简介:“啊,好甜!”糖还是要放在嘴里嚼着吃,才能体会其真正的美味,因为只有这样才能便糖的香甜久久地留在嘴里。
简介:Basedontheinvestigationofthefourdifferentcompositiondentalamalgamal-loysmadebysametechnologricalprocess,therelationbetweenphysicalpropertiesandmicrostructureofthemhasbeendiscussedindetail.Thetheoryfoundationhasbeenexaminedforthedesignofdentalamalgamalloy.Themainconclusionsareasfollows:
简介:Afreeelectronlaser(FEL)withitscharacteristicsofwidewavelengthtunability,ultrashortpulsetimestructure,andhighpeakpowerdensityispredominantlysuperiortoallotherconventionallasersinapplications.Severalexperimentalstudiesonmid-infraredFELirradiationondentalenamelanddentinewereperformedattheBeijingFEL.EXperimentalaimsweretoinvestigatechangesinthehardness,ratiosofPtoCaandCsbeforeandafterirradiationonsampleswithacharateristicabsorptionwavelengthof9.66μm,inthecolorsofthesesamplesurfacesafterirradiationwithdifferentwavelengthsaroundthepeakwavelength.ThetimedependenceoftemperatureofthedentinesamplewasmeasuredwithitspspulseeffectscomparedtothatwithacontinuousCO2laser.FTIRabsorptionspectraintherangeof2.5-15.4μmforsamplesoftheseharddentalsubstancesandpurehydroxyapatitewerefirstexaminedtodecidtheirchemicalcomponentsandabsorptionmaximums.Primaryexperimentalresultewillbepresented.2001ElsevierScienceB.V.Allrightsreserved.
简介:Toquicklyobtainaccurate3Ddataofdentalcastmodel,thispaperproposesa3Dreconstructionmethodfordentalcastmodelbasedonstructuredlight.Thismethodcombinesthestructuredlightwiththemotorturntabletoobtainagroupof3Ddataforthedentalcastmodelfrommultipleangles,andautomaticallyregistersthedental3Ddatafrommultipleanglesthroughtheballcalibrationofturntable.Comparedwiththerealdataofthedentalcastmodel,themaximumerrorofthe3Dreconstructionresultsinthispaperis0.115mm.Thereconstructiontimeofthisprocessisabout130s.Theexperimentalresultsshowthatthemethodhashighprecisionandhighscanningspeedforthe3Dreconstructionofthedentalcastmodel.
简介:Objectives:Polymerizationshrinkageofdentalcompositesremainsamajorconcerninrestorativedentistrybecauseitcanleadtomicro-crackingofthetoothanddebondingatthetooth-restorationinterface.Theaimofthisstudywastomeasurethefull-fieldpolymerizationshrinkageofdentalcompositesusingtheopticaldigitalimagecorrelation(DIC)methodandtoevaluatehowthemeasurementisinfluencedbythefactorsinexperimentsetupandimageanalysis.Methods:Fourcommercialdentalcomposites,PremiseDentine,Z100,Z250andTetricEvoCeram,weretested.Compositewasfirstplacedintoaslotmouldtoformabarspecimenwithrectangular-sectionof4mmmm,followedbythesurfacepaintingtocreateirregularspeckles.Curingwasthenappliedatoneendofthespecimenwhiletheotherpartwerecoveredagainstcuringlightforsimulatingtheclinicalcuringconditionofcompositeindentalcavity.Thepaintedsurfacewasrecordedbyacharge-coupleddevice(CCD)camerabeforeandaftercuring.Subsequently,thevolumetricshrinkageofthespecimenwascalculatedwithspecialistDICsoftwarebasedonimagecrosscorrelation.Inaddition,afewfactorsthatmayinfluencethemeasuringaccuracy,includingthesubsetwindowsize,specklesize,illuminationlightandspecimenlength,werealsoevaluated.Results:ThevolumetricshrinkageofthespecimengenerallydecreaseswithincreasingdistancefromtheirradiatedsurfacewithaconspicuousexceptionbeingthecompositePremiseDentineasitsmaximumshrinkageoccurredatasubsurfacedistanceofabout1mminsteadoftheirradiatedsurface.Z100hadthegreatestmaximumshrinkagestrain,followedbyZ250,TetricEvoCeramandthenPremiseDentine.Largersubsetwindowsizemadetheshrinkagestraincontoursmoother.Butthecostwasthatsomedetailsintheheterogeneityofthematerialwerelost.Verysmallsubsetwindowsizeresultedinalotofnoiseinthedata,makingitdifficulttodiscernthegeneralpatterninthestraindistribution.Speckle
简介:thehydroxya-patite粒子的机械性质上的水吸着的损坏效果增强了Bis-GMA/TEGDMA共聚物(HA/Bis-GMA/TEGDMA)用3D被预言了有限房间模型。聚合物矩阵上的可塑剂效果被看作它的幼仔的模量的一个变化。三个不同房间模型被用来决定在debondingdamage上改变粒子内容,分裂期间力量和潮湿集中的影响。压力分发模式被检验了,压力转移模式澄清了。幼仔Bis-GMA/TEGDMA的模量和破裂力量合成也有或没有损坏的考虑用模型被预言。有thedebonding损坏的考虑的以前的结果在对存在文学的好同意是试验性的数据。我们的建议模型和一条其他的途径的防护效果被讨论。FCC房间模型也被扩大了预言批评负担为损坏并且undamaged合成题目到3点曲折测试。
简介:摘要目的了解系统性洁牙方法对口腔牙菌斑的减少作用,比较系统性洁牙方法和传统洁牙方法对于牙菌斑清楚的差异。方法采用随机抽样的方法抽取某高校不同年级大学生共1000名,均分为试验和对照两组,实验组进行系统性洁牙方法的教学,并在日常生活中进行习惯和意识的强化,对照组不采取任何措施进行传统的刷牙方法,0月基线和6个月随访调查,比较不同组别、不同时间段,调查对象牙菌斑个数(NdGdCOB自倍频微片激光器检测方法)。结果实验后期6月份比较,实验组和对照组牙菌斑差异显著(t=10.23,P=0.00)。实验组0月前侧牙菌斑(42.13±10.21),6月后侧(11.23±5.21),实验组两个时间段比较差异显著(t=10.11,P=0.00)。结论进行系统性的刷牙方法传授和习惯强化,能显著降低人群牙菌斑数量,改善口腔卫生和健康。
简介:Thepurposeofthisstudywastouseathree-componentphotoinitiationsystemcomprising1wt%CQ(camphorquinone),2wt%DMAEMA(2-(dimethylamino)ethylmethacrylate)and2wt%Ph2I+PF6-(diphenyliodoniumhexafluorophosphate)toinitiatethecopolymerizationofthematrixresinswhichcombinebisphenol-S-bis(3-methacrylate-2-hydroxypropyl)ether(BisS-GMA)withtheexpandingmonomerunsaturatedspiroorthoesters2-methylene-1,4,6-trispiro[4,4]nonane(MTOSN),forminimizingthevolumetricshrinkagethatgenerallyoccursduringpolymerization.ItwashypothesizedthatMTOSNwouldexpandvolumetricallyduringpolymerizationunderthethree-componentphotoinitiatorsystemandfurtherreductionsinvolumetricshrinkagewouldbeobtained.Theperformancestudywhichconsistsofdegreeofconversionandconditionofthering-openingreactionsofMTOSN,volumetricshrinkageandmechanicalpropertiesincludingtensilebondstrength,compressivestrengthandVicker'shardnesswerecarriedoutrespectivelybyFouriertransferinfrared,thedilatometerandtheuniversaltestingmachine.Theresultssupportedthatthedentalcompositesbasedontheexpandingmonomerandthree-componentphotoinitiatorsystemengenderedagreaterdecreaseofvolumetricshrinkageandbettermechanicalproperties.