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ABSTRACT: Purpose: The seal of the interface formed at the implant-abutment connection is essential for the long-term success of the implant-supported restoration. The aim of this study was to analyze the mechanical behavior and the effect of cyclic fatigue before and after in the marginal fit of implant-abutment according to the manufacturing technique of the abutment. Materials and methods: Machined titanium abutments (DENTIS), cast abutments with Nickel-Chromium alloy (VeraBond II), and manufacturing custom milled Zirconia abutments (Zirkonzahn) were evaluated. The implant-abutment assemblies were subjected to cyclic loads of 133 N at a frequency of 19.1 Hz for 200,000 cycles. The microgap was measured using Scanning Electronic Microscope and the distribution of compressive stress by the three-dimensional Finite Element (FE) method. Results: The microgap measurement values of the machined abutments were 1.62μm and 1.92μm, cast abutments were 14.14 μm, and 28.44 μm, and the milled abutments were 14.18μm and 20.15μm before and after cyclic fatigue, respectively. Only the cast abutments and the machined abutments showed a statistically significant difference before and after cyclic fatigue (p≤0.05). The FE analysis showed that the critical areas of compressive stress were located at the implant-abutment connection, increasing in the cast abutments and decreasing in the milled and the machined abutments. Conclusion: Cyclic fatigue exerts an effect on the dimensions of the microgap at the implant-abutment interface before and after loading; this microgap depends of the type of abutment material and the manufacturing technique.
RESUMEN: Propósito: El sellado de la interface de la conexión implante-pilar es esencial para el éxito a largo plazo de la restauración implantosoportada. El objetivo de este estudio fue analizar el comportamiento mecánico y el efecto de la fatiga cíclica antes y después en el sellado de la conexión implante-pilar de acuerdo a la ténica de fabricación del pilar. Materiales y Métodos: Pilares mecanizados de titanio (DENTIS), pilares calcinables colados con aleación Niquel-Cromo (VeraBond II) y pilares fresados de Zirconia (Zirkonzahn) fueron evaluados. Los implantes y pilares atornillados se sometieron a una carga de 133 N a una frecuencia de 19.1 Hz durante 200 000 ciclos. El microgap fue medido con el Microscopio Electrónico de Barrido y la distribución del esfuerzo de compresión por el método tridimensional de Elemento Finito (EF). Los valores del microgap de los pilares mecanizados fueron de 1.62μm y 1.92μm, en los pilares calcinables fue de 14.14μm y 20.15μm, y los pilares fresados fue de 14.18μm y 28.44 μm antes y después de la fatiga cíclica, respectivamente. Los pilares calcinables y lo mecanizados mostraron diferencia estadísticamente significativa antes y después de la fatiga cíclica (p≤0.05). El análisis por EF mostró que las áreas críticas del esfuerzo de compresión estaban localizadas en la conexión implante-pilar, aumentando en los pilares calcinables y disminuyendo en los pilares fresados y en los mecanizados. Conclusión: La fatiga cíclica ejerce un efecto sobre las dimensiones del microgap en la interface implante-pilar antes y después de la carga cíclica; este microgap depende del tipo de material y de la técnica de fabricación del pilar.
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Humans , Surgery, Oral , Dental Implant-Abutment Design , Dental Stress Analysis , MexicoABSTRACT
Objective To simulate the biomechanical characteristics of pelvic-ligament-muscle during vaginal delivery and rest, and to explore the injury of levator ani muscles during vaginal delivery, pelvic organ prolapse and stress urinary incontinence. Methods The three-dimensional (3D) nonlinear finite element model of pelvis-ligament-muscle was established to calculate the stress and strain distributions and injury of levator ani muscles under different abdominal pressures and loads. The stress and strain distributions as well as damage of type I, Ⅱ, Ⅲ stress urinary incontinence and pelvic organ prolapse were also calculated. Results The highest equivalent stresses of levator ani were 14, 29, 43, 86, 144, 230 kPa, respectively, when the abdominal pressure was 1 kPa under the load of 3, 5, 8 kPa and the abdominal pressure was 1.5 kPa under the load of 3, 5, 8 kPa. The stresses of type I, Ⅱ, Ⅲ stress urinary incontinence and pelvic organ prolapse were 1.69, 1.01, 0.70, 1.58 MPa. Conclusions Vaginal delivery would result in the damage to the puborectalis and the middle of the pubococcipital muscle, which was consistent with the damage of the anal levator muscle with pelvic floor dysfunction. This study uses scientific method to find out the exact location of pelvic floor injury during vaginal delivery, which can provide references for clinicians to prevent pelvic floor disease and formulate post natal rehabilitation training.
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Objective To establish the 3D hydrogel cell model and apply compressive stress with different intensities, frequencies and durations on osteoclasts, so as to observe the effect of compressive stress on osteoclast differentiation and investigate the appropriate compressive stress solution for inhibiting osteoclast differentiation. Methods M-CSF and RANKL were used to induce bone marrow mononuclear cells into osteoclasts. After the 3D cell-agarose mixture was seeded in compression culture plate, compressive stress was applied on osteoclasts with different intensities, frequencies and durations the next day. The cells in control group were not interfered. The cells were divided as following: G0 (control group), G1 (1%, 0.5 Hz, 4 h), G2 (2%, 0.5 Hz, 4 h), G3 (3%, 0.5 Hz, 4 h), G4 (1%, 1.0 Hz, 4 h), G5 (2%, 1.0 Hz, 4 h), G6 (3%, 1.0 Hz, 4 h). After the loading plan with the most effective intensity and frequency was calculated by statistical analysis, compressive stresses were applied on cells with different durations as following: D1(4 h), D2(8 h), D3(12 h), D4(16 h), and each group had two samples. Once compressive loading was finished, the total RNA extraction from cell-gel constructs were performed and Ctsk mRNA, NFATc1 mRNA, TRACP mRNA, M-CSF mRNA and RANK mRNA were measured by quantitative testing. Results RANK and TRACP mRNA expression significantly depended on intensities and frequencies of the compressive stress (P<0.01), and Ctsk mRNA significantly depended on intensities(P<0.01) while it differed notably with different frequencies (P<0.01). M-CSF mRNA expression with 8 h was much lower than that with 12 h (P<0.01) and 16 h (P<0.05). RANK mRNA expression with 8 h was lower than that with 12 h (P<0.05) and 16 h (P<0.01). In addition, Ctsk and NFATc1 mRNA expression with 16 h was higher than that with 4 h and 8 h (P<0.05). Conclusions In the 3D hydrogel model, 1% intensity, frequency of 0.5 Hz, cyclic compression intervention with 8 h can suppress the differentiation of osteoclasts. The research findings provide the theoretical basis for preventing osteoporosis and improving the peak bone mass by appropriate exercise.
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Objective To study the effects of different parameters (thickness,orthodontic displacement,elastic modulus) from Invisalign on canine displacement and periodontal ligament (PDL) stress during mandibular canine intrusion treatment.Methods Forty-eight different Invisalign models were used to simulate canine intrusion treatment by using the finite element method.Results The initial displacement of the canine and stress on canine PDL were proportional to the thickness,intrusion displacement,and elastic modulus of the Invisalign,and the intrusion displacement had the greatest influence on canine displacement.During canine intrusion treatment,the compressive stress on PDL was the most sensitive and changed easily with the change of parameters.Conclusions The canine displacement may increase with the thickness,intrusion displacement and elastic modulus of Invisalign increasing,however,the stress on PDL will also increase,showing the largest increasing magnitude in compressive stress on PDL meanwhile.Therefore,to accelerate tooth movement in Invisalign treatment,it is suggested to use the assisted devices or some other measures such as attachment,supplement of bracket-wires treatment,or implant anchorage.
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Objective To study the effects of different parameters (thickness, orthodontic displacement, elastic modulus) of Invisalign on canine displacement and periodontal ligament (PDL) stress during mandibular canine intrusion treatment. Methods Forty-eight different Invisalign models were used to simulate canine intrusion treatment by using the finite element method. Results The initial displacement of the canine and stress on canine PDL were proportional to thickness, intrusion displacement, and elastic modulus of Invisalign. The intrusion displacement had the greatest influence on canine displacement. During canine intrusion treatment, the compressive stress on PDL was the most sensitive parameter and changed easily with the change of parameters. Conclusions The increase of Invisalign thickness, intrusion displacement and elastic modulus can increase canine displacement, however, the stress on PDL also increases, with the largest increasing magnitude in compressive stress on PDL. Therefore, to accelerate tooth movement in Invisalign treatment, it is suggested to use the assisted devices or measurements, such as attachment, supplement of bracket-wires treatment, or implant anchorage.
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Objective To study the effects of different parameters (thickness,orthodontic displacement,elastic modulus) from Invisalign on canine displacement and periodontal ligament (PDL) stress during mandibular canine intrusion treatment.Methods Forty-eight different Invisalign models were used to simulate canine intrusion treatment by using the finite element method.Results The initial displacement of the canine and stress on canine PDL were proportional to the thickness,intrusion displacement,and elastic modulus of the Invisalign,and the intrusion displacement had the greatest influence on canine displacement.During canine intrusion treatment,the compressive stress on PDL was the most sensitive and changed easily with the change of parameters.Conclusions The canine displacement may increase with the thickness,intrusion displacement and elastic modulus of Invisalign increasing,however,the stress on PDL will also increase,showing the largest increasing magnitude in compressive stress on PDL meanwhile.Therefore,to accelerate tooth movement in Invisalign treatment,it is suggested to use the assisted devices or some other measures such as attachment,supplement of bracket-wires treatment,or implant anchorage.
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Objective To study the effects of different parameters (thickness,orthodontic displacement,elastic modulus) from Invisalign on canine displacement and periodontal ligament (PDL) stress during mandibular canine intrusion treatment.Methods Forty-eight different Invisalign models were used to simulate canine intrusion treatment by using the finite element method.Results The initial displacement of the canine and stress on canine PDL were proportional to the thickness,intrusion displacement,and elastic modulus of the Invisalign,and the intrusion displacement had the greatest influence on canine displacement.During canine intrusion treatment,the compressive stress on PDL was the most sensitive and changed easily with the change of parameters.Conclusions The canine displacement may increase with the thickness,intrusion displacement and elastic modulus of Invisalign increasing,however,the stress on PDL will also increase,showing the largest increasing magnitude in compressive stress on PDL meanwhile.Therefore,to accelerate tooth movement in Invisalign treatment,it is suggested to use the assisted devices or some other measures such as attachment,supplement of bracket-wires treatment,or implant anchorage.
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Objective To evaluate the viability of adipocytes after they are subjected to different compressive stress in vitro for improvement of autologous fat graft and its clinical application.Methods Fat grafts were harvested from healthy patients who underwent liposuction for body contouring.Then the fat grafts were randomly divided into 5 experimental groups,including control group without any compressive stress,and continuous compressive stress groups (0,25,50,75,and 100 kPa),and the glucose transport test was performed at days 1,2,3 and 4.An MTT assay was also performed after 4 days with continuous compressive stress in each group with the same experimental protocol for control.Routine histological examination was done in all groups to examine possible structural destruction after compressive stress.Results As compared with the control group,the glucose transport test showed transported glucose concentration decreased with an increase in compressive stress in all of the other four groups (P＜0.01),and this effect would increase with action time.MTT assay showed absorbance (A492nm) also decreased with an increase in compressive stress in four days (P＜0.05),the similar fndings of MTT assay on the viability of fat grafts in all five groups and correlated with the glucose transport test (r=0.838,P＜0.01).Histology showed significantly distorted and fractured adipocytes and cell injury rate was to raise with an increase in compressive stress.Conclusions Our study demonstrates the harmful effect on the viability of fat grafts with an increase in compressive stress and therefore we should reduce this effect in clinical application of fat grafts.
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Objective To study the impacts of dynamic compressive stress on the mRNA expression of osteopontin ( OPN ),runt related gene 2 ( Runx2 ),osteocalcin ( OC ),osterix,alkaline phosphatase (ALP) and bone morphogenetic protein 2 (BMP-2) in the osteoblasts of Sprague-Dawley (SD) rats. Methods Osteoblasts extracted from skull periosteum tissue of neonatal SD rats were digested using trypsin and collagenase （Ⅰ）,then were subcultured and amplified in vitro.ALP staining and alizarin red staining were performed to identify the purified cells.The cells were treated with compressive stress at 20,50 or 100 mmHg for 24 h.The expression levels of OPN,Runx-2,OC,osterix,ALP and BMP-2 were measured and quantitatively analysed using a real-time quantitative polymerase chain reaction. Results Under 20 mmHg of dynamic compressive stress the expression levels of OPN,Runx2,OC,osterix,ALP and BMP-2 all were elevated compared with the control group.The peak expression oecured under 50 mmHg pressure. The expression levels did not change significantly compared with the control group under 100 mmHg pressure. Conclusions Moderate dynamic compressive stress can promote the expression of OPN,Runx-2,OC,osterix,ALP and BMP-2 mRNA in osteoblasts,which might be an important mechanism for promoting the union of fractures.
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[Objective]To explore the effect of continuous physiological osteogenic stress on the bone healing of canine iliopectineal crest.[Method]Ten adult mixed breed dogs without significant individual difference were made transverse fracture at bilateral iliopectineal crest 1.5 cm above the dome of acetabulum,which were fixed with ATMFS or steel plate respectively. The animals were sacrificed and specimens were procured at 2,4,6,8 and 12 weeks after operation.Samples from the fracture gaps were investigated by histology of HE and Masson staining,image pattern analysis of new bone formation.[Result]The formation of cartilaginous tissue and the maturity of cortical and trabecular bone and collagen fibers of ATMFS sides were earlier than that of steel sides obviously.There was significant difference of the integrated optical density (IOD) of new bone formation between two groups (P
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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.
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Bicuspid , Dental Enamel , Finite Element Analysis , Tooth CervixABSTRACT
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.
Subject(s)
Bicuspid , Finite Element Analysis , ToothABSTRACT
Objective:To study the effect of compressive stress on expression of connective tissue growth factor(CTGF) in rabbit mandibular condylar chondrocytes in vitro. Methods:CTGF mRNA were determined by semiquantitative RT-PCR in rabbit mandibular condylar chondrocytes cultured in vitro. Results:Within a certain compressive stress, CTGF mRNA were up-regulated with the increase of compressive stress. While under certain compressive stress, CTGF mRNA were gradually up-regulated following the increase of culturing time, and reaching the maximum at 2~6 h, then gradually down-regulated until at 24 h. Conclusion:Application of different compressive stresses can up-regulate the expression of CTGF mRNA in rabbit mandibular condylar chondrocytes. It may be involved in the stress -mediated mandibular condylar cartilage remodeling.
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Objective:To investigate the effects of the different static compressive stress on the proliferation and apoptosis of condylar chondrocytes in vitro.Methods: 0, 12, 24, 36 kPa static compressive stress were applied to the third passage of mandibular condylar chondrocytes for 1 hour respectively. The changes of proliferation and apoptosis of condylar chondrocytes were evaluated by flow cytometry analysis. Results: The index of proliferation and apoptosis of cells decreased with the magnitude value of static compressive stress except 24 kPa group. The most significant decrease of proliferative index and apoptosis index was found in 36 kPa group and 12 kPa group respectively. Conclusion: There might be some corelationships between magnitude of static compressive stress and the proliferation and apoptosis of condylar chondrocytes.
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Objective: To investigate the effects of the cyclic uniaxial compressive stress on RKIP and its mRNA in the rat condylar chondrocytes. Methods:The third-passage chondrocytes were harvested from the mandibular condyles of 2-day-old rats, and a cellular compressive stress device (self-made four-point bending system. Patent No: 01129166.4 & 01256849.x) was used to apply stress on cells at 4 000 ?strain ( 0.5 Hz frequency) for 0, 15, 30, 60, 120 and 240 min. The effects of the cyclic uniaxial compressive stress on RKIP and its mRNA in the rat mandibular condylar chondrocytes were examined by REAL-TIME PCR and Western blot. Results:The results showed that the expression of RKIP and its mRNA changed obviously with 4 000 ?strain compressive stress loading, there are reverse tendency in the expression between RKIP and its mRNA. RKIP mRNA significantly increased at 30min (P
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Objective:To investigate the expression of transforming growth factor-?1 (TGF-?1) in mandibular condylar chondrocytes after the condylar cartilage was stimulated by compressive stress.Methods:20 condylar cartilage samples were obtained from 10 new borne SD rats and cultured for 24 h.Then,10 samples were treated by a static compressive stress with a magnitude of 10 kPa for 1 h.Another 10 samples without stress treatment were used as the controls. At end of stress stimulation, the expression of TGF-?1 in the samples of both groups was examined by immunohistochemistry and image pattern analysis.Results:The grayscale values of TGF-?1 in perichondrium lay of stress treated and control samples were 159.21?19.84 and 174.20?14.47(P
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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.
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Root ResorptionABSTRACT
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.
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Adult , Humans , Dental Arch , Molar , Tooth , Tooth Movement TechniquesABSTRACT
AIM: To investigate the mechanism of proliferation and differentiation of human epidermal stem cells cultured in vitro under the influence of compressive stress.METHODS: Epidermal stem cells were isolated by adhering to type IV collagen and were cultured with conditioned medium,then were detected by Powervision~(TM) two-step immunohistochemical method with keratin 19 and cell cycle analysis.The cultured epidermal stem cells transplanted on silica gel membranes,which were put in a new apparatus,was designed to offer cell culture and intermittent compressive stress(4 kPa,6 kPa,8 kPa,10 kPa,12 kPa) for 2 h,3 times a day simultaneously.A week later,cells on silica gel membranes were identified with keratin 19 and 10 by Powervision~(TM) two-step immunohistochemical method.RESULTS: The new apparatus offered cell culture and intermittent compressive stress simultaneously.The isolated and cultured epidermal stem cells were identified with keratin 19 positive and 84.80 percent of them were showed in G_1 period with cell cycle analysis.Cells on silica gel membranes had been subjected intermittent compressive stress above 8 kPa for a week.The number of the cells was increased,which was more than that in control group.However,some cells identified by immunohistochemical staining with keratin 10 positive were detected among the disposed epidermal stem cells.CONCLUSION: The intermittent compressive stress above 8 kPa induces and promotes epidermal stem cells to proliferate and differentiate,indicating that epidermal stem cells respond to mechanical stress,probably is one of their major biological features.