zirconia implant may 2013

One-piece zirconia oral implants:one-year results from aprospective case series. 2.Three-unit fixed dentalprosthesis (FDP) reconstruction

Kohal R-J, Patzelt SBM, Butz F, Sahlin H. One-piece zirconia oral implants:one-year results from a prospective case series. 2. Three-unit fixed dental prosthesis(FDP) reconstruction. J Clin Periodontol 2013; 40: 553–562. doi: 10.1111/jcpe.12093.

AbstractAim: To evaluate the clinical and radiological outcome of one-piece zirconia oralimplants for three-unit fixed dental prosthesis (FDP) replacement after 1 year.

Materials: Twenty eight patients were recruited for the investigation and signed an informedconsent. All patients were treated with a one-stage implant surgery and a three-unit immediatetemporary restoration on two one-piece zirconia implants. The implants were fabricated of yt-tria-stabilized tetragonal zirconia (y-TZP). The endosseous part of the implants was taperedwith a porous surface. A total of 56 implants were inserted in the 28 patients. A total of 12implants were placed in the upper jaws (six in the anterior area and six in the posterior area)and 44 in mandibles (all in the posterior area). At implant insertion and after 1 year,standardized radiographs were taken to evaluate the peri-implant bone loss. To evaluate anyinfluences from different baseline parameters on the marginal bone loss a univariate analysiswas performed. Clinical soft tissue parameters probing depth (PD), clinical attachment level(CAL), modified bleeding index (mBI) and modified plaque index (mPI) were recorded. Implantcumulative survival rates were calculated using actuarial life table analysis. Changes in the clini-cal variables were assessed using the Wilcoxon Signed Ranks test (PD, CAL) and the Sign test(mBl, mPl). All significance tests were conducted at a 5% level of significance.

Results: After 1 year, one implant was lost resulting in a survival rate of 98.2%. Thepatient was excluded from further analysis. The marginal bone loss after 1 year amountedto 1.95 mm. In 40% of the patients a bone loss of at least 2 mm and in 28% of the patientsa loss of more than 3 mm were observed. The PD decreased for implant and tooth sitesover time, the values being significantly higher for implants than for teeth. Over 1 year, theCAL increased slightly around the implants and decreased around the teeth. At the 1-yearfollow-up, the CAL at the implant sites was statistically significantly higher than at the ref-erence teeth. The mBI was significantly lower at implants than at teeth. The same result wasfound for the plaque index.

Conclusions: A high frequency of increased radiographic bone loss (>2 mm) after 1 yeararound the presented one-piece zirconia implant system was found. The bone loss seems tobe higher compared to the very limited availability of zirconia implant data. Therefore,within the limits of the present investigation, it may be concluded that the presented zirco-nia implant system possibly performs inferior to conventional titanium implants and toother zirconia implants regarding peri-implant bone loss.

Ralf-Joachim Kohal1, Sebastian B. M.Patzelt2,3, Frank Butz3 and

Herman Sahlin4

1Department of Prosthodontics, School of

Dentistry, Albert-Ludwigs University,

Freiburg, Germany; 2Department of

Periodontics, School of Dentistry, University

of Maryland, Baltimore, USA; 3Department of

Prosthodontics, School of Dentistry,

Albert-Ludwigs University, Freiburg,

Germany; 4Nobel Biocare, Gothenburg,

Sweden

Key words: clinical investigation; fixed dental

prosthesis; oral implant; prospective;

three-unit bridge; zirconia

Accepted for publication 3 February 2013

© 2013 John Wiley & Sons A/S 553

J Clin Periodontol 2013; 40: 553–562 doi: 10.1111/jcpe.12093

Zirconia oral implants are a topic ofinterest to dental researchers anddentists. Although, those implantsare on the market for a certain per-iod of time, the scientific backup onthe clinical use of such implants islagging behind or non-existent. Indifferent review articles, the biologi-cal behaviour (i.e. osseointegration)of zirconia implants was elucidated(Wenz et al. 2008, Andreiotelli et al.2009, Silva et al. 2010). A compila-tion of animal experiments in thereview of Silva and co-workers (Silvaet al. 2010) showed that the utilizedzirconia implants developed a similarbone-to-implant contact as did thetitanium implant controls. Numer-ous additional animal experiments,published after the review of Silvaet al. (2010), supported the findingsthat zirconia implants obtained anamount of osseointegration notdifferent from titanium implants(Gahlert et al. 2010, 2012a, Kochet al. 2010, Schliephake et al. 2010,Stadlinger et al. 2010, Aboushelibet al. 2011, M€oller et al. 2012). Someof those investigations could evenshow slightly superior results of thezirconia implants (Koch et al. 2010,Stadlinger et al. 2010, Aboushelibet al. 2011).

The positive biomechanical aswell as pre-clinical biological resultsmight encourage the use of zirconiaimplants and therefore severalimplant companies brought zirconiaoral implants to the market (Silvaet al. 2010) (e.g. Incermed, Lausanne,Switzerland; Z-systems, Oensingen,Switzerland; Bredent medical, Senden,Germany; Ceraroot, Granollers,Spain; Creamed, Marburg, Germany;Metoxit, Thayngen, Switzerland;Dentalpoint, Zurich, Switzerland;BPISystems, Sindelfingen, Germany

– to name a few). The minority ofthese companies has clinical researchdata for their implant systems; andsome of these data are of question-able scientific quality (Andreiotelliet al. 2009, Depprich et al. 2012).For example, when a non-systematicelectronic search (key words: zirc*AND impl*) and a hand search wereperformed, no clinical investigationscould be found for the Incermed sys-tem. Five clinical investigations werefound for the z-systems system (Blas-chke & Volz 2006, Mellinghoff 2006,Lambrich & Iglhaut 2008, Cannizz-aro et al. 2010, Gahlert et al. 2012b)and three clinical investigations forthe White Sky implant system ofBredent medical (Borgonovo et al.2010, 2011, Payer et al. 2012). Twoscientific reports could be located forthe CeraRoot System (Oliva et al.2007, 2010). For the remaining zirco-nia implant systems no scientificliterature regarding implant survival/implant success could be found inpeer-reviewed journals (case reportsexcluded). Apart of the investigationsof Cannizzaro et al. (2010) and Payeret al. (2012), all other reports had alow level of evidence due to a ques-tionable study design (Depprich et al.2012). In this context, another aspectof interest might be that all clinicalinvestigations or reports, in contrastto this study, were published at someperiod after the launch of the respec-tive implant system.

Cohort investigations with a pro-spective study design are rare forzirconia oral implants (Payer et al.2012). Therefore, it was the aim ofthe present cohort investigation toclinically evaluate a zirconia implantsystem prior to market launch. Itwas the objective of this investigationto obtain 1 year data on the survival/success of a newly developed zirconiaimplant system when applied asabutments for three-unit fixed dentalprostheses. The soft and hard tissueresponse around these implants wasthe secondary objective.

Materials and Methods

This study was a prospective investi-gation. 28 patients were recruitedand were informed on the contentand duration of the study. Prior tothe start of the study, they had tosign an informed consent. All 28patients were treated with a one-stage

implant surgery and a three-unitimmediate temporary restorationsupported by two implants. Maininclusion criteria were that the sub-jects were between 18 and 70 yearsold, had to be in need of animplant-supported three-unit fixeddental prosthesis (FDP) supportedby two implants, and had to besystemically healthy. Furthermore, asufficient bone volume in theprospective implant regions had tobe present for receiving implantswith a diameter of at least 4.3 mmand minimal length of 10 mm. Thesubjects had to have a stable occlu-sal relationship with no severe para-functional habits and the implantsites had to be free of infection and/or tooth remnants.

Exclusion criteria were amongothers: alcohol or drug abuse; gen-eral health conditions that did notpermit a surgical procedure, forexample, infectious disease, heartdisease or disease of the circulatorysystem, metabolic disease, bonemetabolism disorders, disturbance ofthe hematopoietic system, haemato-logical disorders, wound healing dis-turbances, disorders of the endocrinesystem and pregnancy. Local contra-indications were, for example,tumours, ulcers. In addition, reasonsto believe that the treatment mighthave a negative effect on the sub-ject’s psychological situation wereexclusion criteria. The need forextended bone augmentation beforeimplant installation to obtain a pros-thetically correct implant positionwas an exclusion criterion as well.However, a minor augmentationprocedure to cover exposed threadsdue to deficient sites was not anexclusion criterion. The investigationwas approved by the ethics commit-tee of the University Medical CenterFreiburg, Freiburg, Germany (inves-tigation number: 337/04).

Pre-treatment examination

Before treatment, the patients’ medi-cal history was recorded and a clini-cal and radiographic examinationwas performed. The areas of implan-tation were evaluated with a conebeam computed tomogram (Newtom3G, Newtom, Marburg, Germany).According to the available bone, thelengths and the diameters of theimplants were selected.

Conflict of interest and source offunding statement

Dr. Kohal was a lecturer for NobelBiocare from 2005 to 2008 andDr. Butz was a lecturer for Nobel Bio-care in 2007. Dr. Sahlin is an employeeof Nobel Biocare, Gothenburg, Sweden.This investigation was supported by agrant from Nobel Biocare, Gothenburg,Sweden grant # T-114. The zirconiaimplants and the zirconia frameworkswere provided by Nobel Biocare.

© 2013 John Wiley & Sons A/S

554 Kohal et al.

Investigational zirconia implants

The yttria-stabilized tetragonal zirco-nia polycrystal implants (y-TZP;zirconia implants) (Nobel Biocare)featured a design similar to the tita-nium one-piece NobelDirectTM

implant (Nobel Biocare, Gothenburg,Sweden). The endosseous part of theimplants was tapered and roughened(ZiUniteTM surface technology, NobelBiocare), (Sennerby et al. 2005). Aporous implant surface was achie-ved by a sintering-on technique ofzirconia slurry onto the implant cylin-der that contained zirconia powderand a burnable pore former. Whilesintering the implant coating, thepore former burnt out, leaving a por-ous implant surface. The topographi-cal analysis of the implant surfacerevealed for Sa (average surfaceroughness) 1.24 lm, for Sds (valuefor the number of peaks per areaunit) 0.09/lm2, and for Sdr (devel-oped surface area) 83% (Sennerbyet al. 2005). The transmucosal part ofthe one-piece zirconia implants wasalso roughened in its apical part,whereas the coronal part, for theplacement of the bridge retainer(abutment part), had a machined sur-face. The implant lengths availablewere 10, 13 and 16 mm and the diam-eters were 4.3 mm Regular Platform(RP) and 5.0 mm wide [WidePlatform (WP)]. All implants wereCE-marked.

Implant placement

The implants were placed underperi-operative antibiotic coverage(Clindamycin 300 mg N1, 3 9 perday, starting 1 day before surgeryand lasting 2 days after the day ofsurgery) and pain control was exe-cuted using ibuprofen. The patientsused the analgesic after the surgeryaccording to their individual needs.

There was no restriction in thestudy design regarding the type ofimplant receiving sites. The implantswere either placed immediately intoextraction sockets or in so calledhealed sites (healing time at least4–6 months). The flap design for theplacement of the implants into thehealed sites was flapless, a soft tissuepunch technique or a full-thicknessmucoperiosteal flap. All implantswere placed according to the manu-facturer’s recommendations.

After implant placement, theimplant abutment part was slightlyprepared for the incorporation of thethree-unit temporary bridge. Allimplants were immediately restoredwith provisionals that were re-linedusing a self-curing acrylic material.All centric and eccentric contactpoints, as well as the approximalcontacts, were removed to avoid anyforces from occlusion onto theimplants. The status quo of the mar-ginal bone was recorded by takingstandardized radiographs with a cus-tomized intra-oral x-ray film holderbite block (Rinn XCP, DentsplyRinn, Elgin, USA). The film holderwas individualized with a self curingacrylic material before implant place-ment. In a malleable condition, theacrylic was attached to the holder.Then, the holder including the x-rayfilm was brought into the intendedposition in the patient’s oral cavity.Care was taken to parallel the align-ment of the x-ray film in the filmholder to the anticipated long axis ofthe implants. After curing of theacrylic material under continuouscooling with water spray, excessmaterial was removed and the filmholder position again inspected intra-orally for fit and alignment. If therewas a problem in alignment or repro-ducibility in the holder position, theentire procedure was repeated until asatisfying result was obtained.

After cementation of the tempo-rary bridges, temporary cement rem-nants (Freegenol, GC Germany, BadHomburg, Germany) were meticu-lously removed. Finally, the patientswere provided with maintenanceinstructions which consisted of rins-ing the oral cavity with a 0.2%chlorhexidine solution and wereinstructed not to clean the surgicalareas with their tooth brush for atleast 1 week. After a week, thepatients were scheduled for woundinspection and for suture removal.Further controls and professionalcleanings of the surgical areas wereperformed after 2, 4, 6 and 8 weeksand then on a monthly basis untilthe delivery of the final prosthesis.

Delivery of the prosthesis

For prosthesis fabrication, impres-sions of the implants were performedafter approximately 6 weeks in thelower jaw and 14 weeks in the upper

jaw. All-ceramic three-unit bridgeswere processed with a zirconiaframework (Procera, NobelBiocare,Sweden) and a glass-ceramic veneer-ing material (NobelRondo, Nobel-Biocare, Sweden). The three-unitfixed dental prostheses were conven-tionally cemented using glass-ionomer cement (KetacTM Cem, 3MEspe, Neuss, Germany). The cementremnants were thoroughly removedand the patients inspected againafter one to three days.

Summary information on patients and

implants

Overall, 28 patients (11 females and17 males; all non-smokers) wereincluded in this investigation and atotal of 56 implants were placedsupporting 28 three-unit fixed dentalprostheses. 24 patients were olderthan 41 years. 12 implants wereplaced in the upper jaws (6 in theanterior area and 6 in the posteriorarea) and 44 in the lower jaws (all inthe posterior area). 30 implants hada diameter of 5 mm and 26 of4.3 mm. Of the 56 implants, fiveimplants (9%) were placed in extrac-tion sockets (two implants in aflapped procedure) and 51 implantsin healed sites (five implants using apunch technique, two implants witha flapless procedure).

Follow-ups

Radiographic assessment

With the application of the individu-alized x-ray holder (long-cone paralleltechnique), standardized radiographswere taken after implant placement,after FDP delivery, and at the 1-yearfollow-up. The radiographs atimplant placement were used asbaseline values. The lower edge ofthe implant abutment part – wherethe transition zone between thestraight abutment part and theimplant threads was located – wasutilized as the reference point for themeasurements of bone remodelling/loss (Fig. 1). Bone remodelling/lossfrom implant placement to the 1-yearfollow-up was evaluated. A calibra-tion of all radiographs was performedusing the known width of the base ofthe abutment part of the ceramicimplants. A radiologist at theGothenburg University, Sweden,evaluated the radiographs indepen-


Zirconia implants for fixed prosthesis 555

dently. She was not involved in theclinical part of the investigation.

Bone remodelling was calculatedfor each side of the implant (mesialand distal) separately, as the differ-ence between bone levels at two timepoints. The average of mesial anddistal remodelling was then calcu-lated for each implant site. Themean value for all implants in eachpatient was further calculated fromthe mean of each implant.

Bone loss criteria and implant successrating

In the present investigation, the rec-ommendation of €Ostman et al.(2007) that more than 1 mm of boneloss during the first year is accept-able for one-piece implants, wasadopted. Therefore, their successgrade I was applied to implantsshowing � 2 mm bone loss after1 year and no clinical and radio-graphic signs of pathology. The suc-cess grade II was applied to implantsshowing no pathology but a boneloss/resorption of � 3 mm at the1-year follow-up.

Clinical evaluation

The follow-ups were scheduled for6 months and 1 year after implantplacement. The clinical evaluationaround the implants as well asaround the adjacent natural teethcomprised the recording of probingdepth (PD), clinical attachment level(CAL), the modified bleeding index(mBI) according to Mombelli et al.(1987), and the modified plaque

index (mPI) also according to Mom-belli et al. (1987). The soft tissuemeasurements were performed usinga periodontal probe. The values forthe PD and for the CAL wererounded to the nearest millimetre.

Statistical analysis

Implant cumulative survival rates werecalculated using actuarial life tableanalysis (Altman 1999). Descriptivestatistics, including mean values andstandard deviations, were used forthe presentation of the bone remod-elling results. A univariate analysisof marginal bone loss from implantinsertion to the 1-year follow-up wasperformed evaluating the effect ofdifferent baseline variables. To evalu-ate the effects of ordered categoricaland continuous baseline variables,Spearman correlation coefficient wasused. The effects of dichotomousbaseline variables on bone remodel-ling were evaluated using the Mann–Whitney U-test. Mean and standarddeviation values were calculated forthe clinical variables (PD, CAL,mBI, mPI) and the values for theimplants were compared to valuesobtained from the neighbour teethusing the Mann–Whitney U-test.Changes in the clinical variables overtime were assessed using the Wilco-xon Signed Ranks test (PD, CAL)and the Sign test (mBl, mPl). All sig-nificance tests were two-tailed andconducted at a 5% level of signifi-cance. All analyses were performedusing SPSS (version 20.0; IBM Cor-poration; Armonk, NY, USA).

Results

Status of follow-up and implant failure

Of the 28 patients, 27 patientsreceived the final FDP. One implantwas lost in one patient prior toreconstruction. The implant wasmobile 2 weeks after insertion andhad to be removed. No signs ofacute infection were detectable. Atthe 6-month follow-up, 25 patientswere seen (two patients did notattend the follow-up due to timeconflicts). At the 1-year follow-up,all 27 patients were available forclinical and radiographic evaluation.

Life-table analysis (on implant level)

One implant, placed into an extrac-tion socket, failed after 21 days andhad to be removed. No furtherimplant losses occurred. The cumula-tive survival rate of the implantsafter 1 year was 98.2%.

Marginal bone remodelling (Marginal bone

loss/gain on patient level) (Table 1 & 2)

The marginal bone loss evaluationfrom implant insertion to prosthesisinsertion could be evaluated for 24patients (for three patients one ofthe x-rays was rated as non-read-able) and for 25 patients (for twopatients the x-rays from the insertiontime point were rated as non-read-able) from implant insertion to the1-year follow-up.

A bone loss of 1.65 mm could beobserved from implant insertion tothe bridge delivery. In two patients(2%), the implant sites gained somebone. However, in nine patients(38%) implant sites lost more than2 mm of peri-implant bone. A boneloss of more than 3 mm occurredaround implants in three patients(13%). Figures 2 and 3 presentradiographs of two patients thatexperienced increased bone loss.

From implant insertion to the1-year follow-up, an average boneloss of 1.95 mm was found. Again,implant sites in two patients (2%)gained some bone. In 10 patients(40%), the implant sites lost morethan 2 mm of bone. The implant sitesin seven patients (28%) lost morethan 3 mm of bone and implant sitesin three patients (12%) even lost morethan 4 mm of peri-implant bone.

Fig. 1. Indication of reference points for the bone level measurements. The coronalreference points differed in height at the mesial and distal implant aspect due to thestarting thread.


556 Kohal et al.

When the success criteria definedaccording to €Ostman and co-workers(€Ostman et al. 2007, 2008) wereapplied to the present findings ofbone loss, 62% of the patients wereclassified as success grade I and 87%as success grade II at the time-pointof FDP installation. At the 1-yearfollow-up, 60% of the patients weresuccess grade I and 72% successgrade II.

The univariate analysis of thebaseline variables possibly influenc-ing the bone loss around theimplants is shown in Table 3. A cor-relation could be found for bone lossand the flap design (p = 0.01).Implants either placed without a flapor implants placed with the punchtechnique showed significantly morebone loss than implants that wereplaced in a flapped approach.

Peri-implant soft tissue evaluation

(on patient level) (Table 4)

At the time-point of the insertion ofthe three-unit fixed dental prosthe-ses, a mean PD of 2.85 mm aroundthe zirconia implants and of2.39 mm around the reference teethwas observed (p = 0.007). At theimplant sites as well as at the toothsites, the PD decreased from pros-theses insertion to the 1-year follow-up. The PD for implants was2.65 mm and for the teeth 1.97 mmat 1 year. The difference betweenimplants and teeth was again statisti-cally significant (p < 0.001). Thereduction in PD was significant forthe teeth (p = 0.002) but not for theimplants (p = 0.284).

The CAL had a mean of3.14 mm at the implant sites and3.04 mm at the reference teeth whenthe bridges were installed. The differ-ence was statistically not significantlydifferent (p = 0.432). Until the

1-year follow-up, the CAL increasedslightly around the implants to3.24 mm (p = 0.584) and decreasedaround the teeth to 2.69 mm(p = 0.059). At the 1-year follow-up,the CAL at the implant sites was

Table 1. Marginal bone remodelling (onpatient level)

Implantinsertion

to Prosthesisinsertion

Implantinsertionto 1-yearfollow-up

Number 24 25Mean value (mm) �1.65 �1.95SD (mm) 1.27 1.71

n (%) N (%)>0 mm 2 (8) 2 (8)0 mm 0 (0) 0 (0)�0.1 to �1.0 mm 7 (29) 7 (28)�1.1 to �2.0 mm 6 (25) 6 (24)�2.1 to �3.0 mm 6 (25) 3 (12)�3.1 to �4.0 mm 3 (13) 4 (16)< � 4.0 mm 0 (0) 3 (12)

Table 2. Bone loss at all individual implant sites

PatientNumber

Mesial boneloss anterior

implant

Distal boneloss anterior

implant

Mesial boneloss posterior

implant

Distal boneloss posterior

implant

1 Radiograph from insertion time point not readable2 �2.3 �1.5 �1.6 �0.33 �0.1 �0.2 �1.3 �1.94 �1.0 0.0 �7.5 X-ray not usable5 �2.5 �4.0 �4.8 �3.66 �4.7 �2.4 1.0 �1.37 �5.1 �2.0 �6.5 �5.48 �1.3 �1.0 1.0 �1.29 �1.8 0.3 �0.5 0.310 1.1 �0.9 �0.9 �0.511 ? �0.4 �0.512 Radiograph from insertion time point not readable13 �1.5 �2.1 �2.7 �2.314 �5.1 �2.0 �4.8 �4.015 3.6 2.5 �1.5 �1.316 �1.8 �1.0 �1.4 X-ray not usable17 �1.5 �2.3 �2.0 �1.618 0.4 �0.9 0.0 2.019 0.3 �2.6 �1.0 X-ray not usable20 �4.0 �4.0 �1.5 �1.221 �1.0 �1.2 �3.4 �2.822 Implant loss, dropout23 �0.9 �0.2 0.2 0.524 �1.0 �1.5 0.5 �1.025 �4.0 �3.5 �5.5 �7.026 X-ray not usable �5.5 �4.0 �5.027 �0.5 �2.0 �5.5 �6.328 �2.3 �4.0 �0.7 X-ray not usable

Fig. 2. The upper radiograph was taken at implant insertion, the lower radiograph atthe 1-year follow-up. An increased bone loss around the distal implant is visible.



statistically significantly higher thanat the reference teeth (p = 0.001).

At bridge installation, the mBI(Mombelli et al. 1987) was slightlyhigher at the implants (0.46) com-pared to the reference teeth (0.35;p = 0.484). At the 1-year follow-up,the mBI decreased at both –implants and teeth – sites. The valuefor implants (0.15), however, wassignificantly different from the teeth(0.30; p = 0.026). The decrease inboth groups was not statistically sig-nificant (implants: p = 0.078; teeth:p = 0.523).

The plaque index (mPI), showed asimilar development over time. Atprosthesis insertion, the mPI was 0.51for the implant sites and 0.51 for thereference teeth (p = 0.669). After1 year, the values dropped signifi-cantly in both groups (implants: 0.09,p = 0.001; teeth: 0.27, p = 0.023). Atthe 1-year follow-up, the implant sitesshowed statistically less plaque thanthe teeth (p = 0.014).

Discussion

This case series is the first report onusing one-piece zirconia oralimplants for three-unit fixed implantsupported reconstructions. In arecent report (Kohal et al. 2012), theindication of implant placement wasthe single tooth restoration. In thecurrent investigation, the indication

was extended towards the rehabilita-tion of patients with a three-unitFDP. The implants were immedi-ately temporized after insertion anddefinitively restored after 8 to16 weeks. During the interval of this1 year investigation, one implantwas lost, giving a survival rate of98.2%. The implant survival rate inour investigation was comparable tothe implant survival rates reportedin investigations over different evalu-ation periods with immediatelyrestored implants (Chaushu et al.2001, Ganeles & Wismeijer 2004,Finne et al. 2007, €Ostman et al.2007, 2008, Nissan et al. 2008,Cooper et al. 2010, Romanos et al.2010, Zembic et al. 2012), and betterthan other investigations on one-piecezirconia implants showing survivalrates of 87.5% to 95% (Cannizzaroet al. 2010, Kohal et al. 2010, Payeret al. 2012). However, for this highsurvival rate the increased bone loss(1.95 mm) after 1 year has to betaken into consideration. The successrate of the implants in our study wasconsiderably lower than the survivalrate when bone loss was considered.The success rate dropped to 60%when applying the success grade I(bone loss � 2 mm) according to€Ostman et al. (2007) and to 72%when success grade II (boneloss � 3 mm) was used. These suc-cess rates after 1 year were signifi-

cantly lower in comparison to theliterature for immediately restoredimplants (€Ostman et al. 2008, Vande Velde et al. 2010, Crespi et al.2012, De Bruyn et al. 2012). Theresults of the present investigationcorroborated the results obtained inthe previous investigation of ourgroup when using the one-piecezirconia implant for single toothreconstruction (Kohal et al. 2012).

Although increased bone loss wasfound radiographically, the clinicalparameters in the present investiga-tion did not indicate the presence ofany peri-implant tissue problem. Alt-though PDs and CALs were signifi-cantly higher around the implantsthan around the teeth, this resultwas shown to be a normal finding.Animal investigations demonstratedthat even in healthy conditions thetip of a periodontal probe was closerto the bone around implants thanaround teeth. It was stated that peri-implant soft tissues did not give asmuch resistance to probing as theperiodontal tissues (Ericsson & Lind-he 1993, Schou et al. 2002). Clinicalinvestigations have also shown thatprobing values around implants aregenerally higher than around teeth.Cutrim et al. (2011) reported mean PDof 3.31–3.39 mm around implants andof 2.37–2.44 mm around referenceteeth after 1 year. The differencebetween implants and teeth was –similar to our investigation – of sta-tistical significance (Cutrim et al.2011). These results were supportedby Wolleb et al. (2012). In theirrecent investigation they showed thatafter a follow-up period of 5 years,the mean pocket PD was 3.72 mmaround implants and 2.36 mmaround teeth.

Since the peri-implant soft tissueconditions did not indicate towardsany pathology (PD: 2.65 mm; mBI:0.15; mPI: 0.09) of the peri-implanttissues, the reason(s) for theincreased frequency of bone loss of� 2 mm have to be attributed tofactors other than an inflammatoryreaction to plaque accumulation andbacterial burden. The univariateanalysis of the marginal bone lossevaluating the effect of differentbaseline variables revealed that theflap design had an influence on peri-implant bone loss. Such a correla-tion, however, could not be found inthe investigation of one-piece zirco-

Fig. 3. The upper radiograph was taken at implant insertion, the lower radiograph atthe 1-year follow-up. An increased bone loss around the distal implant is visible.


558 Kohal et al.

nia implants applied for single toothreconstructions (Kohal et al. 2012).Similarly, no differences on boneloss were reported in other investiga-tions when the flapless/punch tech-nique was compared to raising a flapfor implant placement (Becker et al.2006, Van de Velde et al. 2010,De Bruyn et al. 2011, Zembic et al.2012).

The heterogeneous surgical proto-col of immediate and late placedimplants as well as the flapless andthe punch technique with the rela-

tively small number of subjects haveto be regarded as one limitation ofthis study.

Investigations on other zirconiaone-piece implant systems did notreport on cases with increased boneloss (Cannizzaro et al. 2010, Payeret al. 2012). Cannizzaro et al. (2010)presented a bone loss of 0.7–0.9 mmaround the zirconia implants in theirinvestigation. Payer et al. (2012) pre-sented a mean bone loss of 1.01 mmafter 1 year and 1.29 mm after 2 yearsand the authors did not indicate that

increased bone loss occurred with theuse of their zirconia implant.

Although the increased bone lossin our investigation seemed to be cor-related with flapless approach, thisfinding, however, is not supported byother investigations. Therefore, theremust be other factors related to thebone loss which could not be foundwith the evaluated variables in ourinvestigation. As discussed in thereport on single tooth restorations(Kohal et al. 2012), other authorsreported similar bone loss problemsusing the one-piece Nobel Directimplant design (Albrektsson et al.2007, €Ostman et al. 2007, Sennerbyet al. 2008, Zembic et al. 2012) whichis similar to the zirconia ceramicimplant design. However, severalinvestigations with comparableresearch designs with immediateloading of the Nobel Direct implants(Siepenkothen 2007, Finne et al.2012) as well as two-piece titaniumimplants (Proussaefs & Lozada 2004,€Ostman et al. 2008, Siddiqui et al.2008, Van de Velde et al. 2010, Cres-pi et al. 2012, De Bruyn et al. 2012)presented a marginal bone loss muchlower than in above mentioned inves-tigations and lower than in thepresent investigation on one-piecezirconia implants.

In the investigations reporting onincreased bone loss with the one-piece titanium implants, it was dis-cussed that one possible reason forthe bone loss could have been imme-diate loading (Albrektsson et al.2007). Since we did not use a controlgroup without immediate loading,we cannot support/reject thishypothesis. A further cause for theincreased bone loss might have beenentrapment of cement in the peri-implant sulcus. However, the crownmargins were placed only slightlyintra-crevicularly and utmost carewas given (retraction cords wereplaced during cementation) toremove all cement remnants. How-ever, the increased bone loss in ourinvestigation seems not to be relatedto a single variable but is to beassumed to result from a combina-tion effect of different variables.

Although, our investigation hasbeen a prospective case series, onemajor shortcoming is that it was notdesigned as a randomized controlledclinical trial. A control group featur-ing titanium implants that would

Table 3. Univariate analysis of marginal bone loss from implant insertion to the 1-yearfollow-up (three-unit fixed dental prosthesis)

Mean (SD)

Difference Correlation

95% CI p-value r p-value

Jaw typeMaxilla �2.87 (2.5) �3.4 to 1.3 0.27Mandible �1.83 (2.0)

Ant-postAnterior �2.82 (4.1) �10.8 to 9.0 0.90Posterior �1.93 (2.0)

PositionPosterior mandible �1.83 (2.0) �1.3 to 3.4 0.27Other positions �2.87 (2.5)

SmokingNo �1.98 (2.1) – – – –Yes –

Bruxism before treatmentNo �1.98 (2.1) – – – –Yes –

Bone quality1 �1.31 (1.5) �0.5 to 2.1 0.282–3 �2.13 (2.2)

Bone quantityA �1.31 (1.7) �0.37 0.08B �2.21 (2.2)C �2.52 (2.6)D �5.20 (1.0)

Bone level at placement �0.12 0.87PlatformRP �2.02 (2.0) �1.3 to 1.1 0.97WP �1.95 (2.2)

Implant length10 mm �1.62 (2.3) �0.07 0.4813 mm �2.48 (2.0)16 mm �1.13 (1.4)

Flap designNo flap �4.52 (1.5) 0.41 0.01Punch �4.13 (3.5)Flap �1.66 (1.8)

SiteImmediate �2.65 (1.2) �3.2 to 1.8 0.39Healed �1.94 (2.1)

Bone graftingNo �1.78 (2.2) �1.0 to 1.6 0.31Yes �2.11 (2.0)

Insertion torque� 45 �2.02 (2.2) �1.4 to 1.1 0.69>45 �1.90 (1.8)

SD, standard deviation; CI, confidence interval.



have been treated similarly to theutilized one-piece ceramic implants(immediate provisionalization,cementation of restoration) mightprovide information on whether theobserved problems were related tothe implant design or to the per-formed procedures. Future investiga-tions applying implants made ofhigh performance ceramics shouldinclude a control group and aim tospecifically evaluate the differentinfluencing parameters discussedelsewhere in the article.

Conclusions

The aim of the present cohort inves-tigation was to evaluate the 1-yearsurvival/success rates of a zirconiaimplant system prior to a potentialmarket launch, when used for thetreatment with a three-unit implantsupported FDP. The implant sur-vival rate of 98.2% after 1 year has

to be regarded as satisfactory and ascomparable to other implant investi-gations. However, the implantsshowed a high frequency ofincreased bone loss (� 2 mm) duringthe first year after implant place-ment. Therefore, the success rate wassignificantly lower than the survivalrate. We were not able to relate theincreased bone loss to a single (eval-uated) variable.

Ethical Approval

This clinical investigation has beenconducted in accordance with theethical principles of the WorldMedical Association Declaration ofHelsinki and according to the lawsof Germany. The clinical investiga-tion was undertaken after informingthe patient of the content, risk andbenefits of the study and after writ-ten consent of each participant wasobtained. The investigation has been

independently reviewed and app-roved by the Ethics Committee ofthe University Medical CenterFreiburg, Freiburg, Germany investi-gation number: 337/04.

References

Aboushelib, M., Salem, N., Abotaleb, A. & AbdEl Moniem, N. (2011) Influence of surfacenano-roughness on osseointegration of zirconiaimplants in rabbit femur heads using selectiveinfiltration etching technique. Journal ofOral Implantology. doi:10.1563/AAID-JOI-D-11-00075.

Albrektsson, T., Gottlow, J., Meirelles, L.,€Ostman, P. O., Rocci, A. & Sennerby, L.(2007) Survival of NobelDirect implants: ananalysis of 550 consecutively placed implants at18 different clinical centers. Clinical ImplantsDentistry and Related Research 9, 65–70.

Altman, D. G. (1999) Practical Statistics for medi-cal research, (p. 613). Boca Raton: Chapman &Hall/CRC Press.

Andreiotelli, M., Wenz, H. J. & Kohal, R. J.(2009) Are ceramic implants a viable alternativeto titanium implants? A systematic literaturereview. Clinical Oral Implants Research 20(Suppl 4), 32–47.

Becker, W., Wikesj€o, U. M., Sennerby, L., Qa-hash, M., Hujoel, P., Goldstein, M. & Turkyil-maz, I. (2006) Histologic evaluation ofimplants following flapless and flapped surgery:a study in canines. Journal of Periodontology77, 1717–1722.

Blaschke, C. & Volz, U. (2006) Soft and hard tis-sue response to zirconium dioxide implants - aclinical study in man. NeuroendocrinologyLetters 27, 69–72.

Borgonovo, A., Censi, R., Dolci, M., Vavassori,V., Bianchi, A. & Maiorana, C. (2011) Use ofendosseous one-piece yttrium-stabilized zirconiadental implants in premolar region: a two-yearclinical preliminary re-port. Minerva Stomato-logica 60, 229–241.

Borgonovo, A. E., Arnaboldi, O., Censi, R., Dol-ci, M. & Santoro, G. (2010) Edentulous jawsrehabilitation with yttrium-stabilized zirconiumdioxide implants: two years follow-up experi-ence. Minerva Stomatologica 59, 381–392.

Cannizzaro, G., Torchio, C., Felice, P., Leone,M. & Esposito, M. (2010) Immediate occlusalversus non-occlusal loading of single zirconiaimplants. A multicentre pragmatic randomisedclinical trial. European Journal of Oral Implan-tology 3, 111–120.

Chaushu, G., Chaushu, S., Tzohar, A. & Dayan,D. (2001) Immediate loading of single-toothimplants: immediate versus non-immediateimplantation. A clinical report. InternationalJournal of Oral and Maxillofacial Implants 16,267–272.

Cooper, L. F., Raes, F., Reside, G. J., Garriga,J. S., Tarrida, L. G., Wiltfang, J., Kern, M. &de Bruyn, H. (2010) Comparison of radio-graphic and clinical outcomes following imme-diate provisionalization of single-tooth dentalimplants placed in healed alveolar ridges andextraction sockets. International Journal ofOral and Maxillofacial Implants 25, 1222–1232.

Crespi, R., Cappare, P., Gherlone, E. & Rom-anos, G. (2012) Immediate provisionalizationof dental implants placed in fresh extractionsockets using a flapless technique. International

Table 4. Peri-implant soft tissue evaluation

Implants Ref. teeth Mann–Whitney

Probing depthProsthesis insertionMean (SD) 2.85 (0.73) 2.39 (0.62) p = 0.007n 27 27

1-year follow-upMean (SD) 2.65 (0.62) 1.97 (0.35) p = 0.000n 27 27

Significance testa p = 0.284 p = 0.002Clinical attachment levelProsthesis insertionMean (SD) 3.14 (0.75) 3.04 (1.07) p = 0.432n 27 27


Significance testa p = 0.584 p = 0.059BleedingProsthesis insertionMean (SD) 0.46 (0.55) 0.35 (0.44) p = 0.484n 27 27


Significance testb p = 0.078 p = 0.523PlaqueProsthesis insertionMean (SD) 0.51 (0.49) 0.51 (0.52) p = 0.669n 27 27


Significance testb p = 0.001 p = 0.023

aWilcoxon signed ranks test (two-tailed, a = 0.05).bSign test (two-tailed, a = 0.05).


560 Kohal et al.

Journal of Periodontics and Restorative Den-tistry 32, 29–37.

Cutrim, E. S., Peruzzo, D. C. & Benatti, B.(2011) Evaluation of soft tissues around singletooth implants in the anterior maxilla restoredwith cemented and screw-retained crowns.Journal of Oral Implantology. doi:10.1563/AAID-JOI-D-11-00125.

De Bruyn, H., Atashkadeh, M., Cosyn, J. & vande Velde, T. (2011) Clinical outcome and bonepreservation of single TiUnite implantsinstalled with flapless or flap surgery. ClinicalImplants Dentistry and Related Research 13,175–183.

De Bruyn, H., Raes, F., Cooper, L. F., Reside,G., Garriga, J. S., Tarrida, L. G., Wiltfang, J.& Kern, M. (2012) Three-years clinical out-come of immediate provisionalization of singleOsseospeed() implants in extraction sockets andhealed ridges. Clinical Oral Implants Research.doi:10.1111/j.1600-0501.2012.02449.x.

Depprich, R., Naujoks, C., Ommerborn, M., Sch-warz, F., K€ubler, N. & Handschel, J. (2012)Current findings regarding zirconia implants.Clinical Implants Dentistry and Related Research.doi:10.1111/j.1708-8208.2012.00454.x.

Ericsson, I. & Lindhe, J. (1993) Probing depth atimplants and teeth. An experimental study inthe dog. Journal of Clinical Periodontology 20,623–627.

Finne, K., Rompen, E. & Toljanic, J. (2007) Clin-ical evaluation of a prospective multicenterstudy on 1-piece implants. part 1: marginalbone level evaluation after 1 year of follow-up.International Journal of Oral and MaxillofacialImplants 22, 226–234.

Finne, K., Rompen, E. & Toljanic, J. (2012)Three-year prospective multicenter study evalu-ating marginal bone levels and soft tissuehealth around a one-piece implant system.International Journal of Oral and MaxillofacialImplants 27, 458–466.

Gahlert, M., Burtscher, D., Grunert, I., Kniha,H. & Steinhauser, E. (2012b) Failure analysisof fractured dental zirconia implants. ClinicalOral Implants Research 23, 287–293.

Gahlert, M., Roehling, S., Sprecher, C. M.,Kniha, H., Milz, S. & Bormann, K. (2012a) Invivo performance of zirconia and titaniumimplants: a histomorphometric study in minipig maxillae. Clinical Oral Implants Research23, 281–286.

Gahlert, M., Rohling, S., Wieland, M., Eichhorn,S., Kuchenhoff, H. & Kniha, H. (2010) A com-parison study of the osseointegration of zirconiaand titanium dental implants. A biomechanicalevaluation in the maxilla of pigs. ClinicalImplants Dentistry and Related Research 12,297–305.

Ganeles, J. & Wismeijer, D. (2004) Early andimmediately restored and loaded dentalimplants for single-tooth and partial-archapplications. International Journal of Oral andMaxillofacial Implants 19 (Suppl), 92–102.

Koch, F. P., Weng, D., Kramer, S., Biesterfeld, S.,Jahn-Eimermacher, A. & Wagner, W. (2010)Osseointegration of one-piece zirconia implantscompared with a titanium implant of identicaldesign: a histomorphometric study in the dog.Clinical Oral Implants Research 21, 350–356.

Kohal, R., Bernhart, J. & Sperlich, M. (2010)Clinical evaluation of an alumina-toughenedzirconia oral implant: 1-year follow-up. IADRGeneral Session, July 14-17, 2010, AbstractNo. 943. Barcelona, Spain.

Kohal, R. J., Knauf, M., Larsson, B., Sahlin, H.& Butz, F. (2012) One-piece zirconia oralimplants: 1 year results from a prospectivecohort study. 1. Single tooth replacement.Journal of Clinical Periodontology 39, 590–597.

Lambrich, M. & Iglhaut, G. (2008) Vergleich der€Uberlebensrate von Zirkondioxid- und Titan-implantaten. Zeitschrift f€ur Zahn€arztlicheImplantologie 24, 182–191.

Mellinghoff, J. (2006) Erste klinische Ergebnissezu dentalen Schraubenimplantaten aus Zirkon-oxid. Zeitschrift f€ur Zahn€arztliche Implantologie22, 288–293.

M€oller, B., Terheyden, H., Acil, Y., Purcz, N. M.,Hertrampf, K., Tabakov, A., Behrens, E. &Wiltfang, J. (2012) A comparison of biocom-patibility and osseointegration of ceramic andtitanium implants: an in vivo and in vitrostudy. International Journal of Oral and Maxil-lofacial Surgery 41, 638–645.

Mombelli, A., van Oosten, M. A., Schurch, E. Jr& Land, N. P. (1987) The microbiota associ-ated with successful or failing osseointegratedtitanium implants. Journal of Oral Microbiol-ogy and Immunology 2, 145–151.

Nissan, J., Romanos, G. E., Mardinger, O. &Chaushu, G. (2008) Immediate nonfunctionalloading of single-tooth implants in the anteriormaxilla following augmentation with freeze-dried cancellous block allograft: a case series.International Journal of Oral and MaxillofacialImplants 23, 709–716.

Oliva, J., Oliva, X. & Oliva, J. D. (2007) One-yearfollow-up of first consecutive 100 zirconiadental implants in humans: a comparison of 2different rough surfaces. International Journalof Oral and Maxillofacial Implants 22, 430–435.

Oliva, J., Oliva, X. & Oliva, J. D. (2010) Five-year success rate of 831 consecutively placedzirconia dental implants in humans: a compari-son of three different rough surfaces. Interna-tional Journal of Oral and MaxillofacialImplants 25, 336–344.

€Ostman, P. O., Hellman, M., Albrektsson, T. &Sennerby, L. (2007) Direct loading of NobelDirect and Nobel Perfect one-piece implants: a1-year prospective clinical and radiographicstudy. Clinical Implants Dentistry and RelatedResearch 18, 409–418.

€Ostman, P. O., Hellman, M. & Sennerby, L.(2008) Immediate occlusal loading of implantsin the partially edentate mandible: a prospec-tive 1 year radiographic and 4 year clinicalstudy. International Journal of Oral and Maxil-lofacial Implants 23, 315–322.

Payer, M., Arnetzl, V., Kirmeier, R., Koller, M.,Arnetzl, G. & Jakse, N. (2012) Immediate pro-visional restoration of single-piece zirconiaimplants: a prospective case series - results after24 months of clinical function. Clinical OralImplants Research. doi:10.1111/j.1600-0501.2012.02425.x.

Proussaefs, P. & Lozada, J. (2004) Immediateloading of hydroxyapatite-coated implants inthe maxillary premolar area: three-year resultsof a pilot study. Journal of Prosthetic Dentistry91, 228–233.

Romanos, G., Froum, S., Hery, C., Cho, S. C. &Tarnow, D. (2010) Survival rate of immediatelyvs delayed loaded implants: analysis of the cur-rent literature. Journal of Oral Implantology 36,315–324.

Schliephake, H., Hefti, T., Schlottig, F., Gedet, P.& Staedt, H. (2010) Mechanical anchorage andperi-implant bone formation of surface-modi-

fied zirconia in minipigs. Journal of ClinicalPeriodontology 37, 818–828.

Schou, S., Holmstrup, P., Stoltze, K., Hjorting-Hansen, E., Fiehn, N. E. & Skovgaard, L. T.(2002) Probing around implants and teeth withhealthy or inflamed peri-implant mucosa/gin-giva. A histologic comparison in cynomolgusmonkeys (Macaca fascicularis). Clinical OralImplants Research 13, 113–126.

Sennerby, L., Dasmah, A., Larsson, B. & Iverhed,M. (2005) Bone tissue responses to surface-modified zirconia implants: a histomorphomet-ric and removal torque study in the rabbit.Clinical Implants Dentistry and RelatedResearch 7 (Suppl 1), S13–20.

Sennerby, L., Rocci, A., Becker, W., Jonsson,L., Johansson, L. A. & Albrektsson, T.(2008) Short-term clinical results of NobelDirect implants: a retrospective multicentreanalysis. Clinical Oral Implants Research 19,219–226.

Siddiqui, A. A., O’Neal, R., Nummikoski,P., Pituch, D., Ochs, M., Huber, H., Chung,W., Phillips, K. & Wang, I. C. (2008) Immedi-ate loading of single-tooth restorations: one-yearprospective results. Journal of Oral Implantology34, 208–218.

Siepenkothen, T. (2007) Clinical performance andradiographic evaluation of a novel single-pieceimplant in a private practice over a mean ofseventeen months. Journal of Prosthetic Den-tistry 97, S69–78.

Silva, N. R. F. A., Sailer, I., Zhang, Y., Coelho,P. G., Guess, P. C., Zembic, A. & Kohal, R. J.(2010) Performance of zirconia for dentalhealthcare. Materials 3, 863–896.

Stadlinger, B., Hennig, M., Eckelt, U., Kuhlisch,E. & Mai, R. (2010) Comparison of zirconiaand titanium implants after a short healing per-iod. A pilot study in minipigs. InternationalJournal of Oral and Maxillofacial Surgery 39,585–592.

Van de Velde, T., Sennerby, L. & De Bruyn, H.(2010) The clinical and radiographic outcomeof implants placed in the posterior maxilla witha guided flapless approach and immediatelyrestored with a provisional rehabilitation: arandomized clinical trial. Clinical Oral ImplantsResearch 21, 1223–1233.

Wenz, H. J., Bartsch, J., Wolfart, S. & Kern, M.(2008) Osseointegration and clinical success ofzirconia dental implants: a systematic review.International Journal of Prosthodontics 21, 27–36.

Wolleb, K., Sailer, I., Thoma, A., Menghini, G.& Hammerle, C. H. (2012) Clinical andradiographic evaluation of patients receivingboth tooth- and implant-supported prosth-odontic treatment after 5 years of function.International Journal of Prosthodontics 25,252–259.

Zembic, A., Johannesen, L. H., Schou, S., Malo,P., Reichert, T., Farella, M. & H€ammerle, C.H. (2012) Immediately restored one-piece sin-gle-tooth implants with reduced diameter: one-year results of a multi-center study. ClinicalOral Implants Research 23, 49–54.

Address:Ralf KohalHugstetter Straße 5579106, FreiburgGermanyE-mail: [email protected]



Clinical Relevance

Scientific rationale for the study:Ceramic implants, generally fabri-cated of yttria-stabilized zirconiatetragonal polycrystal, are of cer-tain interest in oral implantologysince several companies havelaunched their systems on the mar-ket. Ceramic implants mightimprove esthetics, reduce plaqueaccumulation and they would bethe only implant treatment forpatients opposing metal devices intheir bodies. However, the safetyand efficacy should have been eval-uated in clinical investigationsbefore market introduction.Through conducting clinical inves-

tigations, the limits of such animplant system can be evaluated.This prospective case series studied aprototype zirconia implant system inpartially edentulous patients in needof a three-unit FDP.Principal findings: The survival rateof the zirconia implant system in thepresent investigation was acceptableafter 1 year and comparable to sur-vival rates of titanium oral implants.However, the mean bone loss of1.95 mm after one year exceeds thebone loss of two-piece titaniumimplants. Furthermore, the fre-quency of bone loss � 2 mm washigher compared to two-piece tita-nium implants. The success rate of

the zirconia implants after one yearwas 60% on patient level whenbone loss � 2 mm was regarded asthe acceptance limit and 72% onpatient level when bone loss� 3 mm was regarded as the accep-tance limit.Practical implications: Our investi-gation showed that the evaluatedzirconia implant seems to performinferior to titanium implants afterone year when applied for fixedpartial denture reconstructions andcannot be recommended for clinicalroutine due to the increased fre-quency of bone loss of more than2 mm.


562 Kohal et al.

zirconia implant may 2013

Documents