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AdvancedDentalBiomaterials

WOODHEADPUBLISHINGSERIESINBIOMATERIALS

AdvancedDental Biomaterials

Editedby

ZohaibKhurshid

ShariqNajeeb

MuhammadSohailZafar

FarshidSefat

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Listofcontributors

Mohamed-NurAbdallah FacultyofDentistry,UniversityofToronto, Toronto,ON,Canada

AzeemAjaz DepartmentofProsthodonticsandDentalImplantology,Collegeof Dentistry,KingFaisalUniversity,Al-Ahsa,KingdomofSaudiArabia

MaiSalehAli FacultyofDentistry,UniversityofToronto,Toronto,ON, Canada;PrivatePractice,Amman,Jordan

SaqibAli DepartmentofBiomedicalDentalSciences,CollegeofDentistry,Imam AbdulrahmanBinFaisalUniversity,Dammam,SaudiArabia

SanamAlmassi AlmassiSpecialistClinic,Tehran,Iran

AhmadA.Alnazzawi DepartmentofSubstitutiveDentalSciences,Collegeof Dentistry,TaibahUniversity,Medina,SaudiArabia

MothannaAlrahabi DepartmentofRestorativeDentistry,CollegeofDentistry, TaibahUniversity,Medina,SaudiArabia

AbdullahAlwadaani DepartmentofProsthodonticsandDentalImplantology, CollegeofDentistry,KingFaisalUniversity,Al-Ahsa,SaudiArabia

MarinaAmaral DepartmentofDentistry,UniversityofTaubate ´ ,Taubate ´ ,Brazil

FaizaAmin DepartmentofScienceofDentalMaterials,DowDentalCollege, DowUniversityofHealthSciences,Karachi,Pakistan

PaulAnderson CentreforOralBioengineering,InstituteofDentistry,QueenMary UniversityofLondon,London,UnitedKingdom

SukumaranAnil DepartmentofDentistry,HamadMedicalCorporation,Doha, Qatar

AndersonCatelan FacultyofHealthSciences,UniversityofWesternSa ˜ oPaulo, PresidentePrudente,Brazil

ElnaPaulChalisserry InterdisciplinaryProgramofMarine-Biomedical,Electrical andMechanicalEngineering,CenterforMarine-IntegratedBiomedicalTechnology (BK21Plus),PukyongNationalUniversity,Busan,SouthKorea

AmritpaulSinghDhillon DentalInstitute,King’sCollegeLondon,London, UnitedKingdom

SergeyV.Dorozhkin Moscow,Russia

TomasDuminis CentreforOralBioengineering,InstituteofDentistry,Bartsand theLondonSchoolofMedicineandDentistry,London,UnitedKingdom

DaghighAhmadiEhsaneh CentreforNanohealth,CollegeofEngineering, SwanseaUniversity,Swansea,UnitedKingdom

AhmedEl-Banna DentalBiomaterialsDepartment,FacultyofDentistry,AinShamsUniversity,Cairo,Egypt

MuhammadA.Fareed AdultRestorativeDentistry,DentalBiomaterialsand ProsthodonticsOmanDentalCollege,Muscat,SultanateofOman

AzitaFarhadiShamsabadi CentreforEnglishLanguageEducation,Nottingham University,Nottingham,UnitedKingdom

ImranFarooq DepartmentofBiomedicalDentalSciences,CollegeofDentistry, ImamAbdulrahmanBinFaisalUniversity,Dammam,SaudiArabia

AmrS.Fawzy UWADentalSchool,UniversityofWesternAustralia,Nedlands, WA,Australia

PegahFirouzmanesh BabolUniversityofMedicalSciences,Babol,Iran

HaniGhabbani DepartmentofRestorativeDentistry,CollegeofDentistry,Taibah University,Medina,SaudiArabia

ShadiGhalami DepartmentofAnatomyandPathology,UniversityofSiena, Siena,Italy

MichaelGlogauer FacultyofDentistry,UniversityofToronto,Toronto,ON, Canada;InstituteofBiomaterialsandBiomedicalEngineering,Universityof Toronto,Toronto,ON,Canada

MarcGrynpas Lunenfeld-TanenbaumResearchInstitute,MountSinaiHospital, Toronto,ON,Canada;DepartmentofLaboratoryMedicineandPathobiology, UniversityofToronto,Toronto,ON,Canada;PrincessMargaretCancerCentre, DepartmentofDentalOncologyandMaxillofacialProsthetics,Toronto,ON,Canada

NaderHamdan DepartmentofDentalClinicalSciences,FacultyofDentistry, DalhousieUniversity,Halifax,NS,Canada

ZoeHancox BiomedicalandElectricalEngineeringDepartment,Schoolof Engineering,UniversityofBradford,Bradford,UnitedKingdom

NasiraHaque DepartmentofBiomedicalandElectronicsEngineering,Schoolof Engineering,UniversityofBradford,Bradford,UnitedKingdom

RobertG.Hill DentalPhysicalSciences,InstituteofDentistry,BartsandThe LondonSchoolofMedicineandDentistry,QueenMaryUniversityofLondon, London,UnitedKingdom

Wei-TeHuang CentreforOralBioengineering,InstituteofDentistry,QueenMary UniversityofLondon,London,UnitedKingdom

ShehriarHusain DepartmentofDentalMaterialsScience,JinnahSindhMedical University,Karachi,Pakistan

SeyedHassanJafari SchoolofChemicalEngineering,CollegeofEngineering, UniversityofTehran,Tehran,Iran

BasselKano DivisionofEndodontics,FacultyofDentistry,McGillUniversity, Montreal,QC,Canada

AbdulSamadKhan DepartmentofRestorativeDentalSciences,Collegeof Dentistry,ImamAbdulrahmanBinFaisalUniversity,Dammam,SaudiArabia

ErumKhan BhitaiDentalandMedicalCollege,LiaquatUniversityofMedical andHealthSciences,Jamshoro,Pakistan;FacultyofDentistry,KingAbdulaziz University,Jeddah,SaudiArabia

ZohaibKhurshid DepartmentofProsthodonticsandDentalImplantology,College ofDentistry,KingFaisalUniversity,Al-Ahsa,SaudiArabia

TiantongLou FacultyofDentistry,UniversityofToronto,Toronto,ON, UnitedStates

MariaMali DepartmentofOrthodontics,IslamicInternationalDentalCollege& Hospital,RiphahInternationalUniversity,Islamabad,Pakistan

JukkaP.Matinlinna DentalMaterialsScience,AppliedOralSciences,Facultyof Dentistry,TheUniversityofHongKong,PrincePhilipDentalHospital,SaiYing Pun,HongKongSAR,P.R.China

Kyung-sanMin SchoolofDentistry,ChonbukNationalUniversity,Jeonju,South Korea

MasoudMozafari BioengineeringResearchGroup,Nanotechnologyand AdvancedMaterialsDepartment,MaterialsandEnergyResearchCentre(MERC), Tehran,Iran;DepartmentofTissueEngineering&RegenerativeMedicine,Faculty ofAdvancedTechnologiesinMedicine,IranUniversityofMedicalSciences (IUMS),Tehran,Iran;CellularandMolecularResearchCenter,IranUniversityof MedicalSciences,Tehran,Iran

ShariqNajeeb IndependentResearcherandPrivatePractitioner,Alberta, Canada;NationalCenterforProteomics,UniversityofKarachi,Pakistan

SeungYunNam InterdisciplinaryProgramofMarine-Biomedical,Electricaland MechanicalEngineering,CenterforMarine-IntegratedBiomedicalTechnology (BK21Plus),PukyongNationalUniversity,Busan,SouthKorea;Departmentof BiomedicalEngineering,PukyongNationalUniversity,Busan,SouthKorea

HafizMuhammadOwaisNasim DepartmentofDentalMaterials,SharifMedical andDentalCollege,Lahore,Pakistan

TourajNejatian EastmanDentalInstitute,UniversityCollegeofLondon,London, UnitedKingdom;NottinghamDentalClinic,Nottingham,UnitedKingdom;Royal CollegeofSurgeonsofEngland,London,UnitedKingdom

RafaelRochaPacheco SchoolofDentistry,UniversityofDetroitMercy,Detroit, MI,UnitedStates

BroukiMilanPeiman CellularandMolecularResearchCenter,IranUniversityof MedicalSciences,Tehran,Iran;DepartmentofTissueEngineering&Regenerative Medicine,FacultyofAdvancedTechnologiesinMedicine,IranUniversityof MedicalSciences,Tehran,Iran

SajjadPezeshki BabolUniversityofMedicalSciences,Babol,Iran

ZeeshanQamar DepartmentofOralandMaxillofacialSurgery,RiyadhElm University,Riyadh,SaudiArabia

Jean-MarcRetrouvey DivisionofOrthodontics,FacultyofDentistry,McGill University,Montreal,QC,Canada

SahbaRezaei SchoolofChemicalEngineering,CollegeofEngineering, UniversityofTehran,Tehran,Iran

FranciscoJavierRodrı´guez-Lozano SchoolofDentistry,UniversityofMurcia, Murcia,Spain

ViniciusRosa FacultyofDentistry,NationalUniversityofSingapore,Singapore, Singapore;CentreforAdvanced2DMaterialsandGrapheneResearchCentre, NationalUniversityofSingapore,Singapore,Singapore

MahsaRoshandel DepartmentofAnatomyandPathology,UniversityofSiena, Siena,Italy

MohammadRezaSaeb ColorandPolymerResearchCenter(CPRC),Amirkabir UniversityofTechnology,Tehran,Iran;AdvancedMaterialsGroup,IranianColor Society(ICS),Tehran,Iran;DepartmentofResinandAdditive,InstituteforColor ScienceandTechnology,Tehran,Iran

FarshidSefat BiomedicalandElectricalEngineeringDepartment,Schoolof Engineering,UniversityofBradford,Bradford,UnitedKingdom;Interdisciplinary ResearchCenterinPolymerScience&Technology(IRCPolymer),Universityof Bradford,Bradford,UnitedKingdom

SaroashShahid CentreforOralBioengineering,InstituteofDentistry,Queen MaryUniversityofLondon,London,UnitedKingdom

ZeeshanSheikh FacultyofDentistry,UniversityofToronto,Toronto,ON, Canada;Lunenfeld-TanenbaumResearchInstitute,MountSinaiHospital,Toronto, ON,Canada;DepartmentofLaboratoryMedicineandPathobiology,Universityof Toronto,Toronto,ON,Canada

DaliaSherief DentalBiomaterialsDepartment,FacultyofDentistry,Ain-Shams University,Cairo,Egypt

SunjaySuri DivisionofOrthodontics,FacultyofDentistry,UniversityofToronto, Toronto,ON,UnitedStates

AhmedTalal DepartmentofRestorativeDentalSciences,CollegeofDentistry, ImamAbdulrahmanBinFaisalUniversity,Dammam,SaudiArabia

WaqasTanveer MaxillofacialProstheticService,DepartmentofProsthodontics, FacultyofDentistry,MahidolUniversity,Bangkok,Thailand

xxvi Listofcontributors

JamesK.H.Tsoi DentalMaterialsScience,DisciplineofAppliedOralSciences, FacultyofDentistry,TheUniversityofHongKong,Pokfulam,HongKongSAR, P.R.China

RizwanUllah DepartmentofOralBiology,SindhInstituteofOralHealth Sciences,JinnahSindhMedicalUniversity,Karachi,Pakistan

DanielVarley MedicalEngineeringDepartment,FacultyofEngineeringand Informatics,UniversityofBradford,Bradford,UnitedKingdom

GauravVasudeva SchoolofDentistry,JamesCookUniversity,Townsville,QLD, Australia;OralHealthServices,Hobart,TAS,Australia

JayachandranVenkatesan YenepoyaResearchCentre,YenepoyaUniversity, Mangalore,India

RafaelPinoVitti DepartmentofDentistry,UniversityofTaubate ´ ,Taubate ´ , Brazil;DepartmentofDentistry,ArarasDentalSchool(FHO|UNIARARAS), Araras,Brazil

SyedAzeemUlYaqin DepartmentofProsthodonticsandDentalImplantology, CollegeofDentistry,KingFaisalUniversity,Al-Ahsa,SaudiArabia

SafiyyaYousaf MedicalEngineeringDepartment,FacultyofEngineeringand Informatics,UniversityofBradford,Bradford,UnitedKingdom

MansourYouseffi MedicalEngineeringDepartment,FacultyofEngineeringand Informatics,UniversityofBradford,Bradford,UnitedKingdom

MuhammadS.Zafar DepartmentofDentalMaterials,IslamicInternational DentalCollege,RiphahInternationalUniversity,Islamabad,Pakistan;Department ofRestorativeDentistry,CollegeofDentistry,TaibahUniversity,Medina, SaudiArabia

MuhammadSohailZafar DepartmentofRestorativeDentistry,Collegeof Dentistry,TaibahUniversity,AlmadinahAlmunawwarah,SaudiArabia

PayamZarrintaj PolymerEngineeringDepartment,FacultyofEngineering, UrmiaUniversity,Urmia,Iran;ColorandPolymerResearchCenter(CPRC), AmirkabirUniversityofTechnology,Tehran,Iran;AdvancedMaterialsGroup, IranianColorSociety(ICS),Tehran,Iran

Introductiontodental biomaterialsandtheiradvances

ZohaibKhurshid1,MuhammadS.Zafar2,3,ShariqNajeeb 4 , TourajNejatian5,6 andFarshidSefat7

1

1DepartmentofProsthodonticsandDentalImplantology,CollegeofDentistry,KingFaisal University,Al-Ahsa,SaudiArabia, 2DepartmentofRestorativeDentistry,Collegeof Dentistry,TaibahUniversity,Medina,SaudiArabia, 3DepartmentofDentalMaterials, IslamicInternationalDentalCollege,RiphahInternationalUniversity,Islamabad,Pakistan, 4NationalCenterforProteomics,UniversityofKarachi,Pakistan, 5RoyalCollegeof SurgeonsofEngland,London,UnitedKingdom, 6NottinghamDentalClinic,Nottingham, UnitedKingdom, 7BiomedicalandElectricalEngineeringDepartment,Schoolof Engineering,UniversityofBradford,Bradford,UnitedKingdom

ChapterOutline

References3 Furtherreading5

Dentalbiomaterialsandtissueengineeringarerapidlydevelopingapproachesbeing usedfortheproductionofneworgansandbodytissues,particularlyforbone implantsordentaltissuereplacements.Yet,overthepastfewdecades,therehas beenawiderangeofresearchconductedontheprovisionoftissueengineereddentalgraftsthathasledtoasignificantimprovementintheproductionofscaffolds withsimilarcharacteristicstoanaturaltooth(ZafarandAhmed,2015).

Tissueengineeringinthe21stcenturyhasbecomeacutting-edgescienceinthe fieldofmedicineanditisexpectedinthenearfuturetoreplacetraditionaltherapies whichcauseenormoussideeffects.Inthetissueengineeringprinciples,oneofthe mainelementsaftercells,environmentalfactors,andsignalingmoleculesisthebiomaterial,whichplaysanimportantroleinsuccessfulfunctionaltissueengineered products.Inrecentyearssignificantimprovementandprogresshavebeenreported inthereconstructionofvarioushumantissuereplacementsandprostheses,includingbone(Sefatetal.,2010,2014),cartilage(DaghighAhmadietal.,2018;Raja etal.,2018),skin(Mahjouretal.,2015;Byeetal.,2014),oraltissues(Nejatian etal.,2017;ZafarandAhmed,2015;Qasimetal.,2018;Najeebetal.,2017),cornea(Deshpandeetal.,2013;Ortegaetal.,2014),nerve(Mohamadietal.,2017; Mohammadietal.,2018),andadiposetissue(Aminietal.,2018).

Themostcommonmethodsusedinthefabricationoftissueengineeringscaffolds, particularlyasdentalbiomaterials,consistofhydrogels,molecularself-assembly,thermallyinducedphaseseparation,solventcasting,particulate-leachingtechniques,and

theelectrospinningprocess(Gentileetal.,2017;Mahjouretal.,2016).Inparticular, fordentaltissueengineeringmuchresearchhasbeencarriedoutusingelectrospinning (Zafaretal.,2016;Qasimetal.,2018),andthisisthemostwidelyusedmethodinthe productionoftissueengineeredteeth.

Dentistry,similarlytomedicineandotherrelatedsubjectssuchasbiomedical engineering,biomedicalscience,pharmacy,andpharmacology,hasbeenrevolutionizedbytheintroductionofnewtechnologies,forexample,dentistsusedigital technologytocarryoutdentaltreatments.Forthisreason,wehaveincludedan interestingchapterondigitaldentistryinthisbook.

Thisbookcoversboththebasicandclinicalsciencesofdentalbiomaterialswith theviewtomeetingtheneedsofresearchersandpractitioners.Inthisbook,the authorsmainlylookatvariousdentalbiomaterials’propertiesandcharacterization techniques,suchasmetalalloys,polymers,composites,andceramics.

Achapterwillfocusondentalgypsumandinvestmentmaterialscoveringcomposition,types,manufacturing,andapplications.Gypsumproductscanbefoundas apowderwhichformsafluidmassoncecombinedwithwaterand,therefore,has thecapabilitytobeshaped,beforefinallyhardeningintoarigid,stablemass.The mainapplicationofgypsumproductsistoreplicatetheshapeoforalstructures, whichwillbediscussedinthischapter.

Acrylicresinisabiomaterialthathastherequiredmechanicalandphysicalproperties(ZafarandAhmed,2014),andithasbeenusedasadenturematerialbothin researchandtheclinic.Muchresearchhasbeendoneonthebiocompatibilityand biodegradabilityofthismaterial(Nejatianetal.,2015).Acrylicresinwillbediscussedinaseparatechapterinthisbook.

Anotherchapterismainlyfocusedondentalamalgam,whichhasbeenusedsuccessfullyinthedentalindustryfordecades.Dentalamalgamiscomposedofamixtureofmetalalloyandliquidmercury.Amalgamismainlyusedfordental restorations.ThecurrenttrendintheUnitedKingdomistophase-downamalgam applicationduetotheincreasingconcernoverthesafetyofmercury,however,itis stillwidelyusedinmanyothercountries,includingtheUnitedStates.Amalgam stayssoftforashortperiodoftimeafteritismixed,whichallowsenoughtimefor ittobecondensedandshapedontothepreparedtooth(Gayetal.,1979;Bates, 2006).

Dentalresincompositesareimportantbiomaterialsthathavebeenincreasingly usedasthemainrestorativematerials(Nejatianetal.,2017;Khurshidetal.,2015). Inthisbookthespecifictypesofcompositesaswellasthepotentialbiological issuesofdentalcompositesarediscussedindetail.Inaddition,resin-baseddental compositesfortoothfillingareaddressedinaseparatechapterduetotheir importance.

Cementsareanotherimportantgroupofbiomaterialsthathavebeenexplored intensivelybyresearchersandclinicians.Aseparatechapterisallocatedtodental cements,includingbase,liner,luting,andtemporarycements,aswellaspulpcappingmaterials.Duetothehighclinicaldemandfordentalcements,thechemistry andapplicationsofglassionomercement(GIC)andnano-GIChavebeendiscussed broadlyhereinthisbook.

Dentalimpressionmaterialshavebeenutilizedasnegativereplicastofabricate dentalmodels.Variousnaturalandsyntheticmaterialshavebeenutilizedasdental impressionmaterials,whicharefrequentlyclassifiedonthebasisoftheirproperties intotwogroups,thatis,elasticandnonelasticfamilies.Inthisbook,impression materialsandtheirpropertiesarediscussedwiththeaimofprovidingapractical guidefordentistsandprosthodontists.

Fiberreinforcedcomposites(FRCs)arecombinationsofconventionaldental resincompositesandglassfibers.Thiscombinationprovidesahighlevelof strengthinthesamewayasthatfoundinboats,lightaircraft,andF1racingcars. Formanydecades,engineershavebeenusingfibersasfillerstoconstructmaterials/deviceswithhighlevelsofstrengthandfracturetoughness.Thatiswhythese materialsattractedattentionasdesirablerestorativematerialsinthefieldofdentistry(Heetal.,2017).FRCshavebeenthecenterofattentionindentistryinthe 21stcenturybecauseoftheirexcellentadhesionandappearance.Nowadaysthese materialshavemanyclinicalapplications,suchasfixedprosthodontics,restorative dentistry,periodontology,orthodontics,andrepairofprostheticdevices(Nagata etal.,2016).FRCsarediscussedindetailinachapterofthisbook.Additionally,a numberofemergingmaterialsthathavebeenextensivelyexploredforvariousdentalapplications,suchasnanomaterials(Najeebetal.,2015,2016a,b,c,d;Zafar etal.,2017),polyether etherketones(Najeebetal.,2016a,b),naturalsilk(Zafar andAhmed,2014),andantimicrobialpeptides(Khurshidetal.,2016a,b,2017, 2018),willbediscussedinpartsofvariouschapters.

TheuseofGICsasdirectrestorativedentalmaterials,whichhavebeenextensivelystudiedandusedindentistry(ZafarandAhmed,2015;Najeebetal.,2016a, b,c,d),isalsodiscussedindetailinthisbook.Otheradvanceddentalbiomaterials arealsocoveredingreatdetailincludingendodonticmaterials,advancedceramics, bonecements,calciumphosphate,bioactiveglasses,graphene,andsilicon,aswell asorthodonticmaterialsincludingwires,orthodonticbrackets,elastomericligatures, andchains.Thefinalchapterdiscussesbiomaterialsusedformaxillofacialprostheticrehabilitation/reconstruction,aswellasbiomaterialsforcraniofacialtissue engineeringandregenerativedentistrywhicharehottopicsinthefieldofbioengineeringandregenerativemedicine.

References

Amini,N.,Vousooghi,N.,Alizade,A.,Ramezani,S.,Joghataei,M.T.,BroukiMilan,P., etal.,2019.Transplantationofadiposetissue-derivedstemcellsintobrainthroughcerebrospinalfluidinratmodels:protocoldevelopmentandinitialoutcomedata.Curr.Stem CellRes.Ther.14(2),191 195.

Bates,M.N.,2006.Mercuryamalgamdentalfillings:anepidemiologicassessment.Int.J. Hyg.Environ.Health209,309 316.

Bye,F.J.,Bullock,A.J.,Singh,R.,Sefat,F.,Roman,S.,Macneil,S.,2014.Developmentofa basementmembranesubstituteincorporatedintoanelectrospunscaffoldfor3Dskintissueengineering.J.Biomater.TissueEng.4,1 7.

4AdvancedDentalBiomaterials

DaghighAhmadi,E.,Raja,T.I.,Khaghani,S.A.,Soon,C.F.,Mozafari,M.,Youseffi,M., etal.,2018.TheroleofphotonicsandnaturalcuringagentsofTGF-β1intreatmentof osteoarthritis.Mater.TodayProcedia5,15540 15549.

Deshpande,P.,Sefat,F.,Ramchadaran,C.,Mariappan,I.,Johnson,C.,Mckean,R.,etal., 2013.Simplifyingcornealsurfaceregenerationusingabiodegradablesyntheticmembraneandlimbaltissueexplants.Biomaterials34(21),5088 5106.

Gay,D.D.,Cox,R.D.,Reinhardt,J.W.,1979.Chewingreleasesmercuryfromfillings. Lancet1(8123),985 986.

Gentile,P.,Mccolgan-Bannon,K.,Ceretto,N.,Sefat,F.,Dalgarno,K.,Ferreira,A.M.,2017. BiosyntheticPCL-graft-collagenbulkmaterialfortissueengineeringapplications. Materials10,693.

He,J.,Vallittu,P.,Lassila,L.V.,2017.Preparationandcharacterizationofhighradio-opaque E-glassfibre-reinforcedcompositewithiodinecontainingmethacrylatemonomer.Dent. Mater.33(2),218 225.

Khurshid,Z.,Zafar,M.,Qasim,S.,Shahab,S.,Naseem,M.,AbuReqaiba,A.,2015. Advancesinnanotechnologyforrestorativedentistry.Materials8(2),717 731.

Khurshid,Z.,Naseem,M.,Sheikh,Z.,Najeeb,S.,Shahab,S.,Zafar,M.S.,2016a.Oralantimicrobialpeptides:typesandroleintheoralcavity.SaudiPharm.J24(5),515 524.

Khurshid,Z.,Zohaib,S.,Najeeb,S.,Zafar,M.S.,Rehman,R.,Rehman,I.U.,2016b. Advancesofproteomicsciencesindentistry.Int.J.Mol.Sci.17(5),728.

Khurshid,Z.,Najeeb,S.,Mali,M.,Moin,S.F.,Raza,S.Q.,Zohaib,S.,etal.,2017.Histatin peptides:pharmacologicalfunctionsandtheirapplicationsindentistry.SaudiPharm.J. 25(1),25 31.

Khurshid,Z.,Zafar,M.S.,Naseem,M.,Khan,R.S.,Najeeb,S.,2018.HumanOralDefensins antimicrobialpeptides:afuturepromisingantimicrobialdrug.Curr.Pharm.Des.24 (10),1130 1137.

Mahjour,S.B.,Fu,X.,Yang,X.,Fong,J.,Sefat,F.,Wang,H.,2015.Rapidcreationofskin substitutesfromhumanskincellsandbiomimeticnanofibersforacutefull-thickness woundrepair.Burns41(8),1764 1774.

Mahjour,S.B.,Sefat,F.,Polunin,Y.,Wang,L.,Wang,H.,2016.Improvedcellinfiltrationof electrospunnanofibermatsforlayeredtissueconstructs.J.Biomed.Mater.Res.PartA 104(6),1479 1488.

Mohamadi,F.,Ebrahimi,S.,Nourani,M.R.,Mansoori,K.,Alizadeh,A.A.,Tavangar,S.M., etal.,2017.Enhancedsciaticnerveregenerationbyhumanendometrialstemcellsinan electrospunpoly(ε-caprolactone)/collagen/NBGnerveconduitinrat.Artif.Cells Nanomed.Biotechnol.46(8),1731 1743.

Mohammadi,A.,Maleki-Jamshid,A.,Sanooghi,D.,BroukiMilan,P.,Rahmani,A.,Sefat, F.,etal.,2018.Transplantationofhumanchorion-derivedcholinergicprogenitorcells:a noveltreatmentforneurologicaldisorders.Mol.Neurobiol.56(1),307 318.

Nagata,K.,Garoushi,S.K.,Vallittu,P.K.,Wakabayashi,N.,Takahashi,H.,Lassila,L.V.J., 2016.Fracturebehaviourofsingle-structurefibre-reinforcedcompositerestorations. ActaBiomater.Odontol.Scand.2(1),118 124.

Najeeb,S.,Khurshid,Z.,Matinlinna,J.P.,Siddiqui,F.,Nassani,M.Z.,Baroudi,K.,2015. Nanomodifiedpeekdentalimplants:bioactivecompositesandsurfacemodification—a review.Int.J.Dent.2015,381759.

Najeeb,S.,Bds,Z.K.,Bds,S.Z.,Bds,M.S.,2016a.BioactivityandosseointegrationofPEEK areinferiortothoseoftitanium:asystematicreview.J.OralImplantol.42(6),512 516.

Najeeb,S.,Zafar,M.S.,Khurshid,Z.,Siddiqui,F.,2016b.Applicationsofpolyetheretherketone (PEEK)inoralimplantologyandprosthodontics.J.Prosthodont.Res.60(1),12 19.

Najeeb,S.,Khurshid,Z.,Zafar,M.S.,Khan,A.S.,Zohaib,S.,Martı´,J.M.,etal.,2016c. Modificationsinglassionomercements:nano-sizedfillersandbioactivenanoceramics. Int.J.Mol.Sci.17(7),1134.

Najeeb,S.,Khurshid,Z.,Agwan,A.S.,Zafar,M.S.,Alrahabi,M.,Qasim,S.B.,etal.,2016d. Dentalapplicationsofnanodiamonds.Sci.Adv.Mater.8(11),2064 2070.

Najeeb,S.,Khurshid,Z.,Agwan,M.A.,Ansari,S.A.,Zafar,M.S.,Matinlinna,J.P.,2017. Regenerativepotentialofplateletrichfibrin(PRF)forcuringintrabonyperiodontal defects:asystematicreviewofclinicalstudies.TissueEng.Regener.Med1,1 8. Nejatian,T.,Sefat,F.,Johnson,T.,2015.Impactofpackingandprocessingtechniqueon mechanicalpropertiesofacrylicdenturebasematerials.Materials8(5),2093 2109.

Nejatian,T.,Khurshid,Z.,Zafar,M.S.,Najeeb,S.,Zohaib,S.,Mozafari,M.,etal.,2017. Dentalbiocomposites(Chapter5).BiomaterialsforOralandDentalTissueEngineering. Elsevier,pp.65 83.

Ortega,I.,Sefat,F.,Paterson,T.,Deshpande,P.,Ramchadaran,C.,Claeyssens,F.,etal., 2014.Combinationofmicrostereolithographyandelectrospinningtoproducemembranesequippedwithnichesforcornealregeneration.J.Vis.Exp91,e51826.

Qasim,S.,B.,Zafar,M.S.,Najeeb,S.,Khurshid,Z.,Shah,A.H.,Husain,S.,etal.,2018. Electrospinningofchitosan-basedsolutionsfortissueengineeringandregenerativemedicine.Int.J.Mol.Sci.19(2),407.

Raja,T.I.,Khaghani,S.A.,Zafar,M.S.,Khurshid,Z.,Mozafari,M.,Youseffi,M.,etal., 2018.EffectofTGF-β1onwaterretentionpropertiesofhealthyandosteoarthriticchondrocytes.Mater.TodayProc.5(7),15717 15725.

Sefat,F.,Youseffi,M.,Denyer,M.C.T.,2010.Imagingviawidefieldsurfaceplasmonresonancemicroscopeforstudyingbonecellinteractionswithmicro-patternedECMproteins.J.Microsc.241(3),282 290.

Sefat,F.,Denyer,M.C.T.,Youseffi,M.,2014.Effectsofdifferenttransforminggrowthfactor beta(TGF-β)isomersonwoundclosureofbonecellmonolayers.Cytokines64,75 86.

Zafar,M.S.,Ahmed,N.,2014.Nanoindentationandsurfaceroughnessprofilometryofpoly methylmethacrylatedenturebasematerials.Technol.HealthCare22(4),573 581.

Zafar,M.S.,Ahmed,N.,2015.Therapeuticrolesoffluoridereleasedfromrestorativedental materials.Fluoride48,184 194.

Zafar,M.S.,Najeeb,S.,Khurshid,Z.,Vazirzadeh,M.,Zohaib,S.,Najeeb,B.,etal.,2016. Potentialofelectrospunnanofibersforbiomedicalanddentalapplications.Materials9 (2),73.

Zafar,M.S.,Khurshid,Z.,Najeeb,S.,Zohaib,S.,Rehman,I.U.,2017.Therapeuticapplicationsofnanotechnologyindentistry.NanostructuresforOralMedicine.Elsevier, pp.833 862.

Propertiesofdentalbiomaterials

2

MuhammadS.Zafar1,2,RizwanUllah3,ZeeshanQamar4, MuhammadA.Fareed5,FaizaAmin6,ZohaibKhurshid7 andFarshidSefat8,9 1DepartmentofRestorativeDentistry,CollegeofDentistry,TaibahUniversity,Medina, SaudiArabia, 2DepartmentofDentalMaterials,IslamicInternationalDentalCollege, RiphahInternationalUniversity,Islamabad,Pakistan, 3DepartmentofOralBiology,Sindh InstituteofOralHealthSciences,JinnahSindhMedicalUniversity,Karachi,Pakistan, 4DepartmentofOralandMaxillofacialSurgery,RiyadhElmUniversity,Riyadh,Saudi Arabia, 5AdultRestorativeDentistry,DentalBiomaterialsandProsthodonticsOman DentalCollege,Muscat,SultanateofOman, 6DepartmentofScienceofDentalMaterials, DowDentalCollege,DowUniversityofHealthSciences,Karachi,Pakistan, 7Department ofProsthodonticsandDentalImplantology,CollegeofDentistry,KingFaisalUniversity, Al-Ahsa,SaudiArabia, 8BiomedicalandElectricalEngineeringDepartment,Schoolof Engineering,UniversityofBradford,Bradford,UnitedKingdom, 9Interdisciplinary ResearchCentreinPolymerScienceandTechnology(IRCPolymer),Universityof Bradford,Bradford,UnitedKingdom

ChapterOutline

2.1Introduction8

2.2Opticalproperties(color)8

2.3Thermalproperties9

2.3.1Temperature9

2.3.2Transitiontemperatures9

2.3.3Heatoffusion(L)11

2.3.4Thermalconductivity(K)12

2.3.5Specificheat(Cp)13

2.3.6Thermaldiffusivity(Δ)13

2.3.7Coefficientofthermalexpansion(α)14

2.4Viscosity14

2.5Electricalconductivityandresistivity15

2.6Mechanicalpropertiesandcharacterizationmethods16

2.7Limitationofmechanicaltestingmethods22

2.8Biologicalproperties22

2.8.1Biocompatibility22

2.8.2Invitrotesting23

2.8.3Invivotesting24

2.8.4Usagetests24

2.9Toxicityandcytotoxicity24

2.10Cytotoxicitytests26

2.11Fluorideandcaries26

2.11.1Fluoridetoxicity27

2.12Carcinogenicity27

2.13Biodegradation28

2.14Bioactivity28

2.15Osseointegration29

2.16Osteoinduction29

2.17Foreignbodyreaction29

2.18Conclusiveremarks30

References30

2.1Introduction

Understandingthepropertiesofdentalbiomaterialsisimportantinordertocompare withthepropertiesoforalhardandsofttissuespriortoanyclinicalapplication. Variousdentalrestorationstendtofailduetoanumberofreasonssuchasdistortion ormechanicalfailure.Thedentalrestorationsaresometimesincompatiblewiththe supportingoraltissuesduetotheinterfaceorsubstratefailure.Althoughnodental biomaterialhasbeenreportedashavingidealpropertiestodate,butitisworth mentioningthattheperformanceandclinicalsuccessofdentalbiomaterialsis stronglyassociatedwiththeirproperties.Inthischapter,variousphysical,mechanical,andbiologicalpropertiesofdentalbiomaterialsandrelatedinteractionare discussed.

2.2Opticalproperties(color)

Colorisperceivedasanendresultofthesensoryresponsetolight(Costa,2016). Thephysiologicalstimuliorsensoryresponseisexperiencedbyanindividual, whereasthelightbeamisconsideredasthephysicalstimuliwhichproducethesensoryresponse.Colorisperceivedduetoreflectionortransmission(partialorcomplete)ofwhitelight.AccordingtoGrassmann’slaw,thenormaleyecan differentiateinthreecolorparameters,whicharedominantwavelengths,luminous reflectance,andtheexcitationpurity(Mausfeld,1998;Grassmann,1853).Thedominantwavelength(λ)isthewavelengthofamonochromaticlightwhichoncombinationwithachromaticcolor(gray)matchestheperceivedcolor(Kleinand Meyrath,2010).Lightwithshort(400nm)andlong(700nm)wavelengthsarevioletandredincolor,respectively(KleinandMeyrath,2010).Thewavelengthrange ofvisiblelight(400 700nm)correspondstospecificcolors(e.g.,blue,green,yellow,andorange).Thispropertyofcolorthatisdistinguishedbylight’swavelength iscalled“hue.”Amongallthecolorsandshades,thereareonlythreeprimarycolorsi.e.,red,green,andblue.Thesethreecolorswhenusedinappropriate

proportionscanproducedifferentcolors,forexample,yellowcolorcanbeproduced byanappropriatecombinationofgreenandred.

Thesecondparameterisluminousreflectanceofcolor(value),whichclassifies objectsequivalenttoaseriesofachromaticscale(Lo ´ pezCameloandGo ´ mez, 2004).Forthelightdiffusingobjects,itrangesfromblacktowhite.Whileinthe caseoftransmittingobjects,itrangesfromblacktoclearorcolorless.Theblackis specifiedasastandardwithluminousreflectanceof0andthewhiteassignedas 100.Thethirdcomponent(saturationofcolor,alsocalled“Chroma”)definesthe degreeofdifferencefromachromaticcolortowardthecolorspectrum;itnumericallyrangesfrom0to1(SakaguchiandPowers,2012).

2.3Thermalproperties

Thermalpropertiesareimportantinregulatingtheperformanceofdentalmaterials. Atthemolecularlevel,thestructuralarrangementandmovementsofatomsare affectedasafunctionoftemperaturevariations.Thereforeitisnecessarytohavean understandingofdifferentthermaltechniquesusedtoidentifythermalpropertiesof dentalmaterials.

2.3.1Temperature

Athermometerorathermocouplecanbeusedtomeasurethetemperaturechanges ofvarioussubstances(Peyton,1952).Forinstanceinthedentalclinics,thetemperaturevariationsareobservedasaresultofheatgeneratedduringcavitypreparation orwhilecuringofresincompositematerials.Factorssuchasheadpiecerotational speedanduseofcoolantsarelikelytoinfluencethetemperaturechangesduring toothcutting(Fig.2.1).Thermocouplesareusedforthemeasurementoftemperaturebyinsertingitnearthedentino-enameljunction.

2.3.2Transitiontemperatures

Anumberofdentalmaterials,suchasdentalwaxes,arehighlysensitivetominute thermalschanges.Thedifferentialthermalanalysisisatechniqueusedtoidentify differentconstituents(suchasparaffinandcarnauba)ofdentalwaxes(Braueretal., 1970;Craigetal.,1965).Athermogramwasdevelopedonobservingtemperature differencesbetweenbothwaxesunderthestandardconditionsusingthermocouples. Temperaturedifferenceswererecordedasafunctionoftemperaturesurroundings. Decreaseintemperaturedifference(ΔT)indicatedanendothermicreactioninthe sample(Braueretal.,1970;Craigetal.,1967).Thesolid solidendothermsat 31.5 Cand35 Cwereobservedasaresultofchangesinthecrystalstructurefor theparaffinwax.Thesolid liquidtransitionendothermswereobservedat52 Cfor paraffinwax;ontheotherhandtheendothermsat68.7 Cand80.2 Cresultfrom meltingofcarnaubawax(Craigetal.,1965;Craigetal.,1967).Thetransitionof

Figure2.1 Thetemperaturefluctuationsinthetoothtissueduringcavitypreparationat variablespeeds(Peyton,1958).

Figure2.2 Thermogramofaparaffin(75%)andcarnauba(25%)waxmixturecomparing theirbehaviorinresponsetolower(0.013MPa)andhigher(0.26MPa)stress(Braueretal., 1970;PowersandCraig,1974).

heatfortwosolid solidtransitionsisapproximately8cal/g,themeltingtransition fortheparaffinwas39cal/gandforcarnaubawax11cal/g(Craigetal.,1965).The penetrationofthetestingindenterwasrecordedusingtwoquantitativestresses 0.013and0.26MPa(Fig.2.2).Atlowerstress(0.013MPa),thepenetrationwas regulatedbythemeltingtransitionofthecarnaubawax.Ontheotherhand,atthe

higherstress(0.26MPa),thepenetrationwasfacilitatedmainlybysolid solidand solid liquidtransitionsofparaffinwax.Nearly44%ofthewaxpenetration occurredbeforethemeltingofparaffinwax,whichiscorrespondingtoitsflowing potential(PowersandCraig,1974).

Anotherimportantpropertycorrelatedwiththethermogramsisthecoefficientof thermalexpansion.Thiscoefficientisraisedapproximatelyfrom300 3 10 6/ Cto 1400 3 10 6/ Cpriortosolid solidtransition.Thepropertyofflowisalso observedtoincreaseinthistemperaturerange.

Thedynamicmechanicalanalysisisanothertechniqueinordertoanalyzethe thermalpropertiesofamaterial.Forthispurpose,athinfilmofdi-methacrylate copolymerissubjectedtotensilestrainataspecificfrequencyof11Hz(Wilson andTurner,1987).Theelasticmodulusandlossoftangentareobtainedbyraising thetemperature.Theglasstransitiontemperature(Tg)ismeasuredfromthe decreaseofelasticmoduluswithtemperaturechanges.TheTgdeterminesthetemperatureatwhichpolymeristransformedtoasofter,rubberystateonheating (WilsonandTurner,1987).Thelowervalueofglasstransitiontemperaturecanbe affectedbythelowerdegreeofalterationofdoublebonds,lesscross-linking,and betterflexibilityofnetworks.Thecoefficientofthermalexpansionofapolymeris alteredattheglasstransitiontemperature.

2.3.3Heatoffusion(L)

Theheatincalories(Cal)orJoules(J)whichisrequiredforconversionof1gof materialfromthesolidphasetotheliquidphase(meltingtemperature)isreferred toasheatoffusion.Theheatoffusioncanbecalculatedby

where L istheheatoffusion, Q referstothetotalamountofheatabsorbed,and m referstothemassofthesubstancebeingmelted.Thus,practically,themassofmaterialisdirectlyproportionaltotheheatrequiredinchangingthetotalmasstoliquid. Theheatoffusionofamaterialiscorrelatedwithmeltingorfreezing.Forthechange inthestatefromasolidmasstoliquefactionitisimportanttoaddheat,aslongthe heatoffusionisretainedbytheliquid,themassremainsmolten.Assoonastheheat isliberatedfromtheliquidstatethematerialsolidifies.Thedifferenceintheenergy contentisofkeyimportanceinordertomaintainthekineticmolecularmotion,an importantpropertyofamaterialinaliquidstate.Theheatoffusionvaluesforcommonlyusedmaterialsarelistedinthe Table2.1 (CraigandPowers,2002).Itcanbe observedfrom Table2.1 thatthevaluesfordentalalloys,particularlysilver,gold, andcopper,arelowerthanthatofmanyotheralloysandmetals.

Table2.1 Heatoffusionofcommonlyused materials(CraigandPowers,2002).

MaterialsTemperature ( C) Heatoffusion (cal/g)[J/g]

Metals

Mercury 393[12]

Gold106316[67]

Silver96026[109]

Platinum177327[113]

Copper108349[205]

Cobalt149558[242]

Chromium189075[314]

Aluminum66094[393]

Compounds

Alcohol 11425[104]

Paraffin5235[146]

Beeswax6242[176]

Glycerin1847[196] Ice080[334]

2.3.4Thermalconductivity(K)

Theheat(incaloriesorjoulespersecond)thatispassingthroughthe1cmthick bodywithcrosssectionof1cm2 whenthetemperaturedifferenceis1 Cisknown asthethermalconductivity.Theunitforthethermalconductivityiscal/s/cm 2 ( C/cm).Changesinthermalconductivityareobservedonvariationinthesurroundingtemperature,butthesechangesarenegligibleincomparisontothatwhich existsbetweendifferentmaterials.

Thereisanimportantroleofthermalconductivityinthedentalmaterials.A classicrepresentationforthethermalconductivitycanbeshownbyanexampleof atoothrestoredwithdentalamalgamfillingordentalcrownmadeofgoldalloyin closeproximitytothedentalpulp.Suchrestorationpossiblywillleadtodiscomfort onuseofhotorcoldfoodproductswhichcanproducechangesinthetemperature. Theeffectofthermalconductivitycanbealleviatedifadequatedentaltissueis intactorcavitylinersareplacedbetweenthetoothstructureandthedentalrestorativematerial,whichhasacapabilityofprovidinginsulationsinceitisapoorthermalinductor.Dentalmaterialsthatprovideadequateinsulationarelistedin Table2.2 (Brownetal.,1970;LisantiandZander,1950).Nonmetallicmaterials havelessthermalconductivitythanmetalsmakingthemdesirableandgoodinsulators.Nonmetallicrestorativedentalmaterialsusuallyhavesimilarthermalconductivitytothoseoftheenamelanddentin.

Table2.2 Thermalconductivityofvariousdentalrestorative materials(Brownetal.,1970;LisantiandZander,1950).

MaterialsThermalconductivity

Cal/s/cm2/( C/cm)J/s/cm2/( C/cm)

Metals

Silver1.0064.21

Copper0.9183.84

Gold0.7102.97

Dentalamalgam0.0550.23

Nonmetals

Gypsum0.00310.013

Compositeresin0.00260.011

Enamel0.00220.0092

Dentin0.00150.0063

2.3.5Specificheat(Cp)

Thespecificheatistheamountofheatenergyrequiredtoraise1gofasubstance’s temperatureby1 C.Waterisusuallyusedasastandardforcomparison.Thetotal energyrequiredinordertoraisethetemperatureby1 Cisdependentonthetotal massofthematerial.Forexample,inordertoincreasethetemperatureby1 C, 100gofwaterrequiresmorecaloriesthanwouldberequiredfor50gofwater. Similarlyduetothevarianceinspecificheatofwaterandalcohol,100gofwater needsahigherdegreeofheatincomparisonwithalcoholofthesameamount. Consideredonabroadspectrum,thespecificheatofliquidsishigherthansolids. Forthemeltingandcastingprocess,ametaloralloy’sspecificheatisofkeyimportancefortheheatrequiredtoraisethetemperatureofmetallicmassuntilitreaches themeltingpoint.Thespecificheatofgoldandgoldalloysislowerthanmajority ofrestorativematerialsanddentaltissues;thereforeheatingforalongerdurationis notrequired.

2.3.6Thermaldiffusivity(Δ)

Themeasurementoftransientheatflowisreferredtoasthermaldiffusivity.The thermaldiffusivityismeasuredas:

where, K, Cp,and ρ representthethermalconductivity,specificheat,andthedensityofthematerial,respectively(Bradyetal.,1974;CarslawandJaeger,1959;Tay

andBraden,1987).Theunitforthethermaldiffusivityismm2/s.Thegoldcrown oramalgamrestorationshavehighthermalconductivityandlowspecificheatand arelikelytocausepotentthermalshockincomparisonwiththenormaltoothstructure.Similartothermalconductivity,thematerialthicknessisimportantinregulatingthethermaldiffusivity(Bradyetal.,1974).

2.3.7Coefficientofthermalexpansion(α)

Thecoefficientofthermalexpansionisreferredtoasdimensionalchangesina materialperunitforthechangeby1 Cintemperature(Fairhurstetal.,1980). Thecoefficientofthermalexpansioncanbecalculatedusingthefollowing equation:

Theunitsforthermalexpansionareexpressedasthenotation/ Casthevalues aresmallandtheyarethereforegenerallyusedinexponentialform,forexample, 12 3 10 6/ C(Fairhurstetal.,1980).

2.4Viscosity

Thefluidviscosityisobservedtohaveadirectrelationwiththeshearrate;it increaseswithincreasingshearrate.Theproportionalityoftheviscosityvariesfor differentfluids.Theviscosityofthefluidsmayvaryaccordingtotheshearrate; thereforefluidcanfurtherbeclassifiedasNewtonian,pseudoplastic,ordilatant. TheNewtonianfluidsarereportedtohaveconstantviscositywhichisindependent ofitsshearrate.ClassicexamplesforNewtonianfluidsaredentalcementsand impressionmaterials.Forthepseudoplasticfluidtheviscositydecreaseswithan increasingshearrate.Thebestexampleforthepseudoplasticsisthemonophase elastomericmaterials(CombeandMoser,1978).Thesematerialstendtohavehigh viscositythereforeonmixingorwhileplacingtheimpressionmaterialcontaining trayintothemouth,itremainsinitsplacewithoutflowing(Herfortetal.,1977). Elastomericmaterialscanbeusedinsyringesastheyencounterhighershearrates whilepassingthroughthesyringetip.Onexitingthesyringetheviscositydecreases by10-fold(Herfortetal.,1977).Thispropertyofmaterialisreferredtoasthixotropy,althoughtheterm“thixotropy”particularlydefinesthealterationsintheviscosityofamaterialwithtime.Amaterialwhoseviscosityincreaseswithincreasing shearrateisreferredtoasadilatantfluid.Indentistry,aclassicexamplefordilatantfluidsisthedenturebaseresins(Vermilyeaetal.,1978).

2.5Electricalconductivityandresistivity

Theconductanceorconductivitycanbedescribedasthepotentialofamaterialto conductelectricalcurrent,orcontrariwise,asthespecificresistanceorresistivity. Ataconstanttemperature,thehomogeneousconductor’sresistanceisdirectlyproportionaltothelengthandinverselyproportionaltothecrosssectionofthespecimenandcanbecalculatedusingthefollowingequation:

Theresistanceispresentedby R,resistivityby ρ,lengthby L,andsectionareaby A.Resistivity(Ω cm)varieswiththetypeofthematerial.Forexample,inthecaseofa 1cm3 cube,thelengthandsectionareaareequaltoeachotherandcanbeexpressedas R 5 ρ (Mumford,1967).Thevariationinohmscanbeusedtounderstandthechanges occurringinthestructureofdifferentalloyswhensubjectedtoheat.Oninvestigation ofelectricalconductivityforthegold copperalloysystem,therearechangesinthe internalcrystalstructureinconjunctionwithitsconductivity.

Theresistivityvaluesofdentalhardtissuesareshownin Table2.3.Resistivity ofthestructureisofkeyimportancetodeterminetheperceptionforpainthreshold whichresultsfromtheapplicationofelectricalstimuliandthedisplacementoffluid intoothstructureduetotheionicmovements(Mumford,1967).Theelectrical resistanceofahealthytoothdiffersfromthatoftheinfectedstructure,aslessresistanceisofferedbythecarioustissues.Anintactenamelstructureisrelativelya poorelectricconductorcomparedtodentin(Table2.3)(Mumford,1967).Theelectricalconductivityofrestorativedentalmaterialsisofkeyconcern.Various researchershavemeasuredtheresistivityofdentalrestorativematerials(Table2.3). Thedentalcementzincoxide eugenolisfoundtohavethehighestresistivity valuesfollowedbythezincphosphatecements.Theglassionomercements’conductivitymatchescloselytothatofdentin.

Table2.3 Theresistivity(Ω cm)valuesofdental hardtissuesanddentalrestorativematerials (Mumford,1967;TayandBraden,1981;Bradenand Clarke,1974;Phillipsetal.,1955).

3 106

3 104

2.5 3 104

R 5 ρ 3 L

16AdvancedDentalBiomaterials

2.6Mechanicalpropertiesandcharacterizationmethods

Thevibranthumanoralatmosphereisabletoinfluencethedentalbiomaterialsused fortoothrestoration.Oneofthekeyrequirementsofdentalmaterialsistomatch thepropertiesofthetoothstructurewhicharerequiredinaparticularapplication (Tillbergetal.,2008).Inordertoidentifytheappropriatemechanicalpropertiesrelevanttoaparticularusevarioustestmethodsareemployed.Therefore,anunderstandingofmechanicalpropertiesallowstodistinguishthepotentialcausesof clinicaldeficienciesrelatedtothemechanicalfailureofdentalmaterialsunderoral load.Thebasicparametertodeterminemechanicalbehavioristounderstandthe stress strainrelationshipfordeformation(Vaderhobli,2011).Mechanicalpropertiesdeterminetheresistancefractureordeformationunderanappliedforceorpressure.Analysisofmechanicalpropertieswillhelptounderstandthefailureand longevityofdentalmaterialsinthedynamicoralenvironmentundervarioustypes ofstressesandforces(DeJageretal.,2006).

Themechanicalbehaviorofamaterialismainlyrelatedtotheresponsetoa forceorload(ZafarandAhmed,2014b,c)andthisbehaviorultimatelydecidesthe usefulnessofamaterialinaspecificapplication.Themechanicaltestingandcharacterizationareusuallycarriedoutaccordingtoexistingstandardssetbyvarious internationalorganizationssuchasamericandentalassociation(ADA),theBritish Standards,ortheFederationDentaireInternationale(McCabeandWalls,2008). Oneofthemainpurposesofthesestandardsistoprovidethetechnicalinformation regardinganunbiasedanddependableselectionprocessforthematerialsusedby healthcareproviders.Certainclaimsofthematerials’qualityarisefrommanufacturersasaresultofstandardtestmethodologiesformechanical,physical,chemical, andbiologicaltests.Themechanicaltestingperformedbythemanufacturersto measuremechanicalpropertiessuchascompressionstrength(CS),tensilestrength, flexuralstrength(FS),wear,modulus,andbiocompatibilitymustbeperformed underthespecifictestingconditionstoidentifythesafestandthemostefficient materialsforspecificclinicalapplications(Basuetal.,2010).

Themechanicalpropertiesdemonstratehowadentalmaterialandthetooth structurereacttotheappliedforces.Thereforeitisimportanttounderstandthe applicationofforceorstressandpressureonamaterial;suchforceswillchange theshapeorstructureofthematerialsifnotresisted.

1. Forceorpressure:Forceisanappliedenergytomoveortodeformamaterial.During thenormalfunctionandbiting,varioustypesofforcesareappliedonthetoothstructure, alveolarsocket,andperiodontalcomplex(VanNoortandBarbour,2013).Forexample, axial,verticalforces,horizontalforces,torsionandbendingforces,oranycombination oftheseforces(Fig.2.3)areappliedtothetoothormaterialsbythemusclesofmasticationwhilebitingandthroughparafunctionalhabits.Externalforcesduetodentaltrauma, orthodontics,andtoothmovementarealsopresent.Threecharacteristicsofforcedeterminetheoutcomeoftheappliedforce,thatis,themagnitude,thedirection,andthepoint ofapplicationofforceandtheseresultinvariousdeformationsofthematerials (Fig.2.3).

Severaltestmethodsaredesignedtomeasurethemechanicalpropertiesofdental materialbydestructivetestingmethodologies,thatis,compressive,tensile,impacttests, hardness,brittleness,fatigue,andwearresistance.Theunitofforceisnewtonorpound.

2. Stressandstrain:Whenaforceisappliedonamaterial,stressisequaltotheforce applieddividedbyperunitarea,thatis,forces/unitarea,andtheunitisNewton/meter square.Stressoraforcethatisappliedtoamaterialproducesastrainwhichisopposite totheexternalforcebutequalinmagnitude.Strainisthechangeinthesize(length)of thematerialdividedbytheoriginalsize(length).Theunitofstressispascal(Pa)or megapascal(MPa).Compressivestressesareproducedwhenamaterialissubjectedto forcesinastraightlinedirectedinthesamedirectiontowardthecenter.Compressive stressproducescomprehensivestrain(SakaguchiandPowers,2012),asshownin Fig.2.4.Tensilestressresultsinamaterialwhentwosetofforcesareappliedina straightlinebutinoppositedirections,thatis,thematerialispulledapart(Fig.2.4). Tensilestressproducestensilestrain.

3. Elasticandplasticregions:Inthestress straingraph,twotypesofstressesarecommon, elasticandplastic,whichproducethecorrespondingelasticstrainandplasticstrain. Elasticstressesdonotproduceanydeformation;thereforeaftertheremovalofelastic stress,amaterialwillcomebacktoitsoriginaldimensionanditremainsunchangeddue toelasticstrain,whereasplasticstressesproducepermanentdeformationandthematerial willnotcomebacktoitsoriginalsizeorshape(SakaguchiandPowers,2012).Several mechanicalbehaviorsaredeterminedfromelasticstrain,forexample,elasticmodulus, flexibility,resilience,andPoisson’sratio.Ontheotherhand,theinitialplasticdeformationregionand/ortheendoftheelasticregionofastress straingraphhelptodetermine theyieldpoint,proportionallimit,elasticlimit,andyieldstrength.

Itisimportanttounderstandstressandstrainbecausetheyareindependentofthe sizeofthematerialused.Forexample,fortwocylindricalshapespecimensofcomposite

Figure2.3 Varioustypesofforcesandpossibledeformationaccordingtoforcedirections.