All-ceramic systems: laboratory and clinical performance

Several all-ceramic systems have been developed in dentistry to meet the increased expectations of patients and dentists for highly aesthetic, biocompatible, and long-lasting restorations. However, early bulk fractures or chippings have led the research community to investigate the mechanical performance of the all-ceramic systems. This overview explores the current knowledge of monolithic and bilayer dental all-ceramic systems, addressing composition and processing mechanisms, laboratory and clinical performance, and possible future trends for all-ceramic materials.     

几丁质/rhBMP2/胶原复合物修复骨缺损的实验研究

目的：研究几丁质作为骨缺损充填材料和rhBMP2载体的可行性。方法：制备多孔几丁质及几丁质/rhBMP2/胶原复合物，进行了几丁质，几丁质/rhBMP2/胶原复合物修复兔颅骨缺损的实验研究。通过X线片，组织学检查评价其骨缺损修复能力。结果：实验结果表明几丁质具有一定的骨引导活性，与rhBMP2复合后，成为既具有骨引导活性，又具有骨诱导活性的复合植骨材料，具有较强的骨缺损修复能力。结论：几丁质适于作为骨替代材料及BMP的载体，但在材料的强度和表面活性上还需要改进。     

Analysis of interfacial fracture in dental restorations

Objectives

To provide a brief summary of the background theory of interfacial fracture mechanics and develop an analytical framework that identifies the critical factors for the analysis of the initiation and propagation of adhesion failure in composite restorations.

Methods

A conceptual framework utilizing interfacial fracture mechanics and Toya's solution for a partially delaminated circular inclusion in an elastic matrix, which can be applied (with caution) to approximate polymer curing induced cracking about composite resins for class 1 cavity restorations.

Results

The findings indicate that: (1) most traditional shear tests are not appropriate for the analysis of the interfacial failure initiation; (2) material properties of the restorative and tooth material have a strong influence on the energy realize rate; (3) there is a strong size effect; and (4) interfacial failure once initiated is characterized by unstable propagation along the interface almost completely encircling the composite.

Significance

The work is important for the analysis of the reliability of composite class I restorations and provides an adequate interpretation of recent adhesion debonding experimental results utilizing tubular geometry of specimens. The approach clearly identifies the critical parameters including; curing strain, material modulii, size and interfacial strain energy release rate for reliable development of advanced restorative materials.     

Bone and cementum as stromal features in Pindborg tumor

A case of calcifying epithelial odontogenic tumor (CEOT) occurring in the left mandible of a 50-yr-old man was characterized by the presence of large masses of calcified collagen. Calcified amyloid acted as the nucleus for the deposition of this material. Because of the close association between both types of calcified material, it is presumed that the calcified amyloid is an inductive stimulus for the stromal cells to differentiate towards production of a collagenous matrix destined to calcify and resembling cementum. The stromal component of CEOT thus seems to be just as odontogenic as the epithelium is.     

根管治疗药物及其材料的细胞毒性研究进展

根管治疗中使用的消毒药物和根充材料对人体的安全性历来受到人们的关注。细胞毒性是评价其安全性的重要指标之一。下面就近年来有关常用根管冲洗剂、根管消毒药物、根管充填材料、根尖倒充填材料和髓腔穿孔修复材料的细胞毒性的研究进展作一综述。     

The effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced acrylic resin denture base material on oral epithelial cells and fibroblasts

Acrylic resin dentures may have cytotoxic effects on oral soft tissues. However, there is sparse data about the cytotoxic effect of fibre-reinforced acrylic resin denture base materials. The purpose of this in vitro study was to determine the effect of two fibre impregnation methods on the cytotoxicity of a glass and carbon fibre-reinforced heat-polymerized acrylic resin denture base material on oral epithelial cells and fibroblasts. One hundred acrylic resin discs were assigned to five experimental groups (n = 20). One of the groups did not include any fibre. Two groups consisted of silane and monomer treated glass fibres (Vetrolex) impregnated into acrylic resin (QC-20) discs. The other two groups consisted of silane and monomer treated carbon fibres (Type Tenox J, HTA). Untreated cell culture was used as positive control. The human oral epithelial cell line and buccal fibroblast cultures were exposed to test specimens. The cytotoxicity of the test materials was determined by succinic dehydrogenase activity (MTT method) after 24 and 72 h exposures. Data were analysed with a statistical software program (SPSSFW, 9.0). A one-way analysis of variance (anova) test and Bonferroni test were used for the comparisons between the groups. All statistical tests were performed at the 0.95 confidence level (P < 0.05). After 24 and 72 h incubation, cell viability percentages of all experimental groups showed significant decrease according to the positive control cell culture. Fibroblastic cell viability percentages of silane and monomer treated fibre-reinforced groups were lower than the unreinforced group. Cell viability of monomer-treated groups displayed the lowest percentages. Elapsed incubation time decreased epithelial cell viability in silane-treated groups. Fibroblastic cell viability was not influenced by elapsed time except the unreinforced group.     

Osteotome sinus floor elevation without grafting material: a 1-year prospective pilot study with ITI implants

OBJECTIVE: The aim of the present pilot study was to evaluate: (1) the predictability of an osteotome sinus floor elevation procedure with ITI-SLA implants without placing a bone grafting material, and (2) the possibility to gain bone height without filling the created space with a bone grafting material. MATERIAL AND METHODS: Seventeen patients received 25 implants protruding in the sinus. Most implants (21/25) were 10 mm long, eight were inserted in type 2 bone, 12 in type 3 and five in type 4 bone. At implant placement, the mean residual bone height (RBH) under the maxillary sinus was 5.4+/-2.3 mm; it was 5.7+/-2.6 mm on the mesial side and 5.1+/-1.9 mm on the distal side. Nineteen implants had less than 6 mm of bone on at least one side and six implants had less than 6 mm on both sides. A healing period of 3-4 months was allowed before abutment tightening at 35 Ncm. The percentage of stable implants at abutment tightening and at the 1-year control was calculated. The endo-sinus bone gain and the crestal bone loss (CBL) at the mesial and distal sides were measured. RESULTS: Abutments were tightened after 3.1+/-0.4 months. All implants but one (96%) resisted the applied 35 Ncm torque. At the 1-year control, all implants were clinically stable and supported the definitive prosthesis. All showed endo-sinus bone gain; the mean gain was 2.5+/-1.2 mm. The mean CBL was 1.2+/-0.7 mm. Endo-sinus bone gain and RBH showed a strong negative correlation (r=-0.78 on the mesial side and -0.80 on the distal side). A good correlation (r=0.73) was found between implant penetration in the sinus and endo-sinus bone gain. CONCLUSION: Elevation of the sinus membrane alone without addition of bone grafting material can lead to bone formation beyond the original limits of the sinus floor. Despite a limited RBH at implant placement, a healing period of 3 months was sufficient to resist a torque of 35 N cm and to lead to a predictable implant function at the 1-year control.     

中药五倍子根管糊剂的组织相容性实验研究

目的：对中药五倍子根管糊剂进行动物皮下埋植实验,评价其组织相容性。方法：在无菌手术条件下将实验材料植入家兔背部皮下,以临床常用根管糊剂（含甲醛根管糊剂、AHPlus糊剂）做对照,埋植后的第1、4和12周分期处死动物,观察埋植体周围组织的炎细胞浸润数和纤维包膜厚度。结果：各实验组埋植体周围组织炎症反应程度随时间递增而降低。其中,五倍子根管糊剂降低速率最高,4周时炎症反应明显低于含甲醛糊剂组和AHPlus组（P〈0.05）;12周时与空白对照组无显著性差异（P〉0.05）。其次为AHPlus组,但到12周时仍有一定的炎症反应,与空白对照组相比有显著性差异（P〈0.05）。含甲醛根管糊剂组降低最慢且在12周时仍有较重的炎症反应。结论：五倍子根管糊剂具有良好的组织相容性。     

牙科可切削云母微晶玻璃呈色的研究

目的 研制用于牙科计算机辅助设计与辅助制作磨牙冠、可提供多种颜色选择的可切削四硅酸氟云母微晶玻璃。方法 采用正交设计技术，对影响微晶玻璃颜色的基础配方、色料组成及热处理制度进行筛选。结果 从基础配方中选择出影响呈色的2个主要因素：晶核剂F含量、Mg^2 ／K^ 比例；从多种色料中选择出主要色料CeO2；从热处理制度中选择出成核制度：650℃保持1h和晶化制度：1000℃或1050℃保持3h～4h,，结论 所研制的云母微晶玻璃，可提供4～5种牙科颜色，其切削性能良好，完全可以满足计算机辅助设计．辅助制作(CAD／CAM)系统的要求。     

不同材料嵌体修复后牙体组织应力分析

目的:研究3种材料嵌体在垂直载荷下牙体组织的应力分布。方法:建立下颌第一磨牙嵌体修复后颊舌向模式图。分别对3种材料及其不同厚度嵌体底部最大主应力进行计算。结果:在同样载荷下,镍铬合金的应力最大、烤瓷次之、复合树脂最小,且应力均与嵌体的厚度成正比。结论:适当减小镍铬合金和烤瓷嵌体的厚度对预防牙体折裂有一定的作用。