上下颌骨后牙区不同骨质参数对微种植体周围骨应力分布影响的三维有限元分析

发布时间：2018-08-05 19:05

【摘要】：目的:在临床正畸治疗中,支抗的控制非常重要,直接影响到了最终的疗效。随着技术的发展,种植体支抗不断完善。与很多传统的支抗相比,种植体支抗具有创伤小,体积小,口内的舒适度好,疗效好等优点,被广泛的应用到了临床治疗中。虽然微种植体在临床中应用广泛,但是骨-种植体界面上过大的应力常常会造成种植体周围骨损伤和骨结合的失败,脱落情况时有发生,成功率约90%。其中一主要影响因素是植入部位周围骨骼的质量。种植体的承载能力与植入部位骨质有很大关系,许多研究表明种植体的稳定性与皮质骨的厚度及密度密切相关,这些骨骼参数主要为:1、植入部位的皮质骨厚度2、皮质骨的密度3种植体周围松质骨的密度。一些研究证明皮质骨厚度越大,皮质骨和松质骨的密度越高就会降低种植体周围的应力集中,然而一些临床研究表明皮质骨密度过大种植体脱落率较高。目前这些参数对种植体临床应用的作用还不清楚,而且基于真实上下颌骨解剖数据的研究很少。三维有限元法常用来评估不同骨骼类型对种植体周围应力分布的影响,从而帮助研究者预测种植体加载后植入部位骨骼的应力分布。总之,微种植体提供强支抗的前提是其自身的稳定性,这与种植体周围颌骨质量和种植体周围骨密度密切相关。但皮质骨、松质骨的厚度及密度对微型种植体稳定性的作用尚不明确。本实验拟根据螺旋CT测量的上下颌骨后部数据,通过建立不同类型骨骼的有限元模型,分析不同骨质参数下微种植体-骨界面应力分布的特征,探讨不同骨质条件对种植体稳定性的影响,为临床工作提供理论依据。方法:1材料与设备实验设备:硬件:windows 7系统,螺旋CT软件:Mimics、ANSYS17.0有限元分析软件材料:纯钛,螺纹状微型种植体。2实验方法2.1上下颌骨螺旋CT扫描及测量从河北医科大学第二医院影像科资料中选取50例上下颌骨螺旋CT扫描的13-45周岁患者数据。纳入要求:1)汉族人口;2)无严重牙列拥挤,无滞留乳牙,无多生牙及牙齿缺失;3)无颅颌面发育畸形,左右侧基本对称,上下颌骨关系正常;4)无口腔颌面部外伤史及手术史;5)无全身骨代谢类疾病;6)无牙周病及牙槽骨病变,未行过牙根尖手术;7)无牙根形态严重畸形;8)图像清晰。扫描层厚0.625mm,将扫描结果进行上、下颌骨的三维重建。测量上下颌骨微种植体常用植入部位(在第二前磨牙与第一磨牙之间颊侧,第一、二磨牙之间颊侧,距离牙槽嵴顶6mm处)的皮质骨的厚度,皮质骨的密度,松质骨的密度,每处测量三次,取平均值。2.2设定骨质参数及计算材料属性根据上、下颌骨皮质骨厚度、密度及松质骨密度的测量结果,以5%及95%的数据为依据,确定皮质骨厚度为厚或薄,上颌骨皮质骨厚度为1.0mm和1.3mm,下颌骨为1.4mm和2.7mm,所得骨密度因为跨度较大,根据实验目的将皮质骨密度定为高、中及低三种数值,上颌皮质骨密度分别为1200Hu、1000Hu及600Hu,下颌颌骨皮质骨密度分别为1400Hu、1200Hu及960Hu,上下颌松质骨密度松质骨密度则定义为高、低两种,上下颌分别为520Hu和820Hu。将所测得的CT值Hu通过公式:Grayvalue=Hu+1024转化为像素值Grayvalue,按照Mimics提供的经验公式:Density=47+1.122*Grayvalue,E-Modulus=-172+1.92*Density计算出不同骨密度相对应的弹性模量见表2。并根据弹性模量定义不同骨质的和种植体的泊松比见表3。3微种植体-颌骨的三维有限元模型的建立3.1上下颌骨模型的建立从进行螺旋CT扫描50个病人中选择一年轻成年男性,选取该病人的CT图像,将其上颌第二前磨牙与第一磨牙之间的部位设定为微种植体的植入部位,并选择此处颌骨的CT断面,断面的外表面为皮质骨,内部为松质骨,在ANSYS软件中将CT断面简化为梯形,断面尺寸:上表面宽15mm,下表面宽13.5mm,高9.5mm。将其导入ANSYS软件中,将此断面沿着上颌骨横断面拉伸成20mm的六面体,构成上颌骨的模型。设定下颌一侧第二前磨牙与第一磨牙之间作为微种植体植入部位,选择此处的颌骨CT断面,断面的外表面是皮质骨,内部为松质骨,在ANSYS软件中将断面简化成六边形。六边形断面尺寸:上表面宽10.89mm,中间宽18.2mm,下表面宽11.94mm,高39mm。然后将面拉伸成长20mm的八面体,构成了下颌骨的模型。3.2微种植体三维有限元模型的建立微种植体的几何形态参照临床常用尺寸:总长度12mm,骨内段长度8mm、颈部直径1.6mm、尖端直径1.4mm、螺纹高度0.3mm、刃状螺纹顶角60o、螺距0.6mm,肩台高度2mm。在ANSYS17.0软件中,通过延伸生成圆柱形螺杆,通过对旋转生成螺纹,再由布尔运算将螺杆和螺纹合成螺钉,建立微种植体模型,见Fig.1。3.3微种植体与颌骨模型的装配3.4植入位置与角度在建立的颌骨模型上,分别在第二前磨牙与第一磨牙之间颊侧,距离牙槽嵴顶6mm,以与颌骨平面成45o植入微种植体。在种植体颈部施加1.96N的与牙槽骨表面平行的水平正畸力。见Fig.2。3.5建立不同参数的颌骨模型根据设定的皮质骨厚度建立包含微种植体在内上下颌骨不同皮质骨厚度的模型,共4个,并根据不同的皮质骨密度和松质骨密度对这四个模型进行二设,建立工况共24个。用Hypermesh软件对该模型进行网格划分,并在微种植体顶部施加平行于颌骨表面的正畸力1.96N,见Fig.2,用ANSYS软件进行三维模拟计算。4定义材料特性假设种植体,皮质骨和松质骨均为连续,均匀,各向同性的线弹性材料,材料变形为弹性小变形。建立相应的接触面,对内外颌骨接触面做绑定连接,假设种植体支抗与颌骨发生骨结合,微种植体与颌骨接触面定义为固定接触。5分析指标沿加力方向通过种植体的中心纵剖有限元模型,记录种植体-骨界面的应力峰值。6数据采集沿加力方向通过微种植体的中心纵剖有限元模型,并每隔0.1mm提取微型种植体-骨界面的应力值和位移值,将所采集的数值制成图表。7数据分析通过分析所采集的数据,研究在1.96 N水平正畸力的作用下上下颌骨不同骨质参数对微种植体稳定性的影响。结果:1建立了不同皮质骨厚度和骨密度下的微种植体-颌骨的有限元模型,它的形态及生物力学相似性高,满足实验的要求;2微种植体-骨界面的应力及位移分布情况:结果显示所有工况的Von-Mises应力分布均主要集中在皮质骨区域内,应力在皮质骨内迅速衰减,松质骨区域内的应力很小;松质骨内的最大应力值位于松质骨和皮质骨的交界处;最大应力峰值出现在U2HL,最小应力峰值出现在U1LH。位移在皮质骨区域内较为集中,位移峰值也位于皮质骨内,并且在皮质骨与松质骨交界处迅速减小,松质骨区域内的位移值较小。相同条件下,上颌骨的位移峰值均较下颌骨的位移峰值大。最大位移出现在U1LL,最小位移出现在L2HH;3皮质骨的厚度对微种植体周围位移分布的影响:当骨密度相同时,皮质骨厚度越大,皮质骨内的位移峰值减少,下颌骨的位移小于上颌。皮质骨的厚度越大,松质骨上的位移峰值越小;4皮质骨厚度对微种植体周围应力分布的影响:当皮质骨密度较高或中等时,皮质骨内的应力峰值几乎不受皮质骨厚度的影响;当皮质骨密度较低时,皮质骨内的应力峰值与皮至骨厚度成正比;皮质骨的厚度越大,松质骨内的应力峰值越小;5皮质骨密度对微种植体周围位移分布的影响:在根据不同皮质骨厚度建立的四个模型中,皮质骨密度越高,皮质骨内的位移峰值相对减小;松质骨内的位移峰值也减小;6皮质骨密度对微种植体周围应力分布的影响:当皮质骨厚度和松质骨的密度恒定时,皮质骨的密度与皮质骨内应力峰值成正相关;皮质骨的密度与松质骨内的应力峰值成负相关;7松质骨密度对微种植体周围位移分布的影响:当皮质骨厚度和密度恒定时,松质骨的密度越高,皮质骨内的位移峰值相对较小;位于松质骨上的位移也相对较小;8松质骨密度对微种植体周围应力分布的影响:当皮质骨厚度和密度恒定时,松质骨密度越高,皮质骨上的应力峰值越小,松质骨上的应力峰值越大。结论:1微种植体骨界面的最大应力及位移均主要集中在皮质骨内,并且在皮质骨和松质骨交界处迅速衰减,在松质骨内应力和位移都很小。2微种植体-骨界面的应力分布与皮质骨厚度及密度都有相关性。在皮质骨厚度越大,位于皮质骨上的应力峰值越大;位移峰值随着皮质骨厚度的增加减小。3种植体周围骨密度是影响种植体稳定性的关键因素。较高的松质骨密度可以减少应力和位移,有利于微种植体-骨界面的应力分布。皮质骨的密度与应力峰值正相关,与位移峰值为负相关关系,因此,植入部位皮质骨的密度不宜过低或者过高。
[Abstract]:Objective: in clinical orthodontic treatment, the control of anchorage is very important and directly affects the final curative effect. With the development of technology, the implant anchorage is constantly improved. Compared with many traditional anchorages, the implant anchorage has the advantages of small trauma, small volume, good comfort in the mouth, good curative effect and so on. It has been widely used in clinical treatment. Although microimplant is widely used in clinical practice, excessive stress on the bone implant interface often causes failure of bone injury and bone binding around the implant, and occurs when abscission occurs. The success rate is about 90%., one of the main factors affecting the bone mass around the implant site, the bearing capacity of implant and the bone implanted. Many studies have shown that the stability of the implant is closely related to the thickness and density of the cortical bone. These parameters are mainly: 1, the thickness of the cortical bone of the implant site 2, the density of the cortical bone 3 around the implant, and some studies have shown that the greater the thickness of the cortical bone, the higher the density of the cortical bone and the cancellous bone will fall. Stress concentration around low implants, however, some clinical studies have shown that the exfoliate rate of cortical bone density is high. The role of these parameters for implant clinical application is not clear, and the study based on the real and mandible dissection is rarely studied. Three dimensional finite element method is used to evaluate the different bone types to the implant week. The influence of the peri stress distribution helps researchers predict the stress distribution of the implant bone after the implant is loaded. In a word, the premise of the strong support is its own stability, which is closely related to the quality of the mandible around the implant and the bone density around the implant. But the thickness and density of the cortical bone and the cancellous bone are the micro species. The effect of the implant stability is not clear. This experiment is based on the data of the upper and lower mandibles measured by spiral CT. Through the establishment of the finite element model of different types of bone, the characteristics of the stress distribution of the implant bone interface under different bone parameters are analyzed, and the effect of different bone conditions on the stability of the implant is discussed and the theory is provided for the clinical work. Basis. Method: 1 material and equipment experimental equipment: Hardware: Windows 7 system, spiral CT software: Mimics, ANSYS17.0 finite element analysis software materials: pure titanium, threaded micro implant.2 test method 2.1 maxillary spiral CT scan and measurement from the Second Medical Department of Hebei Medical University imaging department data from the Second Medical Department of the mandible spiral CT scan 13-45 year old patient data. Included: 1) Han population; 2) no severe dental crowding, no detained teeth, no teeth and tooth loss; 3) no craniofacial malformation, basic symmetry of the left and right sides, normal maxillofacial relationship; 4) no oral maxillofacial history and hand history; 5) no systemic bone metabolism disease; 6) no periodontitis and alveolar bone lesions, 6) No root tip surgery; 7) serious malformation without root morphology; 8) clear image. Scanning layer thickness 0.625mm, scanning the results on, three-dimensional reconstruction of the mandible. Measurement of the upper and lower mandibular implants (the buccal side between the second premolar and the first molar, the cheek between the first, second molar, the distance from the crest of the alveolar ridge to the 6mm) The thickness of the bone, the density of the cortical bone and the density of the cancellous bone were measured three times per place. The bone thickness, density, and the density of the cancellous bone were measured on the basis of the bone thickness, density, and the density of cancellous bone on the basis of the measurement of the bone thickness, density, and the density of cancellous bone on the average value of.2.2. The thickness of the cortical bone was thick or thin, and the thickness of the maxillary cortical bone was 1.0mm and the thickness of the maxillary cortical bone. 1.3mm, the mandible is 1.4mm and 2.7mm, the bone density is large, the cortical bone density is determined as high, medium and low three values according to the experimental purpose. The maxillary cortical bone density is 1200Hu, 1000Hu and 600Hu respectively. The mandibular cortical bone density is 1400Hu, 1200Hu and 960Hu, and the density of the cancellous bone density of the upper and lower mandibular cancellous bone density is defined as high, The lower two, the CT value Hu measured by 520Hu and 820Hu. through the formula: Grayvalue=Hu+1024 converted to pixel value Grayvalue, according to the empirical formula provided by Mimics: Density=47+1.122*Grayvalue, E-Modulus=-172+1.92*Density calculated the modulus of elasticity of different bone density corresponding to table 2. and the definition of different modulus of elasticity according to the modulus of elasticity. The bone and implant Poisson ratio see table 3.3 the three-dimensional finite element model of the micro implant jaw bone of table 3.3 the establishment of a 3.1 upper and lower mandible model selected a young adult male from 50 patients with spiral CT scan, selected the CT image of the patient, and set the position between the maxillary second premolar and the first molar as the micro implant. The implant site, and select the CT section of the jaw bone, the outer surface of the section is cortical bone, and the internal is a cancellous bone. In the ANSYS software, the CT section is simplified as a trapezium. The section size: the width of the upper surface is 15mm, the lower surface is 13.5mm, and the high 9.5mm. is introduced into the ANSYS software, and the section is stretched along the maxillary cross section into the hexahedron of 20mm, and the upper jaw is formed into the upper jaw. Bone model. Set the second premolar and first molar between the mandible and the first molar as the implant site, select the CT section of the jaw bone here, the outer surface of the section is the cortical bone, the internal is the cancellous bone. In the ANSYS software, the section is simplified into hexagon. The hexagon section size: the width of the upper surface is 10.89mm, the middle width is 18.2mm, the lower surface is 11.94m wide 11.94m M, high 39mm. then stretched the surface into the eight surface of 20mm, forming a three-dimensional finite element model of the mandible model of the.3.2 micro implant. The geometric shape of the micro implant was established with reference to the common clinical dimensions: the total length 12mm, the length of the bone segment 8mm, the neck diameter 1.6mm, the tip diameter 1.4mm, the thread height 0.3mm, the blade like thread top 60o, and the pitch 0.6mm, In the ANSYS17.0 software, the shoulder height 2mm. generates a cylindrical screw by extending the screw and the screw and screw synthesis screw by the Boolean operation. The micro implant model is established by Boolean operation. The position and angle of the assembly of the Fig.1.3.3 micro implant and the jaw model are found in the second premolars, respectively, on the established jaw model. The buccal side between the first molar and the top of the alveolar ridge 6mm to implant the microimplant with the plane of the jaw 45o. The horizontal orthodontic force parallel to the surface of the alveolar bone was imposed on the neck of the implant. A different parameter of the jaw bone model was established to establish the different cortex of the upper and lower mandibles, including the microimplant, based on the set cortical bone thickness. The model of bone thickness is 4, and the four models are set up according to the different cortical bone mineral density and the density of the cancellous bone. 24 models are set up. The model is meshed with Hypermesh software, and the orthodontic force parallel to the surface of the jaw is applied to the top of the micro implant. Fig.2 is used to simulate.4 with ANSYS software. The material characteristics assume that the implant, the cortical bone and the cancellous bone are continuous, homogeneous, isotropic linear elastic materials, and the material is deformed into small elastic deformation. The corresponding contact surface is established to bind the contact surface of the internal and external jaw. It is assumed that the implant anchorage is associated with the bone of the jaw, and the contact surface of the implant and the jaw is defined as a fixed contact. The.5 analysis index passes the finite element model of the central longitudinal profile of the implant along the direction of adding force, records the stress peak.6 of the implant bone interface, through the central longitudinal profile finite element model of the microimplant along the direction of the adding force, and extracts the stress and displacement values of the micro implant bone interface every 0.1mm, and makes the figure.7 By analyzing the data collected, the effects of different bone parameters on the stability of the micro implant were studied under the effect of 1.96 N level orthodontic force. Results: 1 the finite element model of the micro implant jaw bone under different cortical bone thickness and bone density was established, and its morphological and biomechanical similarity was high and satisfied the experiment. The stress and displacement distribution of the 2 micro implant bone interface: the results show that the stress distribution of Von-Mises in all conditions mainly concentrated in the cortical bone region, the stress is rapidly attenuated in the cortical bone, the stress in the cancellous bone is very small; the maximum stress in the cancellous bone is located at the junction of the cancellous bone and the cortical bone; the maximum stress peak is at the peak. The value of the minimum stress appears at U2HL, the peak stress peak appears in the cortical bone region, the peak of the U1LH. displacement is more concentrated, the peak displacement is also located in the cortical bone, and it decreases rapidly at the junction of the cortical bone and the cancellous bone, and the displacement value in the cancellous bone is small. The peak displacement peak of the maxilla is larger than the peak displacement of the mandible under the same condition. The minimum displacement appears at U1LL, the minimum displacement appears in L2HH; the thickness of 3 cortical bone affects the distribution of the displacement around the implant: when the bone density is the same, the greater the thickness of the cortical bone, the decrease in the peak displacement in the cortical bone, the lower displacement of the mandible is smaller than that of the maxilla. The greater the thickness of the cortical bone, the smaller the peak displacement on the cancellous bone; the 4 cortical bone thickness to the micro implant. The influence of stress distribution around the body: when the cortical bone density is high or medium, the peak stress in cortical bone is almost unaffected by cortical bone thickness; when the cortical bone density is low, the peak stress in the cortical bone is proportional to the thickness of the skin to the bone; the greater the thickness of the cortical bone, the smaller the peak stress in the cancellous bone, and the 5 cortical bone density to the micro species. The influence of the displacement distribution around the implant: the higher the cortical bone density, the relative decrease in the cortical bone displacement and the decrease in the peak displacement in the cancellous bone in the four models based on the thickness of the cortical bone, and the effect of 6 cortical bone density on the distribution of stress around the implant: when the thickness of cortical bone and the density of the cancellous bone is constant, skin The density of the cortical bone was positively correlated with the peak stress peak in the cortical bone; the density of cortical bone was negatively correlated with the peak stress in the cancellous bone; 7 the influence of the density of the cancellous bone on the distribution of the displacement around the implant: the higher the density of the cortical bone and the density, the higher the density of the cancellous bone and the smaller displacement peak in the cortical bone; located on the cancellous bone. The displacement is relatively small; 8 the effect of the density of the cancellous bone on the stress distribution around the micro implant: when the thickness and density of the cortical bone are constant, the higher the density of the cancellous bone, the smaller the peak stress on the cortical bone and the peak stress on the cancellous bone, the greater the stress and the displacement of the 1 implant bone interface are mainly concentrated in the cortical bone, and At the junction of cortical bone and cancellous bone, the stress and displacement of the cancellous bone are very small in the.2 micro implant bone interface, and the stress distribution of the bone interface is related to the thickness and density of the cortical bone. The greater the thickness of the cortical bone, the greater the peak stress on the cortical bone; the peak displacement decreases with the increase of cortical bone thickness around the.3 implant. Bone density is a key factor affecting the stability of implants. High cancellous bone density can reduce stress and displacement, and is beneficial to the stress distribution of the implant bone interface. The density of the cortical bone is positively correlated with the peak stress and is negatively related to the peak displacement. Therefore, the density of the cortical bone at the implant site should not be too low or too high.
【学位授予单位】：河北医科大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R783.5

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