Longevity of teeth and implants – a systematic reviewC. TOMASI, J. L. WENNSTRO¨ M & T. BERGLUNDH Department of Periodontol...
10 years of follow-up, or if data corresponding to10 years of observation could not be achieved. Studiesin which the rate ...
The mean number of teeth per subject at baseline wasreported in 10 of the studies and ranged from 21 to 26.The incidence o...
Comparisons between teeth and implantsDue to the heterogeneity among the studies a meta-analysis using statistical compari...
alized for mental disease (11). Thus, the three studiesreferred to represent subject samples that may not becomparable to ...
in studies on teeth the subjects may exhibit varyingsystemic and local compromising conditions, whilestudies on implants i...
22. Bergstro¨m J, Eliasson S, Dock J. A 10-year prospective studyof tobacco smoking and periodontal health. J Periodontol....
54. Yanase RT, Bodine RL, Tom JF, White SN. The mandibularsubperiosteal implant denture: a prospective survival study.J Pr...
Longevity of teeth and implants a systematic review
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Longevity of teeth and implants a systematic review

  1. 1. Longevity of teeth and implants – a systematic reviewC. TOMASI, J. L. WENNSTRO¨ M & T. BERGLUNDH Department of Periodontology, Institute of Odontology,The Sahlgrenska Academy at Go¨teborg University, Go¨teborg, SwedenSUMMARY The objective of this systematic reviewwas to describe the incidence of tooth and implantloss reported in long-term studies. Prospective lon-gitudinal studies reporting on teeth or implantssurvival with a follow-up period of at least 10 yearswere considered. Papers were excluded if the dropout rate exceeded 30% or if <70% of the initialsubject sample was examined at 10 years of follow-up. Seventy publications on teeth were identified aspotentially relevant for the focussed question. Theanalysis of the abstracts yielded 37 studies eligiblefor full-text analysis. The inclusion criteria were metin 11 of the publications that included in all 3015subjects. The initial search on implant studies gen-erated 52 publications that possibly could be in-cluded. Following the evaluation of the abstractsand full-text analysis nine publications were foundto fulfil the inclusion criteria. The nine studiesincluded 476 subjects. The incidence of tooth lossamong subjects with a follow-up period of 10–30 years varied from 1.3% to 5% in the majority ofstudies, while in two epidemiological studies onrural Chinese populations the incidences of toothloss were 14% and 20%. The percentage of implantsreported as lost during the follow-up period variedbetween 1% and 18%. In clinically well-maintainedpatients, the loss rate at teeth was lower than that atimplant. Bone level changes appeared to be small atteeth as well as at implants in well-maintainedpatients. Comparisons of the longevity at teeth anddental implants are difficult due to heterogeneityamong the studies.KEYWORDS: implants, longevity, teeth, prospectivestudyAccepted for publication 4 November 2007IntroductionDecision-making in treatment planning should bebased on scientific evidence. In the clinical situationwhen deciding on either treating a tooth disorder orextracting the tooth in favour of implant placement,data that provide guidelines for the choice of strategyare sparse. Although implant therapy is regarded as asafe and reliable method in the treatment of completeand partial edentulism, complications of technical andbiological nature occur (1). The ultimate complicationin implant therapy is the loss of implants, as for teeththe extraction is the definitive failure. To determine thelongevity of teeth and implants, information on theoccurrence of these final events on a long-term basismust be provided.The objective of this systematic review was todescribe the incidence of tooth and implant lossreported in prospective longitudinal studies with afollow-up of at least 10 years. Alterations in marginalbone support at teeth and implants were alsoaddressed.Material and methodsType of studiesProspective longitudinal studies with a follow-up periodof at least 10 years were considered. Thus, cohortstudies, controlled clinical trials and randomized clinicaltrials that provided data on tooth and ⁄or implant lossover the indicated time period were analysed. Studiesreporting life-tables were analysed with respect to theproportion of subjects or implants ⁄ teeth that werefollowed ‡10 years. Publications were excluded if<70% of the initial subject sample was examined atª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd doi: 10.1111/j.1365-2842.2007.01831.xJournal of Oral Rehabilitation 2008 35 (Suppl. 1); 23–32
  2. 2. 10 years of follow-up, or if data corresponding to10 years of observation could not be achieved. Studiesin which the rate of subject dropout at 10 yearsexceeded 30% were also excluded.SubjectsSubjects who were part of epidemiological studies orenrolled in maintenance programmes of treatmentstudies on teeth were included in the review. Implant-related studies comprised edentulous and partiallyedentulous subjects who were treated with endosseousdental implants supporting fixed or removable recon-structions. Studies that reported data on implant-toothconnected prostheses were not included in the review.VariablesNumber and age of subjects included at baseline andthe number of subjects lost to follow-up were recorded.The number of teeth present at baseline and thenumber of installed implants were retrieved, as wellas the number of (i) teeth and implants lost during thestudy and (ii) subjects who had experienced tooth orimplant loss. Data on marginal bone loss around teethand implants were also recorded.Weighted mean values were calculated for thenumber of teeth and implants at baseline and thenumber ⁄ percentage of teeth and implants lost duringfollow-up. For studies in which information on implantloss was not clearly defined, the inverse of the cumu-lative survival rate was calculated.Search strategyA search in PubMed was performed in May 2007 toretrieve articles published in the English language. Thesearch terms used and the resulting matches were asfollows:1 dental implants AND longitudinal studies (1664)2 dental implants AND longitudinal (286)3 dental implants AND clinical trial (810)4 dental implants AND cohort studies (1677)5 dental implants AND prospective studies (534)6 dental implants AND survival (815)7 dental implant AND longevity (54)8 dental implants AND randomized clinical trial (314)9 dental implants AND prospective (1713)10 oral epidemiology AND tooth loss (434)11 oral epidemiology AND longitudinal AND teeth(149)12 oral epidemiology AND periodontal disease (2344)13 oral epidemiology AND caries (2843)14 tooth loss AND prospective (361)15 tooth loss AND cohort (138)16 tooth loss AND longitudinal (200)17 [‘Dental Health Surveys’ (Mesh)] AND tooth loss(516)18 [‘Dental Health Surveys’ (Mesh)] AND bone loss(633)19 [‘Dental Health Surveys’ (Mesh)] AND attachmentloss (958)20 [‘Dental Health Surveys’ (Mesh)] AND implant loss(197)Manual search included bibliographies of previousreviews and of selected publications. Furthermore, a‘search for related articles’ in PubMed was applied forall studies that were evaluated in full text.ResultsTeethFrom the screening of titles obtained from the databasesearch, 70 publications were identified as potentiallyrelevant for the focussed question. The evaluation ofabstracts yielded 37 studies eligible for full-text analysis.11 publications met the inclusion criteria. The 26excluded studies and the reasons for exclusion arelisted in Table 1.The 11 included studies are presented in Table 2. Sixstudies were epidemiological surveys of general popu-lations (2–7), while three publications described sub-jects who were classified as regular dental careattendants (8–10). One study reported data frominstitutionalized patients (11) and one study evaluatedsubjects with untreated periodontitis (12). Three pub-lications were grouped together as they reported onfindings from the same subject sample included in anepidemiological survey (5–7). The follow-up period inthe 11 studies ranged between 10 and 30 years. Inseveral studies the data were reported according to agecategories and for these studies weighted mean valueswere calculated. The age of the subjects at baselinevaried between 20 and 65 years. The total number ofsubjects recorded at baseline in the 11 studies was 3015.The number of subjects examined at the end of thestudies was 2304.C . T O M A S I et al.24ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd
  3. 3. The mean number of teeth per subject at baseline wasreported in 10 of the studies and ranged from 21 to 26.The incidence of tooth loss among subjects with afollow-up period of 10–30 years varied from 1.3% to5% in the majority of studies. Results presented inepidemiological studies on rural Chinese populationsamples, however, revealed an incidence of tooth lossof 14–20% (2, 3). The proportion of individuals thatexperienced tooth loss showed a range of 25–75% withthe highest figure in the studies on the Chinesepopulations and in patients with untreated periodonti-tis. Rosling et al. (2001) reported that the percentage ofsubjects that experienced tooth loss was 64% forpatients with high susceptibility to periodontitis, whileamong subjects with a ‘normal’ susceptibility thecorresponding figure was 26%. Main causes for toothextraction, when reported in the studies, were cariesand tooth fracture.Data regarding marginal bone loss could be retrievedfrom four studies, all from Sweden. The calculated10-year rate of bone loss varied between 0.2 and0.8 mm. For subjects who were evaluated in epidemi-ological studies the corresponding figure was 0.6 mm.ImplantsThe initial search generated 52 publications that possi-bly could be included. Following the analysis of theabstracts 39 of these studies were rejected. Hence, full-text analysis was made in 23 studies, out of which ninepublications were found to fulfil the inclusion criteria.The 14 excluded studies and the reasons for exclusionare listed in Table 3.The nine studies on implants included in this revieware reported in Table 4. The longest follow-up periodwas 20 years. The age of the subjects at the time ofimplant placement ranged between 18 and 80 years.The overall number of subjects who received implantswas 476, while the number of subjects attending a finalexamination was 355.The majority of the studies reported data onimplants of the Bra˚nemark System. Four studiesreported data on implants placed in edentulous jawsto support an overdenture (13–16) while other threestudies regarded implants placed in edentulous jaws tosupport fixed prosthetic reconstructions (17–19). Thetotal number of implants placed in the nine studieswas 1460. The percentage of implants reported as lostduring the follow-up period varied between 1% and18%. Only four studies presented information on thenumber of subjects who had experienced implant loss.The calculated proportion of such subjects in thisgroup of studies ranged between 3% and 29%. Causesfor implant loss were rarely reported. On the otherhand, the timing of implant loss was frequentlydescribed. Between 9% and 100% of the implant lossin the various studies were reported as ‘early loss’, i.e.implants that were removed before the connection ofthe prosthetic reconstruction.Data on the amount of marginal bone loss over a10-year period could be retrieved from eight studies.In these studies the amount of bone loss was given inmm per year or as a difference between the baselineand the final follow-up examination. Most studies alsodescribed the amount of bone loss that occurredduring the first year in function in addition to thesubsequent bone level alterations. The calculated 10-year bone loss varied between 0.7 and 1.3 mm in theavailable studies.Table 1. Excluded publications on teeth and reasons forexclusionReference Reason for exclusionAhlqwist et al. (1999) (20) % Subject dropout >30%Baljoon et al. (2005) (21) SameBergstro¨m et al. (2000)(22) SameBergstro¨m (2004) (23) SameBurt et al. (1990) (24) SameEttinger & Qian (2004) (25) SameFure (2003) (26) SameHalling & Bjo¨rn (1986) (27) SameHamalainen et al. (2004) (28) SameHiidenkari et al. (1997) (29) SameHujoel et al. (1999) (30) SameIsmail et al. (1990) (31) SameJansson et al. (2002) (32) SameKrall et al. (1999) (33) SameKrall et al. (2006) (34) SameNeely et al. (2005) (35) SamePetersson et al. (2006) (36) SameRohner et al. (1983) (37) SameTezal et al. (2005) (38) SameWarren et al. (2002) (39) SameFardal et al. (2004) (40) SameHeitz-Mayfield et al. (2003) (41) Retrospective designScha¨tzle et al. (2003a), Scha¨tzleet al. (2004), Scha¨tzle et al.(2003b) (42–44)Retrospective designEickholz et al. (2006) (45) Regenerative therapyL O N G E V I T Y O F T E E T H A N D I M P L A N T S 25ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd
  4. 4. Table2.ProspectivestudiesonteethStudyFollow-upSubjectsampleAgerangeNo.subjectsDropout(deceased)Meanno.teethbaselineToothloss(%)SubjectsexhibitingtoothlossBonelossin10yearsCausesfortoothlossAxelssonetal.(2004)(8)30yearsGeneralpopulationWellmaintained20–65375118(49)24.83.6%NRNR62%Rootfracture23%EndodonticBaelumetal.(1997)(2)10yearsGeneralEpidemiologicChina20–60+58714725.520%75%NREndodonticOR3.9Buckley&Crowley(1984)(12)10yearsUn-treatedperiodontalpatients15–5882NR14%Perio6%Non-perio61%NRNRChenetal.(2001)(3)10yearsMalesonlyEpidemiologicChina20–5920023(5)25.714.1%NRNRPerio.breakdowncaries,endoGabreetal.(1999)(11)10yearsMentalretardedInstitution41.0mean13621(19)20.717.9%NRNRNRNorderydetal.(1999)(5)Hugoson&Laurell(2000)(7)Laurelletal.(2003)(6)17yearsGeneralEpidemiologic15–60574141(25)24.15%34%0.6mm58%Perio36%CariesPaulanderetal.(2004)(4)10yearsGeneralEpidemiologic50mean42912022.94.1%39%0.54mmCariesandattachmentlosspredictorsoftoothlossRoslingetal.(2001)(9)12yearsHighsusceptibilityNormalsusceptibility45.5mean41.8mean10922561(9)724.123.57.8%1.3%64%26%0.8mm0.3mmNRWennstro¨metal.(1993)(10)12yearsGeneralpopulationPublicdentalclinic18–6529873(8)23.73%25%0.2mmNROR,oddsratio.C . T O M A S I et al.26ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd
  5. 5. Comparisons between teeth and implantsDue to the heterogeneity among the studies a meta-analysis using statistical comparisons between teeth andimplants was not feasible. A graphic illustration of thedifferent studies on teeth and implants with regard tothe outcome of tooth ⁄ implant loss and the sample sizeis presented in Fig. 1. Weighted mean values for lossrates were calculated and plotted when data werereported in subgroups. Tooth studies included largersubject samples than studies on implants. The rate oftooth and implant loss varied between as well as withinthe two categories of studies.DiscussionIn the present systematic review the longevity of teethand dental implants was described. Comparisonsbetween long-term investigations on teeth and im-plants, however, are difficult due to the differences inthe subjects included and the overall lack of implantstudies employing an epidemiological approach instudy design. Thus, implant publications in the currentreview were in general longitudinal cohort studies ofwell-defined groups of subjects who all receivedimplant therapy. In other words, the evaluation in thiscategory of studies was confined to a distinct group ofsubjects who required a certain treatment of partial orcomplete edentulism. The character of tooth studies, onthe other hand, was in most cases entirely different.Although well-maintained groups of subjects wereincluded in some studies, many of the included studieson teeth in the present review comprised ‘untreated’subjects who did not receive appropriate regular main-tenance. In addition, the epidemiological approach thatwas employed in several studies provided a samplerepresenting a general population, while in otherstudies the participants exhibited varying susceptibilityto periodontitis. The differences in the character oftooth- and implant studies must, therefore, be consid-ered in the comparisons of longevity criteria.Many publications that were identified in the Pub-Med search fulfilled the criteria of 10 years of follow-upbut were excluded from the evaluation due to othergrounds. The most common reason for not includingsuch a study on teeth in the present review was the rateof subject dropouts that exceeded 30%. This feature is afrequent problem in epidemiological research usinglarge population samples. The reasons for excludingimplant studies of 10 years of follow-up were different.This finding may be explained by the variations in studycharacter and subject sample between tooth- andimplant studies as discussed above.One particular problem in the evaluation of studies tobe eligible for the present review was the questionwhether the longitudinal study applied a prospective orretrospective design. The decision taken in this reviewto describe the longevity of teeth and dental implantsprompted the selection of prospective studies. In severalidentified publications during the search, the studydesign was clearly stated and described, while in otherreports the description of the study methods raiseddoubts with regard to the use of a prospective orretrospective design. A retrospective design was thecommon reason for excluding studies on both teeth andimplants.The main outcome variable that was evaluated in thecurrent review was tooth- and implant loss. Theincidence of tooth loss varied considerably. Thus, inone study on an untreated old rural population inChina (2) the loss rate was 20%, while in an epidemi-ological study on a general population in China toothloss occurred in 14% (3). A third investigation thatreported a mean tooth loss rate that amounted to 18%was performed in a small cohort of patients institution-Table 3. Excluded publications on implants and reasons forexclusionAuthors ⁄ year Reason for exclusionJemt & Johansson (2006) (46) % subject drop out >30%Attard & Zarb (2003) (47) Retrospective designMerickse-Stern et al.(2001) (48)Retrospective designNaert et al. (2000) (49) <80% of subjects at 10 yearsfollow-upHultin et al. (2000) (50) Subgroup of (51)Bra¨gger et al. (2005) (52) Connection teeth-implantsGunne et al. (1999) (53) Connection teeth-implantsYanase et al. (1994) (54) Non-endosseous implantsNystro¨m et al. (2004) (55) Bone grafting before implantplacementRoos-Jansa˚ker et al.(2006) (56)Cross-sectional withretrospective analysisWiller et al. (2003) (57) Unclear design and descriptionof the study lackinginformationAttard & Zarb (2004a) (17) Retrospective designAttard & Zarb (2004b) (13) Retrospective designZarb & Zarb (2002) (58) Retrospective designL O N G E V I T Y O F T E E T H A N D I M P L A N T S 27ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd
  6. 6. Table4.ProspectivestudiesonimplantsStudyFollow-upSubjectsampleAgerangeNo.subjectsDropout(deceased)No.implantsplacedImplanttypeImplantlossTimingofimplantlossSubjectsexhibitingimplantloss(%)Bonelosson10yearsDeporteretal.(2002)(14)10yearsEdentulousOverdenture56mean529(6)156Endopore8%9%earlyloss15%0.71mmEkelundetal.(2003)(18)Carlssonetal.2000(59)Lindquistetal.1996(60)20yearsEdentulousFixed33–64473(2)at15years17(6)at20years273Bra˚nemark1%66%earlylossNR0.9mmKaroussisetal.(2004)(61)10yearsPeriodontalpatients19–7812738(9)179ITI7.3%NRNR0.74mm9yearsdataLekholmetal.(1999)(51)10yearsPartiallyedentulous18–7012738(5)461Bra˚nemark10%76%earlyloss29%0.7mmMeijeretal.(2004)(15)10yearsEdentulousOverdenture57mean293217(4)5861IMZBra˚nemark7.1%18%75%earlyloss55%earlyloss10%20%NRNaertetal.(2004)(16)10yearsEdentulousOverdenture36–853610(9)73Bra˚nemark2%100%earlyloss3%0.86mmRasmussonetal.(2005)(19)10yearsEdentulousFixed50–80368(3)199Astra3.9%100%earlylossNR1.3mm7yearsdataITI,Straumanndentalimplants.C . T O M A S I et al.28ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd
  7. 7. alized for mental disease (11). Thus, the three studiesreferred to represent subject samples that may not becomparable to those reported in the implant studies ofthe present review. Furthermore, in the studies involv-ing Scandinavian populations the 10-year rate of toothloss was below 5%.Moreover the incidence of implant loss varied. Whilemost implant studies presented loss rates <10% (62),few publications contained data on 17–18% lostimplants. It is evident that a major part of the numberof lost implants reported occurred between the implantinstallation and before the connection of the supra-structure. Three studies reported on implants support-ing overdenture type reconstructions (13–16), whichpooled together did not present higher loss rates thanother studies reported. The finding is in contrast withthe data presented in a previous systematic review onbiological and technical complications in implant ther-apy (1). In this review it was concluded that theincidence of implant loss in overdenture therapy wastwice as high as that when using fixed reconstructionson implants. In one study in the current review twodifferent implant systems were compared using arandomized controlled clinical trial design (15). Thesubjects that were included received an overdenturesupported by two implants of either IMZ or Bra˚nemarkimplants. A significantly larger probing depth for IMZimplants was reported at the 1-year and 10-yearexaminations. The incidence of implants loss at10 years, however, was twice as high in Bra˚nemarkimplants as in IMZ implants.Marginal bone loss was not considered as a suitablevariable for meta-analysis due to the heterogeneity ofdata that was reported. For teeth, such data werefrequently lacking and also in the case when data onbone loss were obtained from attachment level mea-surements, results were presented either in mm ⁄yearor in total mm for the follow-up period. In one studywith long follow-up and more strict maintenance, again in attachment levels at the end of observationperiod was reported. It is interesting to note that therewas no apparent relation between marginal bone lossand the rate of tooth loss rate. The problem ofheterogeneity of data was more pronounced in studieson implants than in studies on teeth. The use of meanbone loss at the subject level may hide the presence ofan implant or a tooth presenting pathological boneloss. Another important consideration in the compar-ison of the longevity of teeth and dental implants isthe fact that the number of years in service for teeth ismuch larger than that of implants despite the studydesign of similar follow-up periods. Thus, in a 40-year-old subject who is enrolled in a longitudinal study, theteeth have already history of about 30 years of service.The corresponding function period for an implant,however, will commence at the time of implantinstallation. A further comment to the data obtainedfrom the implant studies in the present review is thefact that the types of implants that were evaluated areno longer available. The requested follow-up docu-mentation for implants that are currently in useappears to be lacking. Finally, it must be realized thatTooth ( ) vs. Implant ( ) LossRosling 2001Paulander 2004Norderyd 1999Chen 2001Baelum 1997Rosling 2001Axelsson 2004Wennström 1993Buckley 1984Gabre 1999Ekelund 2003Naert 2004Rasmusson 2005Karoussis 2004Deporter 2002Lekholm 1999Meijer 2004Meijer 200405101520250 100 200 300 400 500No. of subjects followed%lossFig. 1. Rate of tooth and implantloss in relation to subject sample.L O N G E V I T Y O F T E E T H A N D I M P L A N T S 29ª 2008 The Authors. Journal compilation ª 2008 Blackwell Publishing Ltd
  8. 8. in studies on teeth the subjects may exhibit varyingsystemic and local compromising conditions, whilestudies on implants in most cases demonstrate idealconditions regarding subject selection and situation oforal tissues.Conclusions1 In clinically well-maintained patients, the survivalrates of teeth were higher than that of implants.2 In well-maintained patients, the bone levelchanges appeared to be small at teeth as well asat implants.3 Comparisons of the longevity of teeth and dentalimplants are difficult due to marked heterogeneityamong the studies. Thus, in most implant studies thesubjects were selected for a dedicated treatmentprocedure, while in studies on teeth most theconditions that existed for a random population weredescribed (epidemiological study).4 The number of subjects evaluated in studies on teethwas considerably larger than that in studies onimplants.Conflicts of interestThe authors declare no conflicts of interests.References1. 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