UnitThirtyTheSurgicalPrinciplesofOsseointegrationRagnarAdellOsseointegration;processanddefinition.Thepossibilityofpermanentlyretainingtitaniumfixtureinvitalremodelingbonewithacapacityofconsiderableloadbearingdependsonanadequatecomprehensionoftheosseointegrationprocess.ProfessorPer-IngvarBranemarkcoinedOsseointigrationasatermintheearly1970s.Itscurrentdefinition-adirectcontactbetweenliving,haversianboneandtheloadedimplantsurface-isbasedonhistologicalandultrastructuralobservationsbutisnotyetfullydefined.However,itiswellsupportedbylong-termradiographicandclinicalstudiesdemonstratingperifixturalboneadaptionandremodelingaswellaslong-termfixturestabilityandload-bearingcapacity.Thereisnoinstantosseointegration.Itsgradualandslowdevelopmentmustbefullyunderstoodinorderforasuccessfulclinicaloutcometobeachieved.AchievingosseointegationThemereuseoftitaniumasanimplantmaterialisbynomeansanyguaranteeofachievingosseointegration.Managingthehostorganismandtissuesshouldattractatleastasmuchinterestasthepropertiesandhandlingoftheimplant.PreoperativehostfactorsGeneralpatientconditionsNoinvestigationssofarhavebeenundertakensystematicallytoevaluatetheinfluenceofdiseases,medications,anddrugsthatmaytheoreticallyaffectwoundhealing-especiallybonehealingandremodeling-afterinstallationoftitaniumfixtures.Severalsuchpatientpreconditionscouldbeconsidered:l.Age2.Sex(duetopostmenopausalosteoporosis)3.Malabsorptionsyndromes(eg,ulcerativecolitis)4.Bonemetabolicdiseases(eg,osteoporosis,osteomalacia,gyperparathyroidism,Paget'sdisease)5.Rheumaticdiseases(eg,rheumatoidarthritis,Sjogren'ssyndrome,systemiclupuserythematosus)6.Hormonaldiseases(eg,diabetes,Cushing'ssyndrome,gyperparathyroidism)7.Coagulationdisordersandanticoagulationmedications8.Systemictreatmentwithglucocorticoides9.Alcoholabuse10.TobaccosmokingStudieshaveinitiallyindicatedthatahigherchronologicalpatientagealoneisnotadeterminingfactorfortheoutcomeoftreatmentwithfixtures,whereastobaccosmokingmaybe.Sofar,thereisinsufficientevidencetosupporttheinstallationoffixturesingrowingjaws.Experimentalstudiesandafewclinicaltrialsindicatethatthefixturesmaynotmovewithincreasingverticalheightofthejaw.Rheumatoidarthritisisnotregardedasacontraindicationfortheuseofosseointegratedimplantsinorthopedicsurgery.Amongthemorethan35,000patientstheworldoverwhohavebeentreatedwithimplantfixtures,anumberareknowntobemedicallycompromisedbyoneorseveralofthefactorslistedabovewithlittleornoinfluenceonthetreatmentoutcome.Thisespeciallyappliestopostmenopausalosteoporosis.Womenareverypronetothiscondition,butanumberofstudieshaveshownhighsuccessratesoftreatmentwithosseointegratedfixturesinwomenpatientsabove50yearsofage.Osteoporosisasapossibly13egativefactorwas,however,notseparatelyanalyzed.Anumberofnon-insulindependentdiabeticshavealsobeenincludedinthesematerialswithnoovertinfluenceontheoutcome.LocalhosttissueconditionsLocalboneosteogenicandremodelingcapacityplustheintegrityofthecoveringsofttissuesdeterminewhetherornotosseointegrationwillresultafterfixtureinstallation,providedsurgeryisperformedstrictlyaccordingtobasicrecommendations.Itshouldbeemphasizedthatlocalhosttissueconditionscanvaryconsiderablyfromoneareatoanotherwithinthesamepatient.Onlyareascoveredbyintactsofttissuesshouldbechosenfortheinstallationoffixtures.Consequently,allpossiblelesionsinskinormucosa(eg,eczema.candidasis,lichenplanus,leukoplakia,erosions)shouldfirstbetreatedbeforefixtureinstallationisattempted.Theinstallationoffixturesunderamucosalorsplitskingraftmustbeconsideredmoreriskythanbeneathanintactintegument.Suchgrafts'haveareducedresistancetomechanicalwear,andtheiroriginalplacementhasgenerallyimpliedandinterferencewiththebondsupplytotheperiosteum.Localbonequantityandqualityshouldideallybemadeupofawell-vascularized-bonearea,slightlylongerthanthefixtureandwithadiameternotlessthan5mm(forastandard3.75mmdiameterfixture).Itisoftheutmostimportantthatthefixtureachievesinitialstability.Thisisbestbroughtaboutifitsmarginalandapicalpartsareengagedincorticalbone.Anycancellousbonepresentshouldideallyhaveahighproportionofbonytrabeculaefurthertosupportthefixture.Itscancellouscompartmentsshouldcontainanosteopotenendosteumandmarrowtissue.Areaswithemptyorfattymarrowcompartmentsshouldbeavoided,asshouldsiteswithasmallratiooftrabeculatosofttissuemarrow.Possibleareaswiththeidealcharacteristicsmatchingthepositionsandinclinationsoffixturesasdesiredfortheplannedsuprastructureshouldbesought.Intheclinicalsituation,oneorseveralofthefollowingcircumstancesmayinfluencetentativefixturesites.LocalanatomyNotallareasinthemaxillofacialregionfulfilltheaboverequirements.Agoodexampleisupperversuslowerjawbone(Fig7-l).Thethinmaxillaryoutercompactlayerwillcontributelittletothestabilizationoffixtures.Initialimmobilizationcanthencomeonlyfromtheapicalendsbeingengagedinthecorticalnasalormaxillarysinusfloor.Maxillarytuberosityareasareverysoft,whereasthestructuralreinforcementsofthemidface-thecanine,zygomatic,andpterygoidareas-providebetterconditionsfortheinitialstabilizationoffixtures.Moreover,atriangularwidening,reinforcedbycorticalbone,canfrequentlybefoundclosetotheincisivecanaleveninseverelyresorbedcases.Thisareaisgenerallyagoodfixturesiteprovidedthemyelinsheathofthenerveisnotengaged.Ifthisoccurs,ossepintegrationwillnotensue.Fig7-1Corticallinings,markedbyarrows,sutablefortheanchorageoffixturestoprovideinitialstability,Corticalboneinthetemporalregionisnotmarked.Hatchedareasinthemidfaceindicatestructuralreinforcementsalsosuitableforfixtureplacement.Anteriormandibularbonebetweenthementalforaminagenerallyprovidesgoodopportunitiesforinitialstabilizationoffixturesbybicorticalanchorageinmarginalandbasalbone.Posteriorlyinthemandible,theupperbordermarginalbonestaysverythinwhilethecancellousboneabovethemandibularcanalstaysverysoft.Thefrontalandzygomaticboneandthebonesofthecalvadaareallbicorticalandhence,inspiteoftheirlimitedthicknessofonlyafewmillimeters,providegoodinitialstabilization.DegreeofresorptionTheedentulousalveolarprocessispronetocontinuousresorption-adenture-relatedordis-useatrophy.Unduepressurefromaresidualpartialopposingbiteorill-fittingdenturesmayaggravatetheresorption.Severeresorptionofthemandiblegenerallyimpliesthattheresidualbasalboneismadeupofpoorlyvascularized,almostentirelycompactbone.Thereverseisalsotrue;thatis,aconsiderableresidualbonevolumeshouldraisedoubtsaboutthepossibilitiesforinitialstabilizationoffixtures.Suchjawsfrequentlycontainanabundanceofverysoftcancellousbone.Thetopicandtechniquesofsimultaneousbonegraftingandfixtureinstallationarecoveredinchapters10,13,14,25,and26.Animportantquestionis,however,whentograftandwhennotto.Twoprinciplesshouldbeconsidered.Oneisthattheload-bearingcapacitydependsonthequalityoftheboneanditstotalinterfacesurfacewiththefixtures.Agreatnumberofevenshortfixturescanconsequentlytakeaconsiderableloadiftheboneisofgoodquality.Theotherprincipleisthattheresorptionofthejawbone,ifpossible,shouldnotbeallowedtoprogresstoofar,asfixturesanchoringabonegraftneedsomevolumeandstrengthof(preferablycortical)basalboneforthecrucialinitialstabilizationofthetransplant.CongenitaldefectsMaxillaryboneadjacenttocleftsisfrequentlyparticularlysoftandoflimitedvolume.Areasofdentalaplasiaareoftencollapsedinthebuccolingualdirection;sufficientbonevolumeforfixtureplacementcanthenonlybefounddeepinthejaw.SurgicaltraumaandinterventionsforpathologyAnybonesurgerystartsahealingandremodelingprocess.Theverygentlesurgeryofafixtureinstallationisnoexception,evenifitsconsequencescanbeforeseentobemild.Althoughdesignedtobeaslittletraumatizingtothetissuesaspossible,itwasshownintherapidlybonehealingrabbitthatthehealingoffixturesitesinthetibiarequiredaremodelingprocessofatleastlyearformostofthefixturethreadstobecomefilledwithosseointegratingbone.Althoughnostudieshavebeenperformedsofar,itistemptingtoassumethattheslower-bone-healinghumanmayrequireamoreextendedperiodoftimeforthesameresulttobebroughtabout.Ifthehealingiscompromisedbylessgentlesurgery,removalofintrabonyPathologicalprocesses(eg,cystsorteethwithperiapicalgranulomas,and/orthetissuesareleftforhealingbysecondaryintention),theneteffectmaybehealingwithscarfibroustissueinsteadofbone.Itisnotuncommontofindonlyfibrousgranulation'tissuecentrallyinextractionsocketsthatearliercontainedteethaffectedbysevereperiodontitis,whichwereextractedbyconventionalmethods.Suchsitesmakefixtureplacementdifficultorimpossible.Consequently,therecommendationisalwaystoremoveanyresidual(pathological)softtissuebythoroughcurettageofthebonywallsandclosetheareaprimarily.Ideally,thisshouldbedonebybringinginfreshperiosteumtopromotehealingbyfirstintention.Littleisknownaboutthelengthoftimethatshouldpassbetweenthesurgicalremovalofpathologicallyalteredtissuesandtheinstallationoffixturestogivethemoptimalhealingcircumstances.Unloadedfixtureshavebecomesuccessfullyosseointegratedafterinstallationindogsocketsprecededbyimmediateextractionofhealthyteeth.Again,however,humanbonehealsataslowrate.Waiting9to12monthsgenerallyprovestobethesafestandmostworthwhilealternativeespeciallyifthepatient'slong-termprognosisofthetreatmentistakenintoaccount.IrradiationInhisdoctoralthesisonCogammairradiationtotherabbittibia,Jacobssonconcludedthatbonehealingwastemporarilydepressedevenafterasingledoseof5Gy.At15Gy,asignificantdepressionofearlyosteogenesiswasobserved.However,ifthisdosehadbeengivenlyearearlier,theboneformingcapacitywouldhavebeenimprovedbyafactorof2.5relativetoimmediatepreoperativeirradiationtraumaofthesamemagnitude.Consequently,anosseousrecoveryafterirradiationwasobserved.Theseresultswere'allrelatedtohealingbone.Maturebonewasrelativelyresistanttoirradiationuptoasingledoseof40Gy,ie,remodelingcontinuedatanormalrateandnovascularchangeswereobservedaftertheirradiation.Clinicaltrialswithfixturesinstalledinpreviouslyirradiatedmaxillary,frontal,andtemporalbonetosupportfacialprosthesesaftercombinedsurgicalandradiologicaltreatmenthaveyieldedpositiveresults.Jacobssonetalreportedon35fixturesinserted9monthsto37yearsafterirradiationtreatmentwith25to86Gy.Withfollow-uptimesfromimplantinsertionof15to44months,only5fixtures(14.3%)wereLost.Onthebasisoftheseinvestigations,treatmentwithfixturesandfacialordentalprosthesesafterirradiationappearsnolongertobeanunattainableobjective,providedtheboneisallowedalongenoughrecoveryperiodaftertheirradiationtrauma.Moreover,irradiatedpatientsfrequentlyarethemostneedyones.Theeffectsoftreatmentwithcytotoxicdrugshavenotbeenstudied.Presentattemptstorevitalizeirradiatedbonebytreatmentwithhyperbaricoxygenpriortotheinstallationoffixtureshaveelicitedpositivepreliminaryresults.Furtherdocumentationis,however,needed.PerioperativefactorforfixtureinstallationImplantproperties.Itisthesurgeon'sresponsibilitytochooseimplantsthatwillmaximizethepossibilityofosseointegration.Thepropertiesofsuchimplantsandtheirinterfacialreactionswiththehost(bone)tissueshavebeenreviewedindetailelsewhereandareonlysummarizedbelow.MaterialCommerciallypuretitaniumisclinicallythebestdomment6dmaterialtoachieveosseointegration.Itssurfaceoxidesareverystableinthebonyenvironmentandcorrosionisminute.Noallergicreactionstothismaterialareknown.Consequently,itishighlybiocompatibleand,moreover,easytomachine.DesignAscrew-shapegivessurfaceenlargementforinteractionwiththerecipientbonetissue,enhancesinitialstabilization,providesresistancetoshearforces,anddistributesloadwellwithinthebone.Incontrasttootherdesigns,screw-shapedtitaniumimplantshavebeenshowntobecometotallyoseointegratedalongtheirentirecircumferenceindogs.SurfacepropertiesTheinterfacialreactionsofthebonetissuearegreatlygovernedbythechemicalandphysicalpropertiesoftheimplantsurface.Thepassivatingtitaniumoxidesandacertaindegreeofsurfaceroughnesspromoteosseointegration.SurfacepurityForobviousreasons,thedesiredsurfacepropertiesshouldnotbechangedbymicrobiologicalormetalliccontaminationduringanypartofthemanufacturing,storing,transportation,sterilization,andsurgeryprocesses.FixturesitepositionsThemostimportantprincipleistoachievegoodinitialstabilityandfullcoverageofthefixturesinwell-vascularized,highlyosteogenicbone.Bicorticalinitialstabilizationshouldbethegoal.Ifthisisnotpossible,onemustresorttoatleastmonocorticalfixation.Possibleareasforbi-andmonocorticalfixationhavebeenreviewedunder"Localanatomy."Theadditionalstabilitythatcanbeachievedbyengagingthelingualcorticalplateofthemandibleshouldbeusedwheneverpossible.Foradequateloaddistributiontotheboneandthefixturesthemselves,thelattershouldbespreadwellapartandplacedalongacurveoranyarrangementotherthanastraightline.Thecenterandtheendsofthetentativesuprastructureshouldbewellsupported.However,thefinaldesignandextensionshouldawaittheexperienceofbonequalityfromfixtureandabutmentsurgeries.Nofigureforanyoptimalinterfixturedistancecanbegivenbecausethisdependsonthevitalityandmechanicalcapacityofboththefixturesitesandtheinterfixtureboneandmayvaryfromoneareatoanother.Aclinicalruleofthumbis,however,thattheinterfixturedistanceshouldnotbelessthanonefixturediameter.Thisapproachalsofacilitateslaterhygieneeffortsbetweenabutments.Theanteriorloopofthemandibularcanalandthenasopalatineductshouldbeavoidedsoasnottointerferewithnervefunctionandosseointegration.NumberoffixturesitesTheavailablebonevolumeindifferentareascanbereasonablywellassessedpreoperativelybypalpationand,especially,bytomographicradiographs.Thesameisnottrueforbonequality,whichcanbeadequatelydeterminedonly'aftersomedrillinghasbeenperformed.Onemayfind,forexample,thatareasplannedasfixturesitesaretotallyunsuitableduetothepresenceofemptyorfattynarrowcompartments.Consequently,thenumberandpositionoffixturescannotbefinallydecideduponuntiltheperioperativeperiod.Withinthejawsitisgenerallyadvisabletostartdrillingforfixturesitesclosetothemidlineandthenpreparethenextonesasfarposteriorlyaspossible,becausethecentralandposteriorsitesstronglyinfluencetheout-comeoftheentiretreatment.Onlythencandecisionsbemadeonanyinterpositionalfixturestobeplaced.Inthetotallyedentulousmandible,placementoffixturesfromonemolarareatotheother(ifthepositionofthemandibularcanalallows)isnotarecommendedprocedure.Themandibleflexessomewhatduringchewing,andrigidconnectionofsuchfixturestoastiffbridgemaycausemicrofracturesintheperifixturalboneduringmandibularflexing.Fororalpurposes,onefixturecancarryonecrownonly,twofixturesprovideminimalsupportforabridgeinpartialedentulism,andfourfixturesaretheminimumforafull-archbridge,providedtheyarespacedwellapartalongacurve.UnpublisheddatafromtheGoteborgteamshowednosignificantdifferencesin5-to12-yearsurvivalratesformaxillaryandmandibularbridgessupportedbyfourorsixfixtures.InclinationoffixturesitesTheinclinationsofthefixturesitesdependon:l.Localboneanatomy.Thedominantprincipleisstillthatthefixturesshouldbetotallyembeddedinbone.Thismaycallforlingualorbuccalpositioningoratiltingofafixturesitetoavoidconcavitiesinthebone.Ifnobonegraftsareplacedintothefloorofthemaxillarysinus,distaltiltingofthemarginalpartsoffixturesitesmayalsobeneededinthefirstpremolarregiontoavoidpenetrationintothemaxillarysinus.Moreover,suchaninclinationfrequentlyallowsadvantagetobetakenofthecanineeminence.2.Jawrelationships.Unlessorthognathicsurgeryisperformedbeforeorpossiblyincombinationwithbonegraftingatfixtureinstallation,pseudoprognathismduetoresorptiongenerallycallsforbuccalinclinationofmaxillaryandlingualtiltingofmandibularfixturesitesintotaledentulism.3.Designofthesuptastructure.Withproperinclinationoffixturesites,penetrationofbridgescrewcanalsthroughbuccalfacingscanbeavoided.Anoverlypalatalinclinationmay,ontheotherhand,resultinabulkybridgethatinterfereswithphonation.4.Desireforparallelism.Ifparallelfixturesitesareprepared,theconstructionofthesuprastructuremaybefacilitated.Thisaspect,howevertakeslastpriority.LengthsoffixturesThelengthsofthefixturesshouldbedeterminedonlyafterall"high-speed"drillinghasbeenfinished.Inparticular,marginalcountersinkingmayreducethedepthofafixturesite,thenftxturesshorterthanoriginallyanticipatedmustbechosen.Thedepthofafixturesiteshouldbemeasuredwithagraded(ball-point)explorertothelowestmarginalboneedge.Majorextrabonyprotrusionsoftheapicalpartsoffixtures(eg,intothemaxillarysinusorthenasalcavities)arenotjustified.Experiencewithsurgicaldisplacementoftheinferioralveolarnervetogainbicorticalfixationinmandibularmolarareasisthusfarlimited.LoadbearingcapacityTheneteffectofalltheconsiderationsdiscussedabovegovernswhatdynamicloadthefixturesareabletobear.Itisthequalityofallperifixturalboneandthetotalinterfacesurfaceofallfixturesthatdeterminetheloadbearingcapacity.Consequently,four15-mm-longfixturesmaybecapableofcarryingthesameloadassix10mmlongones,providedallarestrategicallywellplaced.Thelong-termfixturesurvivalrateisslightlysmallerforthemaxillaethanforthemandible.Theseresultsarelikelytoreflectdifferencesintheload-bearingcapacitybetweenthejaws.Suchdifferencescouldtheoreticallyrequireagreaterfixture/boneinterfaceinthemaxillaeforadequateloaddistribution,thatis,moreorpossiblylongerfixturesthaninthemandible.Traumatothehosttissuesl.Handlingofthecoveringsofttissues.Theleadingsurgicalprincipleoftheosseointegrationmethodhasalwaysbeentominimizetraumatothehosttissues.Incisionsshouldbeplacedtoreduceinterferencewithvascularizationandinareaswherethereislittlefrictional(denture)load.Consequently,individualmodificationsforearlierreinsertionofatemporarydentureoreasieraccessbyplacingtheincisionpalatallyoronthetopofthecrest,respectively,entailgreaterrisksthantheoriginallyrecommendedplacementoftheincisioninthebuccalvestibule.Flapsshouldberaisedbystrictsubperiosteal,almostsuperficiallyintracortical,dissectiontopreservemaximamosteogenicityoftheperiosteum(forreviewseeAdell).Theirwatertightclosureisofgreaterimportancewhenimplantshavebeeninstalledthaniftheflapsrestentirelyonvascularizedbone.Aneasilyoverlookedareaisthemandibularanteriorregion.Ifaverticalmattresssuturetechnique(Fig7-2)oradouble-layerclosureisnotused,evenanexperiencedclinicianmayhavetofacelaterdehiscencesduetotheconsiderablepullfromthementalismuscle.2.Handlingofthebonetissue.Allaspectsoftheprocessofdrillinginbonehavebeencarefullyscrutinizedtoavoidfrictionalheat,andstrictrecommendationshavebeenpublished.Clinicalstudiesindensemandibularbonehaveconfirmedthatiftheserecommendationsarefollowed,thefrictionalheatatdrillingforfixtureswillstaybelowthethresholdlevelof47°Cforlminute.Frictionalheatabovethislevelwillpreventosseointegrationfromtakingplace.Allinvestigationsonthisitemhavebeenperformedwithpretappingofthefixturesites.Ifself-tappingfixturesareinsertedindiscriminatelyindensemandibularcorticalbone-apurposeforwhichtheyarenotintended-frictionalheatcouldbegenerated.Itshouldalsobekeptinmindthatextremelydense,poorlyvascularizedbone,frequentlyseeninseverelyresorbedmandiblesespeciallyinthesymphysisregion,requiresbothaminimumofflapexposuretopreventdevascularizationandanextraprecuttingwitha3.15mmdrilltomakethesubsequentpretappingpossibleand/orpreventexcessheatatthisstage.Fig7-2Correctmethodwatertightclosureinthemandibularanteriorregionbymeansofverticalmattresssutures.Themarginalconicaloutlet.fittingtheconicityofthefixturemount.thecoverscrew,andlatertheabutmentcylinder,isshapedbythe"high-speed"marginalcountersink,whichhasahighperipheralvelocityduetoitsgreatrelativediameter.Themarginalboneiswellcorticatedincertainregionssuchastheanteriormandibleand.thetemporalbone.Inconsequence,thereisatheoreticalriskoffrictionalandthermaltraumatosuchmarginalboneinspiteofgoodaccessibilityoftheareaforirrigation.Moreover.themarginalcorticalboneisdeprivedofpartitssuperficialvascularizationbecauseoftheraisingoftheflaps.Asaresultofthesefactors,osseointegrationcannotbeexpectedanddoenotoccursuperiorlytothemostmarginalthread,cutbytheslowspeedandmuchlesstraumatizingtap.Inaddition,however,itisimportantthattheshelfcreatedbythecountersinkalwaysbewithincorticalbone(Fig7-8).Whenthefixtureistighteneditfirsthitsthisshelfbeforeanyfragilethreadscanbecrashed.Consequently,thickmarginalcorticalboneallowsdeepercountersinking,andthincorticalboneallowslittlemarginalcountersinking.MatchingthefixturetoitsbonesiteMatchingthefixturetothepreparedbonesiteshouldbeperformedwiththeaimofavoidingovertighteningyetcreatinganoptimallit.Overtighteningislikelytocausemarginalcompressionischemia,whichmayresultininadvertenlossofmarginalboneheight.Ontheotherhand,averyclosefitismandatoryforosseointegrationtooccur.Forastudyanddiscussionontheinfluenceofgapsbetweenimplantsurfaceandbone,thereaderisreferredtoCarlsson.Finally,verylooselytexturedbonemaycreateariskysituation,becauseevenwithcorrectlyperformedsurgery,onlyafewtrabeculaetouchthefixturesurfacetoprovidetheinitialstability.PenetrationstonasalcavityandmaxillarysinusTheeffectofpenetrationsoftheapicalendsoffixturesintothenasalcavityorthemaxillarysinushasbeenthesubjectofonlyonestudy.Theexperimentalanimalpartofitshowednoadverseperifixturaltissuereactions.Theclinicalpartshowedsomewhatlowersurvivalratesforpenetratingfixturesascomparedtononpenetratingfixtures.Theseresultscouldnot,however,beexplainedbytheperforationsonly.Dehiscensesinthecoveringsofttissuesandoverloadingofthesoftmaxillaryboneanteriortothesinuscouldconstitutedecisivefactorsaswell.AdjustmentsofthecoveringsofttissuesThesurgicalcreationofthin,nonmobilesofttissuesintheareasoffutureabutmentpenetrationsshouldbepostponeduntilabutmentsurgery.Inthisway,athickandprotectivesofttissuecoverremainsduringthehealingperiodafterfixtureinstallation.PostoperativeconsiderationsHealingtimeWhatconstitutesanadequatehealingtimeforosseointegrationtooccurisinfluencedbymostofthefactorreviewedsofar.Clinicalhealingtimerecommendationsareaminimumof3monthsfordensebone,asinthe'mandit31e,and6monthsforcancelloustypebone,asinthemaxilla.Theserecommendationsarebasedonlong-termclinicalexperienceandaresupportedbyexperimentalanimalstudies.Thus,inalong-termstudythegroupwiththelongestobservationtimehadthelowestfixturesurvivalrates.Themajordifferencebetweenthisandtheothergroupswasthatithadconsiderablyshorterhealingperiodsthanthoserecommendedabove.IntheinvestigationbyJohanssonandAlbrektssonusingtherapidlybone-healingrabbit,onlyanaverageof50%bonetofixturecontactwasobservedafter3months,andittook12monthsuntiltherewasanaverageof85%suchcontact.DirectloadingOneexperimentalstudyhasshownabone-tofixturecontactof40%to90%after3months,evenwhentheimplantsweredynamicallyloadeddirectlyafterinsertion.Presently,thisobservationcannotbetakenasjustificationforanydeviationfromthepresentclinicalroutineofunloadedhealingofthefixturesites.MedicationsThepositiveeffectsofthemedicines(eg,calciumcarbonate,antibiotics,andanalgesics)recommendedforpostoperativeusetopromoteosseointegrationandhealinghavenotbeenscientificallyverified.Theiruseisextrapolatedfromgeneralmedicalknowledge(eg,calciumforosteoporosis).Abutmentsurge