Alteraciones de Reborde Luego de Colocacion de Implantes en Alveolos Frescos en Perros. Araujo, Sukekava y Lindhe.2005

8/12/2019 Alteraciones de Reborde Luego de Colocacion de Implantes en Alveolos Frescos en Perros. Araujo, Sukekava y Lin

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Ridge alterations followingimplant placement in freshextraction sockets: anexperimental study in the dog

Ara ujo MG, Sukekava F, Wennstrom JL, Lindhe J. Ridge alterations following implant

placement in fresh extraction sockets: an experimental study in the dog. J ClinPeriodontol 2005; 32: 645652. doi: 10.1111/j.1600-051X.2005.00726.x. rBlackwell Munksgaard, 2005.

Abstract

Objective: To study dimensional alterations of the alveolar ridge that occurredfollowing implant placement in fresh extraction sockets.

Material and Methods: Five beagle dogs were included in the study. In bothquadrants of the mandible, incisions were made in the crevice region of the third and

fourth pre-molars. Buccal and minute lingual full-thickness flaps were elevated. Themesial root of the four pre-molars root was filled and the teeth were hemi-sected.

Following flap elevation in 3P3and 4P4regions, the distal roots were removed. In theright jaw quadrants, implants with a sand blasted and acid etched (SLA) surface wereplaced in the fresh extraction sockets, while in the left jaws the corresponding sockets

were left for spontaneous healing. The mesial roots were retained as surgical controlteeth. After 3 months, the animals were examined clinically, sacrificed and tissueblocks containing the implant sites, the adjacent tooth sites (mesial root) and theedentulous socket sites were dissected, prepared for ground sectioning and examined

in the microscope.

Results: At implant sites, the level of bone-to-implant contact (BC) was located2.6 0.4 mm (buccal aspect) and 0.2 0.5 mm (lingual aspect) apical of the SLAlevel. At the edentulous sites, the mean vertical distance (V) between the marginaltermination of the buccal and lingual bone walls was 2.2 0.9 mm. At the surgically

treated tooth sites, the mean amount of attachment loss was 0.5 0.5 mm (buccal) and0.2 0.3 mm (lingual).

Conclusions: Marked dimensional alterations had occurred in the edentulous ridgeafter 3 months of healing following the extraction of the distal root of mandibular pre-

molars. The placement of an implant in the fresh extraction site obviously failed to

prevent the re-modelling that occurred in the walls of the socket. The resulting heightof the buccal and lingual walls at 3 months was similar at implants and edentulous sitesand vertical bone loss was more pronounced at the buccal than at the lingual aspect of

the ridge. It is suggested that the resorption of the socket walls that occurs followingtooth removal must be considered in conjunction with implant placement in fresh

extraction sockets.

Key words: bundle bone; modelling; re-modelling; wound healing

Accepted for publication 25 October 2004

The extraction of multiple teeth resultsin an overall diminution of the size ofthe edentulous ridge (e.g. Atwood 1962,1963, Johnson 1963, 1969, Carlsson &Persson 1967, Tallgren 1972, Ulm et al.

1992). Also, following the removal of asingle tooth, marked hard- and soft-tissue alterations will take place withinthe affected region of the alveolar ridge(Pietrokovski & Massler 1967, Schropp

et al. 2003). Further, tissue modellingfollowing multiple as well as singletooth extractions apparently resulted inmore pronounced bone loss in the buc-cal than in the lingual/palatal portions of

Mauricio G. Araujo1,2

, FlaviaSukekava1, Jan L. Wennstrom2 and

Jan Lindhe2

1Department of Dentistry, State University of

Maringa, Maringa, Brazil; 2Department of

Periodontology, Sahlgrenska Academy at

Goteborg University, Gothenburg, Sweden

645

J Clin Periodontol 2005; 32: 645652 doi: 10.1111/j.1600-051X.2005.00726.x Copyrightr Blackwell Munksgaard 2005


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the ridge (Pietrokovski & Massler1967).

In experiments in the dog, Cardaropoliet al. (2003) and Araujo & Lindhe (2005)studied bone tissue reaction to toothextraction and monitored both intra-alveolar and extra-alveolar processes. It

was observed that (i) the intra-alveolarportion of the extraction site becameoccupied by woven bone that, followingthe formation of a cortical hard-tissueridge, became replaced mainly by bonemarrow and (ii) both the lingual and thebuccal hard-tissue walls underwentmarked change. Thus, through the com-bined effect of surface resorption andloss of bundle bone, in particular, thebuccal bone wall was reduced in thick-ness as well as in height (Araujo &Lindhe 2005).

It was recently suggested (Paolantonio

et al. 2001) that the placement of implantsin fresh extraction sockets would preventre-modelling and hence maintain the ori-ginal shape of the ridge. Paolantonio et al.(2001) stated that early implantationmay preserve the alveolar anatomy andthat the placement of a fixture in a freshextraction socket may help to maintainthe bony crest structure. Findingsreported from a clinical study by Botti-celli et al. (2004), however, failed tosupport this hypothesis. Thus, the authorsreported that at sites where implants hadbeen placed immediately following single

tooth extraction, the buccal as well as thelingual bone walls during healing under-went marked re-modelling and resorp-tion. In the 4-month interval betweenimplant installation and re-entry surgery,the distance between the implant surfaceto the outer surface of the buccal andlingual bone walls was markedly dimin-ished (buccal aspect: 50%; lingualaspect: 25%).

The aim of the present dog experi-ment was to study whether the place-ment of an implant in a fresh extr-action site could interfere with hard-

tissue alterations that otherwise wouldoccur in the alveolar ridge following theremoval of a tooth.

Material and Methods

The ethical committee of the Universityof Maringa approved the research pro-tocol. Five beagle dogs about 1-year oldand weighting about 1213 kg eachwere used. During surgical procedures,the animals were anaesthetized withintravenously administered Pentothal

Natriums

(30 mg/ml; Abbot Labora-tories, Chicago, IL, USA). Throughoutthe experiment, the animals were fed apellet diet. In both quadrants of themandible, the third and fourth pre-molars (3P3 and 4P4) were used asexperimental sites. A rubber dam was

placed around 3P3 and 4P4 and wasretained with clamps. The pulp tissueof mesial roots of 3P3 and 4P4 wasextirpated and the canals were filledwith gutta-percha. The coronal portionof the pulp chamber was filled with acomposite material.

In both the left and right quadrant ofthe mandible, continuous sulcus inci-sions were placed along the buccal andlingual aspects of the third and fourthpre-molars and mesial aspect of the firstmolar. On the buccal as well as on thelingual aspect of the ridge, full-thick-

ness flaps were elevated to disclose themarginal 1015 mm of the hard-tissuewall of the ridge. 3P3and 4P4were hemi-sected with the use of a fissure bur. Thedistal roots were carefully removedusing elevators and forceps. The buc-callingual dimension of the freshextraction sockets (Fig. 1) was measuredusing a sliding caliper. The mean buc-callingual width of the 3P3 sites was3.5 0.2 mm and the correspondingdimension of the 4P4 sites was3.9 0.3 mm.

In the two extraction sites of the right

jaw quadrant, implants (Straumann

s

;Standard Implant; 4.1 mm in diameterand 68 mm long; Straumann

s

DentalImplant System; Straumann, Walden-burg, Switzerland) were installed. Therecipient sites were prepared for implantinstallation according to the guidelines

provided by the manufacturer. The floorof the socket was penetrated with roundburs. Subsequently, the recipient sitewas prepared with pilot drills and finallythe canal was tapped by hand using a tapand a ratchet. The implants were placedso that the marginal level of the sand

blasted and acid etched (SLA)-coatedsurface was flush with the buccal bonecrest (BC) (Fig. 2). A healing cap(Straumann

s

Dental Implant System)was attached to the implant. The mobi-lized buccal and lingual flap tissueswere replaced to allow a semi-sub-merged healing (Fig. 3a) of the implantsites (implant sites) and neighbouringmesial tooth portions (involved toothsites). The wound margins were stabi-lized with interrupted sutures.

The corresponding extraction sites inthe left jaw quadrants were left without

implant placement (edentulous sites). Thebuccal and lingual flaps were stabilizedwith interrupted sutures to provide soft-tissue coverage of the extraction sockets(Fig. 3b).

The second mandibular pre-molars inboth mandibular quadrants (2P2) werenot involved in the surgical proceduresbut the distal roots were used as controls(non-involved tooth sites).

The dogs were placed on a plaquecontrol regimen that included tooth andimplant cleaning three times per weekwith the use of toothbrush and denti-

frice. During the first week after sur-gery, the animals received Amoxicillin(500 mg, twice daily) via the systemicroute.

After 3 months of healing, the dogswere sacrificed with an overdose ofPentothal Natrium

s

and perfused,

Fig.1. Clinical photograph illustrating the extraction sockets distal roots of the third andfourth mandibular pre-molars immediately after root extraction. Note that the buccallingualwidth of the extraction socket of the fourth pre-molar is wider than that of the third pre-molar.

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through the carotid arteries, with a fixativecontaining a mixture of 5% glutaralde-hyde and 4% formaldehyde (Karnovsky1965). The mandibles were dissected andplaced in the fixative. Each implant, toothand edentulous site was removed using a

diamond saw (Exacts

Apparatebeau,Norderstedt, Hamburg, Germany). Thebiopsies were processed for ground sec-tioning according to the methodsdescribed by Donath & Breuner (1982)and Donath (1993). The samples were

dehydrated in increasing grades of ethanoland infiltrated with Technovit

s

7200VLC-resin (Kulzer, Friedrichrsdorf, Ger-many). Following embedding in acrylicresin, the biopsy samples were polymer-ized and sectioned in a buccallingualplane using a cuttinggrinding unit

(Exact

s

Apparatebeau).From each implant, edentulous andtooth site, one buccallingual sectionrepresenting the central area of the sitewas prepared. By micro-grinding andpolishing, the sections were reduced toa thickness of about 20 mm and stainedin toluidine blue. The histological exam-ination was performed in a Leitz DM-RBE

s

microscope (Leica, Germany)equipped with an image system (Q-500MC

s

, Leica).

Histometric measurements: The fol-lowing landmarks were identified (Fig. 4):

Implant sitesS: the shoulder of the implantSLA: marginal border of the

SLA-coated surfacethat was located 2.8 mmapical of S

BC: the margin of the BC(buccal, lingual)

PM: margin of peri-implantmucosa

aBE: apical cells of barrierepithelium

At the buccal and lingual aspects, thefollowing distances were measured andexpressed in millimetres: (i) PMBC,(ii) PMaBE, (iii) aBEBC and (iV)SLABC.Tooth sites (involved andnon-involved)

CEJ: cemento-enamel junctionBC: bone crest (buccal/lingual)GM: margin of gingivaaJE: apical cells of the junctional

epithelium

At the buccal and lingual aspects, thefollowing distances were measured andexpressed in millimetres: (i) GMBC,(ii) GMCEJ, (iii) CEJBC and (iV)CEJaJE. At the edentulous sites, thevertical distance between margins ofthe buccal and lingual bone walls wasdetermined in the following way: a lineparallel to the long axis of the healedsocket was drawn (CC) in the centre ofthe section to separate the buccal andlingual compartments. Subsequently,horizontal lines (L, lingual and B,buccal) perpendicular to CC were

Fig.2. Clinical photograph illustrating the experimental sites immediately after implantinstallation. Note that the border of the sand blasted and acid etched-coated surface of theimplants was flush with the buccal bone crest.

Fig.3. (a) Clinical photograph illustrating the wound in the third and fourth pre-molar regionafter sutures had been placed. Two implants and the adjacent involved teeth. Note that thehealing caps at the implants project above the mucosa. (b) The corresponding edentulous siteand adjacent mesial roots of third and fourth pre-molars.

Healing of extraction socket 647


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drawn to project the most coronal por-tions of the buccal and lingual BC to CC. The vertical distance (V) between the

buccal and lingual intersections with CC was measured and expressed in milli-metres.Mean values and standard devia-

tions were calculated for each animal,experimental group and variable.

Results

Clinical observations

All experimental sites healed unevent-fully. Overt signs of soft-tissue inflam-mation (swelling and redness) were seenduring the first few weeks of healing,but at 3 months the mucosa adjacent tomost implants and teeth, as well as thesoft tissue that covered the edentulousridge appeared to be clinically healthy(Fig. 5a, b).

As assessed by clinical means, all 10implants were properly osseointegrated.The SLA surface at the lingualaspect ofthe implants was covered by mucosa atall sites. At two of the 10 implant sites

(both located in the fourth pre-molarsite), the marginal 1 mm of the buccalSLA surface was exposed.

The gingival margin (GM) at the buc-cal and lingual aspects of the involvedand non-involved teeth was found to becoronal to the CEJ.

Histological observations

Implant sites

The histological examination revealed

that the mucosa at the buccal and lingualaspects of the implant sites was coveredby a keratinized oral epithelium that wascontinuous with a thin barrier epithe-lium facing the titanium rod. Apical ofthis barrier epithelium there was a zoneof fibre-rich connective tissue (con-nective tissue attachment) that estab-lished an apparently tight contact withthe implant. At both the buccal andlingual aspects of the implant sites, theconnective tissue immediately lateral tothe barrier epithelium contained smallinfiltrates of inflammatory cells, while

the more apically located connectivetissue attachment was devoid of suchleucocyte accumulations.

The central and outer portions of thebuccal and lingual bone walls were com-prised of lamellar bone that was charac-terized by densely packed secondaryosteons. The bone tissue immediatelylateral to the implant surface appearedto be less mature than the bone in theouter portions of the hard-tissue walls(Fig. 6). This newly formed bone thatwas separated from the old bone bywell-defined reversal lined (Fig. 7)

Fig.4. Schematic drawing presenting the locations of the various histometric measurementswere performed. For details regarding abbreviations, see text.

Fig.5. (a) Clinical photograph illustrating one experimental site (two implants and twoinvolved roots) after 3 months of healing. Note that the peri-implant mucosa as well as thegingiva show no overt signs of inflammation. The margin of the mucosa resides at the smoothportion of the implant. (b) Clinical photograph of two edentulous sites and adjacentinvolved tooth sites after 3 months of healing.

648 Araujo et al.


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contained a large number of bone multi-cellular units.

The bone tissue that was in directcontact with the lingual aspect of theimplant consistently extended to, or close

to, the marginal border of its SLA-mod-ified portion. In seven out of 10 sites, asmall hard-tissue defect (o1 m m indepth) could be observed between the

lingual bone wall and the implant. On the

buccal aspectof all implants, the margin-al termination of the osseointegratedportion of the newly formed bone wasconsistently found at a level markedlyapical of the marginal SLA level. Theexposed portion of the SLA surface

Fig.6. Buccallingual section representing

one implant site after 3 months of healing.Note the location of the bone crest at thebuccal and lingual aspects of the implant.BB, buccal bone wall; I, implant; LB, lin-gual bone wall; PM, peri-implant mucosa.Outlined area5detail presented in Fig. 6.Toluidine blue staining; original magnifica-tion 16.

Fig.7. Higher magnification of the area out-lined in Fig. 5. LB, lingual bone wall; I,implant. Arrows indicate the presence of atypical reversal line. Toluidine blue staining;original magnification 100.

Fig.8. Buccallingual section representing

an involved tooth site. Note that the lingualbone crest is closer to the CEJ (arrows) at thelingual than at the buccal aspect of the tooth.The apical level (aJE) of the junctionalepithelium (arrowheads). BB, buccal bonewall; LB, lingual bone wall; CEJ, cemento-enamel junction. Toluidine blue staining;original magnification 16.

Fig.9. Buccallingual section representingan edentulous site. Note the location ofthe original bone crest (outlined area) atthe buccal (b) and lingual (l) aspects of thealveolar crest. BB, buccal bone wall; LB,lingual bone wall; M, mucosa of the edentu-lous ridge. Toluidine blue staining; originalmagnification 16.

Fig. 10. Buccallingual section. Magnified

microphotograph of (b) the buccal aspect ofthe crest identified (outlined area) in Fig. 8.The dotted line represents the borderlinebetween the old and newly formed bone.Toluidine blue staining; original magnifica-tion 100.

Fig. 11. Buccallingual section. Magnified

microphotograph of (l) the lingual aspectof the crest identified (outlined area) inFig. 8. The dotted line represents the border-line between the old and newly formed bone.Toluidine blue staining; original magnifica-tion 100.



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was in apparent close contact with thebarrier epithelium and/or the connectivetissue of the mucosa.

Tooth sites

Involved teeth. Both at the buccal andlingual aspects of theinvolved teeth, theGM was located coronal to the CEJ. Thesoft tissue at the buccal and lingualaspects of such teeth contained smallinfiltrates of inflammatory cells. Theseinfiltrates consistently appeared in theconnective tissue immediately lateral tothe junctional epithelium. The aJE wasat the lingual aspectof all teeth locatedclose to the CEJ (Fig. 8). At the buccalaspect, however, without fail aJE waslocated a varying distance apical of CEJ.The bone wall was markedly wider atthe lingual than at the buccal aspect of

the involved teeth. The buccal BC waslocated at a longer distance from theCEJ than the corresponding lingual BC.

Non-involved teeth. Both at the buccaland lingual aspects of the non-involvedteeth, the GM was located coronal to theCEJ. The gingiva at the buccal andlingual aspects of such teeth was con-sistently devoid of pertinent infiltrates ofinflammatory cells. The aJE was at the

buccal and lingual aspect of all teethlocated at the CEJ. The buccal bone wallwas thinner than the lingual wall but the

crests were located at a similar distancefrom CEJ.

Edentulous sites

The mucosa covering the healed socketwas lined by an oral epithelium thatharboured a well-keratinized surfacelayer. The underlying, connective tissuewas characterized by its densely packedcollagen fibres and lack of infiltrates ofinflammatory cells. A newly formedhard-tissue bridge covered the entranceof the extraction socket (Fig. 9). This

marginal ridge was mainly made up ofwoven bone, although small areas oflamellar bone could also be observed.The newly formed hard-tissue bridgeextended a varying distance into theextraction socket. Apical of the bridge,the edentulous region was comprised ofcancellous bone dominated by its bonemarrow.

The surface of the buccal and lingualbone walls, was in most portions,covered by a periosteum and exhibitedonly minute signs of re-modelling. Themarginal termination of the original

buccal bone wall was located apical ofits lingual counterpart (Figs 10 and 11).

Histometric measurements

Implant sites (Table 1)

The mean distance between the PM andthe BC at the buccal aspect was3.9 0.5 mm. The corresponding dimen-sion at the lingual aspect was2.6 0.4 mm. The length of the barrierepithelium (PMaBE) was on the average1.9 0.9 mm (buccal) and 1.9 0.4mm(lingual). The mean distance betweenaBE and BC was 1.8 0.8mm (buccal)and 0.7 0.2mm (lingual). The level ofBC was located 2.6 0.4 mm from theSLA level at the buccal aspect and0.2 0.5 mm at the lingual aspect ofthe site.

Tooth sites (Table 2)

Non-involved teeth. The mean dis-tance between the GM and the BCwas 2.6 0.2 m m (buccal) and2.0 0.1 mm (lingual), while the corre-sponding distance between GM and CEJwas 1.7 0.2 m m (buccal) and1.3 0.1 mm (lingual). The BC waslocated on the average 08 0.1 (buccal)and 0.7 0.2 mm (lingual) from theCEJ. The aJE were located at or closeto the CEJ both at the buccal and lingualaspects.

Involved teeth. The distance GMBCwas 2.8 0.5 mm long at the buccaland 1.6 0.6 mm at the lingual aspect

of the involved teeth. At both the buccaland the lingual aspect, the distance GMCEJ was about 1 mm high. The distancebetween CEJ and BC was on the aver-age 1.8 0.7 mm at the buccal and0.8 0.1 mm at the lingual aspect. Themean amount of attachment loss (CEJaJE) was 0.5 0.5 mm (buccal) and0.2 0.3 mm (lingual).

Edentulous sites

The mean vertical distance (V) be-tween the marginal termination of thebuccal and lingual bone walls was2.2 0.9mm.

Discussion

The present experiment demonstratedthat marked dimensional alterationshad occurred in the edentulous ridge ofdogs after 3 months of healing followingthe extraction of the distal root of man-dibular pre-molars. The placement of an

implant in the fresh extraction siteobviously failed to prevent the re-mod-elling that occurred in the walls of thesocket. The resulting height of the buc-cal and lingual walls at 3 months wassimilar at implants and edentulous sitesand the vertical bone level change wasmore pronounced at the buccal than atthe lingual aspect of the ridge. It issuggested that the resorption of thesocket walls that occurs following toothremoval must be considered in conjunc-tion with implant placement in freshextraction sockets.

Table 1. Results of the histometric measurements (mm) at the implant sites

PMBC PMaBE aBEBC SLABC

Buccal 3.9 (0.5) 1.9 (0.9) 1.8 (0.8) 2.6 (0.4)

Lingual 2.6 (0.4) 1.9 (0.4) 0.7 (0.2) 0.2 (0.5)

Mean (SD). PM, margin of peri-implant mucosa; BC, bone-to-implant contact; aBE, apical cells of

barrier epithelium; SLA, sand blasted and acid etched.

Table 2. Results of the histometric measurements (mm) at the non-involved and involved sites

Buccal Lingual

GMBC GMCEJ CEJBC CEJaJE GMBC GMCEJ CEJBC CEJaJE

Non-involvedsite

2.6 (0.2) 1.7 (0.2) 0.8 (0.1) 0 (0.0) 2 (0.1) 1.3 (0.1) 0.7 (0.2) 0 (0.0)

Involved

site

2.8 (0.5) 1.0 (0.3) 1.8 (0.7) 0.5 (0.5) 1.6 (0.6) 0.9 (0.6) 0.8 (0.1) 0.2 (0.3)

Mean (SD). GM, margin of gingiva; BC, bone-to-implant contact; CEJ, cemento-enamel junction;

aBE, apical cells of barrier epithelium.

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In the current experiment, it wasobserved that re-modelling followingtooth extraction was more pronouncedin the buccal than in the lingual bonewall. This is in agreement with datapreviously reported (e.g. Pietrokovski& Massler 1967, Schropp et al. 2003,

Botticelli et al. 2004, Araujo & Lindhe2005). In the present study, it wasfurther documented that the apico-cor-onal height of the buccal hard-tissuewall was reduced considerably morethan that of the lingual wall of thesame extraction socket. This finding isconsistent with data from a dog experi-ment by Araujo & Lindhe (2005), whostudied healing of extraction sockets inbiopsies sampled 1, 2, 4 and 8 weeksfollowing the careful removal of thedistal roots of hemi-sected third andfourth mandibular pre-molars. The his-

tological examination revealed that inthe 8-week specimens, the marginaltermination of the buccal wall waslocated 1.9 mm apical of its lingualcounterpart. The authors suggested thatthis difference between the buccal andlingual bone walls was related to thefollowing:

(i) the early disappearance of the bun-dle bone that, in the presence of atooth, occupies a larger fraction ofthe marginal portion of the bonewall in the buccal than in the lin-

gual aspect of the socket.(ii) the additional surface resorption

that will have a more pronouncedeffect on the delicate buccal than onthe wider lingual bone wall of thesocket.

In this context, it must be realizedthat the surgical trauma inflicted alongwith flap elevation, root extraction andimplant installation may have resultedin bone re-modelling that, to a differentextent, may have influenced the walls ofthe sockets. In order to study the effect

of flap elevation per se on hard- andsoft-tissue re-modelling, two differenttooth categories were selected as con-trols. One category (positive control)was represented by the mesial roots ofthe mandibular third and fourth pre-molars, i.e. roots that were included inprocedures such as rubber dam applica-tion as well as sulcus incision and flapelevation. The distal roots of the secondmandibular pre-molars represented thesecond category of controls (negativecontrols) and included teeth that werenot included in the surgical field and had

not been instrumented prior to or duringthe experiment. The histological exam-ination of the control sites demonstratedthat the untreated teeth were associatedwith a normal periodontium (Table 2).On the contrary, all involved toothsites exhibited signs of attachment loss

(CEJaJE) and bone loss (CEJBC).This finding is consistent with data byWood et al. (1972) and Bragger et al.(1988) and illustrates that surgical trau-ma that includes the separation of theperiosteum from the bone surface willinduce re-modelling of the surface layerof the alveolar bone in the exposed area.

The examination of the involved toothsites further revealed that there was moreattachment and bone loss at the buccalthan at the lingual aspect of the roots(CEJaJE: 1.8 versus 0.2 mm, CEJBC:0.8 versus 0.1 mm). The reason for this

difference is presently not properlyunderstood but may be related to thethicker bone wall that was present onthe lingual surface of the mandibular pre-molars. This suggestion is in agreementwith Wood et al. (1972), who studiedalveolar crest reduction in humans fol-lowing full- and partial-thickness flaps.The authors reported that that Loss ofcrestal alveolar bone height in response tofull-thickness flaps occurred in each ofthe seven patients surgically re-evaluatedand varied from a mean of 0.23 mm to amean of 1.6mm. Further, the authors

concluded that In our patients, teethwith the thinnest radicular bone consis-tently demonstrated the most bone losspostoperatively.

The main finding of the present studywas that the placement of an implant inthe fresh extraction socket failed to influ-ence the process of re-modelling thatoccurs in the buccal and lingual hard-tissue walls of the socket that followedtooth removal. Thus, after 3 months ofhealing, the amount of buccal bone heightreduction (in comparison with lingualbone alteration) was similar at implant

sites and edentulous sites. Thus, the ver-tical discrepancy between the buccaland lingual bone margins was inboth category of sites 42 mm: edentu-

lous sites52.2 mm and implant sites2.4 mm. In other words, the resorptionof the buccal bone wall of the socket wasthree times as great as that observed at thebuccal aspect of the surgically involvedcontrol teeth. This observation is inagreement not only with Araujo &Lindhe (2005) but also with results froma study in humans by Botticelli et al.(2004). They examined dimensional

alterations that occurred in humans dur-ing a 4-month interval following implantplacement in fresh extraction sockets.The authors reported that during healing,the width of the marginal portion ofthe buccal bone wall was reduced mark-edly more than the corresponding lingual

wall.The fresh extraction socket of thethird pre-molar had a smaller buccallingual dimension than that of the fourthpre-molar. This means that during thepreparation of the site for implant instal-lation in the third pre-molar region,more bone had to be removed from themarginal portions of the hard-tissuewalls than was the case at the site ofthe fourth pre-molar. Thus, followingimplant placement, the remaining buc-cal bone wall at the third pre-molar sitewas considerably thinner than that in the

fourth pre-molar site. Despite this dif-ference between the third and fourthpre-molar locations regarding the widthof the buccal bone wall following sur-gery, the vertical reduction of the wallswas following similar healing at the twosites (2.6 0.5 versus 2.6 0.3mm).This means that factors other than thethickness of remaining bone must playimportant roles in bone tissue re-model-ling following implant installation.

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Address:

Mauricio G. Araujo

Department of Dentistry

State University of Maringa

Av. Mandacaru, 1550

CEP 87.080 Maringa

Brazil

E-mail: [email protected]

652 Araujo et al.

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Alteraciones de Reborde Luego de Colocacion de Implantes en Alveolos Frescos en Perros. Araujo, Sukekava y Lindhe.2005