不同长度铸造分体桩核修复重度缺损上颌磨牙三维有限元分析

目的通过三维有限元法分析不同长度铸造分体桩核修复重度缺损上颌第一磨牙后牙体组织应力分布。方法以右上颌第一磨牙为标本,通过CT扫描获得图像信息,采用Mimics三维建模软件、FreeForm视觉设计系统,建立五种不同长度铸造分体桩修复重度缺损上颌第一磨牙的三维有限元模型,利用Ansys有限元软件比较加载后牙体组织的Von Mises应力、最大拉应力分布和变化。结果随着铸造分体桩中颊根桩长度增加,上颌磨牙牙体组织Von Mises应力峰值减小,但拉应力峰值却增大;随着铸造分体桩中腭根桩长度增加,上颌磨牙牙体组织Von Mises应力峰值和拉应力峰值均减小。结论铸造分体桩修复重度缺损上颌第一磨牙时,根桩长度影响牙体组织应力分布。     

牙体缺损程度对后牙桩核冠修复牙本质应力影响的三维有限元分析

目的:比较上颌第一磨牙不同程度牙体缺损桩核冠修复后牙本质应力分布情况,探讨牙体剩余量与牙本质应力分布之间的关系。方法:通过磨片法建立上颌第一磨牙桩核冠有限元模型,比较上颌第一磨牙4种不同程度牙体缺损桩核冠修复后的牙本质应力分布情况。结果:后牙牙体水平向缺损量超过其牙冠牙体量1/2时,牙本质应力峰值较高,缺损量在牙冠牙体量1/2以内,对应力峰值无显著影响。结论:当水平向牙体剩余量大于1/2时,剩余牙体组织所受应力较大,上颌第一磨牙的腭根根分叉处是根折的危险区域。     

不同桩核系统修复上颌第一磨牙的有限元分析

目的：利用有限元法分析不同数目桩、不同材料桩核及不同载荷对磨牙桩核冠修复后剩余牙体组织的应力大小及其分布的影响。方法：采用CT扫描上颌第一磨牙,有限元法建立不同数目桩及不同材料桩核修复上颌第一磨牙后的模型,载荷1以480 N总载荷垂直加载模拟正中咬合,载荷2以200 N总载荷与牙长轴成45°斜向加载模拟咀嚼,采用MSC.Marc软件分析剩余牙体组织的Von Mises应力大小及其分布。结果：随桩核材料弹性模量的增加,牙颈部Von Mises应力峰值减小,牙根内表面的应力值增加;铸造桩组腭根和远中颊根桩修复时,桩周牙本质的应力峰值小于腭根桩修复及腭根和近远中颊根桩修复;载荷2条件下,牙颈部的应力峰值较载荷1条件下的应力峰值小,而牙根内表面的应力峰值较大。结论：桩的数目、桩核材料及载荷大小与方向均对磨牙桩核冠修复后剩余牙本质的应力大小和分布有影响。     

不同桩材料对双根管桩核冠牙本质应力的影响

目的:从生物力学角度研究3种不同桩核材料修复双根管桩核冠前后牙本质中的应力分布,为临床双根管桩核冠选择合适的桩核材料提供科学依据.方法:采用螺旋CT扫描数据建立上颌第一前磨牙的三维有限元模型,在此基础上,分别就平行于牙体长轴加载和与牙体长轴呈45°夹角加载两种情况对铸造Co-Cr合金、铸造金合金、碳纤维桩3种材料进行桩核修复前后的牙本质应力分布情况的数值分析.结果:与桩修复前相比,铸造Co-Cr合金桩修复在两种加载状况下桩尖周围牙本质的最大主应力和Von Mises应力峰值分别增大了67.3%、58.2%、75.8%、81.2%;而采用与牙本质弹性模量相近的材料碳纤维桩修复后,牙本质中的应力分布与修复前相比改变很小.铸造金合金桩修复前后,牙本质中的应力状况改变较为显著.结论:影响桩植入前后的牙本质中应力变化最显著的因素是桩材料的弹性模量.与牙本质弹性模量相近的材料碳纤维桩,适合于双根管桩的修复.     

纤维桩和金属桩全冠修复后下颌第一磨牙残根的有限元应力分析

目的 分析经金属桩和纤维桩全冠修复后下颌第一磨牙残根在静态及动态载荷下,剩余牙体组织应力分布形式和应力大小.方法 利用有限元法分别建立下颌第一磨牙残根纤维桩核冠和金属桩核冠修复的模型,静态载荷为在牙冠表面施加与牙体长轴一致的225N的压力,动态载荷为225N的半正弦脉冲,历时1ms.记录2种载荷下各部位牙本质von Mises应力最大值以及最终时刻的牙本质von Mises应力.结果 2种载荷下,2种桩核系统修复后牙本质最大Von Mises应力都位于牙本质颈部近舌侧.动态载荷下,牙本质最大Von Mises应力超过100Mpa.2种载荷下,纤维桩修复后牙本质各部位的Von Mises应力基本都略小于金属桩修复.动态载荷下,根分歧区的应力明显增大,显著高于其他部位.结论 动态载荷下颈部的应力值大于牙本质的抗折强度.金属桩修复的牙本质应力普遍大于纤维桩,纤维桩能较好地分散应力,可以考虑作为后牙残根的一种较好的修复方式.     

纤维桩对复合树脂修复根管治疗后磨牙影响的有限元研究

目的 探讨上颌第一磨牙根管治疗后树脂充填修复和纤维桩结合树脂充填修复对其牙体及充填体的应力分布的影响。方法 采用计算机体层摄影术（CT）、有限元法建立根管治疗后树脂修复（A组）及纤维桩树脂修复（B组）的上颌第一磨牙模型,以600 N总载荷垂直加载模拟最大咬合力,以200 N总载荷45°斜向加载模拟咀嚼力,分析两组模型的牙体及充填体Von Mises应力特征。结果 A组、B组的牙体Von Mises应力分布模式相似,B组颊侧颈部形成应力集中,应力峰值位于釉牙骨质界;最大咬合力条件下,B组Von Mises应力峰值在牙本质外表面低于A组,内表面高于A组;咀嚼力条件下,B组Von Mises应力峰值在剩余牙体的各部位均较A组低。B组树脂充填体表面的Von Mises应力峰值及高应力区范围均明显小于A组。结论 纤维桩的存在可降低牙本质及树脂充填体的应力峰值,提高患牙抗折强度,而颈部应力集中可能导致牙折发生位置偏高。     

下颌磨牙残冠纤维桩核冠修复的有限元应力分析

目的 分析下颌第一磨牙残冠不同缺损壁数的情况下,不同数目、不同部位的纤维桩核冠修复的应力分布情况和应力大小.方法 利用三维有限元法建立下颌第一磨牙残冠2壁和3壁缺损情况下,不同数目和不同部位的纤维桩核冠修复模型,施加225N垂直向的静态载荷及动态载荷.记录两种载荷下各部位牙本质von Mises应力最大值和最大主应力.结果 下颌磨牙2种缺损状态在动静态载荷下,未植入纤维桩组最大Von Mises应力最大,均高于植入纤维桩组,近中植入2根纤维桩组和植入3根纤维桩组的应力分布最均匀.下颌磨牙3壁缺损在静态载荷下,植入3根纤维桩组最大,Von Mises应力明显小于其他2组.结论 2壁缺损情况下,考虑选择植入1根纤维桩.3壁缺损情况下,可以考虑通过增加纤维桩数量来分散应力,减小牙体折裂风险.     

不同设计桩核的后牙残根核桩冠修复体的三维有限元应力分析

目的采用三维有限元法比较不同长度和数目桩核、不同材料桩核对后牙残根桩核冠修复体牙本质应力大小及其分布的影响,探讨后牙残根桩核冠修复时合理的桩核设计及选材。方法采用CT扫描、Mimics软件及Abaqus软件建立上颌第一磨牙桩核冠的三维有限元模型。根据桩长度和数目的不同、桩核材料的不同,将上颌第一磨牙桩核冠的三维有限元模型分为相应的实验组。在模型咬合面上选取3个载荷点,分别施加80 N的载荷,计算各实验组中牙本质上的Von mises应力、最大主应力、剪切应力的应力峰值及分布方式。结果在桩长度和数目不同时,随着桩长度和数目的增加,牙本质上各项应力峰值呈现不规律变化。在不同桩核材料时,随着桩核材料弹性模量的增加,牙本质上的Von mises应力、最大主应力、剪切应力峰值均减小。结论在本实验研究条件下,不同桩长度和数目、不同桩核材料对后牙残根桩核冠修复体牙本质上的应力峰值和应力分布均有影响。     

上颌中切牙斜形折裂修复设计的有限元分析

目的:通过三维有限元方法分析研究上颌中切牙斜形折裂采用不同方式修复后的应力分布。方法:利用CBCT及三维有限元软件,建立上颌中切牙斜形折裂的有限元模型,并对缺损牙按照3种修复方法建模,分析各组模型在侧向力下的Von Mises等效应力和最大主应力分布与峰值。结果:(1)同种折断模式下,剩余牙体组织等效应力值:纤维桩核冠组最大,5 mm髓腔固位冠组最小;修复体等效应力值:铸造桩核冠组最大,纤维桩核冠组最小;纤维桩核冠组粘结层的等效应力峰值最高。(2)随着肩领高度增加,剩余牙体组织等效应力均减小,纤维桩核冠组和铸造桩核冠组比髓腔固位冠组递减率更大;且舌侧肩领高度增加比唇侧肩领高度增加所造成的剩余牙体组织等效应力递减率更大。结论:完整且高度足够的牙本质肩领是上前牙大面积缺损时采用纤维桩核冠和铸造桩核冠修复的必要条件,当牙本质肩领不完整时,舌侧肩领比唇侧肩领更有利于提高残根的抗折性。当上颌中切牙斜形折裂,肩领不完整时,采用髓腔固位冠修复的应力分布优于桩核冠,其中固位体深度为5 mm的髓腔固位冠可能是最佳修复方式;若采用桩核冠修复,铸造桩核冠比纤维桩核冠更有利于剩余牙体组织应力均匀分布。     

纤维桩与金属桩核修复磨牙牙体缺损的三维有限元应力分析

目的：通过对磨牙牙体破坏较大的牙体缺损，采用纤维桩与铸造镍铬合金桩核、金合金桩核修复进行三维有限元应力分析，为临床应用提供一定的理论依据。方法：运用逆向工程技术法建立上下颌第一磨牙牙尖交错胎及尖对尖咬合状态的三维有限元模型，于上颌第一磨牙牙颈部平面施加均布载荷，进行静力与冲击动力计算，观察牙本质Mohr应力值的变化。结果：静载及动载下3种桩核修复，牙本质最大Mohr值均小于牙本质拉伸极限强度；牙本质最大Mohr值均位于根分歧部位，以纤维桩修复者为小；金合金桩核对减轻牙颈部应力明显；冲击载荷较静载下的应力变化一冲击系数均接近1。结论：3种桩核修复在临床上虽均可行，但建议临床上除牙颈部的的牙体组织过于薄弱或修复牙体组织缺损时固位需要外，尽量不使用桩核；其中，以纤维桩和金合金桩核为好；在有限元应力分析中，静载的研究是可行的。     

CBCT与RVG对下颌恒切牙根管形态评估的对比研究

目的:对比CBCT法与数字化X线成像法(RVG)对下颌恒切牙根管形态评估的差异。方法:对101颗离体牙进行唇舌向及近远中向数字化X线片拍摄和CBCT高清牙列模式扫描,对图像进行根管数目、Vertucci根管分型、根管钙化和根尖口开口位置的评估,并通过CBCT图像建立偏角度投照的三角函数模型,计算偏向投照的角度。结果:CBCT法显示有30颗为双根管,RVG近远中向投照显示有36颗为双根管,卡方检验显示对根管数目和Vertucci根管分型两种方法均具有显著性差异(P<0.05)。两种方法对根管钙化和根尖口开口位置的评估均不具有显著性差异。30颗双根管牙中下颌恒切牙唇舌向双根管的最大距离(LaL)在0~1.5 mm之间的,85.7%的为Vertucci III型,LaL在1.5~2 mm之间的,66.7%为Vertucci IV和V型。以根尖片上双根管显示距离为1 mm计算,LaL在1~2 mm之间的,偏向投照角度为26.6°~45.0°,LaL在0.1~1 mm之间的,偏向投照角度为45.0°~84.3°。结论:CBCT高清牙列模式扫描和RVG投照对于根管数目和Vertucci根管分型的评估具有显著性差异,对于根管钙化和根尖口开口位置的评估不具有显著性差异。LaL在1~2 mm之间时,偏角度投照的临床可操作性较强。     

Integrating other therapies with radiation for head neck cancer: search for optimal solution

Purpose: To review the role of concurrent chemoradiotherapy protocols with special emphasis on selection of appropriate chemotherapy drug, its timing and schedule with respect to radiation fractionation.     

Clinical and pathological aspects on some odontogenic tumors

Odontogenic tumors constitute a very diverse group of lesions that reflects the complex processes of odontogenesis. Controversies over their classification/subtyping, terminology and diagnosis have been persisted, which has direct bearings on therapeutic and/or prognostic implications.     

Can you be too old for oral implants? An update on ageing and plasticity in the oro‐facial sensorimotor system

This review focuses on the capacity of the brain for plasticity and the utility and efficacy of oral implants in helping to restore oro‐facial sensorimotor functions, especially in elderly patients. The review first outlines the components of the oro‐facial sensorimotor system which encompasses both oro‐facial tissues and a number of brain regions. One such region is the sensorimotor cortex that controls the activity of the numerous oro‐facial skeletal muscles. These muscles are involved in a number of functions including reflexes and the more complex sensorimotor functions of mastication, swallowing and speech. The review outlines the use by the brain of sensory inputs from oro‐facial receptors in order to provide for exquisite sensorimotor control of the activity of the oro‐facial muscles. It highlights the role in this sensorimotor control played by periodontal mechanoreceptors and their sensory inputs to the brain, and how oral implants in concert with the plastic capacity of the brain may, at least in part, compensate for reduced sensorimotor functioning when teeth are lost. It outlines findings of ageing‐related decrements in oro‐facial sensorimotor functions and control. The changes in oro‐facial tissues and the brain that underlie these ageing‐related functional alterations are also considered, along with adaptive and compensatory processes that utilise the brain's capacity for plasticity. The review also notes the evidence t hat rehabilitation that incorporates adjunctive approaches such as sensorimotor training paradigms in addition to oral prostheses such as implants may enhance these processes and help maintain or facilitate recovery of sensorimotor functioning in the elderly.     

Chemotherapy using new superselective intra-arterial infusion for advanced oral cancer

Purpose: We developed a new method of superselective intra-arterial infusion via the superficial temporal artery (HFT method: Hattori, Fuwa and Tohnai reported) and preoperatively performed daily concurrent radiotherapy and chemotherapy with docetaxel (DOC) and cisplatin (CDDP) using this method for 46 patients with stage Ⅲ, Ⅳ oral cancer.     

Navigation-guided oral and maxillofacial surgery (reconstructive and plastic, orthognathic, oncology)

Purpose: Advance in the field of compeer assisted surgery enables the surgical procedures to be less invasive and more accurate for the support of diagnosis imaging, pre-operative simulation and intraoperative navigation.     

Clinical evaluation of demineralized bone allograft in a hyaluronic acid carrier for sinus lift augmentation in humans: a computed tomography and histomorphometric study

OBJECTIVES: Natural and synthetic graft materials are used routinely in sinus floor augmentations to help support implants in atrophic maxillary ridges. This clinical study was based on the hypothesis that the clinical effectiveness of demineralized freeze-dried bone allograft/demineralized bone matrix (DFDBA/DBM) in sinus lifts varies when used in combination bone graft substitute materials. To test this hypothesis, DFDBA was used together with one of three materials: in saline plus anorganic bone (DFDBA: Bio-Oss; in hyaluronic acid (DFDBA: HY, 32 : 68, w/w; DBX alone; DBX plus Bio-Oss; and DBX plus tricalcium phosphate granules (beta-TCP). MATERIAL AND METHODS: Thirty-two sinus lift procedures, eight per group, were performed on 26 patients. Before surgery and at 8 months post-surgery when implants were placed, ridge heights were visualized by computed tomography (CT) and measured by morphometric analysis. Cores of bone were removed by trephine at the sites of implant placement; these biopsies from the graft sites were used for histomorphometric analysis. RESULTS: All 32 sinus lift elevations were successful when measured by CT, increasing from an average 2.84+/-0.2 mm before treatment to 15.2+/-0.6 mm after treatment. The percent of each biopsy that was occupied by new bone and incorporated bone graft materials varied with each treatment: DFDBA+Bio-Oss, DBX+Bio-Oss, or DBX alone was higher than that for DBX+beta-TCP by approximately 10%. When comparing only newly formed bone, DBX+beta-TCP treatment resulted in 50% less bone than the other three preparations. All grafted sites received implants as per the treatment plan for each patient. CONCLUSIONS: This study confirmed the hypothesis that new bone formation is dependent on the DFDBA formulation used and demonstrated that DBX, alone or in combination with other materials, can be used successfully for sinus floor elevation.     

氟化泡沫对正畸固定矫治患者牙周指数及牙釉质脱矿的影响

目的:探讨氟化泡沫对正畸固定矫患者牙周指数及牙釉质脱矿的影响。方法:选取2013年6月~2014年6月30例舌侧正畸治疗患者(600颗牙)为研究对象,根据入院时间分为对照组15例(297颗牙)和观察组15例(293颗牙),对照组采取常规口腔卫生措施,观察组在对照组的基础上定期使用1.23%氟化泡沫。随访12 个月,观察两组牙釉质脱矿牙位分布、脱矿指数(EDI)、菌斑指数(PLI)和出血指数(BI)。结果:牙釉质脱矿主要分布于上颌侧切牙、上颌中切牙及下颌前磨牙等;观察组牙釉质釉质脱矿率11.26%明显低于对照组17.51%(χ²=4.666,P<0.05);观察组EDI、PLI、BI等均明显低于对照组(t=9.947, 4.435, 7.789,P<0.05)。结论:舌侧正畸治疗中牙釉质脱矿发生率较高,氟化泡沫有助于减少正畸治疗中的牙釉质脱矿发生,降低牙周指数。     

Tumor microenvironment in oral cancer: novel approaches for immunotherapy

Squamous cell carcinoma of the head and neck (SCCHN), which arises from the squamous mucosal epithelium of the oral cavity, pharynx and larynx, is a major health problem in the US and other parts of the world, especially in developing countries.     

Cone beam imaging: is this the ultimate imaging modality?

This review article provides an overview of cone beam (CB) imaging technology and its role in orofacial imaging, including comparison with two-dimensional (2D) radiography and multislice computed tomography (MCT). The radiation dose levels of CB systems are discussed, with reference to those delivered by MCT and common dental 2D views. The large variation in dose levels delivered by CB systems and the importance of using ultra low-dose CB units are emphasized. Low-dose MCT protocols can be used. CB and MCT image quality are compared. CB is an essential technique that all dental and orofacial clinicians must be familiar with. Where ultra low-dose systems and protocols are used, CB imaging should be considered in day-to-day clinical practice. However, CB imaging is not the technique of choice in many clinical scenarios. Rather than replacing other modalities, CB imaging complements intraoral 2D radiography, panoramic radiography, MCT and other techniques including magnetic resonance imaging, ultrasound and nuclear medicine. MCT is a much more powerful and flexible modality and presently remains the technique of choice over CB imaging in many clinical scenarios. All radiologic examinations, including CB and MCT, should be comprehensively evaluated in entirety. The responsibilities and the radiological skill levels of clinicians involved in imaging as well as the associated ethical and medico-legal implications require consideration.