A Comparison of Teeth and Implants During Maintenance Therapy in Terms of the Number of Disease-free...

A comparison of teeth andimplants during maintenancetherapy in terms of the numberof disease-free years and costs -an in vivo internal control studyFardal Ø, Grytten J. A comparison of teeth and implants during maintenancetherapy in terms of the number of disease-free years and costs – an in vivo internalcontrol study. J Clin Periodontol 2013; 40: 645–651. doi: 10.1111/jcpe.12101.

AbstractBackground: Little is known about the cost minimization and cost effectivenessinvolved in maintaining teeth and implants for patients treated for periodontal disease.Materials & Methods: A retrospective study was carried out encompassing allpatients who had initial periodontal treatment followed by implant placementand maintenance therapy in a specialist practice in Norway. The neighbouringtooth and the contra-lateral tooth were used as controls. The number of disease-free years and the extra cost over and above maintenance treatment for bothteeth and implants were recorded.Results: The sample consisted of 43 patients with an average age of 67.4 years.The patients had 847 teeth at the initial examination and received 119 implants.Two implants were removed 13 and 22 years after insertion. The prevalence ofperi-implantitis was 53.5% at the patient level and 31.1% at the implant level.The prevalence of periodontitis was 53.4% at the patient level and 7.6% at thetooth level. The mean number of disease-free years was: implants: 8.66; neigh-bouring tooth: 9.08; contra-lateral teeth: 9.93. These mean values were not statis-tically significantly different from each other. The extra cost of maintaining theimplants was about five times higher for implants than for teeth.Conclusion: The number of disease-free years was the same for neighbouringteeth, contra-lateral teeth and implants. However, due to the high prevalence ofperi-implantitis, the cost of maintaining implants was much higher than the costof maintaining teeth.

Øystein Fardal1 and Jostein Grytten2

1Private practice, Egersund, Norway;2Institute of Community Dentistry, University

of Oslo, Blindern, Oslo, Norway

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Key words: cost effectiveness; cost

minimization; implants; maintenance; peri-

implantitis; periodontal disease; re-treatment

Accepted for publication 25 February 2013

Periodontal treatment followed bylong-term maintenance has been

shown to be successful in keeping themajority of patients’ teeth (Hirschfeld& Wasserman 1978, Fardal et al.2004, Fardal & Linden 2008). Main-tenance often involves considerablere-treatment and extra cost (Fardal &Linden 2005, Fardal et al. 2012). Anumber of studies have reportedfairly high prevalence levels of peri-implantitis of 7.8%–43.3% (Bergl-

undh et al. 2002, Ferreira et al. 2006,Roos-Jans�aker et al. 2006, Zitzmann& Berglundh 2008, Koldsland et al.2010, Mir-Mari et al. 2012).

A major article estimating cost ofperiodontal disease control was pub-lished by Antczak- Bouckoms &Weinstein (1987). They introducedcost effectiveness, decision-makinganalysis and utility analysis. In addi-

Conflict of interest and source of

funding statement:The authors declare that they do nothave any conflict of interest.The study is self funded by theauthors.

© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd 645

J Clin Periodontol 2013; 40: 645–651 doi: 10.1111/jcpe.12101

tion, quality-adjusted tooth years(QUATY) was adapted from qual-ity-adjusted life years (QUALY)(Broom 1993). For a number ofyears there were few studies thataddressed the economic aspects ofperiodontal disease. Recently, areview article by Gjermo & Grytten(2009) concluded that there was alack of quality studies of the eco-nomic aspects of periodontal ther-apy. Since then, cost effectiveness ofadjunctive antimicrobials (Heasmanet al. 2010), regenerative devices(Listl et al. 2010), sinus lift opera-tions for implant placement (Listl &Faggion, 2010), supportive periodon-tal care (Pennington et al. 2011) andoral health educational programmes(J€onsson et al. 2012) have beeninvestigated. In addition, a reviewarticle re-examining the cost of peri-odontal treatment has been pub-lished (Listl & Birch 2013).

However, little is known aboutthe efforts and cost of maintainingdental implants in patients treatedfor periodontitis. A recent EuropeanWorkshop on implant therapy, con-cluded that there were few studieson the pathogenesis and treatmentof peri-implantitis. Only 6.4% of 982studies addressed the issue, and onlytwo studies that fulfilled the inclu-sion criteria were carried out onhumans (Vignoletti & Abrahamsson2012). In a review article it ispointed out that the following needsto be improved: the quality ofreporting, case definitions andmethods used to study incidence,prevalence and risk factors of peri-implant diseases (Tomasi & Derks2012).

Few, if any, studies haveaddressed the cost effectiveness ofimplant therapy for patients treated

for periodontitis. However, a recentstudy related patients’ direct life costto implant and prosthetic replace-ments (Fardal et al. 2012). The aimof this article was to compare teethand implants during maintenancetherapy in terms of the number ofdisease-free years and costs as partof a quality control measure.

Materials and Methods

Setting and study population

The patients were from one specialistpractice in south-west Norway. Thepractice receives referrals from gen-eral dental practitioners, communitydentists and physicians in rural com-munities with a total population of25–30,000. The area has approxi-mately 25 dentists divided evenlybetween private practice and thecommunity dental service. The inves-tigator is a specialist in periodontol-ogy, is the only periodontal specialistin the area and works in two practicelocations (Egersund and Flekkefj-ord). Data from this practice havebeen used in several studies in whichthe progress of periodontitis has beendescribed, and the effect of differenttypes of periodontal treatment hasbeen investigated (for example see:Fardal et al. 2003, 2004, Fardal &Linden 2008, 2010, Fardal 2006).

Our sample consisted of patientstreated for periodontal disease in thispractice between 1986 and 2012, andwho had received one or severalimplants either after completion ofinitial periodontal therapy or duringthe maintenance phase. All theimplants replaced teeth lost due toperiodontal disease. The implantswere restored with either singlecrowns, implant-supported bridges or

a combination of teeth and implant-supported bridges. To obtain anadequately long observation time, wechose only to include patients withimplants that had been in place for7 years or longer. Our sampleconsisted of 43 patients. The analyseswere also carried out on a samplewith patients for whom the observa-tion period was both longer andshorter than 7 years. This did notinfluence the conclusions. Table 1presents characteristics of thepatients.

Treatment prior to implant placement

All the patients completed a similarcourse of periodontal treatment,which included non-surgical therapyand surgical intervention whenappropriate. Initial therapy includedoral hygiene instruction, scaling androot planing using standard curettes.In the initial phase, scaling and rootplaning were completed without theuse of local anaesthesia. The wholemouth was treated over a series ofvisits at 2–4 week intervals. Oralhygiene was reinforced repeatedlybased on individual needs. Thepatients received a detailed explana-tion of periodontal anatomy and thedisease process involved in periodon-titis. Special emphasis was placed onthe importance of periodontal main-tenance therapy, following the initialdefinitive therapy. Periodontal sur-gery was prescribed for patients whohad sites with bleeding on probingor persistent deep pocketing atreassessment 6 weeks after comple-tion of the initial therapy. Thedecision to have implant therapywas taken jointly by the patient, thereferring dentist and the periodontist(ØF).

Table 1. Description of the patient population

Variable Mean/proportion

Standarddeviation

Range Number ofpatients

Baseline valuesNumber of teeth per patient 19.7 5.5 [7–32] 43Number of implants per patient 2.8 2.0 [1–8] 43Age 51 10.8 [29–74] 43Proportion of patients who smoked 0.63 43Number of cigarettes smoked per day per patient who smoked 15.9 5.9 [5–30] 27Proportion of patients on medication 0.32 43

Changes during the observation periodNumber of teeth lost per patient 4.0 3.7 [0–16] 43Number of implants lost per patient 0.046 0.21 [0–1] 43

© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd

646 Fardal and Grytten

Maintenance treatment after the implant

placement

Maintenance visits with the specialistpractitioner alternated with visits tothe general dental practitioner, sothat all patients were seen in totalbetween two and four times per year.Written instructions were given bothto the referring dentist and the patientoutlining the plans for maintenancetherapy. During each maintenancevisit to the specialist, scaling, rootplaning and polishing of teeth andimplants was routinely performedaccording to the needs of eachpatient. The interval between recallvisits was shortened or lengthened asappropriate according to the stabilityof the periodontal/peri-implantcondition.

During the maintenance period,sites with increasing probing depthwere treated with repeated scalingand root planing. Subsequently, ifthere were clinical signs of residualsubgingival calculus or persistentinflammation, surgical interventionwas performed on teeth and/orimplants. Standard flap operationsdesigned to access diseased root/implant surfaces for cleaning/irriga-tions were used. No attempts weremade to regenerate lost tissue. Inaddition, systemic or topical antibi-otic therapy was used in cases ofacute exacerbation of periodontal/peri-implant disease.

Outcome variables and analyses

Number of disease-free years

On the basis of patient records from2012, we identified all the patientswith implants that had been inplace for 7 years or more. We alsoidentified patients who had hadperi-implantitis that had requiredcomprehensive treatment. For thesepatients, we registered the number ofyears the implant had been in placebefore treatment for peri-implantitiswas required. The diagnosis of peri-implantitis was based on the follow-ing criteria: radiographic proximalbone loss of at least three threadswhen compared with bone levels1 year after loading in addition to thepresence of bleeding and suppuration.

We calculated the sum for thenumber of disease-free years for allthe patients’ implants, and dividedthis sum by the number of patients.

Our outcome measure was then themean number of disease-free yearsper implant per patient. We then cal-culated the 95% confidence intervalfor this mean.

We repeated the same calculation,including the calculation of a 95%confidence interval, for the implant’sneighbouring tooth and the contra-lateral tooth. The baseline was theyear the implant was inserted. In thisway, the number of disease-freeyears for the implant, the neighbour-ing tooth and the contra-lateraltooth was measured from the samestarting point. It was assumed andverified from the patient records thatperiodontal condition was stablearound the neighbouring tooth andthe contra-lateral tooth at the timethe implant was inserted. Implantsand teeth could then be comparedusing the time when implants wereinserted as the baseline. If the confi-dence intervals for the implant, theneighbouring tooth and the contra-lateral tooth overlapped, the suscep-tibility to recurrence of periodontitisand peri-implantitis would be thesame for the implant and the controlteeth.

In the analyses, we did notinclude control variables for thepatient or the dentist. The compari-son between the number of disease-free years was done for the implantand the control teeth for the samepatient. In this way, we automati-cally control for all patient-specificcharacteristics. Also, it was notnecessary to control for specificcharacteristics of the dentist, as allthe periodontal treatment andimplant treatment was carried outby the same clinician (ØF).

Cost of treatment

In the case of comprehensive treat-ment of periodontitis and peri-im-plantitis, we calculated the cost oftreatment of the teeth and theimplants separately. The cost wasbased on the same hourly rate ofnon-surgical and surgical fees forboth implants and teeth (for furtherdetails about how the specialist ser-vices for periodontists in Norwayare organized and financed seeGrytten & Skau 2009). The actualcost per implant was then the totalcost of treatment of peri-implantitisdivided by the number of implants.Correspondingly, the actual cost per

tooth was the total cost of re-treat-ment of periodontitis divided by thenumber of teeth. To adjust for thevariation in time from when thepatient completed his or her initialtreatment to the time when thepatient was re-treated, the cost perimplant/tooth were calculated peryear. The total costs were calculatedbased on the fees the patients paidthe periodontal specialist for treat-ment and the cost for antibiotics hasbeen included.

Results

Description of the patient population

Table 1 shows descriptive statisticsfor the patient population. Therewere 18 male patients and 25 femalepatients. The mean age at baselinewas 51 years. The oldest patient whoreceived an implant was 74 years,the youngest was 29 years. 53.1% ofthe patients got peri-implantitis asso-ciated with one or several implants.53.4% of the patients got periodonti-tis associated with one or moreteeth.

Altogether, 119 implants wereinserted for 43 patients: 2.8 implantsper patient. 16 patients received onlyone implant, while one patientreceived eight implants. Peri-implan-titis occurred with 37 of the 119implants: 31.1% of all implants.Two implants were removed, oneafter 13 years and the other after22 years. There were no differencesin the rate of peri-implantits betweenpatients with single or multipleimplants.

The numbers of patients (inbrackets) according to type ofimplant were: Nobelbiocare TiU(29), Osseotite 3i (8), Strauman (4),Screw-Vent (2). The majority ofimplants were placed in the anteriorregion between the second pre-molars. There were 12 patients withsingle crowns, and seven patientswith implant bridges. 24 patientshad a combination of bridges withteeth and implants. Seven out of thetwelve single implant crowns (58%)developed peri-implantitis, while fiveout of the seven implant bridges(71%) and twelve out of 24combined implant/teeth bridges(50%) developed peri-implantitis.

Altogether, the 43 patients had847 teeth at the initial examination:


Comparing maintenance of teeth with implants 647

19.7 teeth per patient. None of thepatients had less than seven teeth.Periodontal disease developed round64 of the 847 teeth that were presentat the initial examination, and hadto be treated, i.e. 7.6% of all teeth.The mean number of teeth that werelost during the observation periodwas 4.0.

At baseline 27 patients smoked.They smoked on average 15.9 ciga-rettes per day. There were no differ-ences in the level of peri-implantitisbetween smokers and non-smokers (8of 16 non-smokers developed peri-im-plantitis). 14 patients were takingmedication, mainly for cardiovasculardiseases.

Main results

For 37 of the patients it was possibleto compare neighbouring teeth withthe implants. The mean number ofdisease-free years was 8.66 for theimplants and 9.08 for the neighbour-ing teeth. The confidence intervals forthese two means overlapped(Table 2).

Twenty-nine patients had contra-lateral teeth that could be comparedwith the implants. The mean numberof disease-free years was 8.66 for theimplants and 9.93 for the contra-lat-eral teeth. These confidence intervalsalso overlapped (Table 2).

In Tables 3–4 we present addi-tional analyses for smokers versusnon-smokers, and for patients withsingle implant restorations versuspatients with multiple implant resto-rations. Table 3 shows a slightly bet-ter disease-free period for smokersthan non-smokers. However, this isan unusual finding. For all subsam-ples, the confidence intervals for themean number of disease-free yearsper implant/tooth overlapped. Inaddition, the sample is too small toinvestigate this further. Table 4shows that all the confidence inter-vals for patients with one implant

versus patients with more than oneimplant overlapped.

The total cost of treatment ofperi-implantitis was € 13,100 (non-surgical € 5100 and surgical € 8000).The mean cost per implant for thewhole observation period was € 110.After adjusting for the number ofyears the implants had been in place,the cost was € 10.2 per implant peryear (Table 5).

The total cost of re-treatment ofteeth was € 29,450 (non-surgical €

6450 and surgical treatment €

23,000). The mean cost per tooth forthe whole observation period was €

35. After adjusting for the observa-tion time, the cost was € 2.1 pertooth per year (Table 5).

There were no differences in thecost of maintaining the implantscompared with neighbouring or con-tra-lateral teeth. This follows directlyfrom Table 2, which shows thatthere was no difference in the meannumber of disease-free years perimplant/tooth for implant versusneighbouring tooth, and for implantversus contra-lateral tooth.

Discussion

This study was carried out on a sampleof patients who had all been treatedfor periodontitis. They had receivedone or more implants, and had beenunder continual follow-up afterwards.However, the incidence of recurrentperiodontitis and peri-implantitis wasrelatively high, but not markedly dif-ferent from that reported in otherstudies (Berglundh et al. 2002, Fardal& Linden 2005, Ferreira et al. 2006,Roos-Jans�aker et al. 2006, Zitzmann& Berglundh 2008, Koldsland et al.2010, Mir-Mari et al. 2012).

An important finding was thatthe number of disease-free years wasthe same for implants and teeth.This was also the case when the het-erogeneity in the patient populationwas taken into account. None of

these results for smokers versus non-smokers, and for patients with oneimplant versus patients with morethan one implant were different fromwhen the analyses were done on thewhole sample. However, the costsfor re-treatment was markedlyhigher if implants were inserted com-pared to if patients kept their ownteeth. This is because there weremore implants with peri-implantitisthan teeth with recurrent periodonti-tis: when all teeth were comparedwith all implants there was a signifi-cantly lower prevalence of recurrentperiodontitis than that of peri-implantitis. This is in agreement witha systematic review reporting betterlong-term outcomes for teeth thanfor implants (Tomasi et al. 2008).

The underlying assumption forour analyses is that the risk of peri-implantits around a fixture whichhas been placed where a tooth hasbeen lost is similar to the risk ofre-emergence of periodontal infec-tion around a tooth that remains insitu. This assumption may be ques-tionable. To our knowledge, thereare no studies where this assumptionhas been examined. One strength ofour study is that we use a researchdesign that takes into account thepossibility that the risk may varyaccording to local factors (by com-paring implant versus neighbouringtooth), according to site specificity/tooth morphology (by comparingimplant versus contra-lateral tooth)and the mouth as a whole (by com-paring the total number of implantswith the total number of teeth).However, in spite of these compari-sons, the clinical conditions may stillbe different. Even though teeth werelost due to periodontal disease, thisdoes not necessarily imply identicalclinical conditions at implant sitesand sites where teeth could be main-tained. On the other hand, oneadvantage with our study is that weuse three different comparison

Table 2. The number of disease-free years for the implant, the neighbouring tooth and the contra-lateral tooth

Type of comparison The mean number of disease-free years per implant/tooth 95% Confidence interval Range Number of patients

Implant 8.66 [7.33, 9.99] [2–17]Versus 37

Neighbouring tooth 9.08 [7.96, 10.20] [2–27]Implant 8.66 [7.39, 9.93] [2–17]Versus 29

Contra-lateral tooth 9.93 [8.49, 11.37] [3–22]



groups, and the results are similarindependent of which group is used.

In this study, the total failure ofimplants was very low in spite of ahigh prevalence of peri-implantitis.Only two implants were removedafter 13 and 22 years, suggestingthat a very active maintenancetherapy including surgical treatmentof peri-implantitis was successful inmaintaining implants previouslyexposed to disease. The importanceof maintenance therapy for implantshas also been reported previously(Rocuzzo et al. 2010).

Different types of implant sys-tems were used during the studyperiod from 1986 to 2012. Thedifference in surface characteristicscould have influenced the results inthis study as suggested by Renvertet al. (2011). However, as the vastmajority of fixtures used wereNobelbiocare TiU this study did notlend itself to a comparison betweensystems. No apparent differenceswere observed clinically between thesystems.

A relatively high tooth loss ratefrom periodontal disease was found

in this population when comparedwith previous reports from the samepractice setting (Fardal et al. 2004).This underlines the fact that thepatients in this study were high-riskpatients with marked loss of peri-odontal support. In spite of mainte-nance therapy over a number ofyears, these patients lost several teeth.Some of these teeth were replaced byimplants after a healing period.

It is difficult to verify the resultsfrom this study due to a lack ofcomparable studies. Another studyfrom the same practice setting calcu-lated direct life-time patient costs forperiodontal treatment (Fardal et al.2012). However, a number of theoutcomes were extrapolated fromshorter-term studies. Gaunt et al.(2008) examined the cost ofperiodontal maintenance treatment,however, this study was not done inreal time. The strength of this studyis that it is done in real time with no

Table 3. The number of disease-free years for the implant, the neighbouring tooth and the contra-lateral tooth for smokers and non-smokers

Type of comparisonThe mean number of disease-free

years per implant/tooth95% Confidence

interval RangeNumber ofpatients

SmokersImplant 9.50 [8.08, 10.90] [4–17]Versus 24Neighbouring tooth 9.75 [8.53, 11.00] [2–22]Implant 9.28 [7.69, 10.80] [4–17]Versus 18Contra-lateral tooth 10.61 [8.56, 12.66] [6–22]

Non-smokersImplant 7.15 [5.51, 8.79] [2–12]Versus 13Neighbouring tooth 7.84 [6.30, 9.37] [2–12]Implant 7.64 [5.63, 9.65] [2–12]Versus 11Contra-lateral tooth 8.82 [7.11, 10.53] [3–13]

Table 4. The number of disease-free years for the implant, the neighbouring tooth and the contra-lateral tooth for patients with singleimplant restoration and for patients with multiple implant restoration

Type of comparison The mean number of disease-free years per implant/tooth 95% Confidence interval Range Number of patients

Single implant restorationImplant 8.17 [6.28, 10.06] [4–13]Versus 12Neighbouring tooth 8.83 [6.28, 11.38] [2–17]Implant 8.17 [6.27, 9.99] [3–13]Versus 12contra-lateral tooth 10.08 [8.03, 12.13] [7–17]

Multiple implant restorationsImplant 8.92 [7.50, 10.43] [2–17]versus 25neighbouring tooth 9.20 [7.62, 10.78] [2–22]Implant 9.00 [7.29, 10.71] [2–17]versus 17contra-lateral tooth 9.82 [7.78, 11.80] [3–22]

Table 5. Costs for treatment of peri-implantiitis and re-treatment of periodontitis in Euro

Implants (mean) Teeth (mean)

Total costs 13, 100 29, 450Number of implants/teeth 119 847Costs per implant/tooth the whole observation period 110 35Observation period (in years) 10 16Costs per implant/tooth per year 10.2 2.1



extrapolations, the patients served astheir own internal controls and thesame experienced clinician carriedout all the treatment.

In any health economic analysis,it is important to adhere to underly-ing welfare economic theories (Vern-azza et al. 2012). Usually, it isdebatable which tools are best suitedfor a particular clinical study. It istherefore important to examine thereasons why the specific tools werechosen for this study. First of all, itwas decided to define the variablesas a measure of technical efficiency,and therefore to utilize cost minimi-zation and cost effectiveness. How-ever, cost minimization analysisideally should only be used when theinterventions or strategies beingcompared are already known to haveequal effectiveness. In this study, theassumption is that the effectivenessof re-treatment of periodontal dis-ease is the same as for treatment ofperi-implantitis. This suggestion hasnot been verified by other studies,but from a clinical standpoint andfrom the results of the study, itseems reasonable to use this as ahypothesis. A recent Cochrane sys-tematic review (Esposito et al. 2012)reported clinical improvements fromthe treatment of peri-implantitis.However, they did not find thatcomplex interventions were moreeffective than control therapies withsurgical debridement as chosen forthis study. Furthermore, a studyfrom the same clinical setting as inthis study reported that a very activemaintenance therapy often includingsurgical retreatment for the recur-rence of periodontal disease waseffective in the long term, in termsof tooth loss (Fardal & Linden2005). Second, cost effectiveness isusually measured in natural units,and in this study, disease-free yearswere used. However, these measure-ments do not take into account theimpact on the patients in a widersense, and do not answer any ques-tions of allocative efficiency. In apractical sense it is difficult toemploy methods like standard gam-ble, time trade off and qualityadjusted tooth years in a privatepractice setting. A willingness to payapproach has previously beendescribed for periodontal therapy(Matthews et al. 1999). This methodwas considered for this study, how-

ever, it was feared that the patientswould misunderstand this approachand use it to bargain with the dentalfees quoted.

The results of this study shouldbe interpreted keeping in mind thatthey were obtained in a single pri-vate practice in a particular geo-graphic area with a relatively small,heterogeneous sample with a largeproportion of smokers. Thus, gener-alizing may not be appropriate.Regardless of this, our findings showthat the number of disease-free yearswas the same for neighbouring teeth,contra-lateral teeth and implants.However, due to the high prevalenceof peri-implantitis, the cost of main-taining implants was much higherthan the cost of maintaining teeth.

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Address:Øystein FardalKvednabekkvn 4N-4370 EgersundNorwayE-mail: [email protected]

Clinical Relevance

Scientific rationale for the study:Little is known about the effortsand cost of maintaining dentalimplants in patients treated forperiodontitis and how this com-

pares with the active maintenance ofteeth.Principle findings: Neighbouringteeth and contra-lateral teeth andimplants have the same susceptibilityto recurrence of periodontal disease

and peri-implantitis under the sameoral conditions.Practical implications: Active main-tenance treatment is important forthe long-term success of implants forpatients treated for periodontal disease.



A Comparison of Teeth and Implants During Maintenance Therapy in Terms of the Number of Disease-free...

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