2007, 22(2):115-118. DOI: 10.3871/j.1004-7220.2007.2.118.
Abstract:To elucidate the relationship between biomechanics and stomatology, a brief review has been made on the studies and applications of biomechanics in the field of oral medical science. If was found that the principles of biomechanics were applied to explain the clinic and scientific phenomena almost in all sub-divisions of stomatology. Biomechanicsboosts the advancement of stomatology such as scientific researches, the inventions of biomaterials and applicationsand the improvement of medical care quality. Biomechanics is a subdiscipline belonging to the philosophy of medicine. Itis also beneficial to the clinicians in fostering and strengthening the thinking of differentiation of symptoms and signs indiagnosis and treatment. The author indicate that with the development of cytobiology and molecular biology, the biomechanical researches should be at the molecular and cellular level and have a better future.
2007, 22(2):119-120. DOI: 10.3871/j.1004-7220.2007.2.120.
Abstract:There are many problems in clinical dentistry could be related with biomechanics, including orthodontics, mandibular plastic surgery, dental restoration and implantation, etc. Biomechanics now is one of the scientific bases for stomatology. The fundamental principles and approaches of dental biomechanics have been widely used in basic research, solving clinical problems, developing new appliances and innovative technologies in dentistry. This paper briefly reviewed the major dental biomechanical research fields and its main methods.
2007, 22(2):121-126. DOI: 10.3871/j.1004-7220.2007.2.126.
Abstract:Objective To study stress distribution of silastic membrane in dynamic mechanical cell strain unit by self-developed to know about stress of cells at different location. Method 3D Finite element method analysis with software ANSYS 8.0.was made. Based on axis symmetry theory, the model with DOF constraint and displacement load was established to simulate the practical condition for the silastic membrane under the tension. Results The Von mises stress nephogram, displacement nephogram and stress value were obtained via software ANSYS. Conclusion Stress in ring-shaped area is lower than that in marginal and central area with strain of 1%, 5% and 10%. Stress in central and ring-shaped area with 20% and 25% strain looks approximately close to each other but thestress value in central area is still more than that in ring-shaped area.
2007, 22(2):127-132. DOI: 10.3871/j.1004-7220.2007.2.132.
Abstract:Objective By biomechanical research on maxillary canine with invisible orthodontic appliances, analyze the features of the orthodontic forces and effect of invisible appliances. Method A three-dimensional FE model of canine with the invisible appliance was set up, which includes alveolar bone, periodontal membrane and pulp. Aiming at one kind of tooth’s monstrosity, several simulated cases were designed and analyzed numerically. The forces and moments from the invisible appliance were analyzed. The force and stress distributions applied with the invisible appliance were obtained. And the comparative study was made between the invisible appliance and the traditional fixed aligner. Result Applied with both the invisible appliance and the traditional fixed aligner, the maximal stress on tissues around the maxillary canine showed greatly close, and changing tendency of stresses are very similar. Conclusion Good clinical effect can be gained with the properly designed invisible appliance.
2007, 22(2):127-132. DOI: 10.3871/j.1004-7220.2007.2.132.
Abstract:Objective To investigate the influences of torque effect for maxillary anterior teeth retraction using micro- implant anchorage system. Methods The three-dimensional finite element model was constructed using MIMICS software and ABAQUS finite element software. Under the situation of no or with torque and for different torque regions, the movement trend of the central incisor and lateral incisor was calculated and analyzed. Results The tendency of both the central and lateral incisor appears a lingual incline movement with no torque. Under the 100 g·cm torque force, with the region of load torque increasing, the labial movement of the central incisor reduced, and the lingual movement of the lateral incisor became more labial. Conclusions Torque was able to change the movement of teeth effectively. If the load torque decreased from the middle of the two central incisors to the distal direction, the results would be better.
2007, 22(2):133-136. DOI: 10.3871/j.1004-7220.2007.2.136.
Abstract:Objective To explore the best way to make canine bodily movement distally by one step with the invisible bracketless appliances. Methods To simulate the force generated by the invisible bracketless appliance and analyze the stress distribution by the means of finite element method. Then to calculate the mean value of the main stress and Von Mises standard deviation when the canine effected by distal and mesial force (F) with different couples simultaneously and to analyze the stress distribution with different combinations of F and M ratio. Results The canine incline tends to be less by the combination of F and M with proper ratio. Conclusion When M/F=7.257.5, the canine looks more like bodily movement using the invisible bracketless appliances.
2007, 22(2):146-150. DOI: 10.3871/j.1004-7220.2007.2.150.
Abstract:Objective To establish a three-dimensional finite element model of mandible with dental implants for immediate loading, and to analyze stress distribution in the bone around the dental implants with different implant diameter. Methods Three-dimensional finite element model of thread dental implants with immediate loading were constructed using CT scanning and USIS (Universal Surgical Integration System)software developed by ourselves, which including different diameter implants for 3.3 mm、 4.1 mm、 4.8 mm, respectively. The value of Von Mises stress、 strain of implant-bone interface were obtained and analyzed with ANSYS, when the dental implants were loaded with vertical、 buccolingual force of 150 N. Results When loaded with vertical force, the Von Mises stress concentration appeared on the neck of implants, and Von Mises strain were concentrated on the buccal side of the bottom of implants; the peak value of Von Mises stress on the neck of implant in the implant-bone interface for the above three different diameters were 25 Mpa、 17.6 Mpa、 11.6 Mpa and the strain of them were 1 853 με、1 303 με、1 293 με, respectively. When loaded with buccolingual force, the values of both Von Mises stress and strain increased apparently and the concentrations all appeared around the lingual side on the neck of implants , the corresponding peak values for the above three different diameters were 131.1 Mpa、 78.7 Mpa、 68.1 Mpa and the strain of them were 9 622 με、5 892 με、5 816 με,respectively. Conclusion With the addition of the dental implants diameter , the stress and strain on the bone around implants all decreased and it was remarkable especially when the diameter increased from 3.3 mm to 4.1 mm. It shows that the dimension of dental implants with immediate loading would at least be 10 mm×1 4.1 mm, and should avoid load with un-axial strength as possible as it can.
2007, 22(2):156-159. DOI: 10.3871/j.1004-7220.2007.2.159.
Abstract:Objective The cancellous marrow were implanted in the holes of the mandible prosthesis to study whether the cell bone can reach growing stress level under normal human condition. The threshold value of growing stress can combine the prosthesis and mandibular. Method Three types of defection- Central defect, Lateral defect, Hemimandible defect- were simulated in mandibular geometry model, three types of prosthesis were designed accordingly and holes were made in the prosthesis. The cancellous marrow were implanted in those holes and FE software (Ansys8.0) was used to analysis the stress level of cancellous bone. Results Stress level of Cancellous bone in three types of prothesis were studied and the threshold value of growing stress level on cancellous bone was determined. Conclusions The stress of cancellous bone implanted in the prosthesis can reach the bone cell growing level, and this can give guidance in prosthesis design.
2007, 22(2):165-170. DOI: 10.3871/j.1004-7220.2007.2.170.
Abstract:Objective A drainage ware was designed for postoperative care after functional endoscopic sinus surgery. It can prevent the ostium of maxillary sinus from closing, drain the empyemata from maxillary sinus and send the medicament to the field of ostiomeatal complex. Methods Based on the results of numerical simulation of airflow in nasal cavity and the data obtained from Rhinomanometry, the characters of airflow in the middle nasal meatus were acquired. According to the characters, right boundary conditions for the following calculation were assigned. The numerical model of drainage ware was generated. Based on the tow-phase flow theory and finite-volume method, numerical simulation for the liquid in the drainage ware was performed to explain how the drainage ware did its work of draining the empyemata from maxillary sinus and sending the medicament to the place around the surface of wound. By changing the value of tube diameter or viscosity parameters of liquid-phase flow, different results of numerical simulation were acquired. Results After comparing the computational results, the fit value of drainage tube diameter was obtained. Conclusions Through numerical simulation for two-phase flow in the drainage ware it proved that the drainage ware designed in this way can accomplish the work of keeping ventilative, draining the empyemata, sending medicament and preventing the ostium of maxillary sinus from closing.
2007, 22(2):165-170. DOI: 10.3871/j.1004-7220.2007.2.170.
Abstract:Objective The pulmonary artery (PA) in patients with pulmonary hypertension (PH) was investigated by combination of ultrasound with biomechanical method. The present article is to apply mechanical parameters of PA on evaluation of properties of PH clinically. Methods Patients with ventricular septal defect with PH were selected and all cases were underwent interventional test of right heart catheterization. PA pressure and dimension of two-dimensional images were recorded, measuring in 10 points within systole. The systolic increment of both pressure and dimension of PA were calculated. The data of PA pressure and dimension were input into constitutive equations for biomechanical measurement to calculate stress-strain relation in PA. Results With increase of pulmonary pressure, the enlargement of PA dimensions was limited, especially in the high pulmonary vascular resistance subgroup of PH. Both of the constants a and b decreased at the same time significantly (P<0.001) in the subgroup, which showed the predictive value for property of PH. Conclusion Ultrasonic and biomechanical method of PA would be useful in predicting property and pathological process of PH, which would provide a new way in selection of surgical treatment for congenital heart disease with PH potentially.
2007, 22(2):171-176. DOI: 10.3871/j.1004-7220.2007.2.176.
Abstract:Objective This study was undertaken to examine the material characteristics of BG-nHA gradient coatings and the bonding behaviour of the interface between the BG-nHA gradient coating and titanium alloy (Ti-6Al-4V) substrate. Methods The BG-nHA gradient coatings were prepared on the titanium alloy by using hypothermy sintering technology and the characteristics of coatings were evaluated by SEM、EDS、XRD and FITR. The bonding strength between the gradient coatings and the alloy substrate was tested according to ISO 13779-4:2002 before and after immersion in Tris- HCL buffer solution. The mass loss of the gradient coating and the ion released were determined. Results The results showed that the gradient coatings were porous and its surface were composed of rod-like nano-HA crystals. The interface between the coating and titanium alloy was dense and no cracks were found at the interface. The bond strength between coating and Ti-6Al-4V was 39.7±4.4Mpa. The mass loss and released ion increased gradually when immersed in Tris-HCL buffer solution. Conclusion The BG-nHA gradient coatings can be prepared by the hypothermy sintering technology and the bioactive glass reinforced nano-HA coatings have high bond strength to titanium alloy substrate.
2007, 22(2):177-180. DOI: 10.3871/j.1004-7220.2007.2.180.
Abstract:Objective To observe the stability of liquid resistance of cultured human ciliary muscle cells. Methods To observe the time for 7mm high liquid to penetrate through 3 groups of 8、14、20 days cultured 4 passage human ciliary muscle cells on Transwell (5 in each group). Results In groups of 14、20 days cells, the differences of penetrating velocity are within 15% among 60% Transwell、within 30% among 80% Transwell. Conclusion The resistance of cultured human ciliary muscle cells to liquid is almost stable.
2007, 22(2):181-184. DOI: 10.3871/j.1004-7220.2007.2.184.
Abstract:Objective To evaluate the effectiveness of adenovirus mediated human bone morphogenetic protein-2 gene transferred mesenchymal stem cells in the repair of segmental bone defect of long bone. Methods Unilateral rat femoral segmental defect model was used in this study.Thirty-six male Wistar rats were divided randomly into three groups:(1)Adv-hBMP-2 transduced MSC-collagen mix group; (2)Adv-βgal transduced MSC-collagen mix group; (3) untransduced MSC-collagen mix group. Contracted MSC-collagen mix was implanted in the defect site.The 4×106 cells were transplanted in each rat. Serial radiographs of rat femurs were examined at two, four, six and eight weeks postsurgery.Harvested specimens eight weeks postoperatively underwent histological and biomechanical analysis. Results The defects in group I (MSC/Adv-hBMP-2) appeared bone formation radiographically at two weeks postoperatively and united by eight weeks postoperatively. Histological analysis revealed that the defects in group I were filled with coarsd trabecular bone at eight weeks postoperatively. In those of the two control groups demonstrated little or no bone formation. Biomechanical test demonstrated that bending strength of femurs of the study group was 85%±8% to the opposite unoperated side at eight weeks postoperatively. Conclusion Adenovirus mediated bone morphogenetic protein-2 gene transferred syngeneic mesenchymal stem cells can repair segmental defects of long bones.
2007, 22(2):185-191. DOI: 10.3871/j.1004-7220.2007.2.191.
Abstract:Objective To reveal the reaction dynamic mechanism of the adhesive molecules being involved in the fluorescence recovery after photo-bleaching (FRAP) experiment of the "bull’s eye" type’s contact area, and to develop a new method to measure 2D kinetic rates of the adhesion molecules and their retarded diffusion by FRAP experiment. Method For the FRAP experiment of the "bull’s eye" type’s contact area, a coupled diffusion-reaction model of two different adhesive molecular systems is presented firstly, then the physical process of the FRAP is revealed by numerical modeling, and the behavior of the reaction rate and diffusive retarded coefficient in the FRAP is shown by analyzing the numerical results. Results The FRAP of the "bull’s eye" type’s contact area are governed not only by the 2D reaction rate but also by the diffusive retarded coefficient of the adhesive molecules; Firstly, the process of the FRAP is a free molecular diffusive in the edge domain of the "bull’s eye", then the effect of the reaction is more and more significant as time flows, and become a dominant factor. Conclusion The FRAP experiment of the "bull’s eye" type’s contact area can be modeled by our mathematical model, which can also be used to developed a new technique to measure 2D kinetic rates of the adhesion molecules and their retarded diffusion in a stable "bull’s eye" type’s contact area.
2007, 22(2):192-198. DOI: 10.3871/j.1004-7220.2007.2.198.
Abstract:Objective Using WLC model of inhibition neural system numerically analyzes neuron electric spike of crustacean stomatogastric ganglion to obtain the rhythm of gastric mill and pyloric network. Method The simulation method here show that the lateral teeth and the medial tooth of gastric network appear the states of cut, squeeze and grind of the food. Results The rhythm of pyloric network appears the synchronous oscillation of neurons AB, PD and VD. The gastric neural network and pyloric neural network appear the signal transmitting from neuron LPG to neuron VD. Conclusion These numerical results reveal the experiment phenomena of lobster stomatogastric neural system.
2007, 22(2):199-201. DOI: 10.3871/j.1004-7220.2007.2.201.
Abstract:Objectives Research on the compression viscoelasticity property of normal white rat and the osteoporosis femoral compression viscoelasticity property caused by alltransretinois acid to provide bioviscoelastic mechanics parameters for clinic. Methods Choose 30 Wistar white rats of 6-month old with 175-245gand randomly divided into 2 groups with 15 as normal group and 15 as model group alltransretinois acid was given (70mg·kg-1·d-1) to the model group two weeks. At the end of Week 12, execute the model rats to take the femora for telescope, stress relaxation, creep experiments. Results The femora stress relaxation,creep data and the curves of both the normal and model groups were received. The normalization for the stress relaxation and crept experimental data were made to get their functions and the curve. Conclusions The 7200s stress relaxation and the amount of creep indices in the model set were much lower than that of the normal group (P<0.05).
2007, 22(2):202-208. DOI: 10.3871/j.1004-7220.2007.2.208.
Abstract:Objective To study the mechanical principle of pleural indentation (PI) caused by lung cancer. Methods By using the software maths-"Matlab" and Finite Element Analysis-"Ansys", a biomechanics model of the lung was set to analyze the variation of PI in displacement, stress and strain under the pressure of thorax on the basis of clinical CT images. Results (1) The indentation part influenced by the cancer showed little deformation withthe minimum of 0.424 mm, while the indentation part far from the cancer has relatively much more deformation with the maximum of 60.248 mm. (2) During the inhalation, the bigger the Young’s module is, the more the degree of the indentation is; during the exhalation, the bigger the Young’s module is, the less the degree of the indentation is. (3) With the clinical CT picture we explain why the degree of the indentation during the inhalation is more than that during the exhalation. Because during the inhalation, the lung expands and the direction of deformation is opposite to that of indentation, which results in the growth of the depth of the indentation, while during the exhalation, the lung shrinks and the direction of deformation is the same as that of indentation, which brings on the decrease of depth of the indentation. Conclusion The principle for the formation of PI was explained based on the mechanics, which also accords with the clinical circumstances.
2007, 22(2):216-219. DOI: 10.3871/j.1004-7220.2007.2.219.
Abstract:The eukaryotic cytoskeleton is composed of three basic types of filaments and their associated proteins. Itfunctions not only to maintain cell shape, segregate cellular components and form organelles, but also plays important rolein the movement of cells, signals transduction, solute transportation, cell growth, differentiation and the regulation ofgenes expression. The cytoskeleton is sensitive to gravitational changes and can be altered when exposed to themicrogravity. Microgravity can induce changes in the cytoskeleton and affect cell growth, differentiation,mechanotransduction? as well as cell metabolism.