluster analysis for incisal jaw morphology of normal occlusion subjects among different vertical facial skeletal types].

OBJECTIVE: To study the incisal jaw morphology of subjects with normal occlusion and to discuss the relationship between different vertical facial skeletal types and different incisal jaw cluster types. METHODS: After studied by radiographic cephalometry, the incisal jaw morphology of 169 subjects with normal occlusion in early permanent dentition were analyzed by K-mean cluster analysis. RESULTS: Morphology of maxillary or mandibular incisal jaws could be divided into four types separately, including division I, division II, division III and division N. In maxilla or in mandible, the incisal jaw morphology of division I was characterized by wideness and shortness. In contrast, division II was characterized by thinness and length. As for division III and division IV, both of two were intermediate types between division I and division II . In maxilla, it was found that division II was the majority (86.49%) in the high-angle subjects, division III was the majority (47.67%) in the average-angle subjects, and division I and III were the majority (82.61%) in the low-angle subjects. In mandible, it was found that division II was the majority (51.35%) in the high-angle subjects, division IV was the majority (48.84%) in the average-angle subjects, and division III and IV were the majority (69.57%) in the low-angle subjects. CONCLUSION: Owing to the obvious characteristics of morphology in each cluster types and in each vertical facial skeletal types, different clinic considerations must be put forward when we want to move the incisor.

[Cephlometric analysis of the cranial base in class II(1) malocclusions with different vertical types in adolescences].

PURPOSE: To explore the morphology of the cranial base in Class II(1) malocclusions with different vertical types in adolescence. METHODS: The sample of 60 males and 60 females were divided into Class II(1) high-angle group, average-angle group, and low-angle group and normal occlusion group. Each group had 30 cases. Cephalograms were analyzed for all subjects. Data were obtained to have analysis of variance and LSD multiple range test. RESULTS: The cranial floor base angle (Ba-SE-FMS) of three groups with class II(1) malocclusion was increased. The anterior cranial floor angle was more open in the high angle group, and the flexure of the middle cranial floor was increased in the low angle and average angle groups. The 'effective vertical growth' of cranial floor was decreased while the mandibular plane angle was increased. CONCLUSION: The cranial floor base angle(Ba-SE-FMS) was suitable to describe the flexure of the cranial base, and indicated the mechanism of the Class II(1) malocclusion with different vertical types in adolescence.

[Effects of the directions of an extraoral retractive force on the displacement of and stress distribution in palate].

OBJECTIVE: The aim of this study was to assess the effects of varying retractive force directions on the displacement of and stress distributions in palate. METHODS: A three-dimensional finite element model of the nasomaxillary complex was created, consisting of 1638 isoparametric elements and 1827 nodes. An extraoral retractive force of 9.8N was applied to the upper canines in 3 different directions, i.e. parallel, 30 degrees upwards and downwards to the functional occlusal plane. Then we investigated the nature of stress distributions, the directions and amounts of displacement in palate by finite element analysis. RESULTS: In the midpalatal suture and transpalatal suture, all displacement directed to bone suture and increased gradually when the retractive force direction ranged from +30 degrees to -30 degrees. In the midmost part of palate, correlation between stress distributions and retractive force directions was not significant. Relatively compressive stresses were induced in the front and middle of the midpalatal suture, whereas nearly no stress was induced in the back. In the lateral part of palate, compressive stresses were nearly equal to tensile stresses in the front, while tensile stresses were induced in the middle and back. Meanwhile, there was no significant correlation between stress distributions and force directions. CONCLUSION: This study showed that the directions of retractive force had obvious effects on displacement but but little effect on stress distributions.