Influence of different luting agents on the stress distributions of implant-supported all-ceramic single crown

The purpose of this study was to investigate the influence of different luting agents on the stress distribution within the crown, abutment and peri-implant bone of implant-supported all-ceramic single crown. A three-dimensional finite element model of an implant-supported single crown for the first premolar of mandible was created by COSMOS 2.85. Resin-modified glass ionomer and two different resin adhesives were used to cement the crown and abutment. Vertical 600 N and horizontal 225 N loads were applied to stimulate the condition of chewing. The stress distributions within the all-ceramic crown, abutment and peri-implant bone were analyzed. The experimental results show that the stress distributions of all-ceramic crown, abutment, implant and peri-implant bone were similar when different luting agents were used. The result of present study indicated that luting agents had no influence on the stress distributions of implant-supported all-ceramic single crown.     

Stress-based performance evaluation of osseointegrated dental implants by finite-element simulation

In this paper biomechanical interaction between osseointegrated dental implants and bone is numerically investigated through 3D linearly elastic finite-element analyses, when static functional loads occur. Influence of some mechanical and geometrical parameters on bone stress distribution is highlighted and risk indicators relevant to critical overloading of bone are introduced. Insertions both in mandibular and maxillary molar segments are analyzed, taking into account different crestal bone loss configurations. Stress-based performances of five commercially-available dental implants are evaluated, demonstrating as the optimal choice of an endosseous implant is strongly affected by a number of shape parameters as well as by anatomy and mechanical properties of the site of placement. Moreover, effectiveness of some double-implant devices is addressed. The first one is relevant to a partially edentulous arch restoration, whereas other applications regard single-tooth restorations based on non-conventional endosteal mini-implants. Starting from computer tomography images and real devices, numerical models have been generated through a parametric algorithm based on a fully 3D approach. Furthermore, effectiveness and accuracy of finite-element simulations have been validated by means of a detailed convergence analysis.     

单氟磷酸钠制备新工艺研究

利用磷酸与碳酸钠反应生成中间产物，将此中间产物与氟化钠混合后在高温下反应生成单氟磷酸钠。研究中和液pH、干燥温度以及混合物合成温度对产品质量的影响，确定了最佳工艺条件为：中和液pH取3．7，干燥温度为475℃，合成温度为720℃。产品主含量质量分数为99．83％，游离氟含量质量分数0．08％，在100g水中的溶解度47g。     

覆铝钢板搪瓷的低温制备及其密着机理研究

研究了覆铝钢板搪瓷的低温烧成工艺,运用扫描电子显微镜观察了其界面形貌,发现在搪瓷层和金属层的界面形成了铁-铝-瓷釉的复合层。X射线能谱仪分析结果表明界面间的元素扩散十分强烈,并由此促进了覆铝钢板与搪瓷层形成良好的密着。     

高粘度、多功能过氧化脲洁牙凝胶的制备研究

制备了具有洁牙、护牙、抗菌消炎作用的高粘度、多功能过氧化脲洁牙凝胶。该凝胶无毒、无副作用 ,在口腔应用中粘度稳定 ,避免唾液溶解 ,使洁牙成分持久释放 ,提高洁牙效率。研究了过氧化脲的制备方法 ,所制备的过氧化脲质量分数大于 98%。所制备的齿科材料为粘度 30 0～ 4 5 0Pa .s,pH值 5～ 7的无色透明凝胶 ,含过氧化脲质量分数 6 %～ 2 0 % ,稀释剂 4 0 %～ 80 % ,增稠剂 4 %～ 10 % ,pH调节剂 2 %～10 %及稳定剂、抗过敏剂、护牙剂、调味剂等成分。     

Recent Studies on Nonspecific Aspects of Intraoral Adhesion

There is usually a high number of microorganisms present in the oral cavity, yet it takes some time for the first microorganisms to attach in vivo on clean solid surfaces. Similar patterns of microbiological adhesion can be observed in vitro and, conversely, in vivo attachment of non-biological colloidal particles occurs readily. This indicates that primary physical forces rather than biological specificities are responsible for initial adhesion of microorganisms and similarly shaped particles to teeth and restorations. Under physiological conditions, oral adhesive events are probably based on general types of physico-chemical interactions, and might be mainly controlled by the properties of the spontaneously adsorbed biological films that precede particle attachment. A variety of surface physico-chemical techniques, monitoring formation of biological films and attachment of biological, as well as nonbiological particles of colloidal dimensions both in vivo and in vitro on various solid surfaces, indicated that the formation of oral biological films proceeds at high speed and precedes particle attachment. Further, when different surfaces were clinically exposed to saliva and covered with such biological films, their significant original differences in surface properties could no longer be detected. Continuing differences in strength of particle adhesion to these surfaces must result, therefore, from differences in binding of the initial salivary films.     

新型CC—1型正畸粘合剂临床初步观察

介绍了一种含新型基质树脂的粘结性偶联剂的双糊剂型正畸粘合剂,其与牙釉质的剪切强度为21.2MPa。它与粉液型粘合剂相比,具有操作简便,结固时间可调,性能稳定之优点。经正畸临床426个托槽的粘结及1年左右的临床初步观察,该粘合剂性能优良,粘结效果良好。     

Bioceramics: From Concept to Clinic

Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo-skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass-ceramics), or porous for tissue ingrowth (hydroxyapatite-coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long-term (20-year) mechanical reliability under load is still needed.     

一种基于阈值初始化的变分水平集牙菌斑图像分割方法

将变分水平集和图像阀值化两种图像分割方法相结合,在分析灰度图像直方图分布的基础上提出利用图像阈值设定C-V模型的初始化轮廓的新方法,改变了原有C-V模型的初始轮廓线设置中存在的不足.新方法应用于牙菌斑图像分割中能够较好的识别牙齿图像边缘信息,为下一步对牙菌斑进行量化分析提供了良好的数据基础.