A Retrospective Evaluation of 259Single-Tooth Replacements by the

Use of Brânemark Implants Sven Scholander,

Purpose; The main purpose of this retrospective study was to investigate the clihicaloutcome of the treatment with 259 consecutively placed Brânemark system implant-supported single crowns. Materials and Methods: There were 259 implants placed ih 183patients with a mean age of 29.8 years; 230 {89%} were placed in the maxilla and 29(n7ol were placed in the mandible. Ofthe prosthetic restorations, 165 were all-ceramic(68%¡, 79 were metal-ceramic (31%), and 4 were gold-acrylic (1%). The observationperiod ranged from 1 to 9 years. Results: A total of 9 patients (10 implants) was lost tofollow-up. There were 3 implant failures registered, one before loading and one duringthe first year in function; one implant fractured after 6 years in service, giving acumulative success rate for implants of 98.3%. A total of 8 crowns was remade followingprosthetic complications; otherwise, the frequency of adverse events was low. The boneloss was of the same magnitude as in other studies on Brânemark implants as support forsingle crowns. In general, the soft tissue conditions around the restorations were healthyand comparable to those of the patients' natural teeth. Conclusion: This study confirmsthe favorable results presented in other studies on Brânemark implants to support single-tooth restorations. In! j Prosthodont 1999,12:483^91.

Missing one or more teeth, especially in the an-terior regions, may create emotional, esthetic,

and functional problems for the patient- Restoringdentitions in young individuals is generally performedby means of orthodontic treatment, autotransplanta-tion of teeth, or prosthetic rehabilitation.'

The prosthetic treatment options have includeddifferent forms of conventional removable partialdentures (RPD], fixed partial dentures (FPD), resin-

'Consuirant, Department of Pro'ithetic Dentistry, Public DentaiService SitSne. Kristianstad. Sweden,

Reprint requests: Or Sven Scholander, Orai Protetik, Tandvárd-¡huset, 291 33 Kristiamtad, Sweden. Fax: * 46 44 W 06 90. e-maii:sven.scholander@5kane.se

bonded fixed partial dentures (RBFPD), and implant-supported crowns. Failure rates of these variousrestorations have been compared in tbe literature.^"^

Published data concerning FPDs, and to some ex-tent RBFPDs, show divergent and in some respectscontradictory results. For example, in a follow-upstudy of artificial crowns and FPDs, Palmqvist andSwartz^ reported 37o loss over 18 to 23 years. In anearlier study, Schwartz et aP found 20% failures in3 years. In a meta-analysisof durability data on con-ventional FPDs, the calculated overall survival was74% after 15 years.^

It should be noted tbat there are no studies con-cerning FPDs specifically addressing single-tooth re-placements. Functional life spans have been calculated

Volumen, Number 6,1999 483 Internalionai lojrral of Prosthodontics

Retruipective évaluation of 159 Single-Toolh Ksplatemonls

Table 1 Distribution of Impianls by Age and Gender

Age g'OLip

16-20' 21-30 31-40 41 -50 :51

Males 26 57 6 20 13Females 27 75 13 9 13Total 53 132 19 29 26

•Only 2 implants were placed in patients < t8 y old.

Table 2 DistNbution ot Implants by Length and Jaw

MaxillaMandibleTotal

7

22

Implant length (mm)

ID

101121

13

648

72

15

1517

158

18

516

Total'

23029

259

•23 standard 3.7E-mm-d i a meter impiants; 3 standard 3 0-mm, 1 standard4.0-mm, 125 standard self-tapping; 4 conical sell-tapping, 98 MK il seit-tapping

by some authors. In the abovementjoned report bySchwartz et a l / mean life for 3- to 5-unÍt bridges wasestimated to be 12.3 years. Similar figures (9.6 years)for 3- to 4-unit bridges were reported by Walton et al."The most frequent causes of failure seem to be cariesand endodontic problems.

In a meta-analysis of clinical studies on RBFPDs,Creugers and van't' Hof̂ calculated a survival rate of74% after 4 years. In an analysis of the literature re-garding RBFPDs, Priest̂ found that most of the pros-theses ware single-tooth replacements and that dis-lodgment was the most frequent cause of failure;only a few biologic consequences were reported.Short-term surveys demonstrated acceptable successrates, but many studies indicated unexpectedly highfailure rates over extended observation periods. Thistrend was also found with traditionai FPDs.̂

Furthermore, it should be taken into considerationthat with increasing patient demands and cognizanceaboutdifferenttreatment alternatives, traditional FPDsand RPDs have become more and more unaccept-able. Resin-bonded fixed partial dentures are oftenseen as temporary measures, especially in growingpatients.^ Many longitudinal studies have shown pre-dictable iong-term function of endosseous osseoin-tegrated implants in the rehabilitation of edentulousand partially tidentulous patients.^ ^' Data concern-ing implant-supported single crowns have alsodemonstrated high success and survival rates and alow degree of prosthetic complications.'^"^''

The main purpose of this foliow-up study was to fur-ther investigate thp clinical outcome of the treatmentwith implant-supported single crowns on Brânemarksystem implants (Nobel Biocare], and to register the oc-currence and management of complications over time.

Materials and Methods

Thisstudy was initiated in 1989atthe Deparim'.-niofProsthetic Dentistry, Kristianstad, Sweden, '•"• col-laboration with the Department of Oi ' andMaxillofacial Surgery, Central Hospital, Kristiunstad,and the Department of Periodontology, Kristianstad.All patients were treated by specialists in oral surgery,periodontology, or prosthodontics.

The study includes all patients who were referredto the abovementioned centers during the period from1989 to 1996 and subsequently had implants placedfor single-crown restorations. In 1989, 15 implantswereplaced, 27 were placed in 1990, 33 were placedin 1991, 32 were placed in 1992, 45 were placed in1993, 30 were placed in both 1994 and 1996, and 47were placed in 1995, for a total of 259 implants.Dtjring this period, 22 referred patients were rejectedfor treatment, mostly because of anatomic limitations.The majority of these patients was provided witbRBFPDs and are not included in tbe study.

Before treatment, all patients were examined by aprosthodontist and subsequently by the oral surgeonwho later performed the surgery. The indications andprerequisites for implant therapy were carefully eval-uated and necessary complementary examinationsand pretreatments were carried out.

The material comprised 183 patients—87 femalesand 96 males with a mean age of 29.8 years (range16 to 71, median 24 y)—representing 259 implants(Table 1 ), Tooth agenesis (48%) and external trauma(38%) were the main reasonsfor missing or lost teeth.Other reasons were endodontic complications, peri-odontitis, and caries leading to extraction.

A total of 10 (47o) implants (9 in the maxilla, 1 inthe mandible) in 9 (5%) patients was lost to follow-up. There were 5 patients missing during the firstyear, J during the second, and finally, one patientwith 2 implants did not attend the 4-year control. Ofthese patients, 7 moved without disclosing their newaddresses and disappeared from tbe study; 2 patients,whose entire treatment had been paid for by the na-tional insurance system, did not attend the scheduledfoilow-up, as they would have had to pay for the ex-amination themselves. Thus, the percentage ofdropouts was equivalent to 4% of the implants placedand 5% of the treated patients.

Surgical and Prosthetic Procedures

All 259 implants placed were Brânemark implants.Distribution of implants by length and jaw is shownin Table 2. Most patients (n = 135) were provided withone implant, 36 with 2 implants, 12 with 3 implants,and 4 patients with 4 implants. In 12 cases bone

Tiie Intern a Nona i louriuii of Proslhodonlics 484 Volume 12, Number 6, 1999

Scholander Retrospective Evaluation ot 2S9 Smgle-Tooth Replacements

Fig l a Agenesis case. Healing abutment on MK II implant inregion ot maxillary rigtit lateral incisor 1 week atter stage 2surgery.

Fig 1 b Clinical appearance immediately atter cementation (4weeks atter second-stage surgery) ot a CeraOne single crown(Vitadur Alpha teldspathic porcelain. Vita).

grafting was performed 8 to 10 months before implantplacement.

A 2-stage surgical procedure was used to place allimplants, in accordance with the original protocoi de-scribed by Brânemark et al.̂ -'* An incision was madealong the palatal aspect ofthe ridge and extended intothe suicus of the adjacent teeth. If possible, verticalincisions were avoided in the "esthetic zone." Carewas taken not to damage the root surfaces and ce-mentum ofthe neighboring teeth. A full-thickness flapwas raised to sufficiently expose the alveolar bone.

Eighteen guided bone regeneration procedureswere performed during implant placement. Surgicalguide splints were fabricated in clear acrylic resinwhen judged necessary' at the initial examination, andwere used during first-stage surgery to optimize im-plant placement and, if possibie, ensure correct emer-gence profile.

The implants were uncovered after a healing periodof 3 to 4 months in the mandible and 6 to 9 monthsin the maxilla. Duringa period after connection ofthetitanium healing abutment (generally 4 to 5 weeks),the surrounding soft tissue was allowed to heal com-pletely. It was considered important to have a matureand completely healed periimplant mucosa before theprosthetic procedures started (Fig 1 ). The healing abut-ment was removed by the prosthodontist and replacedwith a permanent single-tooth abutment of appropri-ate length.^^'^^ Details ofthe type and length of abut-ments are presented in Table 3.

In the present material 208 (81 %) crowns were ce-mented on CeraOne abutments (Nobel Biocare). Ofthese crowns, 174 were all-ceramic and 34 weremetal-ceramic. Of all 258 restorations, 175 (68%)were all-ceramic, 79 (30.5%) were metal-ceramic,and the remaining 4 (1,5%) were gold-acrylic crowns.

Table 3 Type and Lengtti ot Abutment Cylinders

Abutment

Single DCA 035-089CeraOne

1

1899

Abutment length (mm^

2

2295

3

712

1

4

12

Total*

46208

'2 additional implants were provifled with standard 4.0-mm abutments.

Crown material and distribution by location in thedental arch are shown in Fig 2.

For cementation, zinc-phosphate cement (HarvardCement, Harvard Dental) was used in ali cases withthe ordinar>' type of single-tooth abutment (n = 48)and with 112 crowns on CeraOne abutments. A tem-porary cement (Freegenol, GC) was used in 73crowns, and a glass-ionomer cement (Ketac-Cem,FSPF) was used in 23. The remaining 2 crowns wereconnected to standard abutments by means of a goldscrew according to the protocol. One implant wasfound to be non integrated prior to loading during sec-ond-stage surgery; it was removed and was not pro-vided with an abutment or restoration.

Incases with adequate soft tissue and where implantplacement was assessed as optimal, the submucosalporcelain was designed to mimic the anatomy ofthenatural tooth, including the cementoenamei junction,to obtain a natural soft tissue contour and emergenceprofile. In the laboratory the master cast was madewith a soft tissue replica in polyvinyl siloxane to sim-ulate the periimplant mucosa (Fig 3).

All restorations were fabricated to the existing ¡awrelationships and with the occlusal contacts the nat-ural missing tooth should have had. The 45 crownsin the maxillary canine region were designed to avoidcanine rise during lateral movements.

Volume 12, Number 6, 1999 485 The Intemational Jou

RoHospective Evaluation of 259 Smgle-Tootb Replacements Scholander

45

40

35

5

"S 16

1E

35

30

20

15

5

46

n H115 14

(Féde ratio

145 44

n y 1Nil• I IIIIJJLJL13 12 11 2

Toot 11 n

n Dentaire Internationa

43 42 41 31Tooth

n-y n —

Maxillan = 229

JJ1 u II1 1 y •• 1 1 11 • 2S 23 24 25 26 U'-°"-='^'V

e tooth.numbering system)

Mandibler = 29

n= • I .

32 33 34 35 360,

Fig 2 Crown materiai and distri-bution of the different restorationsin the dental arches.

Fig 3a Completed restoration on master cast. Fig 3b Compieted restoration on master oast with soft tissuereplica in place.

Follow-up Procedures

The prosthetic treatment was performed by oneof 3 experienced prosthodontists. When crowns werefitted, hygienic instruction and clinical control wereperformed. All patients were examined 4 to 6 weeksafter crown placement, then routinely after 1 and 5years. Any examinations between 1 and 5 years weregenerally performed by the patient's own local den-tist, and only occasionally at the specialist clinic.

Clinical evaluation included implant stability andfunction, soft tissue appearance, and occlusal

contacts in centric occlusion and during lateral andprotrusive movements. Further, subjective com-plaints and all complications of surgical, prosthetic,or other nature were registered. The esthetics wassubjectively assessed by both the patients and theclinicians. When the crown design or the shade ofthe facing material differed remarkably from the ad-jacent teeth, this was adjusted; 8% (n = 21) of therestorations were in this way improved at the labo-ratory prior to cementation. Approximately 80 „ ofthe restorations were documented with clinical pho-tographs.

The irternationsi Irmmal of P.ostliücionlics 4 8 6 Volume 1Z, Number 6,1999

Retrospective Evaiuafiori ol 259 Single-Tooth Replacements

Table 4 Lifetatile Analysis of 259 Single-Tooth Implanfs

Time

No, ofsuccessfulimplanfs

No, ofsurvivingimplanfs

No, offailed

implants

No ofimplants

unaccountedfor

Cumulativesurvival rafe

(%)

Cumulafivesuccess rate

(%}

Insertion-loadingLoading-1 y1-2 y2-3 y3-4y4-5 y

6-7 y7-8 y8-9 y9y

2592582441661421131103214102

008

6462382257407

^::....ë:.:..:.:

1100001000

05

22265319423537

9

99,699.299,299.299,299.298,598,598,598,5

99,6 !99 299,299 299,299.298,398.398.3 .398,3

Radiographie Examination

Radiographie examination was performed at base-line (delivery of the restoration) and after 1 and 5years, but only occasionally at the controls betweenscheduled follow-ups. In 79 cases the radiographiebaseline examination was postponed until the controi4 to 6 weeks after cementation. To obtain orthoradialintraoral radiographs, all postoperative examinationsof the implants were taken with a paralleling tech-nique,-^ The radiographs were used to measure thedistance from a reference point on the implant to themost apical marginal bone level at the mesial and dis-tal surf̂ aces of each implant,^^ A magnifying scaleloupe (7X) graduated in 0,1-mm increments was usedand measurements were made to the nearest 0.1 mm.

Statistics

Descriptive statistics were used for the evaluation ofdata. Using the success criteria proposed byAlbrektsson et al,^" the lifetable method was appliedto calculate the cumulative success and survival rates,̂ '

Results

In all, 3 implant failures were registered. One implant(15-mm MKII, Nobel Biocare) in the maxillary right lat-eral incisor region was lost prior to loading. One im-plant (self-tapping, standard, 15-mm) in the maxillaryright central incisor region failed during the first yearin function. According to the surgical records, this im-plant had exposed buccal threads. In addition, one im-plant (standard, 13-mm) placed in the mandibularright premolar region fractured af the level of the thirdthread after 6 years in function. The remaining part ofthe fractured implant was still osseointegrated.

As mentioned earlier, 5 implants were lost to fol-low-up during the first year, 3 during the second, and

2 during fhe third year. Consequently, of 259 implantsplaced, 253 were stable and in function at the 1-yearexamination. Of these, 244 fulfilled the success cri-teria, representing a cumulative success rate of 99,27oafter 1 year of loading and 98,5% after 5 years of load-ing (Table 4),

Minor periimplant mucositis was seen, but in gen-eral, soft tissue conditions around the implant-sup-ported restorations were assessed to be healthy andcomparable to those of the patients' natural teeth(Fig 4), Initially, the esthetic outcome was judged asgood or very good both by the patients and the den-tal staff. This assessment endured at follow-up visits.Only une patient out of 183 left the office dissatisfiedwith the esthetic outcome because of a grayish cer-vical shine through. At the 5-year control, a buccalmucosa! recession that left the crown margin visiblewas observed. The patient accepted the situation butwas still not satisfied.

Complications

The nature and frequency of complications are pre-sented in Table 5, The most frequent complicationwas loose abutment screws, which occurred in 10(3,9%) ofthe restorations. Buccal fistulas appeared inassociation with 8 (3,1%) restorations.

Three months after stage one surgery, 2 implantsexhibited suppurative buccal abscesses in the re-gions corresponding to the apical part ofthe implantA combination of penicillin V and metronidazolewas prescribed and subsequently the apical parts ofthe implants were cut off and removed with the sur-rounding granulation tissue. Both implants osseoin-tegrated successfully. In one patient the apical part ofthe adjacent tooth (maxillary left lateral incisor] wasdamaged by the implant and endodontic treatmenthad to be performed, A total of 8 crowns was remadefollowing prosthetic complications.

Volume 12, Number 6, 1999 487 Tfie Interrational lournal of Proitfiodonties

Reirospeclive Evaluation of 2';')5iiii!Íe-Too!hReplacemems

Fig 4a Soft tissue appearance in maxiiiary ieft incisor regionbefore implant placement.

Fig 4b Sott tissue appearance at the 5-year ccntroi(CeraOne/Vitadur Alpha).

Table 5 Clinical Complications

Abutment type

Observedcompiications

Single-tooth DCA 085-089 CeraOne

Loose abutment screwsBuccai tistuiasCrown tractureRece mentation of crowntvlucosal recessionFractured porceiainOther

•Subséquent ta enternal trauma.

Table 6 Ctianges of Marginal Bone Level BetweenExaminations (mm)

ti/lesialDistai

Mean

0.130.18

0-1 y

SD

0.550.51

n

249349

Mean

0.010.03

1-5 y

SD

0.500.49

n

110110

Marginal 8one Changes

Changes of marginal bone level between examina-tions arc displayed in Table 6. Radiographs of all im-plants were obtained at the baseline examination, of249 implants at the 1 -year control, and of 110 im-plants at the 5-year control. During the first year infunction there was a mean marginal bone lossmesially of 0.12 mm and distaily of 0.18 mm. Themean additional bone loss for the recorded restora-tions during the period between 1 and 5 years was0.01 mm mesially and 0.08 mm distaily.

Discussion

The basic purposes of a dental prosthesis are to cre-ate and/or restore function and esthetics by replacingmissing teeth with no or minimal risks to adjacenthard and soft tissues. In this respect, numerous stud-ies on implant-supported single-tooth restorations, in-cluding the present one, have demonstrated highly fa-vorable results.'-"-^

It is reasonable to assume that the younger the pa-tient is when the prosthesis is inserted, the greater therisk offuture complications and need for new restora-tions. Taking this into consideration, it seems appro-priate to select a more biologically conservative treat-ment to preserve healthy tooth structure. An obviousadvantage with implant-supported restorations is thatthey completely preclude tooth preparation and sac-rifice of healthy tooth structure. In this respect, implant-supported restorations may present the most conserv-ative treatment alternative for single-tooth replacement

In the present study, as well as in other publishedreports on single-tooth implants, the success criteriaused have been extrapolated from those proposed foredentulous patients.^"'^^"" Thus, there is a need fordevelopment of specific success criteria concerningimplant-supported single-tooth restorations. As in allretrospective studies, the outcome is dependent onthe accuracy of patient records. Furthermore, aspointed out by Roos et a l , " the mode of collecting,analyzing, and presenting data varies considerably.Though this study was not designed as a prospectiveone, a common foliow-up form was filled out atbasel i ne and thereafter at the scheduled recal Is. In thatway, the collection and subsequent processing ofdata were simplified.

During the study period a total of 22 referred pa-tients (8%] was rejected for treatment, mostly because

The Internal i on a i lournai of Prosthodonlics 488 3, Number 6,1999

Scholander Retrospective Evalirfllion of 259 5ingle-Toorli Replacements

of anatomic limitations tbat would make it impossi-ble to place impiants without orthodontic or surgicalpretreatment. This is a lower percentage than thatpresented by Andersson et a l /^ although the main rea-son for rejection is tbe same.

After 5 years of loading there was a cumulative suc-cess rate of 98.5%. All of the 22 implants classifiedas survivals at the 5-year control were stable and infunction. At the time of" the 5-year recall, 3 patientswith 4 implants were not clinically examined; thesepatients were contacted by telephone and reportedthat their implants were functional and free fromsymptoms. Another 12 implants were not radiologi-cally examined, and radiographs of 3 implants wereunreadable. The remaining 3 implants did not fulfillthe success criteria, as there was a marginai bone lossof more tban 1 mm during tbe first year in function.Following the initial bone loss, almost no changeswere seen after 1 year in function.

The placement of the crown margin in the periim-plant suicus did not seem to cause any recession ofthe periimplant mucosa, and in general the soft tis-sues around the restorations were assessed to behealthy and comparable to tbose of the patients' nat-ural teeth. These observations regarding the soft tis-sue condition are in accordance with tbe findings inother studies on single-tooth implants."•^^•--

The buccolingual position of the implants wasjudged in each case. According to this assessment, 220implants were placed in an optimal position, ie, withinthe imaginary transversal dimension of the missingtooth, 28 were palatally oriented, and the remaining10 were inclined labiaily. Of tbe 28 more palatallyplaced implants, a ridge-lap crown form was requiredin 21 restorations. All of these patients were madeaware of the potential hygienic problem and were sup-pi ied with an appropriate hygiene protocol. At the fol-low-up controls, no detectable clinical or radiographiedifferences were observed between the groups of im-plants placed in different sagittal positions.

In the present material, the majority of the implant-supported restarations (74.5%, n = 193) was placedin the anterior part of the maxilla. There were 55 im-plants (27%) placed in the premolar regions and 5(2%) in tbe molar regions. In most of the previous stud-ies concerning single-tooth implants, the restorationswere mainly distributed in the same way.''''"'-^^''''-'The anterior part of the maxilla is a favorable area withlow load.^^ Tbis might be of importance for the out-come, since tactile sensitivity is reported to be ap-proximately 3 times less on implants than on teetb.^''It is possible that patients are less able to detect oc-clusal overload on impiants than on teeth. In view ofthis fact, one could speculate about the degree towhich tbis affects the failure rates.

In a retrospective report, Becker and Becker^^ pre-sented findings on 22 patients with 24 implants re-placing single molars. Patients with known bruxismwere not considered for treatment. The cumulativesuccess rate was of the same magnitude as that re-ported in studies with mainly anteriorly placed im-plant-supported single-tooth restorations. An inter-esting finding, however, is that the incidence of screwloosening was greater than in the abovementionedstudies.

Loosened abutment screws have previously been themost common problem for implant-supported singlecrowns with the Brânemark system.'•'""•-^ Since theintroduction of the CeraOne concept, the problemswith loose abutment screws have virtually disap-peared.̂ •''-"This fact is confirmed by the findings in thepresent study. In only 2 of the implants provided withCeraOne abutments did the gold screw become loose,and in both cases this was subsequent to externaltrauma. On the other hand, amongthe48 implants pro-vided with the older type of single-tooth abutment, theproblem occurred in 8 restorations, and in 2 of thesemorethanonce. As reported in other studies, the prob-lems were overcome after replacing the titanium screwwith a gold ailoy screw. It is noteworthy that the loos-ening of the abutment screws happened after therestorations had been in function for several years(mean 4.4, range 2.5 to 9 y). Only 10 of the restora-tions in this material were provided with access holesto the abutment screws. All of the other crowns werecemented onto the abutments intraorally. This mightbe part of the explanation for the relatively low fre-quency of loose titanium abutment screws.

Three all-ceramic crowns fractured during the fol-low-up period. It is possible that these complicationscould have been avoided if metal-ceramic crowns hadbeen chosen. The latter construction was used in theremade restorations. It is a wel l-known fact that the pri-mary weakness of dental ceramics is their low resis-tance to tensile stress.̂ ® When deciding upon mater-ial and crown design in situations where part of therestoration is subjected to high tensile stress, for ex-ample ridge-lap crown forms, the superior strength ofmetal-ceramics should be taken into account. Thisissue has been addressed in a recently published in vitrostudy, wherethreetypesofall-ceramic crowns, with ametal-ceramic control, were subjected to loading untiipart of them fractured.^^ It was concluded that all-ce-ramic crowns are weaker than conventional metal-ceramic crowns; however, based on estimated maxi-mum clinical loading, the all-ceramic crowns fittedwith a core seem lo function satisfactorily on implants.

It appears that many factors can influence bonelevel changes around single implants and adjacentteeth. Fsposito et aP^ found a strong correlation

Volume 12, Numtier 6, 1999 4 8 9 T¡ie Inleinationai lournai of Proslhodonlic

Reiroípective Evaluation oí 259 Single-Tooth Replacements

between the marginal bone loss and ihe I "•.on zonta I dis-tance between the implant and its adjacent tooth.They also found that the loss of bone at neighboringtooth surfaces duritig the interval between preopera-tive examination and crown placement exceeded theloss during subsequent years. In the present study themean marginal bone loss was small. It should be notedthat in 79 cases the radiographie examination at de-livery ofthe restoration was postponed until the rou-tine control 4 to 6 weeks after cementation. One couldspeculate about the extent to which this affects themeasured bone level values. After the first year, mar-ginal bone résorption around the implants remained atthe same level as that reported in studies over 5years.'''i8'20

This study corroborates the favorable results pre-sented in other studies on Brânemark implants tosupport single-tooth restorations. Only 3 (1.2%) im-plant failures—one of them before loading—and alow degree of complications were registered.However, these promising data must be followed upand confirmed by further long-term examinationsover extended observation periods.

Acknowledgments

The author would like to thank the colleagues wtiose cooperationmade this study possible; Drs Torgil iïundcrantz and TorstenAndoff, and Ms Eva Olsson, Department ot Prosthetic Dentistry,Kristianstad; Drs Rolt Nilvéus and Bengt Lewin, Department ofPeriodontology, Kristianstad; Dr Leif Lysell, Department ot Oral &Maxillotacial Surgery, Central Hospital, Kristianstad; and dentaltechnician Birger Fondell, Kristianstad. For valuable assistancewilh the statistics, the author would also like to thank Mrs CamillaBillström, Nobel Biocare, Göteborg,

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Literature Abstracts-

Astra Tech and Brânemark system implants: A prospective 5-year comparativestudy. Results after 1 year.

This study compared two Swedish implant systems (Astra Tech, Astra Tech; and Brânemartf,Nobei Biocare) in a prospective randomized study. Sixty-six patients were equaliy distributed be-tween the two systems; 184 Astra Tech and 187 BrSnemark implants were used in the edentj-lous jaws. Various clinioai and radiographie vanabies, as weii as the time needed tcr the surgioaiprocedures, were registered. This article reports the results after 1 year. The failure rate was0,5% lor tne Astra Tech implants and 4.3% for the Brànemark impiants. This difterence was sta-tisticaiiy significant if the calculations were based on ttie implant figures, but it was not significantwhen the calculations were based on individuals, since five of the eight iosses of Brânemarh im-plants occurred in one patient. The marginal bone loss did not differ between the systems used,but the résorption pattern was somewhat different. The vaiues for plaque accumulation andbleeding on probing did not differ between the systems. However, the time required for the surgi-cal procedures was ionger for the Brànemark implant in both the maxiiia and the mandible. Oneof the oonciusions was that abutment connection witb tbe Astra Tecti implants was simpler andrequired significantly iess time than did the corresponding surgery for the Brânemark impiants,

Âstrand P, Engquist B, Dahlgren S, EngquisI E, Feldmann H, Grondahi K, Ciin Impiant Dent Rei Res?ggg;1:l7_26. References: 13. Reprints: Dr Per Astrand, Department ot Oral and M an i i lof acial Surgery,University Hospital, SE-581B5 Linköping, Sweder>—SP

Condyle position as a predictor of temporomandibular joint internalderangetnent.

The purpose of this study was to examine tbe relationship between oondyle position and disk dis-placement {DD] to further anaiyze this controversial issue. Fifty-two asymptomatic subjects and130 patients with tempcromandibuiar joint (TMJ) pain undenwent iinear tcjmography and mag-netic resonance imaging {MRI] scans ot their TMJs, The resuits showed that symptcjmatic pa-tients with DD more often had distaily positioned condyles (^1% and 48%, respectively, for DDwith and without reduction) than did asymptomatic subjects {23%] or symptomatio joints thatwere normal according to MRI {25%), However, the variation was great and the position of thecondyie was a poor predictor of DD, Both sensitivity and specificity ol this test were low. The au-thors concluded that changing the position of the condyle based on tomography is not justified.

Bonvilla-Aragon H,Tallents RH, KaKberg RW, Kyrkanides S, Moss fflË, J Prosthet Dent1999-82 205-208, References: 26, RepriniB: Dr Ross H, Tallents, 1333 Lake Ave, Rochester, New York14613, Fax: + (716) 458-2610, e mail: rosst@trontiernet.net—>IW

Voliimel2,Number 6,1999 491 The International Journal of Prosthodontics