纤维桩核冠修复上颌中切牙牙体缺损的应力分析

目的研究不同程度缺损的上颌中切牙行纤维桩、全瓷冠修复后纤维桩、粘接剂、牙周膜、牙槽骨等的应力变化,以及这种变化与牙体缺损程度的关系。方法螺旋CT扫描上颌中切牙,运用Mimics软件、Ansys软件建立7种牙体缺损上颌中切牙的三维有限元模型,模拟纤维桩全瓷冠修复、咬合加载,记录纤维桩、粘接剂、牙周膜、牙槽骨的Von Mises应力和最大拉应力。结果纤维桩、粘接剂、牙周膜、牙槽骨的应力大小和分布随牙体组织的减少没有明显变化,粘接剂的应力值在0 mm牙本质肩领时稍增大。结论牙体组织的减少对纤维桩、粘接剂、牙周膜、牙槽骨的应力大小和分布无明显影响。     

不同牙本质肩领高度的上颌中切牙用不同材料桩核冠修复的有限元分析

目的 应用三维有限元法分析具有不同牙本质肩领高度的上颌中切牙,在选用不同材料桩核冠修复后的应力分布。方法 通过螺旋CT扫描、Mimics和Geomagics等软件建立桩核冠修复的上颌中切牙有限元模型,模拟玻璃纤维、氧化铝陶瓷两种材料在0 mm、1 mm、2 mm、3 mm 4种牙本质肩领高度,在上颌中切牙舌侧切1/3与中1/3交界处,与牙体长轴成45°切龈向加载,载荷量为100 N,加载方式为静态加载,分析牙本质内的Von Mises应力和位移。结果 纤维桩和陶瓷桩对上颌中切牙修复后的应力集中区均位于桩尖牙本质中,随着材料弹性模量的升高应力峰值明显增加,陶瓷桩修复的上颌中切牙应力峰值（11.263 0 MPa）明显高于纤维桩修复的应力峰值（9.745 9 MPa）。陶瓷桩材料修复上颌中切牙的Von Mises应力值和位移受牙本质肩领高度的影响较小,随着牙本质肩领高度的降低,Von Mises应力值逐渐下降,最大主应力和最小主应力均逐渐增加,修复后的位移也随牙本质肩领高度的降低而下降。结论 通过建立不同牙本质肩领高度上颌中切牙的桩核冠修复的有限元模型和应力分析,能够预测不同材料对不同牙本质肩领高度的上颌中切牙应力分布的影响,应根据不同牙本质肩领高度选择不同的桩核材料。此外,适当保留牙本质肩领结构对提高修复效果具有重要意义。     

纤维桩修复上颌中切牙的三维有限元研究

目的应用三维有限元法研究上颌中切牙采用全瓷冠修复和纤维桩全瓷冠修复时牙本质的应力变化情况,分析纤维桩修复对上颌中切牙应力大小和分布的影响。方法通过螺旋CT扫描、Mimics软件、ANSYS软件建立不同牙体量上颌中切牙的三维有限元模型,分别行全瓷冠修复和纤维桩全瓷冠修复,模拟咬合加载,记录牙本质的von Mises应力和最大拉应力。结果相同牙体量的上颌中切牙,采用纤维桩全瓷冠修复时牙本质的应力值小于全瓷冠修复时的应力值,应力分布基本相似。结论纤维桩的应用能降低上颌中切牙牙体组织的应力峰值,有利于降低牙折的风险,并且不改变原有应力分布模式。     

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。     

牙本质领对桩冠修复牙牙体应力的影响--三维有限元研究

目的：研究牙本质领对牙体应力的影响，揭示箍效应的力学本质。方法：建立上中切牙桩核修复的三维有限元模型，分析100N静载荷下，牙本质领高度由0～2mm按0．5mm递增，共5种情况下，牙体内Von Mises应力的变化和分布规律。结果：①在100N载荷下，牙体内Von Mises应力由桩末端向牙颈部方向逐渐升高，并在颊侧根颈1／3和颈缘形成两个应力高峰区。②增加牙本质领高度可以降低牙体内Von Mises应力峰值。结论：牙本质领对牙体具有一定的保护作用，临床上应尽量保留冠部牙体组织。     

上中切牙桩核冠修复的三维有限元研究

目的：将桩长与牙本质领结合起来进行研究，揭示二者对牙体应力的影响。方法：建立上中切牙桩核修复的三维有限元模型，分析牙本质领分别为0mm和2mm时，桩长的变化对牙体应力的影响。结果：桩越深入牙体，牙体内最大主应力、Von Mises应力越大。在桩长相同的情况下，牙本质领高度越大，牙体内的综合应力水平越低。结论：减少桩长和增加牙本质领高度可协同降低牙体应力。     

牙本质肩领位置对下颌切牙抗折强度影响的研究

目的:利用体外力学测试和有限元分析结合的方法,研究下颌切牙进行桩核冠修复后,不同形态的牙本质肩领对患牙抗折强度的影响.方法:针对下颌切牙设计五组不同形态的牙本质肩领,桩核冠修复后在电子万能试验机上进行抗折试验,研究牙本质肩领位置变化对牙体抗折强度的影响;对下颌切牙进行CBCT扫描,获取三维CT扫描数据,利用Mimics,Geomagic,Ansys等软件建立下颌切牙不同牙本质肩领形态的桩核冠修复模型,模拟咬合加载,分析von Mises应力分布情况.结果:保留颊侧牙本质肩领和2.0 mm完整牙本质肩领时的抗折强度较大,保留舌侧牙本质肩领和近中侧牙本质肩领时的抗折强度其次,无牙本质肩领时抗折强度最小.保留完整2.0 mm牙本质肩领时,剩余牙体组织的应力分布情况与保留颊侧牙本质肩领时和保留舌侧牙本质肩领时的应力分布情况接近,应力分布较为均匀,应力相对较小;而保留近中侧牙本质肩领和无牙本质肩领时均在牙颈部舌侧位置出现了不同程度的应力集中,应力相对较大.结论:保留2.0 mm完整牙本质肩领可以有效提高患牙的抗折强度;在修复下颌切牙的过程中,尽量保留颊侧牙体组织有助于增强修复后牙体的抗折强度.     

三种桩材桩核修复上颌中切牙光弹模型的建立

目的:为分析不同弹性模量桩对根管壁应力分布的影响,建立上颌中切牙桩核修复的光弹模型.方法:以环氧树脂模拟上颌中切牙牙根部、牙槽骨;室温硫化硅橡胶模拟牙周膜;复合树脂制作核,建立桩为成品纤维桩、铸造钛合金、铸造镍铬合金的上颌中切牙桩核修复光弹模型.结果:建立了表面光洁、透明度高,几何尺寸接近实际情况,牙根、牙槽骨、牙周膜弹性模量比接近于1.37:1:0.0003的光弹模型.结论:该模型可以用于分析不同弹性模量桩对根管壁应力分布影响的光弹性实验.     

上中切牙全瓷冠修复后牙本质的三维有限元分析

目的：研究上颌中切牙进行全瓷冠修复后牙本质的应力分布情况。方法：应用三维有限元法进行分析,模拟在最大咬合力120N时,分别以与牙体长轴成30°、40°、45°和50°角加载的情况下,4种不同全瓷冠材料IPS EmpressⅡ,In-Cream Alumina,In-Cream Zirconia,Vita MarkⅡ修复上颌中切牙后牙本质的应力分布。结果：应用不同全瓷冠材料修复后,牙本质上的应力分布相似,但加载力角度的增加会使张应力改变很大。结论：进行上颌中切牙全瓷冠修复时,需要注意修复后上下颌中切牙的角度,否则可能会造成牙本质的损伤。     

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.     

不同剂型玻璃离子水门汀溶解性比较研究

目的:研究、比较不同剂型玻璃离子水门汀的溶解性和表面微观形态改变,为临床使用提供依据.方法:将3M树脂加强型玻璃离子水门汀(水粉剂型)、GC玻璃离子水门汀(水粉剂型)及GC玻璃离子水门汀(双糊剂型)分别在人工唾液中浸泡30 d,冷热循环15000次,烘干测重,比较前后质量变化,计算溶解率,并用扫描电镜观察表面微观改变.结果:不同剂型的玻璃离子水门汀溶解率由高到低分别为3M树脂加强型玻璃离子水门汀(水粉剂型)、GC玻璃离子水门汀(水粉剂型)、GC玻璃离子水门汀(双糊剂型).3种玻璃离子水门汀经浸泡溶解后,SEM扫描表面微观形态可观察到GE玻璃离子水门汀(双糊剂型)表面形态改变较少,其他2组玻璃离子水门汀表面微观改变较多.结论:双糊剂型玻璃离子水门汀理化性能及溶解率均低于传统水粉剂型,是未来临床修复治疗的的良好选择.     

Evidence of the validity of a model of determinants of quality of restorative dental care

A model describing the relationship between self-reported quality of restorative dentistry and dentist characteristics for 119 Montana general dentists is presented. The best predictors formed a significant model explaining 22% of the variance of the quality measure. Results are contrasted with a previous estimation of the model for 102 Washington general practitioners. Evidence for the external validity of the model is presented.     

《口腔医学》杂志2007年度有关信息的分析

目的通过对《口腔医学》2007年全年文献的回顾和分析,了解我国口腔临床医学的研究现状。方法阅读2007年《口腔医学》全年的文献,对各种信息进行了分类汇总,根据设计类型对临床一次性文献进行了分类,并对其中的试验性研究文章进行质量分析。结果《口腔医学》2007年全年的一次性文献274篇,基础和临床文献分别为108和166篇,以临床文献为主(60.58%)。在临床研究文献中,属于观察性、分析性和试验性的文献分别为97、9和60篇,观察性文献所占比例为36.14%,高于以往的报道。60篇观察性文献中,全都设有对照;统计方法应用得当者44篇;真正做到随机、盲法的分别只有4和2篇。结论我国口腔临床方面的研究水平近年来提高明显,但设计的科学性方面有待提高。     

Design of clinical trials of traditional therapies of periodontitis

The present paper on the design of clinical trials of periodontal therapy first addresses the issue of the etiology of periodontal disease. It is suggested that most if not all forms of destructive periodontal disease are caused by microorganisms and that there are different forms of disease with different microbial etiologies. The progressive nature of destructive periodontal disease is subsequently discussed and it is emphasized that, in a given patient, periodontal sites which show signs of inflammation and attachment loss may not over a period of several months and years show further sign of attachment loss. The present methods of assessing periodontal disease do not allow us to discriminate between potentially active and inactive sites in untreated patients. The significance and variability of indicators of periodontal disease such as bleeding on probing, probing pocket depth and probing attachment level measurements are discussed. The errors inherent in the various measurements are analyzed and suggestions are presented describing how alterations in any of the above parameters could be identified and presented in a clinical trial. Of concern for the statistical analysis of clinical data of periodontal disease is the definition of the "experimental unit". For a number of years, the "experimental unit" in periodontal trials was the patient. It is clear, however, that different sites within the same individual show different patterns of disease progression and lesion morphology and often respond differently to periodontal therapy. Statistical analyses must consequently be designed which recognize differences in site-to-site infection and lesion morphology within a common host. Until such analyses are available, the investigator should be wary of pooling data within the same individual, since such pooling may obscure meaningful alternatives which may take place in individual periodontal sites. Some goals of periodontal therapy are subsequently identified. 4 goals are discussed more in detail, namely: to establish conditions which will allow the patient to maintain a dentition without further breakdown of the periodontium; to reduce pocket depth to establish an anatomy in the dentogingival region which with proper maintainance care will prevent the re-establishment of the subgingival infection; to gain attachment as a result of treatment; to assess the effect of a certain chemotherapeutic agent on periodontal disease.     

口腔医学专业本科毕业生就业现状的调查分析和教育思考

目的研究口腔医学专业的教学如何面向市场,推出令用人单位满意的人才。方法采用问卷调查的方法对浙江省内有代表性的19家包含口腔医疗服务单位进行了调查,同时进行大学生就业心态调查问卷调查。结果医学生的就业心态出现多元化;毕业生不再一味追求高学历,更多的人选择了先就业后进修的道路。大多数用人单位着眼于提高医务人员的服务水平和质量,对毕业生的综合素质有了更高的要求。结论学校要尽力拓宽毕学生的就业渠道,提供更多的就业信息,树立面向基层的观念。     

Experimental evidence of formation of imines in the course of reduction of hydrazones

The reduction of hydrazones is generally suggested to proceed through a reductive cleavage of the nitrogen–nitrogen bond followed by a reduction of the carbon–nitrogen bond. This sequence of reduction processes is here supported for fluorenone (V) and benzophenone (VI) hydrazones as well as by a comparison of the reduction of fluorenone and benzophenone hydrazonium ions (I,III) with corresponding imines (II,IV). Another proof of the presence of imines as intermediates is the splitting of four-electron waves of hydrazones V and VI and hydrazonium ions I and VIII into two waves at pH < 2. This has been interpreted as due to differences in slopes dE_1/2/dpH and pK_a-values of protonated hydrazine derivatives on one side and corresponding imines on the other. In this pH-range imines formed in reductions of VI and VIII are reduced in a single two-electron wave, those of I and V in two one-electron steps. Fluorenone imine (II) is sufficiently stable to allow recording of time-independent current–voltage curves between pH 6 and 11. In this pH-range the imine (II) is reduced in two one-electron steps. Benzophenone imine (IV) has been found stable between pH 4.6 and 12. At pH 4.6–8 the reduction of the imine IV takes place in a single two-electron step, at pH 8–12 in two one-electron steps. Final proof of the initial cleavage of the N–N bond is presented by comparison with the reduction of nitrones.     

正常青年Monson球面半径的测量研究

目的测量正常青年Monson球面半径。方法选择60名(男30名,女30名)正常青年制取全口印模,应用立体摄影成像的原理与方法对Monson球面半径进行测量和统计学处理。结果Monson球面的半径平均为10.173 cm,大于理论值10.160 cm,差异有显著性(P<0.01);男、女性球面半径差异无显著性。结论本实验所得到的数据可作为全口义齿修复中记录颌位关系的一个参量。     

口底癌34例临床分析

目的探讨口底癌的临床特性、治疗方法及预后。方法对我院自1992—2002年住院治疗的34例口底癌患者进行回顾性分析。结果34例口底癌患者中,男28例(82.4%),女6例(17.6%),男女比为4.7∶1,平均发病年龄58岁。发病部位:前口底22例(64.7%),后口底12例(35.3%)。淋巴结转移率41.2%。单纯手术组、化疗加手术组、放疗加手术组、化疗加手术加放疗组的5年生存率分别为45.5%、60.0%、50.0%、62.5%。结论口底癌以中老年患者好发,男性居多。易发生淋巴结转移,综合疗法疗效较好。     

Evaluation of efficacy of chemiluminescence for diagnosis of leukoplakia

ObjectiveLeukoplakia is the most common potentially malignant disorder preceding oral cancer. Chemiluminescence has been developed as an adjunct to conventional examination for the diagnosis of these potentially malignant disorders. This study was conducted to assess the efficacy of chemiluminescence in the diagnosis of leukoplakia and to compare the results with histopathological examination.Study designA total of 50 patients with leukoplakia were included from the outpatients attending the Department of Oral Medicine and Radiology, Dental Hospital, Bengaluru, Karnataka, India. These patients were subjected to conventional oral examination followed by chemiluminescent examination with Vizilite (Zila, Fort Collins, CO, USA) and biopsy for histopathological confirmation.ResultsThe sensitivity, specificity, positive predictive value, and negative predictive value of chemiluminescence were 93.75%, 55.56%, 78.95%, and 83.3%, respectively. The overall accuracy of chemiluminescence was 80%. A statistically significant association was observed between histopathology results and chemiluminescence results.ConclusionAlthough it is an easy, safe, minimal time consuming, and noninvasive technique, it has only adjunctive utility and it does not replace biopsy for the diagnosis of leukoplakia.