包含真实螺纹形态的牙种植体三维有限元模型的建立

目的：建立包含真实螺纹形态的牙种植体三维立体有限元模型，为深入研究螺纹型牙种植体骨界面力学规律和种植体的外形优化设计提供模型支持。方法：采用画图软件SolidWorks绘出螺纹型牙种植体和局部下颌骨骨块三维立体模型，利用ABAQUS有限元分析软件，建立三维有限元模型：对种植体上端施加一斜向载荷，分析骨块内应力、应变分布情况。结果：建立了与螺纹型牙种植体实体相一致的三维有限元模型，施加载荷，确定应力、应变的大小及分布。结论：探索了一种可行的建立包含真实螺纹形态的种植体三维立体有限元模型的方法，建立的种植体有限元模型与实体具有高度的相似性，可用于研究螺纹型种植体骨界面应力、应变的分布规律，并为种植体螺纹形态的力学优化设计研究提供模型支持。     

微型种植体下颌骨三维有限元模型的建立

目的探索一种可行的建立包含微型种植体不同植入方向及角度的下颌骨三维有限元模型的方法,为支抗种植体相关研究提供模型支持。方法本文基于CT数据,采用CAD（Pro/E）及ANSYS软件,用轮廓延伸法建立简化下颌骨模型,模拟临床实际常用植入部位,建立微型种植体不同植入方向及角度的下颌骨三维有限元模型。结果建立了5个真实螺纹形态的微型种植体植入的下颌骨有限元模型。结论本实验建立的有限元模型的几何相似性、生物力学相似性及临床适应性均达到实验要求,为支抗种植体三维有限元分析提供了一种准确、灵活、快速的平台。     

Pro/E的自适应功能在建立螺纹型牙种植体骨块三维有限元模型中的应用

目的：探讨利用Pro／E软件自适应功能建立包含不同螺纹形态、不同螺距牙种植体的下颌骨骨块的三维有限元模型的方法。为不同螺纹界面的力学分析,螺纹的优化设计提供分析平台。方法：使用pro／E软件建立包含不同螺纹形态、不同螺距的牙种植体的下颌骨骨块三维实体模型,导入ansys workbench9．0有限元分析软件中,进行单元划分、初始应力的验证分析,建立三维有限元模型。结果：螺纹角度、尺寸与设定相同,形状同真实螺纹完全一致,力学分析结果与文献报道一致。结论：探索了基于Pro／E软件自适应功能建立含有不同螺纹形态、不同螺距牙种植体的下颌骨骨块的三维有限元模型的方法,提高了建模的准确性,灵活性和速度,所建模型能够满足不同螺纹界面应力的力学分析的要求,也为螺纹的优化设计提供分析平台。     

下颌牙种植体即刻加载三维有限元模型的建立

目的:建立包含即刻加载螺纹种植体的下颌骨三维有限元模型,以深入研究牙种植体即刻加载骨界面的力学分布规律。方法:以女性无牙牙合下颌骨为标本,采用螺旋CT扫描,DICOM格式保存。将DICOM数据导入计算机,用自主开发的通用外科手术集成系统(UniversalSurgicalIntegrationSystem,USIS)和ANSYS软件进行划分单元建模,并模拟ITI螺纹种植体的真实形态,在下颌骨前牙区植入3颗种植体,模拟种植体即刻加载的状态,将种植体骨界面定义为滑动摩擦。结果:建立了结构精确的含即刻加载螺纹种植体的下颌骨三维有限元模型,牙种植体螺纹螺旋形态连续一致。结论:本实验建立的有限元模型的几何相似性、生物力学相似性及临床适应性均达到实验要求,为进一步研究牙种植体即刻加载的骨界面力学分布提供了良好的基础。     

带凹槽螺纹种植体三维有限元模型的建立

目的：利用CAD软件的自适应功能建立包含Branemark TiUniteTM型带凹槽种植体骨块三维有限元模型。方法：应用pro/E软件根据种植体相关参数,建立牙种植体、冠修复体、松质骨和皮质骨三维实体模型,利用自适应功能生成装配体,导入Ansys Workbench10.0CAE软件中,进行单元划分建立有限元模型,应力加载后进行模型准确性的检测。结果：建立了包含真实螺纹种植体的下颌骨骨块三维有限元模型。结论：应用Pro/E软件自适应功能建立包含种植体的下颌骨骨块的三维有限元模型,为种植修复三维有限元分析提供了一种准确、灵活、快速的平台。     

微小种植体支抗的三维有限元分析

目的 利用三维有限元进行微小种植体应力分析,寻找最适合正畸临床使用的微小种植体。方法 利用ANSYS软件建立10mm×20mm×30mm的颌骨骨块三维有限元模型;同时建立的长度为7mm、9mm、11mm,螺纹顶角为30°、60°、90°的9种圆柱状有螺纹微小种植体三维有限元模型;模拟微小种植体植入颌骨内并建立植入后模型,对微小种植体骨界面进行应力分析。结果 经ANSYS软件对微小种植体骨界面的应力分析,在不同角度的微小种植体中,螺纹顶角为60°的微小种植体三维有限元模型周边最大应力值最小,最适于临床使用。不同长度的微小种植体中,长度为7mm的微小种植体三维有限元模型周边最大应力值明显大于其他两种,不适用于正畸临床。9mm和11mm微小种植体三维有限元模型周边最大应力值差别不大,11mm微小种植体三维有限元模型周边最大应力值略小于9mm微小种植体三维有限元模型周边最大应力值。结论 螺纹顶角为60°,9mm以上的微小种植体适于正畸临床做为支抗使用。     

三种螺距对种植体初期稳定性影响的有限元研究

目的：利用即刻负载有限元模型,研究种植体不同螺纹螺距因素对初期稳定性的影响。方法：利用Pro／E软件、Hypermesh软件及ABAQUS有限元软件,建立四类种植体即刻负载的三维有限元模型,比较3种螺纹螺距（0．8mm、1．6mm、2．4mm）在分别垂直和水平加载时,对种植体初期稳定性的影响。结果：对不同螺纹螺距种植体来说,垂直加载和水平加载时0．8mm螺距螺纹种植体微动最小,2．4mm螺距螺纹种植体微动最大。结论：螺纹的螺距对垂直相对位移有影响,对水平相对位移影响不大。随着螺距的增加,种植体对抗垂直向载荷的抵抗力减弱。水平加载时,螺纹的螺距对颈部微动影响不明显。     

种植体支抗三维有限元模型的建立

目的：建立人磨牙缺失区下颌骨正交各向异性种植体支抗三维有限元模型,为精确分析支抗种植体系统的生物力学特性奠定基础。方法：以人磨牙缺失区下颌骨为标本,取其缺牙区颌骨断面形态输入计算机,通过ANSYS5．5（Swanson Analysis Systems,Inc.Houston,USA)有限元分析软件将面轮廓作样条曲线拟合处理,形成逼真、光滑的颌骨断面轮廓图,然后采用断面拉伸技术重建牙齿缺失区下颌骨的三维模型,再将已做成的的种植体三维模型与下颌骨模型拟合并对其进行单元网络智能划分后建模。结果：建立起有效的种植体支抗三维有限元生物力学分析模型。结论：模型的几何相似性,生物力学相似性及临床适应性均佳,可以模拟支抗种植体在正畸载荷状态下骨界面应力分布状况。     

含不同种植体的腭部三维有限元模型的建立

目的:通过建立一个含不同直径、不同长度种植体的上颌骨三维有限元模型,并进行应力分析,选出最佳的支抗种植体。方法:采用螺旋CT扫描、数字影像传输、CAD技术、UG和ANSYS软件相结合的方法,建立部分上颌骨三维有限元模型,将不同直径、不同长度的支抗种植体植入腭部。结果:建立了符合生物力学研究需要的含腭部种植支抗的部分上颌骨三维有限元模型,探索出一条数字化程度高的三维有限元建模方法。结论: 应用螺旋CT扫描、数字影像传输以及UG、ANSYS软件相结合的方法,建立含支抗种植体的部分上颌骨三维有限元模型是切实可行和有效的。模型与生物实体真实结构具有良好的几何相似性,为有限元研究提供科学的参考依据。     

含牙种植体下颌骨三维有限元模型的建立

目的:提出一种较快建立含牙种植体的下颌骨三维有限元模型的方法,为口腔生物力学的研究提供数学模型基础。方法:利用螺旋CT扫描,数字影像传输与转录以及UG软件相结合的办法建立含牙种植体的下颌骨三维有限元模型。结果:建成后的三维有限元模型与实体组织具有良好的几何相似性,模型可以根据需要进行旋转、缩放、透视、剖开等多种方式观察,可以提出组成模型的不同面和体来观察某一部分的情况,还可以根据不同的研究目的和要求删除和添加材料或组织,以及改变组织和材料的特性。结论:将CT扫描技术与有限元方法相结合,建立的三维有限元模型能较真实地模拟实际情况,为口腔生物力学的研究和临床种植设计提供了研究手段。     

不同锥度根管锉对根管壁抗折强度的影响

目的：比较不同锥度镍钛根管锉对根管壁抗折强度的影响,并探讨有限元分析在根管治疗中的应用价值。方法：选取24颗离体下颌前磨牙,去除冠部后,随机分为 A、B、C、D 4组。A、C 2组使用0.04锥度Z-K3镍钛锉进行根管预备,B、D 2组使用0.06锥度Z-K3镍钛锉进行根管预备。对根管预备后的C、D 2组进行3次2 mm切片处理。从A、B组中随机选取2个样本,使用micro-CT进行扫描。将扫描模型导入不同软件,进行优化,并建立装配体模型,导入Ansys进行有限元分析。使用万能试验机与加力棒对样本施加100 N的力,直到样本任一处发生折裂,记录断裂载荷并进行对比分析。结果：有限元分析结果显示,0.04、0.06锥度模型的最大应力值分别为138.88 MPa和78.812 MPa。A、B组样本平均断裂载荷分别为490.12 N和501.83 N,C、D组牙切片的最大平均断裂载荷出现在颈部,分别为93.61 N和141.53 N。从颈部,到中部,再到尖部,根管的平均断裂载荷依次减小。结论：对于形态正常的下颌前磨牙,使用0.06锥度的镍钛旋转锉对根管进行处理,得到的根管抗折强度比使用0.04锥度处理更高。三维有限元分析法可以指导在根管治疗中选择合适锥度的锉,以降低根折发生率。     

Periodontal ligament hydrostatic pressure with areas of root resorption after application of a continuous torque moment

OBJECTIVE: To evaluate the risk of root resorption, individual finite element models (FEMs) of extracted human maxillary first premolars were created, and the distribution of the hydrostatic pressure in the periodontal ligament (PDL) of these models was simulated. MATERIALS AND METHODS: A continuous lingual torque of 3 Nmm and 6 Nmm respectively was applied in vivo to the aforementioned teeth. After extraction, FEMs of these double-rooted teeth were created based on high-resolution microcomputed tomographics (micro CT, voxel size: 35 microns). This high volumetric resolution made the recognition of very small resorption lacunae possible. Scanning electron micrographs of the root surfaces were created as well. This enabled the investigation of advantages and disadvantages of the different imaging techniques from the viewpoint of the examination of root resorption. Using the FEMs, the same loading conditions as applied in vivo were simulated. RESULTS: The results of clinical examination and simulations were compared using the identical roots of the teeth. The regions that showed increased hydrostatic pressure (>0.0047 MPa) correlated well with the locations of root resorption for each tooth. Increased torque resulted in increased high-pressure areas and increased magnitudes of hydrostatic pressure, correlating with the experiments. CONCLUSION: If hydrostatic pressure exceeds typical human capillary blood pressure in the PDL, the risk of root resorption increases.     

Root canal systems of the mandibular and maxillary first permanent molar teeth of south Asian Pakistanis

AIM: The purpose of the present ex vivo study was to investigate variations in the root canal systems of mandibular and maxillary first permanent molar teeth of South Asian Pakistanis. METHODOLOGY: The root canal systems of a sample of 30 mandibular and 30 maxillary first permanent molar teeth extracted from South Asian Pakistanis were studied using a clearing technique. RESULTS: The mesial roots of the mandibular molar teeth typically presented with two canals (97%) of type II, IV or VI configuration. The distal roots of these teeth presented with a single canal (50%) of type I or V configuration or with two canals (50%) of type II, IV or VI. The prevalence of four root canals in two-rooted mandibular first permanent molar teeth was 47%. In maxillary molar teeth the mesial roots with a single canal (47%) were type I or type V; those with two canals (53%) were type II, IV or type VI. The distal and palatal roots that presented as a single canal (100%) were type I or type V configuration. The prevalence of four root canals in three-rooted maxillary first permanent molar teeth was 53%. CONCLUSION: It is concluded that four root canals in mandibular and maxillary first permanent molar teeth of South Asian Pakistanis is a common occurrence. The distribution of the different configurations of root canal systems in this population differed from that in Caucasian groups, suggesting that variations in root canal systems may be attributed to racial divergence.     

国产微螺钉种植体支抗压低牙齿动物实验研究

目的研究国产微螺钉种植体支抗压低磨牙过程中种植体-骨界面结合状况及种植体稳固度。方法4条成年Beagle犬分别于双侧下颌前磨牙根尖下植入国产微螺钉种植体共8枚。植入后即刻以种植体为支抗对下颌前磨牙施以压低力，力值100g，时间3个月。加力结束后进行种植体及其周围组织的组织学检查。结果所有被加载的8枚种植体均保持良好稳固度，无移位。下颌前磨牙垂直高度平均减小3．12mm，同时出现了一定程度的颊侧倾斜，未见明显根尖及根分歧牙骨质吸收。加载种植体平均骨整合率为39．5％。结论微螺钉种植体支抗可以完成牙齿的压低移动并可保持良好稳固度。骨整合主要发生在种植体-皮质骨界面，松质骨中极少发生骨整合。     

Group distal movement of teeth using microscrew implant anchorage

The purpose of this study was to quantify the treatment effects of distalization of the maxillary and mandibular molars using microscrew implants. The success rate and clinical considerations in the use of the microscrew implants were also evaluated. Thirteen patients who had undergone distalization of the posterior teeth using forces applied against microscrew implants were selected. Among them, 11 patients had mandibular microscrew implants and four patients had maxillary implants, including two patients who had both maxillary and mandibular ones at the same time. The maxillary first premolar and first molars showed significant distal movement, with no significant distal movement of the anterior teeth. The mandibular first premolar and first and second molars showed significant distal movement, but no significant movement of the mandibular incisor was observed. The microscrew implant success rate was 90% over a mean application period of 12.3 +/- 5.7 months. The results might support the use of the microscrew implants as an anchorage for group distal movement of the teeth.     

Stress distribution of oval and circular fiber posts in amandibular premolar: a three-dimensional finite element analysis

PURPOSE

The aim of the present study was to evaluate the effects of posts with different morphologies on stress distribution in an endodontically treated mandibular premolar by using finite element models (FEMs).

MATERIALS AND METHODS

A mandibular premolar was modeled using the ANSYS software program. Two models were created to represent circular and oval fiber posts in this tooth model. An oblique force of 300 N was applied at an angle of 45° to the occlusal plane and oriented toward the buccal side. von Mises stress was measured in three regions each for oval and circular fiber posts.

RESULTS

FEM analysis showed that the von Mises stress of the circular fiber post (426.81 MPa) was greater than that of the oval fiber post (346.34 MPa). The maximum distribution of von Mises stress was in the luting agent in both groups. Additionally, von Mises stresses accumulated in the coronal third of root dentin, close to the post space in both groups.

CONCLUSION

Oval fiber posts are preferable to circular fiber posts in oval-shaped canals given the stress distribution at the post-dentin interface.     

固定桥不同桥体龈端形态修复下颌第一磨牙的三维有限元分析

目的 应用三维有限元分析法探讨不同桥体龈端形态对固定桥基牙及牙周膜应力分布的影响.方法 利用健康成人牙列的锥形束CT(CBCT)原始数据,通过三维建模软件建立下颌第一磨牙缺失,第二前磨牙与第二磨牙为基牙的双端固定桥,并模拟三种不同桥体龈端形态,即改良鞍式、改良盖嵴式、船底式.利用Ansys 17.0对已建立的三种不同龈...     

Treatment of open bite with microscrew implant anchorage.

Open bite treatment with microscrew implant anchorage is discussed in relation to vertical control of the posterior dentoalvelar dimension. Maxillary microscrew implants provided anchorage for intruding the posterior teeth and retracting the anterior teeth; mandibular microscrew implants were used to apply intrusion force distal to the mandibular first molars to prevent mesial tipping of the posterior teeth during space closure. Closing the mandibular plane after intruding the maxillary posterior teeth and bodily mesial movement of the mandibular posterior teeth contributed to facial profile improvement. The efficacy and potency of microscrew implants in open bite treatment are discussed.     

Root form and canal morphology of mandibular premolars in a Jordanian population

AIM: To investigate the root canal anatomy of mandibular premolars in a Jordanian population. METHODOLOGY: Nine hundred extracted mandibular premolars were examined. After the length of the teeth was measured, the presence of developmental grooves and furcated roots was noted. Following the preparation of access cavities, pulp tissue was removed and the canal systems were stained. The teeth were then rendered clear by demineralization and immersion in methyl salicylate. Cleared teeth were examined and the following features were evaluated: (i) type of root canals; (ii) presence and location of lateral canals; transverse anastomosis; (iii) location of apical foramina; and (iv) frequency of apical deltas. RESULTS: The mean lengths of first and second mandibular premolars were 22.6 mm (18-27.5 mm) and 22.2 mm (16-26.5 mm), respectively. Although the majority of the specimens corresponded to Vertucci's classification scheme, analysis of this large data set revealed four additional root canal morphologies. Variable root canal morphologies were found in the mandibular first premolars; two separate apical foramina were found in 33% of the teeth with two canals, compared to 6.2% with one apical foramen. Teeth with three separate apical foramina were scarce (2.2%). The majority of the mandibular second premolars had a single canal; 72% of teeth possessed type I canal systems, whilst 22.8% of the roots had two canals with two separate apical foramina. CONCLUSIONS: The prevalence of multiple canals in the investigated Jordanian mandibular premolars was high, especially for the second mandibular premolar, in comparison with previous studies performed on populations of different racial origin.