Comparison of Different Implant-Supported Fixed Restoration Types: A Literature Review

Background: The screw and cement-retained implant-supported fixed prosthesis has advantages and disadvantages. However, current research comparing the properties of these restorations is lacking. Objectives: The aim of the study was to review the current literature on the properties of screw and cement retained implant supported restorations. Material and Methods: A literature search was conducted from January 2010 to December 2023, using 4 databases to identify research. Sixty studies met the inclusion criteria. Results: Cement-retained restorations have some advantages. Passive fit is easier to achieve, and eliminating occlusal access holes can help with the occlusal adjustments in cemented restorations. However, in case residual cement is not completely removed after cementation, it becomes a predisposing factor for peri-implantitis and marginal bone loss. The main advantage of screw-retained restorations is the retrievability, which can be achieved without damaging the restoration or fixture. However, in case the implant is not ideally positioned, the location of the screw access channel can negatively affect the aesthetics of the screw-retained restorations. In addition, porcelain fracture and screw loosening occur more frequently in screw-retained restoration. Conclusions: Screw and cement-retained restorations display specific advantages and disadvantages;nevertheless, the selection of one retention method over another depends on the clinical scenario.

Comparison of Maxillary Implant-Supported Prostpesis in Irradiated and Non-Irradiated Patients

In order to investigate the influence of radiation therapy after the treatment of maxillary implant-supported prostheses, 27 patients received a total of 131 implants in maxilla after oral cancer treatment and/or reconstructive surgery. Among them, 25 received maxillary implant-supported prostheses. The cumulative survival rates of implants and prostheses were evaluated by the product-limit-estimates method according to Kaplan-Meier. The cumulative survival rate of implants and prostheses in irradiated patients was compared with that in non-irradiated patients by statistical Log-rank test. The results showed that 112 implants were observed after implant loading. The implants cumulative survival rate was approximately 65 % for overall patients. The cumulative prosthesis successful rate was approximately 88 % for all 25 patients. Log-rank test analysis revealed that there was a significant difference in cumulative implants survival rates between non-irradiated and irradiated maxillary bone (P<0. 01). It was concluded that the implants and prostheses in irradiated patients have significantly lower survival rates than in non-irradiated patients.

Porcelain fracture of metal-ceramic tooth-supported and implant-supported restorations: A review

Metal-ceramic restorations are widely used in dentistry with a high degree of general success. However, fracture of these restorations does occur and usually frustrates both the dentist and the patient. Objective: This literature review discusses the factors that may lead to the fracture of these restorations whether they are tooth-supported or implant-supported with the aim of making dentists and technicians aware of these factors to avoid them. Factors reviewed include: technical factors, dentist-related factors, inherent material properties, direction, magnitude and frequency of applied loads, environmental factors, screw-retained implant-supported restorations, and posterior cantilevered prostheses. Material and Methods: A netbased search in “Pubmed” was performed and combined with a manual search. The search was limited to articles written in English. Conclusions: the published literature revealed that the factors predisposing to fracture of metal-ceramic restorations may be related to the technician, dentist, patient, environment, design of the restoration, or to inherent structure of ceramics and others. However, if the dentist and technician understand these factors and respect the physical characteristics of the materials, most of those are avoidable.

Implant-Supported Full Fixed Prostheses with a Removable Oro-Nasal Obturator for the Edentulous Maxilla with Palatal Fistula due to Surgical Procedures for Oral Cancer

Open oro-nasal defects resulting after oral tumor resection need structural and functional rehabilitation using dental prostheses. Conventional removable prostheses have usually been indicated and performed for prosthodontics. When the patient has an edentulous maxilla, the unfavorable stability of the prosthesis will cause dysfunction of mastication and pronunciation. To achieve improvement of the impaired functional situation, implant-supported full fixed prostheses (IPSPs) for the edentulous maxilla with a removable obturator offer a reasonable solution. We present herein the case of a 70-year-old Japanese man who has presented with oro-nasal defect due to surgical procedures for oral cancer. He was treated with implant-supported full fixed prostheses in a conventional two-step procedure. After prosthesis treatment, a palatal obturator was set. The patient has shown no clinical or radiological evidence of failure as of 24 months after the end of treatment. Functional evaluation of mastication and pronunciation showed dramatic improvements. For a patient with an edentulous maxilla and palatal fistula, full-arch fixed prostheses supported by a combination of axially and non-axially positioned implants and a removable oro-nasal obturator, using the anterior alveolar bone, without bone transplantation or maxillary sinus elevation, could offer an effective, minimally invasive treatment alternative.

A new method of calculating crown projection area and its comparative accuracy with conventional calculations for asymmetric tree crowns

This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and integration.This novel method and other four existing methods of calculating CPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size,shape,and asymmetry.The four existing methods included the polygonal approach and three ways of calculating CPA as the area of a circle using the arithmetic,geometric and quadratic mean radius.Comparisons were made across a sequence of eight non-consecutive numbers(from 2 to 16)of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of means.The sequence covered the range of the number of crown radii measured for calculating the CPA of a tree in the literature.A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative measure.With a slight overestimation of 2.2%on average and an overall mean error size of 7.9%across the numbers of crown radii that were compared,our new method was the least biased and most accurate.Calculating CPA as a circle using the quadratic mean crown radius was the second best,which had an average overestimation of 4.5%and overall mean error size of 8.8%.These two methods remained by and large unbiased as crown asymmetry increased,while the other three methods showed larger bias of underestimation.For the conventional method of using the arithmetic mean crown radius to calculate CPA as a circle,bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown asymmetry.This study reveals and demonstrates such relationships between the accuracy of CPA calculations and crown asymmetry and will help increase awareness among researchers and practitioners on the existence of bias in their CPA calculations and for the need to use an unbiased method in the future.Our new method is recommended for calculating CPA where at least four crown radius measurements per tree are available because that is the minimum number required for its use.

Differential modulation of crown allometry and stem growth at gap edges in five European tree species by drought conditions

Background In Central Europe,forests are increasingly affected by various disturbances,resulting in an increasing gap formation in the canopy.In order to support goal-oriented management,more knowledge is required about the acclimation of the crown and its effects on the basal area growth of trees at the edge of a gap.Methods This work compared trees'growth and crown structure at the edge of a transient gap,with a gap size of more than 80m^(2),with trees in the stand that were at least 30m away from the gap.A total of 249 European beeches(Fagus sylvatica L.),Norway spruces(Picea abies L.Karst),Scots pines(Pinus sylvestris L.),oaks(Quercus spp.;Quercus petraea(Matt.)Liebl.,Quercus robur L.),and silver firs(Abies alba Mill.)were examined on long-term experimental plots in southern Germany.Various crown measures were developed and calculated using high-resolution terrestrial laser scanning(TLiDAR)to capture the three-dimensional crown structures.Growth responses to edge conditions were measured based on tree rings.Using linear mixed models,we predict the basal area increment of edge trees relative to trees in the stand under wet and dry soil moisture conditions after the gap formation.Results We identified i)species-specific acclimation of the crown of edge trees after the gap formation,ii)under wet soil moisture conditions a growth increase of 25%–45%for beech,pine,and oak edge trees and growth losses of 5%–60%for spruce and fir and iii)coniferous tree species benefited from the edge position regarding their basal area increment under dry soil moisture conditions and deciduous tree species grew regardless of the soil moisture conditions at the edge of a gap.Conclusion Gaps have a species-specific effect on the habitus and growth of edge trees and can have both positive and negative impacts on silviculture.

Interfacial engineering through lead binding using crown ethers in perovskite solar cells

In the domain of perovskite solar cells(PSCs),the imperative to reconcile impressive photovoltaic performance with lead-related issue and environmental stability has driven innovative solutions.This study pioneers an approach that not only rectifies lead leakage but also places paramount importance on the attainment of rigorous interfacial passivation.Crown ethers,notably benzo-18-crown-6-ether(B18C6),were strategically integrated at the perovskite-hole transport material interface.Crown ethers exhibit a dual role:efficiently sequestering and immobilizing Pb^(2+)ions through host-guest complexation and simultaneously establishing a robust interfacial passivation layer.Selected crown ether candidates,guided by density functional theory(DFT)calculations,demonstrated proficiency in binding Pb2+ions and optimizing interfacial energetics.Photovoltaic devices incorporating these materials achieved exceptional power conversion efficiency(PCE),notably 21.7%for B18C6,underscoring their efficacy in lead binding and interfacial passivation.Analytical techniques,including time-of-flight secondary ion mass spectrometry(ToF-SIMS),ultraviolet photoelectron spectroscopy(UPS),time-resolved photoluminescence(TRPL),and transient absorption spectroscopy(TAS),unequivocally affirmed Pb^(2+)ion capture and suppression of non-radiative recombination.Notably,these PSCs maintained efficiency even after enduring 300 h of exposure to 85%relative humidity.This research underscores the transformative potential of crown ethers,simultaneously addressing lead binding and stringent interfacial passivation for sustainable PSCs poised to commercialize and advance renewable energy applications.

三次CVC、五次CVC及SmartCrown辊形控制特性对比研究

通过对三次连续变凸度(continuously variable crown,CVC)、五次CVC及SmartCrown三种辊形方程进行推导分析,得出了各自的板形控制特性,提出了各自的辊形设计方法。研究表明:三次CVC只具备二次凸度控制能力,控制特性简单;五次CVC可根据二次及四次凸度控制需要灵活设计,凸度比在窜辊过程中并非恒定;SmartCrown四次凸度控制能力受形状角影响,凸度比恒为负值。

An Evaluation of Crown Structure and Site Index to Determine Crown Closure in Eucalyptus urophylla × E. grandis Stands in Guangxi,China

Eucalyptus forests are grown in many parts of the world for their commercial value and use in construction projects. Density management becomes im- portant as a means to attain the management goals in these forests. Changes in canopy and tree crown structure were quantified for Eucalyptus urophylla x E. grandis forests at different ages to determine when canopy closure occurs and the onset of competition begins. Site index was developed for these forests to determine whether site quality affects the canopy structure. Site index had little effect in the forests sampled, with the forest canopy on the better sites becoming slightly more elongated. Based upon crown projection ratio and crown diameter： dbh （diameter at breast height） ratio, it appears that crown closure occurs by age 4 years in these forests. The age at which this occurs was also checked and verified with the evaluation of relative spacing, RS （the ratio of the mean distance between trees to the average dominant height of the stand）. The RS value displayed a rapid decline until age 4 years, and then became relatively flat through age 21 years. The rapid height growth during the first 3 years with no change in density accounted for this rapid decrease. By age 4 years, reductions in the number of trees due to mortality began to have more of an influence on this value, resulting in a more gradual de- cline. The implications for management are discussed.

一种基于五次CVC和SmartCrown复合辊型的板形控制方法

为改善轧机的板形调控能力,在分析连续变凸度CVC辊型和SmartCrown辊型特性的基础上,提出了一种基于五次CVC和SmartCrown的复合辊型的板形控制方法。将五次CVC和SmartCrown辊型在控制板形缺陷方面的特性相结合,采用分解与迭加的方法重新确定其二次和四次凸度及调控能力。通过设计实例和效果分析验证,表明该方法有效改善了五次CVC和AVC辊型因辊径差较大不利于板形控制的缺点。

Calix[4]Crowns类化合物在分离铯中的应用

Calix[4]Crowns类化合物作为超分子识别材料能够有效地分离铯,并能很好地应用在溶剂萃取、液膜萃取、色谱分离等领域。介绍了Calix[4]Crowns类化合物及其复合超分子材料对铯离子的识别和分离效果,为寻求对Cs(Ⅰ)有优异配合能力的Calix[4]Crowns类有机配体结构及相应的功能材料提供参考。

[｛Pt_4(en)_4(NHCO^tBu)_4｝｛Tl(18-crown-6)｝_2](PF_6)_6的合成与晶体结构(英文)

The compound [｛Pt4(en)4(NHCOtBu)4｝｛Tl(18-crown-6)｝2](PF6)6 has been synthesized by a simple one-potmulticomponent reaction. Its structure was determined by X-ray single crystal diffraction analysis. The cation ofthe compound consists of one linearly arranged [Pt4(en)4(NHCOtBu)4]4+ chain and two [Tl(18-crown-6)]+ ions located atthe two ends of the platinum chain. The complex crystallizes in a triclinic P1 with a=1.060 5(1), b=1.252 3(1), c=2.015(2) nm, α=107.430(2)°, β=91.032(2)°, γ=101.910(2)°, V=2.489 6(4) nm3, Z=2, R1=0.074 4, wR2(I>2σ(I))=0.2225, S=1.062. CCDC: 294083.

Research on Crown Grafting of Seedling Cashew Trees

Objective] The study was aimed to improve the yield and quality of cashew. [Method] Through the comparative analysis, the survival rate, new germi-nation and yield characteristics of the cutting stems with different heights by stem grafting and bark grafting. [Result] The best cutting stem height of cashew should be in 100-150 cm, when the number of new germinated shoots was 85.5-87.7. Stem grafting could significantly improve the survival rate of the shooting branch （92.7%）, growth condition of which was better than that of bark grafting, and it also had no clip cortex. The yield of stem grafting was significantly higher than that of bark grafting, and it could reach up to 18.1 kg/plant in 4 years. The branches from stem grafting had significantly better ability in resisting the wind damage than those from bark grafting. [Conclusion] The study provided references for the crown grafting of cashew planting in China.

Smart Crown轧辊轧制钨板过程有限元分析

针对传统轧制工艺轧制钨板过程中,轧辊易损坏、钨板轧废严重等现象,基于有限元分析软件,研究利用Smart Crown轧辊轴向移动轧制钨板,根据要求设计了一款Smart Crown轧辊。从辊形、应力、应变以及磨损方面,分析钨板轧制情况,发现同等轧制条件下,Smart Crown轧辊轴向移动轧制钨板的新工艺优于传统钨板轧制工艺。

Application of the Plate Crown Prediction

The program of the plate crown optimal prediction applied in the plate mill of Wuhan Iron and Steel(Group) Co. Ltd. is described. Optimal prediction is programmed in ALPHA 4000. The original profile, wear, expansion and deformation of work rolls are introduced into the program. The plate crown is controlled by the original profile of work rolls and the draft whose objective is the optimal plate crown. The run schedule is also optimized through the optimal prediction of the plate crown.

不同针阔叶树蒸腾耗水特性及单位面积耗水量估算

为探究针阔叶树种单木蒸腾耗水规律,以河北省雄安新区主要造林树种针叶树油松和阔叶树楸树作为研究对象,运用热扩散式探针法(TDP)对油松(Pinus tabuliformis)、楸树(Catalpa bungei)的树干液流速率进行监测,并调查样木的冠幅、胸径、冠高和冠幅投影面积等林木因子,分析林木耗水量与林木因子的相关性,将实测的林木因子与耗水量拟合,建立不同林木因子与林木耗水量方程。结果表明:(1)不同冠幅投影面积的油松和楸树的液流速率及耗水日变化过程均呈昼高夜低的单峰型曲线;两个树种整体表现为冠幅投影面积越大,液流速率和耗水量越高,楸树的时均耗水量和日累计耗水量均高于油松。(2)两个树种的耗水量均与冠幅投影面积、冠幅、胸径呈极显著正相关关系(P<0.01);冠幅投影面积与日累计耗水量具有较高的相关性与较好的拟合效果,两树种的日累计耗水与冠幅投影面积的相关系数分别为0.773、0.901,确定系数(R~2)分别为0.596、0.811;油松和楸树平均单位冠幅投影面积日累计耗水量分别为0.290 6、0.302 3 kg·m^(-2)·d^(-1)。

TOOTH CROWN DEFORMABLE DESIGN BASED ON DIRECT MANIPULATION OF FFD

A flexible and adaptable design method for the tooth crown is presented based on the direct manipulation of free-form deformation （FFD）. The correct shape of the tooth crown can be obtained by adding, modifying, and deleting constraint points or load points based on stretching and compressing operation. Finally, an example is given to illustrate the method to be efficient.

基于WindowsCE和CROWN集群技术的DTVSP模式

摘 要：基于嵌入式操作系统技术、多媒体数据文件切片方案及网络电视、数字电视标准等提出了基于WindowsCE与Linux集群的DTVSP架构模型，并针对DTVSP模式中客户端功能的实现进行探索，使网络功能、（未来）用户个性化功能与安全性都予以充分的体现；同时使分布式DTVSP的整体功能与事件的管理成为可能。

纤维桩联合不同冠部修复方式修复穿髓型非龋性颈部缺损牙体的力学分析

背景:使用纤维桩修复穿髓型非龋性颈部缺损可以改变牙齿的应力分布,显著降低患牙折裂风险,但关于纤维桩改善牙体抗折性的力学机制及穿髓型非龋性颈部缺损的最佳冠部修复方式尚有争论。目的:综述纤维桩修复穿髓型非龋性颈部缺损后的应力分布模式,在各种受力状态下的抗折能力与断裂模式,以及纤维桩联合不同冠部修复方式的最新研究进展。方法:应用计算机在PubMed和中国知网数据库中检索2008年9月至2023年9月发表的相关文献,英文检索词为“non-carious cervical lesions,endodontically treated teeth restoration,endodontically treated teeth stress distribution”,中文检索词为“非龋性颈部缺损,根管治疗后牙体修复,根管治疗后牙齿应力分布”,最终纳入56篇文献进行分析。结果与结论:穿髓型非龋性颈部缺损根管治疗后,应用纤维桩修复可部分改善牙齿颈部应力,同时不会增加牙根纵裂的风险;使应力分布更加均匀,提高牙齿的抗折性。使用纤维桩修复的非龋性颈部缺损牙齿若折断,其断裂模式显示出有利的、可恢复的或可修复的断裂模式。纤维桩联合瓷贴面或贴面式嵌体可能会成为修复穿髓型非龋性颈部缺损的一种较理想微创修复方法。

Smart Crown技术的研究与应用

介绍了Smart Crown板形控制技术的原理及技术特点,根据Smart Crown辊型曲线方程推导了轧辊等效凸度方程。生产实践证明,使用Smart Crown工作辊后,轧机板形控制能力显著提高,轧辊磨损均匀,工作周期显著延长。