Hippo-YAP signaling pathway regulates autophagy of human periodontal ligament cells under cyclic tensile stress / 华西口腔医学杂志

OBJECTIVES@#This work aimed to investigate the molecular mechanism of cyclic tensile stress (CTS) stimulating autophagy in human periodontal ligament cells (hPDLCs).@*METHODS@#hPDLCs were isolated and cultured from normal periodontal tissues. hPDLCs were loaded with tensile stress by force four-point bending extender to simulate the autophagy of hPDLCs induced by orthodontic force du-ring orthodontic tooth movement. XMU-MP-1 was used to inhibit the Hippo signaling pathway to explore the role of the Hippo-YAP signaling pathway in activating hPDLC autophagy by tensile stress. The expression levels of autophagy-related genes (Beclin-1, LC3, and p62) in hPDLCs were detected by real-time quantitative polymerase chain reaction. Western blot was used to detect the expression levels of autophagy-related proteins (Beclin-1, LC3-Ⅱ/LC3-Ⅰ, and p62) and Hippo-YAP pathway proteins (active-YAP and p-YAP) in hPDLCs. Immunofluorescence was used to locate autophagy-related proteins (LC3-Ⅱand p62) and Hippo-YAP pathway proteins (active-YAP) of hPDLCs.@*RESULTS@#CTS-activated autophagy in hPDLCs and expression of autophagy-related proteins initially increased and then decreased; it began to increase at 30 min, peaked at 3 h, and decreased (P<0.05). CTS increased the expression of active-YAP protein and decreased the expression of p-YAP protein (P<0.05). When XMU-MP-1 inhibited the Hippo-YAP signaling pathway (P<0.05), active-YAP protein was promoted to enter the nucleus and autophagy expression was enhanced (P<0.05).@*CONCLUSIONS@#The Hippo-YAP signaling pathway is involved in the regulation of autophagy activation in hPDLCs under CTS.

Numerical Simulation for the Safe Retention Value of Residual Stromal Bed Thickness in Laser-Assisted in situ Keratomileusis / 医用生物力学

Objective To study the effects of different residual stromal bed thickness (RSBT) in laser-assisted in situ keratomileusis (LASIK) surgery on geometric deformation and stress changes of the cornea under different intraocular pressures (IOP), and evaluate safety of the three retention values (250, 280, 300 μm). Methods The models of normal cornea and corneas with different RSBT after surgery were established by the finite element software ABAQUS. Appropriate loading and boundary conditions were set and then the corresponding displacement and stress were calculated. Results The apical displacement of the postoperative cornea (RSBT=250 μm) under IOP=2.66 kPa was basically the same as that of the normal cornea (RSBT=550 μm) under IOP=5.32 kPa. RSBT=280 μm was in the low risk area of keratoconus, while RSBT=250 μm was in the high-risk area. At a value between 280 μm and 300 μm of RSBT, the stress distribution was nearly consistent with that of the normal cornea. With RSBT=300 μm, the stromal layer of the cornea lost 40% of the strongest strength against tissue tension. Conclusions RSBT=250 μm is the minimum retention value for LASIK surgery. RSBT=250 μm is the high risk value. With RSBT=330-340 μm, LASIK surgery is safe enough for most patients.

Tensile stress distribution in maxillary central incisors restored with cast-made and prefabricated dental posts

AIM: To analyze and compare the tensile stress distribution in endodontically treated teeth restored with cast-made (Ni-Cr and gold) and prefabricated (titanium and glass fibre) dental posts. METHODOLOGY: Four threedimensional finite element (FE) models of a maxillary central incisor restored with Ni-Cr cast-made (Model Ni-Cr), gold cast-made (Model GO), prefabricated titanium (Model TI) and prefabricated glass fibre (Model FP) posts were constructed. An oblique loading of 100N was applied to each three-dimensional model. Tensile stress distribution within the root dentine and at the post and surrounding structure interfaces were analysed. RESULTS: In all the FE models studied, a higher magnitude of tensile stresses was observed on the palatal aspect of the cervical dentin as compared to the labial aspect and progressively decreases from the outer to the inner part of the root. The gold cast-made and glass fibre post models showed significantly less tensile stress concentration in the post-core component than the other experimental models. The maximum tensile stress was seen on the palatal aspect of the Ni-Cr compared to other posts. The higher magnitude interfacial tensile stress concentration was observed in a pulpless tooth restored with a Ni-Cr cast-made post, followed by titanium and gold castmade posts, respectively. However, the minimum interfacial tensile stress was noticed in a pulpless tooth restored with a glass fibre post. CONCLUSION: Glass fibre posts tend to transfer tensile stress more homogenously within the tooth and at interfaces than the other types of investigated posts.

Simulation analysis on optimial loading scheme of resetting tensile stress for clavicular fractures / 医用生物力学

Objective To investigate the optimal scheme about the external loading of resetting tensile stress for clavicular fractures, so as to provide some mechanical references for optimal design of external fixators for clavicular fractures. Methods The shoulder CT scanning data from a volunteer were used to establish the three-dimensional model of human left shoulder by Mimics software. In order to better simulate the actual human shoulder, the ligament tissues were added in the model and the constraints of muscles were considered, and the experimental model for simulation analysis on resetting tensile stress was established. By 3 simulation experiments, the impacts from directions of resetting tensile stress, positions of action points and value ranges were simulated and analyzed, respectively. The resetting tensile stresses obtained from clavicle of the shoulder model under various external loading cases were simulated by orthogonal test methods. Results When the (angle between the horizontal plane projection of shoulder force which was loaded by external fixator and the coronal axis ) was greater than 45°, clavicle could obtain the resetting tensile stress, which became greater with the angle increasing. When (angle between the sagittal plane projection of shoulder force which was loaded by external fixator and the sagittal axis) was 30°-45°, the resetting tensile stress of clavicle was the maximum. The farther the position on which the loads from external fixator was exerted from the horizontal position of clavicle, the larger the resetting tensile stress of clavicle was. Conclusions The results of orthogonal test show that the optimal resetting tensile stress is produced with parameter combination of θ=65°, η=50°, acting on the center of humerus head of the shoulder

Simulation analysis on optimial loading scheme of resetting tensile stress for clavicular fracture / 医用生物力学

Objective To investigate the optimal scheme about the external loading of resetting tensile stress for clavicular fracture,so as to provide some mechanical references for optimal design of external fixators for clavicular fracture.Methods The shoulder CT scanning data from a volunteer were used to establish the three-dimensional model of human left shoulder by Mimics software.In order to better simulate the actual human shoulder,the ligament tissues were added in the model and the constraints of muscles were considered,and the experimental model for simulation analysis on resetting tensile stress was established.By 3 simulation experiments,the impacts from directions of resetting tensile stress,positions of action points and value ranges were simulated and analyzed,respectively.The resetting tensile stresses obtained from clavicle of the shoulder model under various external loading cases were simulated by orthogonal test methods.Results When the θ (angle between the horizontal plane projection of shoulder force which was loaded by external fixator and the coronal axis) was greater than 45°,clavicle could obtain the resetting tensile stress,which became greater with the angle θ increasing.When η (angle between the sagittal plane projection of shoulder force which was loaded by external fixator and the sagittal axis) was 30°-45°,the resetting tensile stress of clavicle was the maximum.The farther the position on which the loads from external fixator was exerted from the horizontal position of clavicle,the larger the resetting tensile stress of clavicle was.Conclusions The results of orthogonal test show that the optimal resetting tensile stress is produced with parameter combination of θ =65°,η =50°,acting on the center of humerus head of the shoulder.

Simulation analysis on optimial loading scheme of resetting tensile stress for clavicular fracture / 医用生物力学

Objective To investigate the optimal scheme about the external loading of resetting tensile stress for clavicular fracture,so as to provide some mechanical references for optimal design of external fixators for clavicular fracture.Methods The shoulder CT scanning data from a volunteer were used to establish the three-dimensional model of human left shoulder by Mimics software.In order to better simulate the actual human shoulder,the ligament tissues were added in the model and the constraints of muscles were considered,and the experimental model for simulation analysis on resetting tensile stress was established.By 3 simulation experiments,the impacts from directions of resetting tensile stress,positions of action points and value ranges were simulated and analyzed,respectively.The resetting tensile stresses obtained from clavicle of the shoulder model under various external loading cases were simulated by orthogonal test methods.Results When the θ (angle between the horizontal plane projection of shoulder force which was loaded by external fixator and the coronal axis) was greater than 45°,clavicle could obtain the resetting tensile stress,which became greater with the angle θ increasing.When η (angle between the sagittal plane projection of shoulder force which was loaded by external fixator and the sagittal axis) was 30°-45°,the resetting tensile stress of clavicle was the maximum.The farther the position on which the loads from external fixator was exerted from the horizontal position of clavicle,the larger the resetting tensile stress of clavicle was.Conclusions The results of orthogonal test show that the optimal resetting tensile stress is produced with parameter combination of θ =65°,η =50°,acting on the center of humerus head of the shoulder.

Simulation analysis on optimial loading scheme of resetting tensile stress for clavicular fracture / 医用生物力学

Objective To investigate the optimal scheme about the external loading of resetting tensile stress for clavicular fracture,so as to provide some mechanical references for optimal design of external fixators for clavicular fracture.Methods The shoulder CT scanning data from a volunteer were used to establish the three-dimensional model of human left shoulder by Mimics software.In order to better simulate the actual human shoulder,the ligament tissues were added in the model and the constraints of muscles were considered,and the experimental model for simulation analysis on resetting tensile stress was established.By 3 simulation experiments,the impacts from directions of resetting tensile stress,positions of action points and value ranges were simulated and analyzed,respectively.The resetting tensile stresses obtained from clavicle of the shoulder model under various external loading cases were simulated by orthogonal test methods.Results When the θ (angle between the horizontal plane projection of shoulder force which was loaded by external fixator and the coronal axis) was greater than 45°,clavicle could obtain the resetting tensile stress,which became greater with the angle θ increasing.When η (angle between the sagittal plane projection of shoulder force which was loaded by external fixator and the sagittal axis) was 30°-45°,the resetting tensile stress of clavicle was the maximum.The farther the position on which the loads from external fixator was exerted from the horizontal position of clavicle,the larger the resetting tensile stress of clavicle was.Conclusions The results of orthogonal test show that the optimal resetting tensile stress is produced with parameter combination of θ =65°,η =50°,acting on the center of humerus head of the shoulder.

Appropriate Tensile Mode and Timing of Applying Tension to Promote Tendon Gel Regeneration

“Tendon gel” secreted from a parent tendon is regenerated for tendon repair by applying tension. However, the details of the tensile stimulus have not been clarified. This study aimed to evaluate an appropriate tensile stimulus mode and the optimal timing of applying tension to promote tendon gel regeneration. Tendon gel was prepared using a film model method in mice and was preserved in vivo for 3, 5, and 10 days. Unlike tendon gel on day 3 or day 5, a fibrous structure developed in the tendon gel on day 10 when tension was applied. Infrared spectroscopy revealed that characteristic peaks appearing for the tendon gel on days 3 and 5 disappeared on day 10. Disappearance of the peaks indicated maturity of the tendon gel, and it showed the optimal timing for tension application to the tendon gel. The effect of tensile load on tendon gel preserved for 10 days was investigated using a tensile test, a creep test, or a cycle test. In the tensile test, tendon gel was elongated into a thin cord of collagen fibers with an increase in stress, and the maximum diameter of the collagen fiber was approximately 50 times larger than that in the normal Achilles tendon of mice. The results suggest that the diameter of the oriented collagen fiber is controllable by adjusting the applied load and the time in mature tendon gel.

Effects of cyclic tensile stress on metabolism and apoptosis of chondrocytes inrat / 中华物理医学与康复杂志

Objective To investigate the effect of cyclic tensile stress (CTS) on the metabolism inand apoptosis of rat chondrocytes.Methods Primary rat chondrocytes were cultured on a Bioflex plate for one day and then stretched cyclically for 24 hours at a frequency of 0.5 Hz using a Flexcell-5000T apparatus.The cells were divided into 5 groups according to their stretching ratio:0％ (the control group),2％,6％,10％ and 14％.After the stretching,Col Ⅱ,Aggrecan,MMP-13 and ADAMTS-5 mRNA were measured using qPCRs,and the NO and PGE2 levels were measured using ELISA kits.Moreover,TUNEL staining and Annexin V-FITC/PI were used to analyze the apoptosis of chondrocytes.Results Compared with the control group,the average levels of Col Ⅱ and Aggrecan mRNAdecreasedin 10％ and 14％ groups [(0.738±0.11) and (0.58±0.13),(0.75±0.11) and (0.55±0.09)].In those groups,the MMP-13 [(2.47±0.47) and (2.88±0.36)] and ADAMTS-5 mRNA level [(2.39±0.33) and (2.75±0.49)],the NO [(6.96±0.96) and (8.28±0.82)] and PGE2 level [(6.83±0.66) and (7.15±0.71)] had increased significantly.In the 6％ group the average levels of Col Ⅱ(1.76±0.30) and Aggrecan mRNA (1.93±0.14)of 6％ group were significantly higher than the control group,but the NO level of the former (3.07±0.20) was significantly lower than the control group (3.89 ± 0.33).The apoptosis rate of chondrocytesin 2％ and 6％ groups were (0.065±0.013) and (0.063 ± 0.147),without significant differences to that of the control group (0.045 ± 0.008).However,compared with the control group,apoptosis in the 10％ and 14％ groups [(0.135 ±0.026) and (0.184±0.020)] increased significantly.Conclusion The effect of cyclic tensile stress on chondrocyte metabolism and apoptosis was magnitude-dependent.Ten percent and 14％ CTS can increase the catabolism and apoptosis of chondrocytes.Ten percent and 14％ strain can increase the catabolism and apoptosis of chondrocytes.Cyclic 6％ strain can increase the anabolism of chondrocytes,but 2％ strain has no impact on metabolism or apoptosis.

Changes in FoxO1 expression of MC3T3-E1 cells during continuous tensile stress induced osteogenic differentiation / 医用生物力学

Objective To study the effect of continuous tensile stress on expression of Forkhead box protein O1 (FoxO1) in MC3T3-E1 cells in vitro during osteogenic differentiation, and explore the role of FoxO1 in the mechanism of continuous tensile stress induced-osteogenic differentiation. Methods MC3T3-E1 cells were seeded and applied with tensile stress at the frequency of 1 Hz and amplitude of 10% by FX-4000TTM mechanical loading system. MC3T3-E1 cells were divided into control, 1 h, 4 h, 6 h, 12 h, 24 h, 48 h, 72 h group, respectively, according to the time subjected to the tensile stress. Alkaline phosphatase (ALP) staining, real-time PCR, Western blotting and immunofluorescence were applied to detect the effects of continuous tensile stress on osteogenesis ability of MC3T3-E1 cells, mRNA and protein expression of FoxO1, and allocation of FoxO1 in MC3T3-E1 cells. Results (1) Continuous tensile stress could promote the osteogenic differentiation of MC3T3-E1 cells. Compared with the control group, the mRNA expression of ALP increased significantly at 24 h, 48 h, and the mRNA expression level of osteocalcin (OCN) reached the peak value at 72 h, which was significantly higher than that in the control group. The mRNA expression of runt-related transcription factor-2 (Runx2) significantly increased at 4 h as compared to the control group, and Runx2 protein level changed accordingly. The ALP staining results of the stress group and control group were significantly different. (2) Continuous tensile stress could increase mRNA and protein expression of FoxO1. The mRNA expression of FoxO1 markedly increased at 24 h, and its protein expression significantly elevated at 12 h. (3) FoxO1 was expressed in the nucleus and cytoplasm at 6 h, and then significantly increased in the cytoplasmat at 24 h. Conclusions 10% continuous tensile stress can stimulate the osteogenic differentiation of MC3T3-E1 cells, up-regulate the mRNA and protein expression of FoxO1 and change the allocation of FoxO1 in MC3T3-E1 cells. The investigation on the change rules of FoxO1 expression and allocation under mechanical stimulation will provide the experimental basis for studying the role of FoxO1 in mechanical stimulation.

The role of the hydrogen sulfide signal system in rat bone marrow-derived mesenchymal cells osteogenesis under tensile stress / 实用医学杂志

Objective To evaluate the impact of hydrogen sulfide signal system during the process of rat bone marrow-derived mesenchymal cells osteogenesis under tensile stress. Methods After the H2S signal system of cell rooms regulated by tool drugs (Group A with propargylglycine;Goup B with PBS;Group C with GYY3147), 4 000 μ strain tensile stress were applied on rat BMMCs by four-point bending apparatus for 60 minutes. Four hours later, the H2S signal system and cystathionine-γ-lyase were detected. Meanwhile, the change of the alkaline phosphate, osteocalcin, procollagen typeⅠN-terminal propeptide, and runt-related transcription factor 2 mRNA level were also examined to evaluate the osteogenic ability. Results With the increase of H2S expression, the osteogenic capacity gradually increased, while the osteogenic capacity was compromised after the endogenous cystathionine-γ-lyase was inhibited. Conclusion The H2S signal system plays an important role during BMMCs osteogensis under tensile stress. The up-regulation expression of H2S may promote osteogenesis during distraction osteogenesis.

Effects of cyclic mechanical stretch on BMP-2 expression in RA and OA fibroblast-like synoviocytes / 医用生物力学

Objective To explore the role of mechanical stimulation in synovium under different pathological conditions through studying the effects of cyclic mechanical stretch on the expression of bone morphogenetic protein 2 (BMP-2) in rheumatoid arthritis (RA) and osteoarthritis (OA) fibroblast-like synoviocytes (FLS). Method 6% and 0.5 Hz stretch generated by Flex cell 4000 tension systems was applied on normal, RA and OA FLS of human knee joint source under normal and inflammatory conditions for 2 h or 6 h, respectively. Results Cyclic mechanical stretch of 6%, 0.5 Hz had no significant effects on the expression of BMP-2 in normal, RA and OA FLS at 2 h, while in RA FLS it increased significantly at 6 h. Inflammatory cytokines (IL-1β) didn’t influence normal FLS at 2 h, but made BMP-2 mRNA significantly increased at 6 h. IL-1β increased BMP-2 mRNA of RA FLS significantly both at 2 h and 6 h. IL-1β increased BMP-2 mRNA of OA FLS significantly only at 2 h, but had no significant effect at 6 h. The co-effect of IL-1β and cyclic mechanical stretch induced the ascension of BMP-2 expression significantly in normal and RA FLS at 2 h, and in normal, RA and OA FLS at 6 h. Conclusions Response of BMP-2 mRNA to mechanic stimulation and IL-1β in normal, RA and OA FLS were different. Inflammation may play a more important role than mechanical stimulation in the pathogenesis of RA and OA. Synergetic effect in inflammation and mechanical stimulation were found in OA FLS at 6 h, which reveals that they may co-act in the occurrence and development of OA.

Effects of mechanical tensile stress on the expression of ODF mRNA in osteoblasts differentiated from rBMSCs in vitro / 医用生物力学

Objective To investigate the correlation between mechanical tensile stress and the expression of ODF mRNA in osteoblasts differentiated from rBMSCs, and elucidate the mechanism for osteoclastogenesis regulated by osteoblasts in bone modeling and remodeling during the process of orthodontic tooth movement. Method rBMSCs derived osteoblasts were isolated and cultured in vitro, and subjected to static mechanical tensile stress of 1, 3, 5 kPa or dynamic tensile stress of 3, 5 kPa at 0.017 Hz using the cellular tensile stress system for 24 h. The control groups were subjected without any strain. Cells were collected in 0, 3, 6, 9, 12, 24, 48 h respectively after stress loading. The expression patterns of ICAM-1 mRNA were examined by semiquantitative RT PCR assay. Results ODF mRNA level significantly decreased after dynamic tensile strain, compared with the control groups；the effects of inhibition did not positively correlated with the magnitude of strain; the expression of ODF mRNA gradually decreased at 6 h, significantly decreased at 9 h, then slightly rebounded and still stayed at a considerably lower level, reached the minimum transcription at 48 h. Conclusions The mechanical tensile strain can regulate osteoclastogenesis by inhibiting the expression of ODF in osteoblasts derived from rBMSCs. It could lead to a better understanding of the molecular basis for osteoblast osteoclast communication in bone resorption induced by the application of mechanical strain during the orthodontic tooth movement.

Stress analysis of maxillary premolars with composite resin restoration of notch-shaped class V cavity and access cavity; Three-dimensional finite element study / 대한치과보존학회지

The purpose of this study was to investigate the distribution of tensile stress of canal obturated maxillary second premolar with access cavity and notch-shaped class V cavity restored with composite resin using a 3D finite element analysis. The tested groups were classified as 8 situations by only access cavity or access cavity with notch-shaped class VS cavity (S or N), loading condition (L1 or L2), and with or without glass ionomer cement base (R1 or R2). A static load of 500 N was applied at buccal and palatal cusps. Notch-shaped cavity and access cavity were filled microhybrid composite resin (Z100) with or without GIC base (Fuji II LC). The tensile stresses presented in the buccal cervical area, palatal cervical area and occlusal surface were analyzed using ANSYS. Tensile stress distributions were similar regardless of base. When the load was applied on the buccal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth with class V cavity were slightly higher than that of the tooth without class V cavity. When the load was applied the palatal cusp, excessive high tensile stress was concentrated around the loading point and along the central groove of occlusal surface. The tensile stress values of the tooth without class V cavity were slightly higher than that of the tooth with class V cavity.

Effects of occlusal load on the stress distribution of four cavity configurations of noncarious cervical lesions: a three-dimensional finite element analysis study / 대한치과보존학회지

The objective of this study was to investigate the effect of excessive occlusal loading on stress distribution on four type of cervical lesion, using a three dimensional finite element analysis (3D FEA). The extracted maxillary second premolar was scanned serially with Micro-CT. The 3D images were processed by 3D-DOCTOR. ANSYS was used to mesh and analyze 3D FE model. Four different lesion configurations representative of the various types observed clinically for teeth were studied. A static point load of 500N was applied to the buccal and lingual cusp (Load A and B). The principal stresses in lesion apex, and vertical sectioned margin of cervical wall were analyzed. The results were as follows 1. The patterns of stress distribution were similar but the magnitude was different in four types of lesion. 2. The peak stress was observed at mesial corner and also stresses concentrated at lesion apex. 3. The compressive stress under load A and the tensile stress under load B were dominant stress. 4. Under the load, lesion can be increased and harmful to tooth structure unless restored.

Effects of occlusal load on the cervical stress distribution: A three-dimensional finite element study / 대한치과보존학회지

The objective of this study was to investigate the effects of various occlusal loads on the stress distribution of the buccal cervical region of a normal maxillary second premolar, using a three dimensional finite element analysis (3D FEA). After 3D FE modeling of maxillary second premolar, a static load of 500N of three load cases was applied. Stress analysis was performed using ANSYS (Swanson Analysis Systems, Inc., Houston, USA). The maximum principal stresses and minimum principal stresses were sampled at thirteen nodal points in the buccal cervical enamel for each four horizontal planes, 1.0 mm above CEJ, 0.5 mm above CEJ, CEJ, 0.5 mm under CEJ. The results were as follows 1. The peak stress was seen at the cervical enamel surface of the mesiobuccal line angle area, asymmetrically. 2. The values of compressive stresses were within the range of the failure stress of enamel. But the values of tensile stresses exceeded the range of the failure stress of enamel. 3. The tensile stresses from the perpendicular load at the buccal incline of palatal cusp may be shown to be the primary etiological factors of the NCCLs.

Hypertrophy of the Patellar Tendon induced by Local Injection of TGF-beta1 in Mature Rats / 대한정형외과연구학회지

PURPOSE: The effects of local injection of TGF-beta1 on the normal patellar tendon and the characteristics of remaining tendon after the partial resection of hypertrophic one were investigated. MATERIALS AND METHODS: TGF-beta1 was injected into the right patellar tendon of mature rats weekly for 3 weeks. Histological study, biomechanical analysis and the transmission electron microscopic evaluation were done. Half of hypertrophic tendon was resected at 4 weeks after the last injection and the same analyses were RESULTS: TGF-beta1 treated tendon increased in cross sectional area but decreased significantly in maximum tensile stress. The hypertrophic tissue was mainly composed of small collagen fibrils. After the partial resection of hypertrophic tendon, there was no significant difference in maximum tensile stress between remaining and control tendons. There were relatively larger collagen fibrils in the remaining tendon tissue than in non-resected hypertrophic one. CONCLUSION: Local injection of TGF-beta1 induced the hypertrophy of normal tendon. After the partial resection of hypertrophic tendon, the remaining one showed the more similar biomechanical properties to normal one.

A FEM analysis for initial stress on the upper canine by orthodontic force of intrusion arch wire activation / 대한치과교정학회지

The purpose of this study was to find the distribution and measurement of compressive and tensile stress when intrusi- on arch wire is forced engage with upper canine and to analysis stress at each section through FEM. And we compare compressive and tensile ratio at each section. The results were as follows. 1. At FA point and cemento-enamel junction of upper canine, compressive and tensile force ratio is about the same. 2. At apex, compressive force is the four times as tensile force. ; In intrusion, we show root resorption at apex. 3. At Cemento-enamel junction, the compressive and tensile force show the maximun value except FA point.

An analysis of stress distribution in the case of unilateral molar expansion with precision lingual arch by finite element method / 대한치과교정학회지

Orthodontic tooth movement is closely related to the stress on the periodontal tissue. In this research the finite element method was used to observe the stress distribution and to find the best condition for effective tooth movement in the case of unilateral molar expansion. The author constructed the model of lower dental arch of average Korean adult and used .032" x .032" x 60mm TMA wire. The wire was deflected in the horizontal and vertical direction to give the 16 conditions. The following results were obtained; 1. When the moment and force were controlled properly the movement of anchor tooth was minimized and the movement of moving tooth was maximized. 2. As the initial horizontal deflection increased the buccal displacement of both teeth was also increased. As the initial vertical deflection increased the lingual movement of anchor tooth and the buccal movement of moving tooth increased. 3. When the initial horizontal and vertical deflection rate was 1.5 the effective movement of moving tooth was observed with minimal displacement of anchor tooth.