A 15-year study of osseointegrated implants in the ... · between vital bone and...

Int. J. Oral Surg, 1981: 10; 387-416

(Key words: edentulousness ..implants, endosseous; osseointegrattan "rehabilitation, oral)

Review article

A I5-year study of osseointegrated implantsin the treatment of the edentulous jaw

R. ADELL, U. LEKHOLM, B. ROCKLER AND P.-I. BRANEMARK

Department ofOralSurgery, Department ofOralRoentgenDiagnosis, LaboratoryofExperimental Biologyat theDepartment ofAnatomy, University ofGdteborg,and the Institute for AppliedBiotechnology, Giiteborg, Sweden

ABSTRACT - Osseointegration implies a film, direct and lasting connectionbetween vital bone and screw-shaped titanium implants of defined finish andgeometry -fixtures. Thus, there is no interposed tissue between fixture and bone.Osseo integration can only be achieved and maintained by a gentle surgicalinstallation technique, a long healing time and a proper stress distribution whenin function.

During a 15-year period (1965-1980), 2768 fixtures were installed in 410edentulous jaws of 371 consecutive patients. All patients were provided withfacultatively removable bridges and were examined at continuous yearlycontrols.

The surgical and prosthetic technique was developed and evaluated over a pilotperiod of5 years. The results of standardized procedures applied on a consecutiveclinical material with an observation time of 5-9 years were thought to properlyreflect the potential of the method.

In this group, 130jaws were provided with 895 fixtures, and of these 81% of themaxillary and 91% of the mandibular fixtures remained stable, supportingbridges. In 89% of the maxillary and 100% of the mandibular cases, the bridgeswere continuously stable. During healing and the first year after connection ofthe bridge, the mean value for marginal bone loss was 1.5mm, Thereafter only 0.1mm was lost annually.

The clinical results achieved with bridges on osseointegrated fixtures fulfill andexceed the demands set by the 1978 Harvard Conference on successful dentalimplantation procedures.

Edentulousness, inadequately compensated forby dentures, may not only imply impaired oralfunction and loss of alveolar bone but is alsooften accompanied by reduced self-confidence.

Efforts29,3049,14,59 have been made to provide

edentulous patients with fixed bridges, attachedto oral implants (for reviews see IZIKOWITZ29

,

ADELL et al:', NATIELLA et al:", BRA.NEMARK

et al.", SCHNITMAN & SCHULMAN59). A great

number of these methods assume the existenceof a connective tissue capsule which surroundsthe implant and isolates it from the adjacentbone'2,8,4o;66,21,44,54,23. The presence of such a

"pseudo-periodontium" has, however, resultedin inadequate long-term resistence of the periimplant tissues to mechanical, chemical andmicrobial trauma61,11,4,,19,32,65.

By installation of pure titanium implants of a

0300-9785/81/060387-30$02.50/0 © 1981 Munksgaard, Copenhagen

388 ADELL, LEKHOLM, ROCKLER AND BRANEMARK

"",,Fig.T, Mechanical components (fixture, abutment, attachment screws) made of pure titanium and constitutingthe anchorage unit for the bridge. (a) fixture, (b) cover screw, (c) abutment, (d) centre screw, (e) plastic cap, (f)surgical pack, (g, h, i) copings for model work, (k) gold cylinder, (I) gold screw.

OSSEOINTEGRATED IMPLANTS 389

defined finish and geometry - fixtures according to the osseotntegration procedurev-v,6, a firm, intimate and lasting connection can becreated between the implant and the vital hostbone, which remodels in accordance with themasticatory load applied (Fig. 1).

A 10-year follow-up study of bridges onosseointegrated fixtures" installed in a consecutive series of patients from the firstapplication of the procedure in a clinicalmaterial showed that continuous bridge stability could be achieved in 99% of lower and76% of upper jaws. After additional clinicalprocedures the long-term results were 100%bridge stability in lower and 94% in upper jaws.

The effects of bone anchored bridges on theentire masticatory system have been studied byHARALDSON & CARLSSON2 6 and HARALDSON25

•

They showed that the patients were restored to amasticatory function equal to or approachingthat of dentate persons with the same extensionof dentition. Moreover, the patients weresubjectively very satisfied with the functionalcapacity of their fixed bridges. Treatment withbone anchored bridges not only provided oralrehabilitation but was also reflected in rehabilitation of the patient from medical, social andpsychiatric points of view":".

The purpose of the present paper is to give asummarizing review of material, methods and

results from 15 years clinical use of osseointegrated fixtures in the treatment of theedentulous jaw.

Materials and methodsFrom July 1965to September 30th 1980a totalof2768 fixtures were installed in 191 upper and219 lower edentulous jaws of 371 patients. In405 of the 410 operated jaws, bridges wereattached to fixtures via mucosa-perforatingelements - abutments. In the remaining 5 jawsthe treatment was not completed due to death ofthe patient, or for psychiatric reasons.

In 34 of the patients, bone anchored bridgeswere placed in both jaws. The sexdistribution inthe total material was 38% male and 62%female. The mean age at installation of fixtureswas 53 years (s *=11) with a range of 20 to 77years. The entire material has been followedcontinuously at one-year intervals.

The evolution of the clinical procedures wasdivided into three time periods:I, Initialperiod(July 1965- March 1968), when

experimental knowledge'? was introduced tothe clinical situation.

2. Development period (April 1968-June 1971),during which certain modifications of the

* s == standard deviation of a single measurement.

Table 1. Total number of fixtures and %distribution of supplementary fixtures of the total number of fixtures

Upper jaw Lower jaw

Total Supplementary Total Supplementaryno. fixtures no. fixtures

Development group 232 22% 195 11%Routine group I 472 15% 423 9%Routine group II 277 12% 398 4%

Total 981 10161997

The observation time for the development group is 10-15 years, for the routine group I 5-9 years and for theroutine group II 1-4 years. These observation times are valid for all following tables which refer to these threeproject groups.


method were introduced, due to differencesbetween the experimental and the clinicalconditions.

3. Routine period (July 197I-September 1980),when only minor technical adjustments wereaccomplished.

In the following, only those cases with anobservation time exceeding one year will bereviewed. Results based on observation timeslessthan one year are regarded as uncertain andclinically insignificant. 24 upper jaws have beenexcluded and have been reviewed separately"since in these cases the resorption of the jawbone wasso severethat lasting integration couldnot be obtained in the remaining bone alone.Autologous bone grafts from the iliac crest orthe tibial metaphysis were used in combinationwith osseointegrated fixtures. Thus, of the totalmaterial, 1997 fixtures in 146 upper and 172lower jaws of 284 patients remain for long termevaluation and constitute the material of thispaper (Tables 1 and 2).

The reviewed material will be presented asfollows.

Development group, consisting of both theinitial and development periods together, withan observation time of 10-15 years.

Routine group I, consisting of the routineperiod with an observation time of 5-9 years.

Routine group II, consisting of the routineperiod with an observation time of 1-4 years.

The number of fixtures and jaws treated withjaw-bone anchored bridges in the various

observation periods are given in Tables 1 and 2.The following separate or combined indi

cations for treatment with bone anchoredbridges on osseointegrated fixtures have beenused.1. Insufficient retention of a denture, generally

due to extreme resorption of the alveolarprocess.

2. Mental inability to accept a denture in caseswith technically adequate or inadequatedenture retention.

3. Functional disturbances, e.g, severe nauseaand vomiting reflexes, caused by a denture.

A preoperative denture period of at least oneyear was required for a majority of the patientsin order to evaluate the rehabilitation effects oftreatment with optimally adjusted removabledentures and to provide sufficient time for bonehealing after tooth extraction. The meanpreoperative denture period for the materialwas 12 years (range from I month to 46 years).In 20jaws (II upper and 9 lower), i.e. 6% of thereviewed material, the time between extractionof teeth and installation of ajaw-bone anchoredbridge was less than I year. These patients,except for 4 cases, belonged to the developmentgroup.

In the opposite jaw, 38% of the patients hadtheir own teeth or bridges on natural teeth, 10%wore removable partial dentures and 52% fulldentures at the time of fixture installation.

The patients were preoperatively classifiedinto 3 groups according to the degree of alveolar

Table 2. Total number of jaws and %distribution of exchanged bridges

Upper jaw Lower jaw

Total ExchangedObservation periods no. bridges

Development group 33 61%Routine group I 64 20%Routine group II 49 6%

Total 146318

Total Exchangedno. bridges

32 71%66 9%74 4%

172


Fig. 2. Different steps at fixture installation in a lower jaw. Fixture sites, usually 6, are prepared in the anteriorpart of the edentulous mandible between the mental foramina (see also Fig. 4). Steps 3-7 are performed at about1500 rpm and 8-10 at 15 rpm. (1) incision, (2) reflection offlap, (3) explorative drilling, (4, 5, 6) gradual wideningof fixture site, (7) preparation of fixture site entrance, (8) threading of fixture site, (9) installation of fixture, (10)application of cover screw, (ll) suturing, (12) condition after healing. (a, b, c) show the anchorage anatomy atmoderate, advanced and extreme resorption.


bone resorption, see BRANEMARK et al.14.

Moderate resorption was found in 10%, ad-vanced resorption in 80% and extreme resorption in 10% of the total material.

7Fig. 3. Different steps at fixture installation in anupper jaw. Fixture sites are prepared in the premolar,canine and incisor regions, anterior to the recesses ofthe maxillary sinus (see also Fig. 4). (a, b, c) illustratethe anchorage anatomy in the incisor region atmoderate, advanced and extreme resorption. (1) and(2)gradual widening of the fixture site, (3) installationof fixture in the threaded site, (4) application of coverscrew, (5) suturing of mucoperiosteal flap, (6)condition after healing, (7) topography offixtures in acase of moderately resorbed jaw bone showing theposition of the fixtures in relation to the maxillarysinus and the nasal cavity.

OSSEOINTEGRATED . IMPLANTS 393

Treatment procedureA thorough clinical and radiographic examination ofthe patients was performed as described in an earlierreport':'. The patients were accepted for treatmentaccording to previously published guidelines" after ajoint decision by a team including members ofdifferent odontological and medical specialities,especially oral surgery, prosthodontics, oral roentgenographic diagnosis, psychiatry and ENT.

The surgical procedure was performed in two steps,fixture installation and abutment connection. Theprinciples for these operations have been presentedearlier".

The installation offixtures comprised the followingbasic steps (Figs. 2 and 3) performed under premedication and local anaesthesia. The buccalmucoperiosteum was incised horizontally at about half the heightof the residual alveolar process . A lingually orpalatally pedicled mucoperiosteal flap was raised bysharp dissection close to the bone surface . Thedissection was carried out laterally until the neurovascular bundles from the mental foramina or theosseous covering of the anterior parts of the maxillarysinuses could be identified. At the reflection of flapsdetachment ofperiosteum from the bone was kept at amin imum . The number and direction of the fixturesites were established by explorative drilling with aconventional round burr. This procedure also gaveinformation on the character of the cortical and thecancellous bone, respectively. Fibrous, nonmineralized remnants of former extraction alveoliwere sometimes found and were either removed oravoided as fixture sites.

6 fixture sites were generally prepared in the regionbetween the mental foramina or - in the upper jawbetween the anterior walls of the maxillary sinuses(Fig. 4). In order to keep a relative parallelismbetween the fixture sites, preparation was generallystarted close to the midline and the first fixture sitewas carefully oriented with regard to the residual bonevolume, the opposite jaw and the planned direction ofthe bridge teeth. A direction indicator was installedinto the first site and the remaining fixture sites wereprepared accordingly. Specially designed spiral drillsof successively increasing dimensions were used at aspeed of about 1500 r.p.m . The entrances of the siteswere finally adjusted by a special counter-sinkprocedure, which gave them proper topography withregard to fixtures , fixture holders, cove r screws andabutments. The most crucial parts of the preparationincluded careful threading of the fixture sites andinstallation of fixtures, both procedures performed ata rotational speed of 10-15 r.p.m, The fixtures werepartly self-tapping and had vert ical and horizontalcanals in their apical parts for bone ingrowth. Allbone preparations were carried out with a minimum

- - - - -- - ---'

b

Fig. 4. Fixture topography in 3 typical anatomicalsituations of alveolar bone resorption is shown injawswith moderate (a), advanced (b) and extreme (c)preoperative bone resorption.

of torque force and under profuse irrigation withsaline at room temperature. Finally, manual controland additional Lightening with a rachet wrench wasperformed and the fixtures were provided with smallcover screws.

The operation was finished with careful readaptionof the flap by means ofinterrupted polyamid mattress4/0 sutures attempting full periosteal covering of theentire anchorage region. Postoperatively, the patientswere asked to bite on gauze rolls for 1 h in order toprevent or reduce hematoma and oedema formation.Liquid and semi-solid food and saline mouth washeswere prescr ibed for the first postoperative week afterwhich the sutures were removed. V-penicillin wasgiven I h preoperatively and then regularly for thefirst 10 postoperative days. 2 weeks after the

394 ADELL. LEKHOLM. ROCKLER AND BRANEMARK

operation the denture was relined but no direc t fixtureloading was allowed for another 3-4 months in thelower and 5-6 months in the upper jaw.

After the healing period an abutment operation wasperformed. At this procedure the cover screws wererelocalized (Fig . 5) and exposed by small separateincisions on the top of the crest after which thecovering gingiva above each fixture was circularlyexcised by use of a punch .

The cover screws were removed and abutmentsattached La the fixtures. The length of the abutmentswas chosen with regard to the thickness of themucoperiosteum, i.e, the depth of the canals cut by thepunch. A clamp-like instrument was used to grip theouter cylinder in order to prevent the torque forcebeing transferred to the fixture site when tighteningthe central abutment screw to the fixture. Wheneverpossible the abutments were made to penetratethrough an attached part of the mucosa. When theresidual width of the attached mucosa was too narrowor when its localization was not compatible with thatof the fixtures , the abutment passages had to be placedin areolar mucosa. Finally the incisions were sutured

on both sides of the abutment and the surfaces of thecut gingival canals were pressed against the outerabutment cylinders. The operation field was coveredby a surgical pack for I week, retained by healing capsattached to the abutments.

The prosthetic treatment started about 2 weeksfollowing the abutment operation. Its details are givenin BRANI!MARK et al:",

The bridges (Figs . 6 and 7) resembled those used onteeth and were attached to the abutments via screws invertical canals through the occlusal or lingualsurfaces. The panties and the lingual sections weremade ofa gold framework while buccal, occlusal andincisal parts were made of an acrylic material. Aprecise fit between the gold framework and theabutments was the aim. The bridges were extended toinclude a maximum of 2 teeth distally to the mostposterior fixtures in the lower and only I tooth in theupper jaws. All bridges were facultatively removable.Great care was taken to design the bridges withsufficient periabutment spaces for oral hygienemeasures.

The ora/ hygtcne program comprised audiovisual

6

Fig. 5. Different steps at abutment installation. (I) identification ofposition of cover screw, (2) and (3) exposure of cover screw, (4)circular excision of gingiva above cover screw, (5) removal of coverscrew, (6) application of abutment, (7) abutment and fixture lockedtogether, (8) proximal suture, healing cap and surgical pack applied.

7 8


information, individual training and printed instructions, At every postoperative registration, the patientswere retrained if necessary, In principle the hygieneprogram resembled that routinely used inperiodontology.

Postoperative registrationsClinical examinations. Regular clinical examinations

were performed on all patients at 3-month intervalsduring the first year after completed prosthetictreatment, and thereafter at least annually. Themarginal periabutment tissues were examined regarding possible gingivitis. Occlusion, bridge stability andstress distribution were also checked.

17 consecutive patients from routine group II weresubjected to a more detailed investigation of the

Fig.6, Bridge design in a lower jaw with pontics and lingual surfaces made in gold and with facings and occlusalsurfaces in acrylic. The bridge is provided with pontics only distal to the abutments, The pontics have very smallconvex surfaces towards the gingiva. The manufacture of the gold framework with acrylic teeth is schematicallysummarized at 3 stages of production.


•..;;.) .•.•..~\,.r'e.•.\"~IM-... :}'.·.··.·.··'.' ".:'ii· ....'....

1"1. IJ;j.. "."" /.1 IIIFig. 7. Reconstruction of 2 cases of edentulous upper and lower jaws. The case to the left, with an observationtime of 12 years, was provided with bridges made of gold and porcelain. The yearly loss of anchoring boneamounts to 0.1 mm as revealed at roentgenological examination. The case to the right, with an observation timeof 3 years, received bridges consisting of a gold framework and acrylic teeth (ef Fig. 6). The bridges are alsoshown in the articulator. The yearly loss of anchoring bone amounts to 0.1 mm in this case. The radiogramsshow the situation after 12 and 3 years, respectively.


Fig. 8. Diagrammatic illustration of the principle formeasuring marginal bone height in radiograms usingthe fixture as dimensional reference.

an absolute serial identity. The results of measurements ofmarginal bone height changes in roentgenograms, taken according to the free hand technique,have been published separately'v-". Only thoseroentgenograms which had good contrast and clearlydefinable fixture threadings and bone margins wereused. In the present study these roentgenograms werere-examined. Thus, the selected roentgenogramsfulfilled the requirements of the standardized roentgenographic method described", with the exceptionthat stereo-pairs were not regularly available.

marginal tissue. These registrations comprised scoring of plaque and gingival indices, defined as the %number of periabutment quadrants affected.Registration of clinical pocket depth in the samequadrants and of proximal marginal bone heightvariations were also performed. Altogether 101fixtures from 7 upper and 10 lower jaws wereexamined in the manner described. These will bereferred to as sample A below (Table 3).

Roentgenological examination. No roentgenogramswere taken during the initial healing period':' to avoidpossible negative effects of diagnostic X-rays on thedifferentiation of healing bone tissue. Radiographicexaminations were first performed 1 week after theabutment operation and 6 and 12 months postoperatively. Each fixture was then examined at least onceduring the following l2-month period. Characteristics of the peri-fixtural bone as well as the conditionand mutual fitting of the mechanical componentswere always considered. For the different time periodsand treatment groups the fixtures were analyzed withregard to marginal bone height changes. When 2 ormore registrations were performed per year, the meanvalue of the marginal bone levels was calculated. Lossof marginal bone was measured and related to fixedreference points on each fixture, medially and distallyclose to the fixture surface (Fig. 8).

During the initial and developmental phases of theproject, roentgenograms were taken with a free handtechnique aiming at reproducing the fixtures withsharp threadings in the roentgenograms, but without

....oo~o

....oo~

Table 3. Composition and purpose of samples A, Band C

Fixtures Bridges (jaws)

Sample

Upperjawno.

Lowerjawno.

Upperjawno.

Lowerjawno. Purpose

AI yearTotal

BDevelopment groupRoutine group IRoutine group IITotal

C1-10 yearsTotal

42 59101

53 2755 3945 85

304

326

7 10 Analysis of marginal17 soft tissue reactions

7 58 7 Analysis of complications7 12

46

Analysis of marginalbone loss


A standardized method" for serial identical roentgen examination with a strictly parallel technique wasdeveloped during the routine part of the project. Allroentgenograms taken accordingly were used formeasurements of changes in marginal bone heights.The marginal bone levels were defined after stereoscopic examinations.

Consequently the material included 2 parts. Onepart (development group and early parts of routinegroup I) was based both on re-examined roentgenograms ofthe former method and later roentgenogramsof the same fixtures according to the latter method.The other part (late parts of routine group I androutine group II) included all fixtures, where marginalbone height changes were followed by the standardized serial identical method.

Processing of data". All findings from the clinicaland roentgenological registrations constituted thebasis for a general computerized follow-up system.Dates of insertion as well as individual fixture,abutment and bridge characteristics were included forall components together with information concerningthe opposite jaw.

Comments on methodsIndications for treatment, preoperative examinations, surgical and prosthetic procedureshave in all essentials been in agreement with theoutlines given by BRANEMARK et al;": It should,however, be stressed that preoperative jaw boneanatomy had no decisive influence on patientselection. The patients rather represented a verywide variety of jaw bone topography rangingfrom a moderate degree of resorption to acompletely resorbed alveolar process.

The difficulties in recalling patients, residingall over the country, at strict intervals for such along period as that covered by the present paperare obvious. Despite these obstacles it waspossible to recall every patient for annualexamination, only a few yearly controls beingmissed due to illness of the patients.

Cases could appear where osseointegration ofsingle fixtures was not achieved or was later lost.Due to the advantage ofusing separate fixtures,

supplementary installations could be performedwhen required to maintain bridge stability. Thepatient continued to wear a stable functioningbridge, while the supplementary fixture wasbeing integrated. After connection of theabutment, the bridge had to be adjustedaccordingly or a new bridge manufactured.

To enable evaluation of marginal bone heightchanges, the roentgenograms should meet thetechnical demands delineated above, thepatients should return at regular intervals andthe clinical data should be properly documented. Parts of the material did not meet all thesecriteria and could therefore not be completelyanalyzed. Registrations ofmarginal bone levelswere performed at varying intervals until theintroduction of the standardized roentgenographic method in the development group andthe early stages of routine group I.

The roentgenographic examination ofpatients with osseointegrated fixtures entaileddistinct advantages compared with that of thedentate patient. The presence of built-inmeasuring elements - the titanium fixtures - ofknown length and topography and with sharpthreadings provided dimensional references formeasurement of the marginal bone height.

The necessity of an inter-disciplinary approach between the medical and odontologicalspecialities involved has been clearly demonstrated during the continuing clinical development of the osseointegration method.

ResultsAnchorage functionThe anchorage function depends on both

ANCHORAGE FUNCTIONI

Fig. 9. Principle combination of factors determininganchorage function.

• The handling of numerical data of our computerized registration system by instruction nurseBarbro Svensson and senior system programmerMatz Engstrom is gratefully acknowledged.

ISTRESS

DISTRIBUTION

ISOFT TISSUE

BARRIER


Table 5. Number and % distribution of jaws withcontinuously stable bridges

jaws and for routine group II, 6% and 4%,respectively (Table 2).

Osseointegration. Clinically stable fixtureswere enclosed by a trabecular bone of normalappearance and were in intimate contact withthe surrounding bone (Fig. 10) as evaluated atroentgenographic examination. Bone remodelling around the fixtures became - within thelimits of the method used - radiographicallyvisible (Figs. 1Od-e) in about 10% of the fixturesites after an observation time of 2-3 years, asan increasing perifixtural radiopacity.

Osseointegrated fixtures were almost impossible to remove, i.e, their osseous attachment could not be broken. This was particularlyevident in 3 cases where the fixtures had lostmore than 2/3 of their marginal bone height.Attempts at extracting the fixtures with appli-

Upper jaw Lower jaw

persisting osseointegration and main tained marginal bone height (Fig. 9).

The anchorage function, defined as the ratiobetween the number of stable, osseointegratedfixtures supporting a bridge, in relation to thetotal number of installed fixtures is given for thethree observation periods in Table 4. For theroutine groups, the anchorage function was 8188% for maxillary and 91-97% for mandibularfixtures. The majority of fixture losses occurredwithin the first 3 years after fixture installation,and particularly during the first postoperativeyear (Table 4). The patients enjoyed continuously stable bridges (bridge stability) during thesame time intervals in 89-96% of the upper andin 100% of the lower jaws (Table 5).

The number of jaws where supplementaryinstallation of fixtures was required in order tomaintain continuous bridge function is presented in Tables 6 and 7. There is a drasticreduction in the requirement for these procedures between the development and theroutine groups. Exchange of bridges for thisreason has been performed in 61% of the upperand 71% of the lower jaws in the developmentgroup. The corresponding figures for routinegroup I were, 20% for upper and 9% for lower

Development groupRoutine group IRoutine group II

26 79%57 89%47 96%

32 100%66 100%74 100%

Table 4. Number and %distribution of persisting fixtures

Upper jaw

Entire Afterperiod I year


111 48%383 81%243 88%

61%84%

Lower jaw

After Entire After After3 years period I year 3 years

53% 123 63% 79% 74%82% 385 91% 91% 91%

388 97%

Table 6. Number and %distribution of reoperated upper jaws; one or several fixtures were installed at eachoperation


One operation

11 33%10 16%3 6%

Two operations

4 12%2 3%

Three or severaloperations

5 15%I 2%


cation ofa maximum ofmanual torque force viaan extraction forceps demolished the fixtures

but they could not be fractured out of their bonesites.

a b c

d eFig, 10. Roentgenographic analysis of long-term bone reaction at osseointegrated fixtures in completelyedentulous jaws. (a) Maxillary fixtures after 6 years of bridge function. Note the close relation of the obliquefixture to the anterior wall of the maxillary sinus. (b); (c) Two maxillary fixtures after 5 (b) and 7 (c) years,respectively, of bridge function. A radiopaque zone can be seen to develop around the fixtures indicating bonetissue remodelling. (d) Two lower jaw fixtures after 7 years of bridge load. (e) Mandibular fixture after 15yearsof bridge load showing increased density of anchoring remodelled bone. (I) The roentgenologic technique usedenables identification of non-osseointegrated fixtures. The mandibular fixture indicated by * is surrounded by athin sheath of connective tissue as visualized by a radiolucency. The other fixture in this radiogram remainsosseointcgratcd.

Fig. /2. Clinical status of marginal soft tissues at bridges on osseointcgrated fixtures in edentulous jaws: (a)upper jaw after 10 years (original bridge construction - acrylic teeth on chrome-cobalt framework); (b) lowerjaw after 10years (original type of bridge) ; (c) lower jaw after 3years (present bridge type- gold framework andacrylic teeth) showing healthy, attachcd periabutment mucosa; (d) is a detail of the abutment area of the lowerjaw shown in (e); (e) lower jaw after 3 years (present type of bridge) with healthy movable periabutment mucosa;(f) is a detail of the abutment area of the lower jaw shown in (e); (g), (h), (i) detail of the mucosa at the distal leftabutment in the lower jaw shown in (e), (I) with bridge attached (g), after removal of bridge (h), after removal ofabutment to visualize the condition of the deep mucosa (i).

9

OSSEOINTEGRATED IMPLANTS

c

e

401


Table 7. Number and ~{; distribution of reoperated lower jaws; one or several fixtures were installed at eachoperation

One operation Two operationsThree or several

operations


12 38%2 3%3 4%

9 28%4 6%

2 6%

s=standard deviation, N=number of observations.

Table 9. Mean annual marginal bone loss (in mm)during follow-up periods

periods, i.e. from fixture installation to the endof the first year after bridge connection andamounted to a mean of 1.2 mm for all groups.The mean yearly decrease in the follow-upperiod, i.e. after the first year had passed, was0.1 mm (s=OA) for upper and 0.1 mm (s=O.8)for lower jaws in the development group. The

0.1 0.1(s=O.4 N=179) (s=0.8 N=184)0.1 0.1(s=0.6 N=1145) (s=0.5 N=963)0.1 0.1(s=0.6 N=69) (s=0.6 N=130)

Lower jawUpper jaw

DevelopmentgroupRoutinegroup IRoutinegroup II

Connective tissue anchored fixtures, i.e.where osseo integration had not been originallyaccomplished or had later failed, were clinicallymore or less mobile and easy to remove either bymere extraction or by a torque movement. Suchfixture sites were lined by a thin, generallythreaded soft tissue, which could be removedfrom the bone walls like a cyst capsule. In theroentgenograms it appeared as a thin perifixtural radiolucency (Fig. 10f).

Marginal bone height. The marginal boneheight depends on both proper marginal stressdistribution (ef Introduction) and on adequatefunction of the marginal soft tissue (cf Fig. 9).

The results of the roentgenological examination of the changes in marginal bone heightare presented in Tables 8 and 9 and illustrated inFigs. 10 and l1. Bone loss occurred predominantly during the healing and remodelling

Table 8. Mean marginal bone loss (in mm) during the healing period (from fixture installation to abutmentconnection) and during the the remodelling period (first year after abutment connection)

Upper jaw Lower jawhealing remodelling healing remodelling

Development group 1.2 0.1 0.7 0.1(s==O.9 N=207) (s=0.8 N=43) (s=0.9 N= 147) (s=O.4 N=58)

Routine group I 1.3 0.2 1.0 0.4(s=l.l N=358) (s=0.9 N = 153) (s=I.O N=211) (s=0.6 N=86)

Routine group 1I 0.7 0.6 0.3 0.8(s=l.O N=431) (s=0.8 N=227) (s=0.5 N= 1006) (s=O.8 N=358)

s =standard deviation, N= number of observations.

When interpreting these figures it should be emphasized that there is a great variation in the duration of thehealing time for the development group and the lirst period of routine group 1.As a consequence the remodellingperiod also differs between the various groups, not in duration but with respect to its time relation to fixtureinstallation.

OSSEOINTEG RATED 1M PLANTS 403

corresponding figures for routine group I were0.1 mm (s=0.6) and 0.1 mm (s=0.5) and forroutine group II 0.1 mm (s=0.6) and 0.1 mm(s = 0.6), respectively (Table 9). The figuresgiven include cases with fractured fixtures.

Marginal soft tissues. The marginal periabutment tissues were generally found to beclinically healthy (Fig. 12), even when theperiabutment mucosa was movable, provided

adequate oral hygiene was maintained. Thegingival index for the entire material at the latestobservation time - defined as the % ofperiabutment quadrants with gingivitis - was6.7% (s= 19.5). Cases with gingivitis generallyresponded well to improved oral hygieneprocedures.

The thickness of the mucoperiosteum thatcovered the fixtures at the abutment operations

-70 -75 -80

-72 -74 -76 -80

-72 -74 -76 -78 -80

Fig. 1J. Sequential roentgenograms of osseointegrated fixtures in edentulous jaws illustrating the behaviour ofthe marginal bone as an indicator of anchorage function. (A) Mandibular fixture at first registration and after 5and 10years, respectively. (B) Mandibular fixture followed for 8 years. (C) Maxillary fixture observed with 2year intervals for 8 years.


initially determined the clinical depth of theperiabutment pockets, as defined by probing.During the remodelling period there was asuccessive adaptation of the mucoperiosteumwhich became thinner and more finn.

In sample A (Table 3) the mean plaque andgingival indices were 13.7% (s=21.5) and 7.6%(s= 10.8), respectively , 1 year after abutmentconnection. The mean clinical pocket depth was2.6 mm (s= 0.9) at the same time.

Adjacent structuresThere have been no cases with persistingparesthesia or anaesthesia in adjacent nerves.When osseointegrated fixtures were in contactwith the maxillary sinus or the nasal cavity,there were no adverse symptoms. Allergicreactions did not occur in the mucosa aroundthe abutments.

ComplicationsA sample of304 fixtures in22 upper and 24 lower jawsfrom 16 males and 27 females selected at random andrepresentatively reflecting the composition of theentire material was analyzed regarding the frequencyof complications. This is called sample Bbelow (Table3).

Loss ofanchorage function. Fixture anchorage waslost basically because of 3 different types of tissuereactions.

Osseointegration might not have been achieved dueto surgical trauma or because of perforation throughthe covering mucoperiosteum during healing.Osseo integration could also be lost at an early stage asa result of repeated overloading with microfractures ofthe perifixtural bone. Finally, the fixtures could belost because of progressive marginal bone losssubsequent to persisting gingivitis, successively depriving the fixture of its osseous support. Loss offixtures in sample B during the healing and bridgeloaded periods is reviewed in Table 10. The healing

period is defined as the time from fixture installa tio nto abutment operation. Generally, mobile fixturesduring this period were not identified until abutmentconnection. For the routine periods no majordifferences in the number of lost fixtures could beobserved between healing and bridge loaded periods.The gradual refinement of the surgical method isreflected in the successively increasing number offixtures which became osseointegrated (Table 10).The pro gressively better results may be related toimproved fixture topography in relation to theresidual jaw bone , to refined care of the naps and thehost bone at fixture installation, at suturing andduring the healing period and to longer healingperiods .

When fixtures were lost, their replacement had tobe considered. Provided a sufficient number ofosscointegrated fixtures remained, i.e. generally 4,having strategic positions with regard to the loaddistribution, additional installation of fixtures wasnot necessary. If the remaining fixtures were notsufficient in numbers or in adequate positions toprovide bridge support, supplementary fixtures wereinstalled as a rule during the second year. Thetreatment included the following steps. The mobilefixture was extracted and the thin encapsulatingsheath of non-mineralized connective tissue wasthoroughly removed from the walls of the fixture site.A muco-periosteal flap was mobilized to ensure atight cover of the entrance to the site. After 9-12months, new bone had formed with just a smalldimple in the marginal bone as a remnant of theprevious fixture site, and the same region could againbe used for fixture installation". Meanwhile thepatient could usually wear the original bridge,sometimes after reduction of the load applied to theremaining fixtures, e.g. by shortening of the bridgeextension. With proper care this kind ofcomplicationdid not create any significant bone loss.

If a sufficient amount of bone for supplementaryfixture installation was not present, grafting of boneas described by BRANEMARK et al:"' and by BREINE &BRANEMARKI 2 was the treatment of choice.

Finally , extreme cases appeared-upper jaws onlywhere return to a removable denture was the only

Table 10.Number and %distribution of mobile fixtures during healing and bridge loaded periods in sample B

Healing periodUpper jaw Lower jaw

Bridge loaded periodUpper jaw Lower jaw

Development groupRoutine group IRoutine group 11

13 25%II 20%2 4%

3 11%6 15%2 2%

4 8%9 16%

8 30%5 13%1 1%

OSSEOINTEGRATED 1MPLANTS 405

realistic alternative. A definite return to a denture wasnecessary for 9 jaws (2.8%) of the entire material. In 4of these upper jaws there was extreme resorption andthe patients refused grafting of bone or were hesistantabout such a procedure. 2 patients did not want to bereoperated after some of their fixtures had fracturedbecause of inadequate bridge alignement to theabutments and subsequent undue stress concentration. 1 patient was not reoperated for psychiatricreasons, another patient was too old for reoperationto be considered and one patient died soon afterhaving lost his upper bridge. In 4 of the 9 jawsdescribed, the bridges had been stable for 2-6 yearsbefore failure.

Gingival complications. Three types of gingivalcomplication occurred, namely early perforation,proliferative gingivitis and fistulae .

Early perforation of the covering mucoperiosteumduring healing was often caused by decubital ulcersbeneath the denture. Its frequency is indicated by anoccurrence of 4.6% in sample B (Table 3). Activesurgical measures were instituted with excision ofbordering gingiva and full flap coverage of theperforation site.

When the marginal gingiva covered or closelyapproached the abutment-bridge junction this createdunfavourable conditions for local tissue hygiene . As aresult proliferative gingivitis occurred in 6.7% of thefixtures reported in sample B (Table 3). This requiredlonger abutments, gingivectomy or flap proceduresafter adequate plaque control had been established.Apically repositioned flap operations and vestibularplasties were used to correct cases with inadequatewidth of attached gingiva and marginal muscle pull onthe periabutment gingiva.

Fistulae penetrated the mucosa at about the level ofthe abutment-fixture connection in 1.5% of fixturesconnected to abutments in sample B (Table 3).Fistulae especially occurred in those cases where thegingiva covered the abutment-bridge junction. Atdisconnection of the actual abutment in these cases,bacterial plaque were regularly found extending fromthe abutment-bridge junction along the centralabutment screw. Adequate treatment consisted ofsurgical excision ofthe fistulous tract together with allgranulation tissue circularly encapsulating the regionof the abutment-fixture connection. The abutmentswere cleaned and sterilized and sealing agents wereapplied between the abutments and the bridge .Finally, the patients' hygiene efforts were particularlydirected towards this area. Presently, the abutmentsare permanently sealed with an inert elastic materialplaced between the central screw and the outercylindrical component.

Mechanical complications. In the total material of1997 fixtures, 69 fixtures (3.5%: 54 maxillary and 15

mandibular) in 37 jaws (25 upper and 12 lower jaws)fractured at different levels. These fractures occurred1-6 years after fixture installation, most of them after5 years, only occasional fractures occurring after 7years. In 26 of these jaws (70.3%), the fixtures hadbeen connected to an intermediate type of bridgeresembling that conventionally made on teeth insevere cases of periodontitis. The pontics and thelingual as well as the occlusal surfaces were made asheavy, rigid gold constructions with acrylic facings.Earlier a nd later in the project a less bulky bridgeconstruction but with an optimal fit was used. Thisresulted in a subsequent marked decrease in thenumber of fractures.

Fixture fractures were often associated withaccelerated marg inal bone loss (Fig. 13). In a sampleof 326 fixtures with various observation times calledsample C (Table 3), 8% were found to have a marginalbone loss ofabout 3 mm a year. At re-examination ofthese fixtures, mechanical complications like screw,fixture and even bridge fractures, resulting ininadvertent stress concentrations, could always bedemonstrated. In 5% of sample C there was a boneloss per year of 1mrn, probably caused by a period ofstress concentration or long lasting gingivitis. In 87%,the yearly marginal bone loss was 0.1 mm,

Small tooth movement, due to periodontal remodelling, can compensate for slight incongruenciesbetween a gold bridge and prepared teeth after thebridge has been connected. The same poss ibilities,however, did not exist when the bulky gold bridgeswere tightly screwed to fixture abutments, whichcould not move at all. Ifabsolute mutual congruencybetween bridge and abutments was not obtained,stress concentrations were induced in the fixtures.This was considered to be the most likely cause of thefrequent fixture fractures that occurred in conjunction with these bridges. The risk appeared to beaccentua ted when the flxtures could be subjected tosudden sharp loads carried through the bridge in caseswith porcelain or gold occlusal surfaces in theopposite jaw. Intense efforts have been taken toincrease the precision in the fi tting between the bridgeand the abutments.

Other mechanical complications were fractures ofbridges, of bridge locking screws or of abutmentscrews . These complications occurred in 4.9% , 1.5%and 3.0%, respectively in sample B(Table 3) and couldbe due to underdimensioning of mechanical COmponents and/or inadequate stress distribution.

Discussiona verall rehabilitation effects

When examining edentulous patients who

406 ADELL. LEKHOLM, ROCKLER AND BRAN EM ARK


applied as candidates for treatment with fixedbridges on osseointegrated fixtures a great dealof hidden suffering was revealed, which wasearlier inaccessable to therapeutic measures dueto the lack of documented clinical alternativesto conventional removable dentures. Manyedentulous patients thus preoperatively complained of gastrointestinal disturbances, reduced masticatory function, lack of selfconfidence and as a consequence, often had torefrain from studies, professional work andsocial relationshipsv".

The potentials of a rehabilitation methodshould be evaluated with regard not only to thecompensation achieved for the local tissuedefect but also to its influence on the totalsituation of the patient. In this respect theeffects of the treatment were in many cases quiteobvious'? as the patients normalized their socialrelations and enjoyed a considerably improvedself-confidence. Furthermore, after oral rehabilitation, previous intentions for studies oroccupation could be persued.

Anchorage functionIn routine group I (5-9 years) persisting fixtureanchorage of 81%for upper and 91%for lowerjaws was obtained (Table 4). The results fromroutine group II (1-4 years) indicate that evenbetter results can be expected in the future.

The anchorage function is an overall representation of results obtained with regard to

fixture integration. It represents the quotientbetween the number of osseointegrated bridgesupporting fixtures and the total number oforiginally installed implants, no attention beingpaid to the cause of the fixture loss.

For the patient, bridge stability and functionis of greater interest for his total rehabilitationthan the fate of individual fixtures, although thelatter control the long-term prognosis.Continuous bridge stability was achieved in 8996% of the upper and 100%of the lower jaws forthe routine groups (1-9 years, Table 5). In someof the cases, 1 or 2 fixtures were lost andreplaced by new ones after bone had re-formedin the fixture sites.

The above-mentioned fixture and bridge"survival ratios" both reflect the somewhatbetter results obtained in lower jaws. Upperjaws generally had less total volume of boneavailable for anchorage due to vertical resorption which was often accentuated in cases wherea residual anterior frontal dentition was presentin the opposite jaw. Insufficient bone quantitycould also be related to anteriorly expandedmaxillary sinuses, to wide nasal cavities or tosmall bucco-palatal dimensions of the residualalveolar process, which often appeared to be asthin as cardboard, although the height of theresidual bone could be considerable. The lack ofsufficient width of bone for fixture installationin upper jaws was often not revealed bypreoperative routine roentgen examinations.

%100

90

80

70

60

50

40

'a20

10

.... ....... NON FRACTURED fIXTURE

3m 9m 9 YQ;lrs10

Fig. 13.Typical behaviourof anchoringboneclosetofractured fixtures. In this case onefixture- the mostdistal fixture on the right side- remained intact andthe 5 other fixtures fractured due to inadequatealignment of thebridge.Whentheabutment togetherwith the fixture fragment could move relative to thestill bone-anchored part of the fixture, the mucoperiosteum showed inflammatory reactions. Therewasconcomitant and progressiveloss of bone.When,however, repair had been performed with an adequately aligned bridge, the yearly loss of anchoringbonethenreturnedto normallevels - as shownin thediagram - and the gingiva was healthy. * indicatestime of fracture.


The inadequate bone anatomy of the upper jawsoften required a time-consuming surgical exploration to locate sufficient amount of bone. Ifthis procedure was not successful the use ofpreformed or immediate bone auto grafts asdescribed by ADELL1, BRANEMARK et al?",BREINE & BRANEMARK11 and LINDSTROM et al.39

had to be considered. Moreover, maxillary bonedensity was generally less than that of the lowerjaw. The problem was not only to achieveosseointegration of fixtures in the maxilla, butalso to maintain it in the long run. Apparentlythe stress distribution was a more critical factorin the upper than in the lower jaw" because ofdiscrepancies in bone biomechanics. This wasshown to be especially true if the occludingsurfaces were made ofporcelain or gold. Acrylicocclusal surfaces appeared to act as some kindof shock absorber or were successively grounddown by the patient, thereby compensating forpossibly remaining minor occlusal irregularities. For the same reasons, the upper jaw wasalso more sensitive to any discrepancies in theadaptation ofthe bridge to the abutments. Withthis background, it was not surprising that inthose cases where a definite (2.8% of the totalnumber of jaws) return to removable dentureswas necessary, all cases were upper jaws.

Our clinical experience indicates that treatment of the edentulous upper jaw often requiresmore technical skill than the lower jaw. Thelong-term clinical results achieved for evenseverely resorbed upper jaws indicate that thefunctional prognosis for the upper jaw is almostas good as for the lower jaw. These casessometimes had remaining bone which did notallow anchorage for more than 4 fixtures andrequired careful surgical handling of the tissue,proper design and alignment of the bridge andcareful successive adjustment of the occlusion.The special requirements on technique andresources in the treatment of upper jaws should,however, be considered when indications fortreatment are evaluated. Patients who wereedentulous in both the upper and the lower jawoften complained of predominant problems

from the lower jaw. For the above reasonstreatment with bone anchored bridges incompletely edentulous cases always started inthe lower jaw. The patients often expressed theirsatisfaction with wearing a denture in the upperand a fixed bridge in the lower jaw and nofurther treatment was required.

The results of the development group withregard to persisting fixture anchorage in bothjaws (Table 4) and continuous bridge stability inupper jaws (Table 5) reflect the more heterogenous therapeutic approaches used during thisproject period. Although the same basic principles of treatment were applied, too short ahealing time for obtaining osseointegration inresidual bone with varying biomechanicalcharacteristics, was sometimes allowed in thisgroup.

OsseointegrationWhat evidence do we have for the existence ofpermanent integration of titanium fixtures injaw bone?1. In experimental studies in dogs' it was not

possible by useoforthodontic applicances tomove fixtures by variation of either thedirection or the magnitude of the loadapplied.

2. In the clinical material, fixtures whichroentgenographically appeared osseointegrated, could not be extracted or even rotated.This was also true for cases with just a fewfixture threadings remaining in bone, when aconsiderable loss of marginal bone heighthad occurred. On the other hand, fixtureswhich were surrounded by a perifixturalradiolucency were easy to remove.

3. Clinically stable fixtures in the roentgenograms were surrounded by normal trabecularbone in intimate contact with the fixturesurface. Mobile fixtures, on the other hand,lacked this contact as they were surroundedby a thin perifixtural radiolucency.

4. In several cases a perifixtural radiopacitydeveloped around integrated fixtures, indicating a successive load-related bone


remodelling. This gradual corticalizationalso occurred within primarily cancellousbone and even within autologous bonegrafts",

5. Histologic sections of fixture sites!4." forclinically stable fixtures have shown remodelled bone with osteocyte-filled lacunaein close approximation to the fixture surfaces. No non-mineralized connective tissuehas been shown interposed between thefixtures and the bone sites. Such a sheath oftissue was regularly present - clinically andhistologically - if the fixtures had shown anyevidence of clinical mobility. This is in fullaccordance with earlier experimental findings'", The possibility even exists of a directbonding between the fixture surface and theenveloping bone".

6. 10 osseointegrated and bridge-supportingfixtures were removed together with thesurrounding tissues for scanning and transmission electron microscopic analyses". 9fixtures were removed from maxillary sitesand 1 from a mandibular site. In I of thepatients 6 upper jaw fixtures were removedfor psychiatric reasons; the remaining fixtures wereremoved because offractures. Theobservation times were 30 to 90 months.Until removed for the above reasons, thesefixtures were included in the reviewedmaterial.

Cell processes from both bone andmarrow cells were strongly adherent to thetitanium surfaces and could be seen glued tothe titanium oxide surface of the fixtures byan amorphous ground substance layer ofproteoglycans of a few hundred A thickness.There was an intimate topographic relationship between the fixtures and the bonewithout any interposed non-mineralizedconnective tissue. No signs ofcorrosion werenoticed as only calcium was found on thefixture surfaces, with no titanium on theinvesting bone at ion probe analysis".

7. At one osseointegrated fixture of the abovematerial, ALBREKTSSON et al:" were success-

ful in cutting (and producing transmissionelectron miscroscope sections) through theimplant and the investing bone withoutdisrupting the mutual connection. An intactbone-implant interface without interveningconnective tissue was revealed at analysis.

The long term stability and capacity of thefixtures to carry occlusal load and stress fromvarious directions through the years even underunfavourable mechanical circumstances appearto be a result of the fact that the fixtures wereosseointegrated. So far, no corresponding longterm consecutive clinical results have beenpublished for endosseous implants in completely edentulous jaws.

Marginal bone heightMarginal bone was lost both during the healingperiod when the fixtures were covered bymucoperiosteum, and later, after abutmentconnection. During the healing period, morebone was lost in upper than in lower jaws, whilethe reverse was true for the remodelling period,i.e, the first year after abutment connection(Table 8). This might berelated to differencesinremodelling capacity and rates between maxillary and mandibular bone. Because of the richvascular supply and the cancellous character ofthe maxillary bone much of the necessaryremodelling after fixture installation couldoccur during the healing period, while theslower reacting compact mandibular bonedemanded an extended period of time for thesame purpose. The decreasing values of marginal bone loss during the healing period (Table8) for the 3 project periods isprobably explainedby successive refinement of the surgical technique. The higher values for bone loss in theremodelling period (Table8)might beexplainedby the higher torque forces applied at installation of fixtures" in the routine groups.

The total marginal bone loss from thebeginning ofthe healing period to the end of theremodelling period was, however, almost equalin all the 3 groups and was about 1.2 mm.During the follow-up periods, i.e. the observ-


ation time after the first year with the fixturesbridge-loaded, the mean annual bone loss was0.1 mm in the routine groups (Table 9). Thus, itappears that - with regard to marginal boneheight - a reliable long-term prognosis can beestimated after 1 year.

The marginal bone loss could be attributed toseveral factors:1. Effects of surgical trauma such as detach

ment ofthe marginal periosteum, removal ofmarginal bone and bone damage at drilling.

2. Inadvertent stress distribution to the marginal bone by forced tightening of thefixtures at installation" or by later inadequate loading. This could be related to anumber of factors.a. Trauma from occlusion and/or from

unfavourable relations between thejaws, even with a properly designedbridge.

b. Defective bridge design concerning adaptation to abutments, occlusal adjustment, extension, etc.".

3. Physiological resorption of the edentulousjaw.

4. Gingivitis which, if untreated and allowed toprogress down to the periosteum, may in thelong run cause bone resorption.

The annual decrease in marginal bone heightfor the follow-up periods is comparable with oreven less than the loss of attachment level ormarginal bone height at teeth reported forpatients after treatment for severe periodontitiswith the same postoperative control intervals,6-12 months3

1,62,53 and control groups inNYMAN et al."; ROSLING et aU6

, ROSLING etaJ.57, AXELSSON & LINDHE7 • In some of theinvestigations referred t05OO5 6 the controlpatients lost about 1nun of periodontal supportper year. Provided that the periabutment andperifixtural tissues react in the same way as theperiodontium to the presence of microbialplaque, even better results than hitherto obtained might be expected with more frequenthygiene controls for patients with bone anchored bridges (test groups in LINDHE &

NYMAN3S, NYMAN et al?", ROSLING et aU 6 ,

ROSLING et aU7, AXELSSON & LINDHE7) . This

would require a different organization of ourcontrol system, e.g. referring patients with boneanchored bridges at regular intervals to localhygienists or to regional clinical centres. Itshould also be observed that the present figuresfor marginal bone height decrease includedthose cases where fixtures had fractured. Suchfractures often caused a severe loss of bone.After adequate treatment, however, even thesefixtures remained integrated with favourableprognosis.

The amount ofmarginal bone loss was also ingood agreement with the yearly loss of boneheight reported for edentulous jaws in patientswith removable dentures" .••,63,2o. The loss ofbone in such cases may be due to lack ofmechanical stimuli, transferred to the jaw bone.In this context it is of interest to note that as timeprogresses the marginal bone level can remainat a more coronal levelclose to the fixtures thanfurther away. This could be interpreted asthough the fixtures exerted a stimulatinginfluence on the remodelling perifixtural bone.The same view is supported by model studies"and by histologic findings from experimentalseries" showing a horizontal architecture ofperifixtural bone trabeculae emanating from thetip of the fixture threadings. It is also supportedby roentgenographic examinations of fixturesshowing increasing perifixtural radiopacitythrough the years.

When interpreting postoperative variationsin marginal bone heights at fixtures, it isimportant to keep in mind the varying preoperative topography ofthe marginal bone. In agreat number of cases the residual alveolar crestwas extremely thin in the bucca-lingual direction, a condition which had no apparentrelation to the clinical width or height of thegingival crest and which was not always fullyrevealed by the roentgenographic examination.In order to provide complete osseous coverageof the fixture it was in such cases necessary toresect some marginal alveolar bone locally until


a sufficient bucco-lingual width was reachedwith regard to the fixture diameter (Fig. 11).Moreover, it was necessary to provide space forthe fixture holder - also representing abutmentdimensions - at installation of the fixtures. Themarginal defects which were thus createdsurgically may, especially after remodelling,erroneously be diagnosed as vertical bonedestruction due to their geometric similaritywith such defects at teeth with periodontitis.

Marginal soft tissuesThe marginal periabutment tissues shouldconstitute a functional barrier between the oralenviromnent and the host bone by sealing offthe osseous fixture site from noxious agents,and thermal and mechanical trauma. Theultimate function of the soft tissue barrier isreflected in the long term changes of themarginal bone height.

It might be tempting to apply periodontalinvestigative methods to study the condition ofthe tissues surrounding fixtures and abutments.Until the possible relevance of these methodshas been proved for a situation which is verydifferent from that of the tooth, these methodscan, however, not be reliably used for revealingthe status of the tissues surrounding osseointegrated implants.

If granulation tissue occurred at the junctionof abutment and fixture it was a commonoccurrence that the inflammatory exudate didnot pass between abutment and mucoperiosteum into the gingival pocket, but was insteaddrained via a fistula penetrating the buccalmucosa. This indicates that there may be a bondbetween the gingival pocket lining and theabutment surface. A connection of this kinddoes not appear inconceivable in the healthystate since relationships closely resemblingnormal epithelium-enamel junctions have beenfound between gingiva and various restorativematerials", The same also holds true forimplant abutments according to JAMES &KELLN35

, JAMES & SCHULTZ36 and SCHLEGEL etal:", Finally, it should be noted that a

junctional epithelium, which is necessary for anormal epithelial attachment to tooth surfaces,can be regenerated from oral epithelium",

The concept of a direct attachment betweengingiva and abutment was strongly supportedby ALBREKTSSON et al.6 where electronmicroscope analysis of abutments removedfrom patients showed epithelial cells of normalsize and shape, glued to the titanium oxidesurface by a thin layer of proteoglycans. Noinflammatory cells were found in this region.These findings are in full accordance with thehistologic observations of BRNEMARK et al,",

It is important to maintain adequate oralhygiene in caseswith bridgeson osseointegratedfixtures. As a majority of the patients in ourmaterial resided far from the clinic, the numberof oral hygienecheck-ups after the first year waslimited to I or 2 visits a year. The patients were,however, highly motivated for plaque control asthey had earlier experiences of edentulousness,often caused by periodontitis. At a recentcontrol of our entire material, plaque at theabutment-gingival junction was found to causegingivitis in 6.7% of the periabutment quadrants. There appeared to be less plaque formation, however, on abutments than on dentalsurfaces in corresponding positions. This maybe explained by differences in surface characteristics between teeth and titanium".

At the 101 fixtures and abutments examinedone year after bridge connection, sample A,(Table 3) the mean values for gingivitis andplaque %indices were 7.6and 13.7,respectively.This is regarded as a satisfactory result considering the 6-month intervals between the oralhygiene re-instructions in this group.

Plaque may not be the only cause of gingivitisat abutments and fixtures. Even if the movablemucosa around the abutments was generallyclinically healthy, cases were seen where themucosa had apparently been traumatized by themost marginal fixture threadings after somebone resorption had occurred. The passage ofabutments should therefore be preferably located in attached gingiva. If sufficient width of

412 ADELL, LEKHOLM , ROCKLER AND BRANEMARK

3m Sm 1

60

••••••••••••••__•••• AODlTlONAl FIXTURES

1~1ili:0W~E~R;..JA_W BRJDGES

.............................. III ............... AODITrONAl FIXTUR ES

'o:"::-....II&I.::.••::.:.:.:.=.:••:.:.::•.::;••:.:.~•.:.-.:.:.:.:.:::••::.::••• IFI )I;TURE$.BONEHEIGHT

3m lim 1

50

40

90 - lilt.....

80

70

80

50

40

30

20

10

30

20

10

MethodThe principle prerequisites for osseointegration- as described by BRANEMARK et al." and byALBREKTSSON et al." - are the implant material,its design and finish, the condition of theinvesting bone , a delicate surgical technique and

Fig. 14. Diagrammatic representation of clinicalresults obtainedin a consecutive series of edentulouscases, treated with osseointegrated bridges andfoll owed for 10years with yearly controls. The %ofintegrated fixtures, stable bridges and behaviour ofanchoring bone - as evaluated by roentgenologicassessrnent ofmarginal boneheight- isshown, as wellas the number of additional fixtures installed.

attention to those cases which had an observation time exceeding 5 years . It is reasonable toexpect that the results of the development groupshould be less favourable than those of theroutine periods . Therefore, the results ofroutine group I with 895 fixtures in 130 jaws(Tables 1and 2), are regarded as those presentlymost correctly reflecting the po tentials of theosseointegration method (Fig. 14).

% UPPER JAW

1_~~====90-1 IDoes

MaterialA majority of the patients had a long period ofedentulousness compensated with dentures.Generally their alveolar processes were resorbed to an advanced degree. They had longtried to adapt themselves to function withremovable dentures but with poor results.Besides,no realistic therapeutic alternatives hadbeen available to them, so far . In many cases acomplex psycho-social insufficiency situationhad developed which was revealed during thetreatment.

It should be emphasized that this review isbased on a consecutive material of completelyedentulous jaws represent ing a great number ofextremes with regard both to age variations anddifferences in jaw bone anatomy and quality.

For 65 jaws the observation time exceeded 10years (Development group, Table 2) and for afurther 130jaws the observation time was morethan 5 years (Routine group I, Table 2). Forbridges on teeth, a maximum function time of10years is regarded as a very good result and a15-year bridge function is regarded excellent".17. The 5-year limit is a common reference timefor comparison of results ofdifferent treatmentmethods in the medical and odontologicalliterature (ef IZIKOWITZJ O

) . It was also specifically used and recommended by the 1978Harvard Conference", assessing and evaluatingvarious oral implantation procedures. It thusappears fair to evaluate the results with special

such a tissue was not available, gingivovestibular plasties were performed with encouraging results. The surgical procedures werefacilitated by the possibility of retaining asurgical pack under the fixed bridge .

The mean pocket depth for sample A (Table3) was 2.6 mm, a value which at teeth wouldhave indicated a healthy situation. This sampleof fixtures and abutments is continously beingfollowed. After a further 2-year period, biopsiesof the marginal soft tissues at these abutmentswill be taken in order to elucidate the truenature of the gingivo-abutment junction.


a sufficiently long healing period before exposing the implant to the load of a bridge.

Choice of implant material, design and finish.Titanium was chosen as implant material as ithad favourable mechanical properties in relation to bone'". In theory, a potential capacitywas also regarded to exist for the formation of achemical bond between the firmly adherenttitanium oxide layer and the tissues. Titaniummay in fact be regarded as a ceramic rather thana metal" because of this stable oxide layer.Furthermore, titanium has been reported tohave a low toxicity and to be most resistant tocorrosive forces in the body environment (forreview see ALBREKTSSON et al.6

) .

The screw design provides superior mechanical stability and great initial resistance toshear forces in comparison with other surfaceenlarging designs, as e.g, in those incorporatingporosity of the implant surface. A microgrooved surface has empirically been found topromote osseointegration14.

Surgical treatment. An important feature ofthe osseointegration method is the emphasis puton efforts to minimize any damage to the hosttissues, by e.g. contaminants, thermal orsurgical trauma. The surgical method is notcomplicated but requires a great deal ofprecision and care - the limits for acceptabletissue handling being much narrower than ingeneral oral surgery. Any divergence from theprinciple ofleast possible trauma at installationof the fixtures increases the risk for loss ofosseointegration and subsequent occurrence ofa thin perifixtural zone ofconnective scar tissue.This especially applies to the effects of thermaltrauma as studied by LUNDsKoa41.

Bone cutting in relation to bone trauma hasrecently been thoroughly reviewed byLINDSTROM et al:", the recommendations givenbelow being emphasized. Any drilling in bonetissue should be performed under constant andprofuse irrigation'4.4,.2s,,1. All cutting instruments should be well sharpened51.52.4s, t • .4, and

should be designed to allow for the cooling fluidto pass to the very bottom of the site under

preparation, thus also removing cut material.The drill pressure and the drill speed shouldboth be kept low64,3J,, ' .

If preparation of bone tissue is carefullyhandled in the manner described, a highpercentage of osteogenic cells can survive andremain active, even after transplantation (forreviewsee ALBREKTSSON et al:", ALBREKTSSON4,

BREINE & BRANEMARK").The potentially osteogenic periosteal cells

should be preserved byminimal surgical traumato the mucoperiosteal flap (BRANEMARK &BREINEt2

, MELCHER & ACCURSI46, ADELLJ) and

the bone surface should not be deprived of itsperiosteal vessels if avoidable!".

Prosthetic treatment. "Atraumatic" surgerymust be followed by "atraumatic" prosthodontics, i.e. a prosthodontic treatment where fullattention during all phases is paid to properstress distribution. Otherwise, an initially established osseointegration may later be lost dueto undue local stress concentrations", Thisespecially applies to 4 situations - relining ofthe denture after fixture installation in order toavoid decubital ulcers, designingfree extensionsof the bridge, adaptation and fitting of thebridge to the abutments, and finally, adjustmentofthe occlusion to the opposingjaw. If the latter3 factors are not given due attention, fracturesof the mechanical components: bridge, screws,abutments or fixtures, or microfractures of thebone anchoring the fixtures willsooner or lateroccur.

In severely resorbed cases, there were ofteninverted relations in the sagittal plane betweenthe residual upper and lower alveolar processesin the frontal region. The bridges had tocompensate for both the loss of teeth and for thesevere resorption of the alveolar bone in thevertical and horizontal directions. This calledfor a special design of upper jaw bridges!" withincreased cantilever effects onto the fixtureswhich, as stated above, were often situated inbone of reduced mechanical strength. Thedesign of upper jaw bridges not infrequentlyentailed some initial difficulties in giving the


patients pleasing esthetics and adequate phonation. The bone anchored bridges so far useddid not include a prosthetic substitute tocompensate for resorption of the alveolarprocess in the horizontal plane.

Summary and conclusion1. Osseointegration impl ies a direct and in

timate incorporation in vital bone ofthreaded titanium fixtures of defined finishand geometry.

2. Osseointegration can be achieved if'fixturesare inserted with a delicate surgical technique and are allowed to heal without loadfor periods of not less than 3-4 months inlower and 5--6 months in upper jaws.

3. In upper jaws 81 %of the originally installedfixtures remained stable and supportedbridges after 5-9 years. Continuous bridgestability was achieved in 89% of these jaws.

4. In lower jaws 91%of the original fixtureswere stable and bridge supporting after 5-9years. Continuous bridge stability wasattained in 100% of these jaw s.

5. The mean bone loss was 1.5 mm during thehealing period and the first year afterabutment connection. Thereafter only 0.1mm of marginal bone was lost annually inthe group observed for 5-9 years.

6. In the routine case the fixtures and theirabutments are surrounded by hard and softtissues which have remained healthy forfollow-up periods of up to 15 years, thusfar.

7. The small number of fixture losses and thelow values of the mean annual marginalbone loss in the follow-up periods indicatethat a reliable prognosis can be made in theind ividual case after the first year haspassed.

The results also point to the greatconfidence with which the patients can relyupon the anchorage of their bridges.

8. The fixture-supported bridges have beenshown esthetically, phonetically and func-

tionally to restore the masticatory system ofedentulous patients for , so far , 15 ye ars.

9. The method, in all respects, fulfills and evenexceeds the demands by the 1978 HarvardConfe rence" on a successful dental implantation procedure.

10. Treatment with bridges on osseointegratedfixtures implies not only an oral rehabil itation but also a considerable positive

impact on the psycho-social situation of thepatient, earlier suffering from edentulousness, inadequa tely compensated bydentures.

References1. ADELL, R.: Regeneration of the periodontium .

An experimental study in dogs. Scand. J. Plast ,R eCOilS/I' . Surg , 1974: 8: Suppl , II.

2. ADELL, R. & BRANEMARK, P.-I. : Unpublisheddata , 1970.

3. ADELL, R., HANSSON, B. 0 ., BRANEMARK, P .-I. &BREINE, U.: lntraosseous anchorage of dentalprostheses. II. Review of clinical appro aches .Scand. J. Plast . ReCOilS//, . Surg , 1970: 4: 19-34.

4. ALBREKTSSON, T. : Healing of bone grafts. 111 vivostudies of tissue reactions at autografting ofbonein the rabbit tibia. Thesis. Faculty of Medicine .University of Goteborg, Goteborg, 1979.

5. ALBREKTSSON, T. & ALBREKTSSON, B. :Microcirculation in grafted bone. A chambertechnique for vital microscopy of rabbit bonetransplants. A cta Orthop , Seand. 1978: 49: 1-7.

6. ALBREKTSSON, T., BRANEMARK, P.-I., HANSSON,H. A . & LINDSTROM, J.: Osseointegrated titaniumimplants. Acta Orthop. Seand. 1981: 52: 155-170.

7. AXELSSON, P. & LINDHE, J.: Effect of controlledoral hygieneprocedures oncaries and periodontaldisease in adults. J. Clin. Periodontal. 1978: 5:133-151.

8. BABBUSH, C. A. : Endosseous blade-vent implants : a research review. J. Oral Surg. 1972: 30:168-175.

9. BLOMBERG, S. : Rehabilitering med kakbensforankrad bettersattning. II. Klinisk-psykiatriskaaspekter. Tandliikartidningen 1972: 64: 669- 675.

10. BLOMBeRG, S., BRANeMARK, P.-I. & CARLSSON,G. E. : Psyko-sociala effekter av behandling medkakbensforankrade broar pa osseointegreradeimplantat. In manuscript. To be published inLdkurtidningen 1982.

II. BREINE, U. & BRANEMARK, P .-I.: Reconstructionof alveolar jaw bone. An experimental and


clinical study of immediate and preformedautologous bone grafts in combination withosseointegrated implants. Scand. J. Plast.Reconstr, Surg, 1980: 14: 23-48.

12. BRANEMARK, P.-I. & BREINE, u.. Formation ofbone marrow in isolated segment of rib periosteum in rabbit and dog. Blood 1964: 10: 236252.

13. BRANEMARK, P.-I., BREINE, U., ADELL, R.,HANSSON, B. 0., LINDSTROM, J. & OLSSON, A.:Intra-osseous anchorage of dental prostheses. 1.Experimental studies. Scand. J. Plast. Reconstr.Surg. 1969: 3: 81-100.

14. BRANEMARK, P.-I., HANSSON, B. 0., ADELL, R.,BREINE, U., LINDSTROM, J., HALLEN, O. &OHMAN, A.: Osseointegrated implants in thetreatmen t of the edentulous jaw. Experience froma 10-year period. Scand. J. Plast, Reconstr. Surg.1977: 11: Suppl. 16, and as a monograph fromAlmqvist & WikselJ International, Stockholm1977.

15. CARLSSON, G. E.: Personal communication 1980.16. CARLSSON, G. E. & PERSSON, G.: Morphologic

changes of the mandible after extraction andwearing of dentures. A longitudinal, clinical andX-ray cephalometric study covering 5 years.Odontol. Revy 1967: 18: 27-54.

17. CHIARENZA, A.: The implant sulcus. OralImplantol. 1974: 4: 330-342.

18. CoSTICH, E. R., YOUNGBLOOD, B. J. & WALDEN,J. M.: A study of the effects ofhigh speed rotatoryinstruments on bone repair in dogs. Oral Surg,1964: 17: 563-571.

19. CRANIN, N. A., RABKIN, M. F. & GARFINKEL, L.:A statistical evaluation of952 endosteal implantsin humans. J. Am. Dent. Assoc. 1977: 94: 315320.

20. CRUM, R. J. & ROONEY, G. E. : Alveolar bone lossin overdentures: A 5-year study. J. Prosthet,Dent. 1978: 40: 610-613.

21. DOMS, P.: The tissue response to endosteal bladeimplants - microradiographic and tetracyclinemarking (part I). Oral Implantol. 1974: 4: 470474.

22. GLANTZ, P.-C.: Personal communication 1973.23. GROSS, U. & STRUNZ, V.: Der Gewebeersatz in

der experimentellen Kieferchirurgie unter allgemein pathologischem Aspekt. DIsch. Zahnaerztl. Z. 1980: 35: 5-10.

24. HANSSON, B. 0.: Success and failure of osseointegrated implants in the edentulous jaw.Swed. Dent. J. 1977: 1: Supp!. I.

25. HARALDSON, T.: Functional evaluation 0/bridgeson osseointegrated implants in the edentulous jaw.Thesis. Faculty of Odontology, University ofGoteborg, Goteborg 1979.

26. HARALDSON, T. & CARLSSON, G. E.: Bite forceand oral function in patients with osseointegratedoral implants. Scand. J. Dent. Res. 1977: 85: 200208.

27. HEDEOARD, B.: Personal communication 1980.28. HUGHES, A. N. & JORDAN, B.A.: The mechanical

properties of surgical bone screws and someaspects of insertion practice. Injury 1972: 4: 2538.

29. IZIKOWITZ, L.: Den dentala implantationsprotetiken - en oversikt jamte nagra synpunkter pitprognosen. Sverig. Tandliik. Fiirb. Tidn. 1968: 60:932-948.

30. IZIKOWlTZ, L.: A long-term prognosis for thefixed saddle-bridge. Astudy of I00 constructions.J. Oral Rehab. 1976: 3: 25-40.

31. JACOB, C. H., BERRY, J. T., POPE, H. M. &HOAGLUND, F. T. : A study of the bone machiningprocess - drilling. J. Biomech, 1976: 9: 343-349.

32. JACOBS, H. G.: Zur Entwicklung del' enossalenImplantalogie. Zahnaerztl. Mitt. 1979: 69: 254260.

33. JACOBS, R. L.: Fundamental investigations of thebone cutting process. Proc. Bull. Hosp. Joint Dis.1977: 38: 4.

34. JACOBS, R. L. & RAY,R. 0.: The effect of heat onbone healing. A disadvantage in the use of powertools. Arch. Surg, 1972: 104: 687-691.

35. JAMES, R. A. & KELLN, E. E.: A histopathologicalreport on the nature of the epithelium andunderlying connective tissue, which surroundsoral implants. J. Biomed. Mater. Res. (Symp.)1974: 8: 373-383.

36. JAMES, R. A. & SCHULTZ, R. L.:Hemidesmosomes and the adhesion of junctionalepithelial cells to metal implants. A preliminaryreport. Oral Implantol. 1974: 4: 294-302.

37. LIGHTNER, L. M., O'LEARY, T. J., DRAKE, R. B.,CRUMP, P. P. & ALLEN, M. F.: Preventiveperiodontic treatment procedures: Results over46 months. J. Periodontol. 1971 : 42: 555-561.

38. LINDHE, J. & NYMAN, S.: The effect of plaquecontrol and surgical pocket elimination on theestablishment and maintenance of periodontalhealth. A longitudinal study of periodontaltherapy in cases of advanced periodontal disease.J. Clin. Periodontol. 1975: 2: 67-77.

39. LINDSTROM, J., BRANEMARK, P.-I. &ALBREKTSSON, T.: Mandibular reconstructionsusing the preformed autologous bone graft.Scand. J. Plast, Reconstr. Surg. 1981: 15: 29-38.

40. LINKOW, L. I., GLASSMAN, P. E. & ASNIS, S. T.:Macroscopic and microscopic studies of endosteal blade-vent implants (six months study).Oral Implantol. 1973: 3: 281-309.

41. LUNDSKOG, J.: Heat and bone tissue. An


experimental inves tigation of the thermal properties of bone tissue and treshold levels forthermal inju ry . Scand. J. Plast, Reconstr. Surg,1972 : 6: Supp!. 9.

42. Mi\NDERSON, R. D .: Experimental intra-osseousimplantation in the jaws of pigs. Dent. Practit ,Dent. Rec. 1972 : 22: 225-23 1.

43. MATTHEWS, L. S. & HIRSCH, C. M. :Temperatures measured in human cortical bonewith drilling. J . Bone Joint . Surg : 1972: 54A: 297308.

44. MEENAGHAN, M. A., NATlIlLLA, J. R ., ARMITAGE,J. E., GREENE, G. W . JR. & LIPANI, C. S.: Thecrypt surface of blade-vent implants in clinicalfailure: an electron microscopic study. J.Prosthet. Dent. 1974: 31: 681-690.

45. MEENAGHAN, M. A ., NATIELLA, J. R., ARMITAGE,J. E. & WOOD,R.: Evaluation of the crypt surfaceadjacent to metal endosseous implants: anelectron-microscopic study in clinically successfulimplants. J . Prosthet, Dent. 1974: 31: 574-581.

46. MELCHER, A. H. & ACCURSI, G. E.: Osteogeniccapacity of periosteal and osteoperiosteal flapselevated from the parietal bone of the rat. Arch.Oral Bioi. 1971 : 16: 573-580.

47. MIOR, 1. & SELVIG, A. : The Periodontium. InMJOR,1. & PINDBORG, J. J. (eds.) : Histology ofthehuman loath, Munksgaard, Copenhagen 1973, p.134.

48. Moss, R. W.: Histopathologic reaction of bone tosurgical cutting. Oral Surg ; 1964: 17: 405-414.

49. NATIELLA, J . R., ARMITAGE, J. E., GREENE, G . W.JR. & MEENAGHAN, M . A. : Current evaluation ofdental implants. J . Am. Dent, Assoc. 1972 : 84:1358-1372.

50. NYMAN, S., ROSLING, B. & LINDHE, J. : Effect ofprofessional tooth cleaning on healing afterperiodontal surgery. J. Clin . Periodontol. 1975: 2:80-86.

51. PETERSON, L. T.: Fixation ofbones by plaster andscrews. J. Bone Joint Surg, 1947: 29: 335-347.

52. PEYTON, F. A.: Temperature rise and cuttingefficiency of rotating inst rum ents. N.Y. Dent. J.1952: 18: 439-450.

53. RAMFIORD, S. P., KNOWLES, J. W., NISSLE, R . R .,SHICK, R . A. & BURGETT, F. G . : Longitudinalstudy of periodontal therapy. J. Periodontal.1973 : 46: 66-77.

54. REEDY, M. T ., DEVORE, D . T. & THOMPSON, V.P.: Histological and physical evaluation ofvitreous carbon endosteal implan ts. OralImplantol, 1974: 5: 85-92.

55. ROCKLER, B.: Radiographic technique for serialidentical examination of oral osseo integratedtitanium implants. In manuscript. To be published 1982.

56. ROSLlNG, B., NYMAN, S. & LINDHE, J . : The effectof systemic plaque control on bone regenerationin in frabone pockets. J. CUn. Periodontal, 1976:3: 38-53.

57. ROSLING, B., N YMAN, S., LINDHE, J. & JERN, B. :The healing po tential of the periodontal tissuesfollow ing differen t techn iques of perio dontalsurgery in plaq ue-free dentitions. J. CUll.Periodontal. 1976 : 3: 233-250.

58. SCHLEGEL, D ., REICHART, P. A. & PFAFF, U. :Expe rimental bacteremia to demonstrate thebarrier function of epithelium and connectivetissue surrounding oral endosseous implants. Int.J. Oral Surg, 1978: 7: 569-572.

59. SCHNITMAN, P. A. & SHULMAN, L. B. :Recommenda tions of the consensus developmentconference on dental implants. J. Am. Dent,Assoc. 1979: 98: 373-377.

60. SCHROEDER, H . E. & LISTGARTEN, M . A. : Finestructure of the developing epithelial attachment ofhuman teeth . Monographs in developmentalbiology. 1971: 2: S. Karger, Basel, p. 105.

61. SOUTHAM, J. C. & SELWYN, P. : Structural changesaround screws used in the treatment of fracturedhuman mandibles.Br . J . Oral Surg , 1971 : 8: 21122!.

62. SUOMI, J. D ., WEST, T. D., CHANG, J. J. &MCCLENDON, B. J.: The effect of controlled oralhygiene procedures on the progression of peri.odontal disease in adults : Radiographic findings.J. Periodontal. 1971: 42: 562-564.

63. TALLGREN, A. : The continuing reduction of theresidual alveolar ridges in complete denturewearers : a mixed -longitudinal study covering 25years. J. Prosthet, Dent, 1972: 27: 120-132.

64. THOMPSON, H. C, : Effect of drill ing into bone . J.Oral Surg , 1958: 16: 22-30.

65. ZARB, G. A., SMITH, D. C., LEVANT, H. C .,GRAHAM, B. S. & ZING, G. W. : The effects ofcemented and uncemented endosseous implants.J. Prosthet , Dent, 1979: 42: 202-210.

66. WEISS, C. M., JUDY, K. W. & CHIARENZA, A. R. :Precornpacted coined titanium endosteal bladeimplan ts. Orallmplantol. 1973: 3: 237-260.

67. WICTORIN, L. : Bone resorption in eases withcomplete upper denture. Acta radiol . 1964 : 2:Supp!. 228.

Address :

R. AdellDepartment of Oral SurgeryFaculty of OdontologyUniversi ty of GoteborgBox 33070S-400 33 GtiteborgSweden

A 15-year study of osseointegrated implants in the ... · between vital bone and...

Documents

Transcript of A 15-year study of osseointegrated implants in the ... · between vital bone and...