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.

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.

Developing nonlinear additive tree crown width models based on decomposed competition index and tree variables

Crown development is closely related to the biomass and growth rate of the tree and its width(CW)is an important covariable in growth and yield models and in forest management.To date,various CW models have been proposed.However,limited studies have explicitly focused on additive and inherent correlation of crown components and total CW as well as the influence of competition on crown radius from the corresponding direction.In this study,two model systems were used,i.e.,aggregation method system(AMS)and disaggregation method system(DMS),to develop crown width additive model systems.For calculating spatially explicit competition index(CI),four neighbor tree selection methods were evaluated.CI was decomposed into four cardinal directions and added into the model systems.Results show that the power model form was more proper for our data to fit CW growth.For each crown radius and total CW,height to the diameter at breast height(HDR)and basal area of trees larger than the subject tree(BAL)significantly contributed to the increase of prediction accuracy.The 3-m fixed radius was optimal among the four neighborhoods selection ways.After adding decomposed competition Hegyi index into model systems AMS and DMS,the prediction accuracy improved.Of the model systems evaluated,AMS based on decomposed CI provided the best performance as well as the inherent correlation and additivity properties.Our study highlighted the importance of decomposed CI in tree CW modelling for additive model systems.This study focused on methodology and could be applied to other species or stands.

Prediction of tree crown width in natural mixed forests using deep learning algorithm

Crown width(CW)is one of the most important tree metrics,but obtaining CW data is laborious and timeconsuming,particularly in natural forests.The Deep Learning(DL)algorithm has been proposed as an alternative to traditional regression,but its performance in predicting CW in natural mixed forests is unclear.The aims of this study were to develop DL models for predicting tree CW of natural spruce-fir-broadleaf mixed forests in northeastern China,to analyse the contribution of tree size,tree species,site quality,stand structure,and competition to tree CW prediction,and to compare DL models with nonlinear mixed effects(NLME)models for their reliability.An amount of total 10,086 individual trees in 192 subplots were employed in this study.The results indicated that all deep neural network(DNN)models were free of overfitting and statistically stable within 10-fold cross-validation,and the best DNN model could explain 69%of the CW variation with no significant heteroskedasticity.In addition to diameter at breast height,stand structure,tree species,and competition showed significant effects on CW.The NLME model(R^(2)=0.63)outperformed the DNN model(R^(2)=0.54)in predicting CW when the six input variables were consistent,but the results were the opposite when the DNN model(R^(2)=0.69)included all 22 input variables.These results demonstrated the great potential of DL in tree CW prediction.

Replacement of Unesthetic Posterior Metal Crowns with Monolithic Zirconia Crowns: A Case Report

Advances in metal-free materials and the popularization of Computer-Aided Design and Manufacturing (CAD/CAM) have led to the wide clinical use of all-ceramic crowns for esthetic restorations. A 72-year-old woman presented to our hospital with unesthetic restorations on the right upper and lower posterior teeth. Intraoral examination revealed poorly fitting metal crown margins. Defective prostheses were removed, and provisional restorations were provided to stabilize the mandibular position. Optical impressions and the maxillomandibular relationship were recorded using an intraoral scanner, and monolithic zirconia crowns were fabricated using CAD/CAM technology for complete veneer crown restorative treatment. Occlusal examination revealed an improvement in occlusal force distribution at initial examination (right side: 33.5%, left side: 66.5%) after placement of the zirconia crowns (right side: 54.9%, left side: 45.1%). Occlusal force and occlusal force distribution area also showed an increasing trend. The Oral Health Impact Profile short form (OHIP-14) score decreased from 7 points at initial examination to 0 points after prosthodontic treatment. Appropriate diagnosis and treatment planning contributed to the increased occlusal force and balanced occlusal force distribution. Therefore, the present case indicates the potential of monolithic zirconia crowns to achieve both esthetic and stable functional outcomes.

Changes in concentrations and transcripts of plant hormones in wheat seedling roots in response to Fusarium crown rot

Fusarium crown rot(FCR) is a soilborne disease causing severe yield losses in many wheat-growing areas of the world. Diseased plants show browning and necrosis of roots and stems causing white heads at maturity. Little is known about the molecular processes employed by wheat roots to respond to the disease. We characterized morphological, transcriptional and hormonal changes in wheat seedling roots following challenge with Fusarium pseudograminearum(Fp), the main pathogen of FCR. The pathogen inhibited root development to various extents depending on plants' resistance level. Many genes responsive to FCR infection in wheat roots were enriched in plant hormone pathways. The contents of compounds involved in biosynthesis and metabolism of jasmonic acid, salicylic acid, cytokinin and auxin were drastically changed in roots at five days post-inoculation. Presoaking seeds in methyl jasmonate for 24 h promoted FCR resistance, whereas presoaking with cytokinin 6-benzylaminopurine made plants more susceptible. Overexpression of TaOPR3, a gene involved in jasmonic acid biosynthesis, enhanced plant resistance as well as root and shoot growth during infection.

Assessment of Cork Oak Decline Using Digital Multispectral Imagery in Relation with in Situ Crown Condition

Cork oak in Maamora forest is experiencing the dieback phenomenon. The evaluation of the latter in this forest has gained the importance over time and with the solicitation of managers to objectify its phytosanitary situation. Aiming at prioritizing management actions, remote sensing seems to be an effective tool to inquire about stands’ health conditions and their evolution. To this end, this study aims at mapping and validating health status of cork oak stands in Maamora. Sentinel 2 images in 2015 and 2020 were processed to calculate the differential normalized difference water index (NDWI), revealing vegetation moisture variation caused by drought. A statistical method based on thresholds was used to map cork oak dieback stands, those with no changes and those recovered. Results have shown that 54.63% of cork oak in Maamora forest have not changed in terms of phytosanitary situation between 2015 and 2020, 31.10% of oak stands are afflicted by a slight decline and 12.97% by a severe decline. Areas with slight or strong recovery remain minimal and represent 1.04% and 0.25% respectively. Ground data indicated that the map generated displayed a good distinction between stands severely and slightly declined with a global accuracy of 66.66%. Therefore, further research elaborating an advanced vegetation index reflecting the various factors of dieback would be of much importance.

Li^(+)-ion bound crown ether functionalization enables dual promotion of dynamics and thermodynamics for ambient ammonia synthesis

Electrosynthesis of ammonia from the reduction of nitrogen is still confronted with the limited supply of gas reactant in dynamics as well as high activation barrier in thermodynamics.Unfortunately,despite tremendous efforts devoted to electrocatalysts themselves,they still fail to tackle the above two challenges simultaneously.Herein,we employ a heterogeneous catalyst adlayer-composed of crown ethers associated with Li^(+)ions-to achieve the dual promotion of dynamics and thermodynamics for ambient ammonia synthesis.Dynamically,the bound Li^(+)ions interact with the strong quadrupole moment of nitrogen,and trigger considerable reactant flux toward the catalyst.Thermodynamically,Li^(+)associated with the oxygen of crown ether achieves a higher density of states at the Fermi level for the catalyst,enabling effortless electron transfer from the catalysts to nitrogen and thus greatly reducing the activation barrier.As expected,the proof-of-concept system achieves an ammonia yield rate of 168.5μg h^(-1)mg^(-1)and a Faradaic efficiency of 75.3%at-0.3 V vs.RHE.This system-level approach opens up pathways for tackling the two key challenges that have limited the field of ammonia synthesis.

Wave Force on the Crown Wall of Rubble Mound Breakwaters at Intermediate Depths

Rubble mound breakwaters with a crown wall are a common coastal engineering structure.The wave force on crown walls is an important parameter for the practice engineering design.Particularly,the wave force on crown walls under intermediate depths has been studied through physical model tests and numerical simulations.In this study,a three-dimensional numerical wave flume was developed to investigate monochromatic wave interactions in a rubble mound breakwater with a crown wall.Armor blocks were modeled in detail.The Navier-Stokes equations for two-phase incompressible flows,combined with shear stress transport k-ωturbulence model and volume of fluid method for tracking the free surface,were solved.A set of laboratory experiments were performed to validate the adopted model.Subsequently,a series of numerical simulations were implemented to examine the impacts of different hydrodynamic parameters(including wave height,incident wave period,and water depth)and the berm width on the wave force of the crown wall.Finally,a comparison of the experimental results and Martin method shows that the latter method is not suitable for this experimental scope.New empirical formulas are proposed to predict the wave force on crown walls under intermediate depth.The results can provide a basis for the design of crown wall of rubble mound breakwaters at intermediate depths.

Third-Order Nonlinear Optical Responses of Bis(15-crown-5)-stilbenes Binding to One-or Two-Alkali Metal Cation(Li^(+),Na^(+)and K^(+))

Bis(15-crown-5)-stilbenes containing crown ether parts have been widely used in a variety of chemical applications,such as cation detectors,because of their ability to selectively bind to alkali metal cations,Bis(15-crown-5)-stilbenes and its derivatives with complexation of one-or two-alkali metal cation(Li^(+),Na^(+)and K^(+))have been theoretically investigat-ed by quantum chemistry methods.The coordination of alkali cations results in partial shrinkage of crown ethers,which directly affected natural distribution analysis charges and molecular orbital energy levels.The number of alkali metal ions has significant effects on absorption spectra and mean second hyperpolarizability.When one alkali metal ion was added to the anticonformer of bis(15-crown-5)-stilbene,the absorption spectra were obvious-ly redshifted and the mean second hyperpolarizability values were slightly increased;while two alkali metal ions were added to bis(15-crown-5)-stilbene,the absorption spectra were ob-viously blue shifted and the mean second hyperpolarizability values decreased.On the other hand,as the radius of the alkali ions increased,the mean second hyperpolarizability values of the compounds increased gradually.It is indicated that the mean second hyperpolarizability value is sensitive to the number and radius of the alkali metal cations,thus the third order nonlinear optical response can be used as a signal to detect the number and type of alkali met-al ions.

生物活性陶瓷iRoot BP Plus^(■)在儿童年轻恒前牙复杂冠折牙髓切断术中的应用

目的:观察生物活性陶瓷材料iRoot BP Plus^(■)(Innovative BioCeramix Inc,Vancouver,BC,Canada)在儿童年轻恒前牙复杂冠折牙髓切断术中的应用,并对其预后进行分析,为该术式的更广泛应用提供临床参考。方法:收集2017年3月至2022年9月因恒前牙复杂冠折就诊于北京大学口腔医院急诊科,行以生物活性陶瓷iRoot BP Plus^(■)为盖髓剂的牙髓切断术患者。根据患者术前根尖片和初诊病历显示为年轻恒牙者,纳入97颗年轻恒牙进行研究。收集患者初诊及复查时的临床及影像学检查资料,临床检查包括根尖孔形成情况、松动度、牙冠颜色、牙髓活力测试(冷测)、有无脓肿和瘘管,影像学检查包括根周膜连续性、根尖周低密度影像、复诊时盖髓剂下方牙本质桥形成情况、髓腔及根管钙化情况,并对上述结果进行分析。结果:最终纳入有复诊记录的64例患者共75颗患牙,其中男性37例(57.8%),女性27例(42.2%),就诊时平均年龄为9.1岁,平均随访时长19.3个月。采用iRoot BP Plus^(■)盖髓的牙髓切断术后6个月成功率为96.0%,术后1年成功率为94.7%。术后复查2年以上者共23例,累计失败6例。成功率在患牙就诊时距外伤的时间是否超过24 h组中(P=0.61)以及是否松动组中(P=0.28)的差异无统计学意义。结论:对无移位性损伤的年轻恒牙复杂冠折患牙,采用iRoot BP Plus^(■)盖髓的牙髓切断术1年成功率很高,该术式具备广泛推广价值。

回鹘戴三叉冠人物身份再考

回鹘三叉冠造型独特,是研究回鹘文化的重要历史遗存,关于其佩戴者身份众说纷纭,主要包括回鹘王、回鹘王子、元帅及乐师等。然而,这些解读往往缺乏系统性的论证与深入分析。本研究在现有观点的基础上,首先对回鹘三叉冠佩戴者的身份进行了细致的梳理与分类,通过比对图像资料与文献资料,将三叉冠的形制及其象征的身份进行了归类,指出其身份象征随时间的演变而发生变化。并采用物质文化史的研究方法,探究了三叉冠在回鹘文化中身份象征演变的深层原因。研究发现:回鹘在西迁前,受到萨满教及阿尔泰系部落生活方式的影响,三叉冠主要象征回鹘王或部落首领。西迁后,随着生活方式的转变和佛教的兴盛,三叉冠的身份象征逐渐世俗化,扩展到王子、贵族以及高级军官。

三种梨简化棚架栽培树形树冠与产量形成差异比较分析

以梨双臂顺行式树形为对照,对单干单主枝、双干双主枝2种改进型简化棚架栽培树形早期树冠与产量形成进行多年跟踪调查分析.结果表明,与梨双臂顺行式树形相比,单干单主枝、双干双主枝2种树形主干增粗较慢、主枝增长较快,差异达显著或极显著水平;大、中、小型3类结果枝组数量峰值分别出现于定植后第5年、第3年、第3年,均提早1年以上;定植当年至定植后第5年形成花芽数量更多,差异达显著或极显著水平;定植后第2至第6年单位面积累计产量分别增加3009.93、2830.18kg/667m^(2),累计纯收益分别增加23429.44元/667m^(2)与21991.44元/667 m^(2),加快树冠形成与缩短进入盛产期和回收建园成本时间的作用显著.

恒前牙外伤冠折露髓患儿术后预后不良的危险因素分析及模型构建

目的探究断冠再接术联合活髓切断术治疗儿童恒前牙外伤冠折露髓不良预后的危险因素,同时基于筛选出的危险因素构建风险列线图模型,并对构建的模型进行验证。方法选取98例儿童恒前牙外伤冠折露髓患儿为研究对象,均为2020年1月至2023年12月间在本院行断冠在接术联合活髓切断术治疗者。将受试者根据预后结果分为预后良好组和预后不良组,收集两组患儿临床资料,筛选患儿术后预后不良的危险因素。基于危险因素构建预后不良风险列线图模型,并对构建的模型进行验证。结果98例患儿中有18例发生预后不良,预后不良率为18.37%(18/98)。预后不良组牙髓暴露时间>24 h、牙龈炎、露髓孔直径>1 mm、口腔溃疡、牙周炎、牙根发育程度(根尖接近形成)占比高于预后良好组(P<0.05)。牙髓暴露时间>24 h、牙龈炎、牙周炎、牙根发育程度(根尖接近形成)均是影响恒前牙外伤冠折露髓患儿术后预后不良的危险因素(P<0.05)。列线图风险模型预测恒前牙外伤冠折露髓患儿术后预后不良受试者工作特征(ROC)曲线下面积(AUC)、95%CI、灵敏度、特异度分别为0.868、0.633~0.992、95.10%、79.30%(P<0.001)。列线图预测模型C指数为0.842(95%CI:0.789~0.994),预测值与实际预测值均在理想曲线附近,且Hosmer-Lemeshow拟合优度曲线检验χ^(2)=2.743,P=0.671。结论本研究综合牙髓暴露时间、牙龈炎、牙周炎、牙根发育程度等4个危险因素构建的风险列线图模型对患儿预后不良具有较高的预测价值。

基于Stacking集成学习的热轧带钢凸度诊断模型

在热连轧生产过程中,凸度是重要的质量指标,过程数据的非平衡性限制了数据驱动模型的预测效果,为提高模型的预测精度,提出一种融合SMOTE和Stacking集成算法的热轧带钢凸度诊断模型。首先,采用SMOTE过采样方法处理凸度相关数据集,降低数据非平衡分布导致的影响;然后,构建以轻量级梯度提升机(LightGBM)、支持向量机(SVM)、K近邻(KNN)和随机森林(RF)为基学习器,逻辑回归(LR)为元学习器的Stacking集成模型,最后,使用某2160 mm热轧带钢实际生产数据进行模型验证。研究结果表明,诊断模型的准确率、少数类召回率、平衡F分数、几何平均值和ROC曲线下面积分别为0.9580、0.9595、0.9573、0.9589和0.9579,与XGBoost、LightGBM、KNN、SVM和随机森林模型对比,预测效果最优,证明了Stacking集成算法能够有效增强诊断模型的泛化能力,具有优良的诊断性能。

一种新型的用于萃取铷的冠醚功能化磁性固相纳米材料

本研究成功制备了一种新型的用于萃取铷的冠醚功能化磁性固相纳米材料(CFE)。通过溶剂热法合成了Fe_(3)O_(4)纳米颗粒磁核,利用3-氨丙基三乙氧基硅烷在碱性环境下的酯水解反应,在磁核表面包覆SiO_(2)并修饰氨基,制备了Fe_(3)O_(4)@SiO_(2)-NH_(2)中间产物,再利用4′-羧基苯并-18-冠6-醚上的羧基与修饰在Fe_(3)O_(4)@SiO_(2)-NH_(2)表面的氨基在1-乙基-(3-二甲基氨基丙基)碳二亚胺盐酸盐的催化下发生酰胺化反应,将该冠醚修饰在中间产物的表面,制备了CFE新型材料。分析了Fe_(3)O_(4)、Fe_(3)O_(4)@SiO_(2)-NH_(2)、CFE的微观形貌、磁化性质、X射线衍射性质、红外吸收性质、元素组成,佐证了材料被成功制备,验证了CFE对Rb^(+)的萃取能力,研究了溶液pH对Rb^(+)萃取效果的影响。结果表明,室温下萃取30 min,在pH为13时CFE对Rb^(+)具有最佳的萃取效果,萃取率为90.0%。

年轻恒牙外伤性冠折露髓时间与初诊叩痛对预后的影响

目的探讨外伤引起的年轻恒牙冠折露髓患者经活髓切断术或直接盖髓术后预后不良的独立危险因素,并评价露髓时间、初诊叩痛对牙髓预后的影响。方法回顾性分析2018年3月至2020年9月河北省承德医学院附属医院收治的219例外伤引起的年轻恒牙冠折露髓患者的临床资料。患者初诊治疗为活髓切断术或直接盖髓术且于术后1年进行随访。采用单因素和多因素logistic回归分析影响牙髓预后不良的独立危险因素,并通过受试者操作特征(ROC)曲线分析上述独立危险因素对牙髓预后不良的预测价值。结果经术后1年随访,治疗失败20例,成功199例,活髓切断术总成功率为90.87%。单因素分析结果显示,根尖发育情况、露髓时间、初诊叩痛与牙髓预后不良有关(P<0.05),而年龄、性别、受伤原因、受伤牙位、温度试验结果、牙髓电活力差值、露髓孔直径、患牙松动度、治疗方案与牙髓不良预后无关(P>0.05)。多因素logistic回归分析结果显示,初诊叩痛(+++)是影响牙髓预后不良的独立危险因素(P<0.05)。ROC曲线分析结果显示,初诊叩痛(+++)预测牙髓预后不良的曲线下面积为0.860,敏感度为0.832,特异度为0.865。结论初诊叩痛(+++)是外伤引起的年轻恒牙冠折露髓患者预后不良的独立危险因素,且对预后不良的预测价值较高,而露髓时间与牙髓预后无明显相关性。

金冠豆角籽粒淀粉组成及性质研究

为了明确金冠豆角淀粉的基本性质,本文以提取盐溶蛋白后剩余的金冠豆角籽粒豆渣为原料,采用水提法提取淀粉,观察淀粉颗粒形态,测定其组成、粒径、理化性质及体外抗消化特性。结果表明,金冠豆角籽粒淀粉中直链淀粉和支链淀粉的含量分别为47.39%和52.07%,淀粉的颗粒形态与豌豆淀粉类似,呈卵圆形或球型,颗粒表面光滑完整,粒径为75.10μm。金冠豆角籽粒淀粉的峰值粘度(212.20 RVU)、衰减值(68.50 RVU)较低,但回生值(96.80 RVU)高于玉米淀粉;金冠豆角籽粒淀粉糊化的起始温度(T_(0))、峰值温度(T_(p))显著高于豌豆淀粉(P<0.05)。金冠豆角籽粒淀粉的凝沉值在90 min时接近80%,凝沉速度显著高于玉米淀粉,透光率介于豌豆淀粉和玉米淀粉之间,持水性(WHC)和持油性(OHC)值分别为1.08和1.00 g/g,凝胶硬度小,属于易凝沉淀粉,其抗性淀粉(RS)含量为68.43%,高于玉米淀粉和豌豆淀粉(P<0.05),具有良好的抗消化特性。

小麦茎基腐病抗性位点研究进展

对小麦茎基腐病(FCR)抗性位点研究进行综述。目前,在小麦所有的21条染色体上定位了140个抗性QTL,含10个抗性基因,虽然报道的抗性位点很多,但主效位点不明确,严重影响小麦FCR抗性改良进程。分析了小麦FCR抗性位点研究中的主要问题,提出了统一抗性鉴定标准、增强成株期抗性研究等建议,以明确抗FCR主效位点/基因并开发分子标记,通过分子标记辅助选择促进FCR抗性改良进程。

聚醚醚酮、氧化锆及钴铬合金制作的套筒冠内冠耐磨损性及固位力比较

目的:比较使用聚醚醚酮(PEEK)、氧化锆及钴铬合金制作的套筒冠内冠的耐磨损性及固位力。方法:制作24个圆锥状金属基牙代型,分别使用钴铬合金、氧化锆和PEEK制作其上内冠各9个,使用钴铬合金制作外冠24个,对所有外冠外及内冠内表面进行喷砂处理后待用。根据内冠制作材料的不同,将所有试件分为A、B、C三组,每组9个内冠及8个外冠。A组:内冠为钴铬合金材料;B组:内冠为氧化锆材料;C组:内冠为PEEK材料。每组随机选取一个内冠使用扫描电镜观察外表面,并称重其余所有内外冠。将内冠粘接于基牙代型上,对基牙金属代型和外冠进行包埋。在万能拉力试验机上模拟摘戴循环10000次,观察并记录未循环、循环1000次、循环5000次与循环10000次时的固位力。去除包埋及粘接材料后再次进行称重,记录重量变化。电镜下观察内冠表面磨损情况。结果:3组固位力差异有统计学意义(P<0.001),并随着摘戴次数的增加,A组固位力逐渐下降,B、C组先升高后降低;未循环时,A组固位力>B组>C组,循环10000次后,A组和C组固位力>B组。C组内冠相对质量损耗大于A、B组,外冠相对质量损耗小于A、B组(P<0.017)。循环10000次后,A、B、C组表面粗糙度较实验前均有所增加,C组表面磨损更严重。结论:PEEK作为内冠材料可提供不低于钴铬合金和氧化锆内冠的固位力,耐磨损性能较钴铬合金和氧化锆内冠差,但对外冠的磨损较小。