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Clinical and scanning electron microscopic analysis of fractured dental implants: a retrospective clinical analysis
Kyung-Hwan Kwon1,2, Kyu-Bong Sim2, Jae-Won Cha2, Eun-Ja Kim2, Jae-Min Lee2
1Department of Oral and Maxillofacial Surgery, School of Dentistry, Wonkwang University, 2Wonkwang Dental Research Institute, Iksan, Korea
Abstract (J Korean Assoc Oral Maxillofac Surg 2012;38:371-8)
Many longitudinal studies have reported the successful osseointegration of dental implants, with survival rates approaching 90-95%. However, implants regarded as a “success” may have also failed to undergo osseointegration. A variety of complications and failures have been observed, including implant fracture - a rare and delayed biomechanical complication with serious clinical outcomes. Given the increasing popularity of dental implants, an increase in the number of failures due to late fractures is expected. This study sought to determine the rate of implant fractures and factors associated with its development. This retrospective evaluation analyzed implants placed at Wonkwang Dental Hospital (from 1996 to the present). In our study we found that the frequency of dental implant fractures was very low (0.23%, 8 implant fractures out of 3,500 implants placed). All observed fractures were associated with hybrid-surface threaded implants (with diameter of 4.0 or 3.75 mm). Prosthetic or abutment screw loosening preceded implant fracture in a majority of these cases.
Key words: Peri implant fracture, Scanning electron microscopic [paper submitted 2012. 5. 24 / revised 2012. 7. 24 / accepted 2012. 7. 27]
While implants rarely fracture, thiscomplicationstill
meritsconsiderationforpatientsandcliniciansalike.Many
authorsreportverylowratesoffracture.Giventheincreasing
popularityofdentalimplants,thenumberoffailuresdueto
lateimplantfractureisalsoexpectedtoincrease.In1992,
TolmanandLaney3reported3implantfracturesinastudyof
1,778implantsplaced(0.17%).Balshi4reportedthat8outof
4,045implantsfractured(0.2%).Allfractureswereassociated
withmarginalboneloss.Majorityoftheselattercases(6of
8)involvedsupportingposteriorprostheses,withallpatients
experiencinglooseningorfractureofprostheticgoldscrews
orabutment screwsprior to implant fracture.Similarly,
Rangertetal.5 found39patientswith fractured implants
among10,000implantsplaced.Theyreportedfracturerates
of0-6%inthemaxillabutonly0-3%inthemandible.An
earlystudybyAdelletal.2recordedanimplantfracturerate
of3.5%,withmostofthesefracturesoccurringafter5years
ofclinicalfunction;note,however,thatthisrelativelyhigh
ratemayhavebeenduetotheinclusionofimplantsinserted
whilethetechniquewasstillbeingdevelopedandthelonger
maximumfollow-upperiodof15years2.AccordingtoBalshi4,
implantfracturesmayresultfrom(1)defectsinimplantdesign
I. Introduction
Dental implantshave revolutionized the treatmentof
patientssufferingfromtoothloss.Theintroductionofosseo-
integrateddentalimplantsgavethesepatientsafunctional,
estheticsolutiontopartialor totaledentulism.Osseointe-
grated threaded titaniumscrew-type implants rarely lose
integrationafter the firstyearofclinical function1, and
dental implantscanbesuccessfulona long-termbasisat
veryhighrates2.Nevertheless,variouscomplicationshave
beenobservedover theyears.Asoneof themajor types
oflatefailure,implantfailurecanoccurformanyreasons.
Inparticular, the2-stageexternalhexscrew-typeimplant
systemshavebeenreportedtoexhibitunacceptablyhighrates
ofmechanicalfailure.
Kyung-Hwan KwonDepartment of Oral and Maxillofacial Surgery, School of Dentistry, Wonkwang University, 895, Muwang-ro, Iksan 570-711, Korea TEL: +82-63-859-2922 FAX: +82-63-857-4002E-mail: [email protected]
This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
CC
CASE REPORThttp://dx.doi.org/10.5125/jkaoms.2012.38.6.371
pISSN 2234-7550·eISSN 2234-5930
*ThispaperwassupportedbyWonkwangUniversityin2012.
J Korean Assoc Oral Maxillofac Surg 2012;38:371-8
372
clinicalphotographswereevaluatedtoconfirmthelocation
ofthefracturedimplant,presenceorabsenceofcantilevers
in theprosthesis,occlusalmaterial,andnumberof teeth
replacedbytheprosthesis.Finally,thetherapeuticsolutions
offeredineachcasewereanalyzed.Twofracturedimplants
wereanalyzedbySEM.Allof thefractures involved4.0
mmimplants,andnofractureofany5.0mmimplantwas
reported.
Inaseriesof3,500implantsdocumentedduringthestudy
period,werecorded8 implant fracturesora0.25%rate.
These8fracturedimplantsconsistof53iOsseotiteimplants
(Biomet3i,PalmBeachGardens,FL,USA),1LCRestore
implant(LifecoreBiomedicalInc.,Chaska,MN,USA),and2
OsstemUSimplants(OsstemInc.,Seoul,Korea).Thelengths
of the fractured implants ranged from11.5 to13.0mm,
whereasthediameterwas4.0mminallcases(n=8).There
weremoremalepatientsthanfemales(5:1),andthemean
patientagewas56.7years(48-70).Mostofthefractures(n=6)
involvedimplant-supportedfixedprostheses,whereasonly
2fracturedimplantsweresupportingoverdentures.Agreat
majorityofthefracturedimplants(n=6,75%)werelocated
inthemolarorpremolarregions(5inthemolarregions,1
inapremolarregion),whereastheother2wereinthecanine
regions.Moreoftheimplantfractureswerelocatedinthe
upper jaw(n=6)thaninthelowerjaw(n=2).Mostof the
implantshadfracturedwithin3-4yearsofloading.Mostof
thepatientswithimplantfractures(83%)exhibitedbruxism
andclenching.Withregardtothemanagementapproaches,
6fracturedimplantswereremovedentirelywithhelpfrom
explantationtrephines.Nofurtherimplantplacementproved
necessary in1case(implant-supporteddenture),whereas
additional implantswereplacedduring thesamesurgical
interventioninthe7othercases.Nocasewasmanagedby
andmanufacturing, (2)non-passive fitof theprosthetic
framework,and(3)physiologicalorbiomechanicaloverload.
Fractureof the implantfixturepresentsseveralclinical
challenges6.First, thefracturedfragmentmustberemoved
atraumatically tominimizeboneloss.Second,animplant
siteofadequatelengthanddiametermustbere-established.
Finally,osseointegrationofthereplacementfixturemustbe
achievedbeforeinitiatingrestorativereplacement.
Thisscanningelectronmicroscopic(SEM)studyaimed
atexaminingfracturedimplantsforthepresenceoffatigue
striations,dimpledsurfaces,porosities,ordefectsof the
titaniumandmanufacturingdefects7.AccordingtoMorganet
al.8,thepathognomonicmarkoffracturesresultsfromfatigue
failure.
Targeting6patients, this studysought toevaluate the
clinicalandSEMfindingsoffracturedimplantstoanalyze
thecausesofimplantfracture.Wewouldalsoliketodiscuss
thepossiblemechanismsbywhichtheputativeunderlying
factorscontributetoimplantfractureaswellashowthese
casesaremanagedwithreferencetothereviewedarticleson
thesubject.
Eight implant fracturesoccurringbetween1996and
2010weredocumented.(Table1)Atotalof8implantwere
analyzedoutofanestimated3,500 implantsplaced.The
computerrecordsof6patientstreatedatWonkwangDental
Hospitalwereexaminedtogatherthefollowingdata:patient’s
ageandsexandthelocationof thefracturedimplant; the
dateof implantfracture; thetype, length,anddiameterof
theimplantanditspositioninthedentalarch; thetypeof
prostheticrehabilitationinvolved,thenumbersofabutments
andpontics; thepresenceorabsenceofdistalextensions
orcantilevers; the loading timebefore the fracture,and;
thepresenceofparafunctionalactivity.Radiographsand
Table 1. Case presentations of patients with fractured implant fixtures
No. Sex Age Implant type Placement site Date of placement Date of fracture
Patient 1
Patient 2
Patient 3
Patient 4
Patient 5
Patient 6
F
M
M
M
M
M
59
50
51
70
69
52
3i Osseotite hybrid4×11.5 mm3i Osseotite hybrid4×11.5 mm3i Osseotite hybrid4×11.5 mmRestore implant system4×11.5 mmOsstem hybrid4×13 mm3i Osseotite hybrid4×11.5 mm
#16 single
#16 single edentulous
#17 single
#14 single
#13, #22
#46, #47 bridge
December 2004
April 2006
June 2001
September 1999
March 2008
April 2000
September 2008
December 2007
April 2008
May 2008
May 2008
November 2005
Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of fractured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Clinical and scanning electron microscopic analysis of fractured dental implants: a retrospective clinical analysis
373
II. Cases Report
1. Case 1
InDecember2004,apartiallyedentulous59-year-old
femalepatientunderwentplacementof single titanium
implants(Osseotite;Biomet3i)inthesiteofthemaxillary
posteriormolar(#26).Theimplantwasplacedtoocclude
with#36and#37simultaneously.One4.0×11.5mmtitanium
implantwasplacedinthemolarregionoftheleftmaxilla.
Theemptyspacewasslightlynarrowmesiodistally,andno
distalcantileverwaspresent.(Fig.4)Thepatientshowedno
evidenceofbruxism,andtheconditionofheralveolarridge
theremovalofthecoronalportionofthefracturedimplant
withposteriorrectificationoftheapicalfragment.
Scanningelectronmicroscopyrevealedstriationsonthe
fracturedsurfacesoftheclinicalspecimenssimilartothose
seenonthelaboratory-fatiguedspecimensandincontrastto
thedimpledsurfacesoftheoverloadedspecimens.(Figs.1-3)
Therewerenoporositieswithinthetitanium,andthefracture
linesweresituatedindifferentplanes.Thefracturedsurfaces
exhibitedadimpledaspectcharacteristicoftensilefracture.
Fig. 1. Scanning electron microscopy views of the fracture. High power view of the fractured surface of titanium implant; magnification x400. Fracture cross-section has a different plan.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 2. It was possible to see that the titanium surface presented many porosities.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 3. At low-power scanning electron microscopic magnification (original magnification x30), it is possible to observe that no porosity is present inside the titanium and that the fractures appeared in different planes. The fractured surface exhibits a dimpled aspect, characteristic of a tensile fracture.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 4. Initial panoramic radiograph. This view shows missing state (#26, #36, #37) where implant is placed.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
J Korean Assoc Oral Maxillofac Surg 2012;38:371-8
374
periapicalradiographshowedthepresenceoffracture.The
fracturedimplantwasretrievedwithatrephine.
2. Case 2
A50-year-oldmalereportedthatasinglemaxillaryposte-
riormolarhadbeenextractedduetoanendodonticproblem
andaperiodontaldisease.(Fig.8)Thepatienthadnorelevant
medicalhistory;hewasanon-smokerwithnohistoryof
parafunction.Note,however,thathehadahigh-stressoccu-
pation.
Afterthediscussionwiththepatientandafullevaluation
including radiographic assessment and studymodels,
wasfavorableforimplantplacement.Definitiveprosthesis
wasplacedinSeptember2005.
Fouryearsafter (September2008) implantplacement,
thepatientvisitedtheofficecomplainingofdiscomfortof
the leftmaxillarymolarofherupper jawwith loosening
ofthecrown.Theclinicalexaminationrevealedexcessive
horizontalmovementof thecrownand swellingof the
adjacentmucosa.Verylittleforcewassufficienttoremove
thecrowntogetherwiththeupperthirdoftheimplant.(Fig.5)
Radiographstakenat the4-yearfollow-upvisitshoweda
fracturelineinthe3rdthreadoftheimplant.(Figs.6,7)Deep
pericoronal“cup” resorptionaround the implant fixture
fracturewhichwouldindicateimplantoverloadingwasnot
present.InSeptember2008,theimplantwasmobile,anda
Fig. 5. Removal finding of healing abutment and coronal fragment of implant.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 6. Final prosthodontic view finding (Patient 1).Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 7. At 3-year follow-up radiograph after final prosthodontic restoration, implant fixture fracture was evident.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 8. The panoramic radiograph of a 50 year old male with existing restoration were 2 ITI implant system on left maxillary posterior molar area. These had been extracted 1 month ago (2006 Jan 20) previously possibly due to endodontic or structural problem.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Clinical and scanning electron microscopic analysis of fractured dental implants: a retrospective clinical analysis
375
the titanium.(Figs.2,10).Weconsidercomplete implant
extractiontobethetreatmentofchoiceinsuchcases.
III. Discussion
Thelong-termmaintenanceofosseointegrationseemstobe
areasonableexpectation,butthisneitherensurestheongoing
survivalofthedentalrestorationsupportedbytheimplantnor
guaranteestrouble-freeprostheticservice.Osseointegrated
threadtitaniumscrew-typeimplantsrarelyloseintegration
afterthefirstyearofclinicalfunction.Note,however,that
implantfailurecanoccurforotherreasons,anditisoneof
themajorcausesofdelayedfailure3-5,8.Manycliniciansand
patientshave regardedsuchosseointegrated implantsas
successfulforsometimebeforedelayedfailureoccurs.There
are2maincausesofadelayedimplantfracture:(1)lossof
supportingtissuecausedbyinfectionorperi-implantitis,and;
(2)mechanicalproblemsincludingfractures3,9.
Since osseointegrated implants have noperiodontal
ligament, occlusal traumatism cannot occur.Adverse
forcesgeneratedbyocclusalactivitymayinsteadresult in
themechanicalcomplicationsofimplantcomponents, i.e.,
screwloosening,screwfracture,orfixturefracture5,10.Asan
infrequentcomplication,implantfractureaffectsonly0.16-
3.8%of implants3,4,6,7,9.Eckertetal.11 reportedanimplant
fracturerateof0.6%inboththemaxillaandthemandible.
AccordingtoJemtandLeckholm12,1implantfracturedoutof
the259implantsloaded.Amulticenterretrospectiveanalysis
of174ITIimplantsusedforsingle-toothreplacements(86.6%
restoringthesingleemptyspacewithasingleimplantwas
decided.Subsequently, inApril 2006, an11.5mmLC
Restore(LifecoreBiomedicalInc.)regular-platformimplant
fixture(diameter,4.0mm)wasplacedunderlocalanesthesia
usinga traditional2-stageprocedure.TheUniversityof
California,LosAngeles(UCLA)abutmentwasplacedin
December2006,and thegold restorationwas inserteda
month later.The restorationof themaxillary firstmolar
conformed to theexistingcanine-guidedocclusionwith
posteriordisocclusioninprotrusion.Itwasretainedwithgold
slottedscrewsinsertedunder10Ncmtorque.
Regularstandardfollow-upcheckswereuneventfuluntil
September2007(Fig.9),atwhich timeprostheticscrew
looseningwasnotedbutnoproblemwasdetectedwith
theabutments.Unfortunately,3months later, thepatient
complainedof crown loosening.Hedescribed “screw
looseningsimilartothemobilityoftheimplantcrown”.Upon
removaloftheprosthesispartoftheabutment,thescrewcame
offalongwiththegoldcrownand2ndpremolar.Apanoramic
radiographshowedfracturedmaxillaryfirstmolarimplantand
extractionofthe2ndpremolar.Thisimplantwasfractured
intheareaofthe3rdthread(borderofthemachinedsurface
androughsurface-hybridimplantsurface).Theprosthesis
wasremovedagainwhenthedistalfixturewasobservedat
thesamevisittohavefracturedatthealveolarbonemargin,
leavingtheabutmentscrewintactwithintheabutmentSEM
showedmetal-tearingstriationsonthecross-sectionalsurface
of the fractured fixture.Porositieswerepresentwithin
Fig. 9. Upper second premolar was demonstrated mobility and fractured at cervical area. Overload-induced bone resorption seemed to precede implant fracture (Patient 5). There was no fracture sign in implant fixture.Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
Fig. 10. At low-power scanning electron microscopic magnifi-cation (x30), tearing striation are present (Case No. 5).Kyung-Hwan Kwon et al: Clinical and scanning electron microscopic analysis of frac-tured dental implants: a retrospective clinical analysis. J Korean Assoc Oral Maxillofac Surg 2012
J Korean Assoc Oral Maxillofac Surg 2012;38:371-8
376
machined surface in thecoronal region ismore readily
debridedofbiofilm,ahybriddesignwasassumedtoensure
bettermucosalhealthand lower the riskofperi-implant
diseasesofosseointegratedimplants17.Arecentstudyfound
apositivecorrelationbetweentheamountofbonelossafter
6monthsandthelengthofthemachinedsurfaceforvarious
implantsystems;thusrelatingbonelosstothelevelofthe“secondthread.”Jungetal.18reportedsignificantmarginal
bonelossmorethan3mmlonginmachinedcoronalregions.
Suchbonelossmaybeattributabletothelackofeffective
mechanicalloadingbetweenthemachinedcoronalregionof
theimplantandthesurroundingbone.AccordingtoPiaoet
al.17,themachinedsurfacesofhybrid-designimplantswere
associatedwithmorebonelossthanthoseofrough-surface
implants.Apparentlythemostimportantindicatorofthestart
ofanimplantfracture,suchmarginalbonereabsorptionmay
oftenextendbeyondtheactualfractureline.Webelievethat
thesurfacesofhybrid-designimplantshavedifferentbone-
implant-contactratiosoraffinitiesforosseointegrationand
consequentlydifferentbendingandtensilestrengthsintheir
upperandlowerthirds;thusmakingthemlessabletoresist
occlusalforcesandparafunctionalactivity.Thisseemstobe
themechanismofimplantfractureinthesecases.
Thespecificbone losspatternseen in implant fracture
caseshasbeendescribedasaprimarycauseandamechanism
offracture5-7.Coronalboneresorptionincreasesthebending
stressoftheimplantbecauseofthelossofsupportingbone8.
Inaddition,thistypeofboneresorptionusuallyextendsto
thelevelcorrespondingtotheendof theabutmentscrew,
reducingtheresistancetobendingofthisregion.Bothclinical
andexperimentalanimalstudies4,5,7haveshownthatimplant
overloadinducesresorptionofthemarginalbone.Whensuch
reabsorptionextendsapicallybeyondthe3rdimplantthread,
itreachesastructurallyweakzonecoincidingwiththeend
oftheprostheticscrewandtheborderofthehybridsurface.
Thiscontributes tofatigueatapointof lowresistance to
torque.Rangertetal.5haveshownusingacombinationofin
vitrostudiesandbendingtestinginthelaboratorythatmetal
fatiguecancausefractures.Thewarningsignsofsuchfatigue
includeloosening,torsion,orfractureofthepostscrewsand
ceramicfracturesoftheprosthesis.Thesesignsindicatemetal
fatiguethatwillultimatelyleadtofractureifnotcorrectedon
time.
Galvanic implantcorrosioncanalsocontribute tofrac-
tures17,18.Corrosionof themetalcrownmaybecausedor
acceleratedbydifferences in theelectricpotentialsof the
implant (madeofpure titanium)and thecrown(madeof
placedinposteriorsites)reportednofixturefractures13.The
frequencyofimplantfractureinourserieswas0.24%.
Therearemanycausesof implant fractures, including
butnot limited to location, implantdiameter,mechanical
problems,andbruxism3-8.Themainriskfactorsforimplant
fractureseemtobe(1)bendingoverload5,(2)manufacturing
imperfections4, (3) restorationdesign14, (4)accuracyof
restoration fit2, (5)number,dimensions,andpositioning
of implants5,14, (6)marginalbone loss2, (7)occlusaland
parafunctionalhabits2,5,7,and(8)chemicalfactors(galvanic
implantcorrosion)15,16.Regardingtheeffectofthelocation
oftheimplant,Rangertetal.5reportedthat90%offractured
implants are located in the regions of themolars and
premolars.Thisagreeswithourfinding, i.e.,majorityof
fracturesareintheregionsofmolarsandpremolars,although
theexactproportionisslightlygreaterthanthatofourcases.
Wereportedthatmoreoftheimplantfractureswereinthe
upperthaninthelowerjaw.Anotherobserver,Balshi4,found
thatimplantfracturesoccurringintheregionsofpremolars
andmolarswereevenlydistributedbetweenthemaxillaand
mandible.Ourseriesshowedasignificantdifferencebetween
thenumbersoffracturesineachjaw.
Another important factor is implantdiameter.All8of
ourfracturedimplantshaddiameterof4mm.Eckertetal.11
andBalshi4foundthatallfracturedimplantshaddiameter
of3.75mm.Implantdiametersof4.0mmand3.75mmare
similarintheclinic.Implantswithsmalldiameterstendto
befracturedmoreeasily than thosewith largediameters,
especiallywhenplacedinaposteriorlocation.Accordingto
SiddiquiandCaudill15,animplantwithdiameterof5.0mmis
3timesstrongerthanonewithdiameterof3.75mm,whereas
a6.0mmimplantis6timesstrongerthana3.75mmimplant.
Anotheradvantageoflargerimplantsisthattheyaremore
biomechanicallyappropriatefor replacing largeposterior
teeth.
Manyretrospectiveclinicalstudieshavereportedhighrates
ofscrewlooseningand/orfractureassociatedwith2-stage
externalheximplantsystems.Wealsofoundanassociation
ofimplantfracturewith2-stageexternalheximplantsystems
havinghybrid-typesurfaceimplants.Theimplantfractures
inourstudycasesallinvolvedhybrid-typeimplantfixtures.
Thecrestmodulesofmachinedhybrid-design implants
aremostoftendesigned less for loadbearing than for
minimizingplaqueaccumulationandactingasabridgeto
theload-bearingstructureoftheimplantbodyinsubmerged
implants12.Still,themachinedsurfaceofahybriddesigndoes
noteffectivelydistributetheocclusalforce.Sinceasmooth,
Clinical and scanning electron microscopic analysis of fractured dental implants: a retrospective clinical analysis
377
placementofadditionalimplants.
7)Ensureperfectfit:resolderandassesspassivefit.
Periodicandcarefulperiodontalandprosthodonticevalu-
ationandanalysisshouldbeperformedbeforeandafter
implant restoration.Perfect passive fit and adaptation
accordingtothebiomechanicalprinciplesmustalsobecon-
sideredwhenplanningtheplacementofimplantsinpartially
andcompletelyedentulousridges.It is important toknow
andapplysuchmeasuressince theywill reduce the risk
of implantfractures.Ifnecessary,prosthodonticmeasures
shouldbetakentooptimizeocclusiontoachieveadequate
occlusalcontactandavoidundesiredforces.
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nickel-chromium-molybdenumalloy).Contrarytocommon
belief,titaniumisahighlyreactivemetal.Cathodictomost
metals,itmayaccelerategalvanicattackonlessnoblemetals
whentheyarecoupledtogether.Theparametersthataffectthe
magnitudeofthisgalvaniccorrosionincludethedifferencein
electrolyticpotentialbetweenthemetalsandthecontactarea
oftheinterface.Inparticular,theelectrolyticpotentialofa
givenmetalisconstant.Thedifferencecanbeminimizedby
fabricatingrestorationsfromametalalloywithanelectrolytic
potentialsimilarorclosetothatoftitanium.Alternatively,
thecontactareabetweentheimplantandtherestorationmay
beisolatedwithcement(suchaszincphosphatecement)19.
Reducing theactual surfaceareaofcontactbetween the
2metals isnotrecommended,asdoingsowillreducethe
retentionofrestoration15.Therefore, thepossibilityofgal-
vaniccorrosionmustalwaysbeconsideredwhenchoosing
ametallicalloyforthecrown.Note,however,thatthereis
currentlylittleadditionalevidencetosupporttheroleforthis
phenomenonasamajorcontributortoimplantfractures.We
generallymanagefracturedimplantsbycompleteextraction
usingatrephineburrtopulloutthefracturedimplantfixture.
Whenthepercentageofcontactwithboneishigh,andthe
fractureislocatednottoofarfromtheapicalarea,however,
restorationof the connectionbetween thepost and the
implantmaybeavalidoption.Therefore,confirmingthe
conditionof thefractureradiologically isessentialbefore
determiningwhethertoextractthefragment.
This investigationdemonstrated that the fracturesof
thefixturecomponentsof thesedental implantsoccurred
due to fatigueunderphysiological loads,withmarginal
alveolarbonelossaroundthefixture.Itisimportanttoavoid
mechanicalproblemsandexcessivebonereabsorption to
prevent implant fracture.Wewould like to suggest that
cliniciansconsideradoptingthefollowingmeasures:
1)Avoidplacinghybrid-typeimplantfixtures.
2)Carefullycontrolocclusalforces:eliminateallposterior
contactsinmandibulareccentricmovements.
3)Performstaggeredplacementof implants: avoida
straight-lineconfiguration.
4)Avoidorminimizeposteriorcantileversandbuccolin-
gualoffsetsparticularlyinpartiallyedentulouspatients.
5)Whenchroniclooseningofgoldorabutmentscrewsor
fractureofcomponentsotherthantheimplantsoccurs,
criticallyreassesstheprosthesis,re-tightentheabutment,
use1goldscrew,andcheckthefit.
6)Pronouncedbruxersorclencherswhohaveexperienced
multiple implantfracturesshouldbemanagedbythe
J Korean Assoc Oral Maxillofac Surg 2012;38:371-8
378
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ofmarginalbonearounddental implants.IntJOralMaxillofacImplants1996;11:811-8.
19. YokoyamaK,IchikawaT,MurakamiH,MiyamotoY,AsaokaK.Fracturemechanismsofretrievedtitaniumscrewthreadindentalimplant.Biomaterials2002;23:2459-65.
72:623-34.16. TurpinYL,TardivelRD,TallecA,LeMennAC.Corrosion
susceptibilityoftitaniumcoveredbydentalcements.DentMater2000;16:57-61.
17. PiaoCM,Lee JE,Koak JY,KimSK,Rhyu IC,HanCH,etal.Marginalbone lossaroundthreedifferent implantsystems:radiographicevaluationafter1year.JOralRehabil2009;36:748-
