Modeling of the buccal and lingual bone walls of fresh extraction sites following implant installation

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1 Muricio G. Arújo Jn L. Wennström Jn Lindhe Modeling of the uccl nd lingul one wlls of fresh extrction sites following implnt instlltion Authors ffilitions: Muricio G. Arújo, Deprtment of Dentistry, Stte University of Mring, Prn, Brzil Jn L. Wennström, Jn Lindhe, nstitute of Odontology, Shlgrensk Acdemy t Göteorg University, Göteorg, Sweden Correspondence to: Dr Muricio G. Arújo Ru Silv Jrdim 49/03, Mring Prn Brzil Tel./Fx: þ e-mil: muricio@cicli.com.r Key words: one modeling, dehiscence, dogs, histometry immedite implnts Astrct Ojective: To determine whether the reduction of the lveolr ridge tht occurs following tooth extrction nd implnt plcement is influenced y the size of the hrd tissue wlls of the socket. Mteril nd methods: Six egle dogs were used. The third premolr nd first molr in oth qudrnts of the mndile were used. Mucoperiostl flps were elevted nd the distl roots were removed. mplnts were instlled in the fresh extrction socket in one side of the mndile. The flps were replced to llow semi-sumerged heling. The procedure ws repeted in the contr lter side of the mndile fter 2 months. The nimls were scrificed 1 month fter the finl implnt instlltion. The mndiles were dissected, nd ech implnt site ws removed nd processed for ground sectioning. Results: Mrked hrd tissue ltertions occurred during heling following tooth extrction nd implnt instlltion in the socket. The mrginl gp tht ws present etween the implnt nd the wlls of the socket t implnttion disppered s result of one fill nd resorption of the one crest. The modeling in the mrginl defect region ws ccompnied y mrked ttenution of the dimensions of oth the delicte uccl nd the wider lingul one wll. Bone loss t molr sites ws more pronounced thn t the premolr loctions. Conclusion: mplnt plcement filed to preserve the hrd tissue dimension of the ridge following tooth extrction. The uccl s well s the lingul one wlls were resored. At the uccl spect, this resulted in some mrginl loss of osseointegrtion. Dte: Accepted 20 April 2006 To cite this rticle: Arújo MG, Wennström JL, Lindhe J. Modeling of the uccl nd lingul one wlls of fresh extrction sites following implnt instlltion. Clin. Orl mpl. Res. 17, 2006; doi: /j x Copyright r Blckwell Munksgrd 2006 Oservtions mde on cdver specimens (Rogers & Appleum 1941) indicted tht following tooth loss in the mxill, the height of the ridge ws reduced nd its crest shifted pltlly. Tylmn & Tylmn (1960), in textook chpter, stted tht following the removl of teeth, the uccl lveolr one plte resored much fster thn the pltl plte. n the mndile, the uthors climed, the mount of one resorption following tooth loss ws rther similr in the uccl nd lingul wlls of the ridge. These clims, however, were not sed on mesurements ut on necdotl informtion. Johnson (1963, 1969) monitored dimensionl chnges tht occurred in 19 sujects (ged yers) scheduled for tooth extrction nd complete denture therpy. Before nd t vrious intervls fter the removl of the teeth, cst models of the ridge were produced nd scnned to disclose dimensionl ltertions. Johnson (1963) showed tht following tooth extrction, (i) there ws reduction of oth the height (2.5 7 mm) nd width (30 7 mm) of 606

2 Aru jo et l. Bone modeling following implnt instlltion C SLA B/ 1 mm 2 mm 3 mm Fig. 1. Clinicl photogrph illustrting the position of the implnts plced in the distl extrction socket of the mndiulr third premolr () nd first molr (). Note tht the width of the mrginl gp is lrger t the molr thn t the premolr site. the lveolr process, (ii) most chnge occurred in the first months, while (iii) minor dditionl diminution of the ridge continued over periods rnging etween 10 nd 20 weeks. Pietrokovski & Mssler (1967) exmined plster csts of the mndile nd mxill from 30 ptients with complete nturl dentition nd mesured the width of the vrious dentte segments. t ws oserved tht the uccl nd the lingul/ pltl dimensions of the lveolr ridge of the right nd left side of the jws were lmost identicl. Susequently, 149 dentl csts were identified tht hd one tooth missing on one side of the jw while the contr lterl tooth ws still present. Mesurement of mount of lveolr ridge resorption tht hd occurred fter tooth extrction ws otined y series of mesurements in the edentulous nd the opposite dentte regions. The uthors concluded: the mount of resorption ws greter long the uccl surfce thn long the lingul or pltl surfce in every specimen exmined, lthough the solute mounts nd differences vried widely. Pietrokovski & Mssler (1967), in ddition, demonstrted tht the mount of tissue ttenution ws greter in the edentulous molr region thn in the incisor nd premolr regions of oth the mxill nd the mndile. Schropp et l. (2003) studied chnges of the lveolr ridge tht took plce following single-tooth extrction in 46 p- tients ged etween 20 nd 73 yers. The ltertions were studied in rdiogrphs nd on csts tken immeditely fter tooth extrction nd t 3, 6 nd 12 months of follow-up. The uthors reported tht following tooth extrction, the width of the ridge ws reduced pproximtely 50% nd tht most chnge occurred during the first 3 months of heling. The chnge in the molr region ws greter thn in the premolr regions nd more pronounced in the mndile thn in the mxill. n this context, it must e relized tht dt descriing ridge ltertions in the stu- Fig. 2. Schemtic drwing descriing the different lndmrks from which histometric mesurements were performed. SLA, mrginl level of the rough implnt surfce; C, mrginl level of the one crest; B/, mrginl level of one-to-implnt contct; 1, 2, nd 3 mm represent the levels t which the width of the uccl nd lingul wlls ws determined. dies referred were otined from mesurements tht included oth the hrd nd the soft tissues of the ridge. No ttempt ws mde to seprte the contriution of the Fig. 3. Clinicl photogrph illustrting the implnt sites fter 12 weeks of heling. The peri-implnt mucos t oth the molr () nd premolr () sites hd norml texture nd color nd ws free of signs of inflmmtion. 607 Clin. Orl mpl. Res. 17, 2006 /

3 Arújo et l. Bone modeling following implnt instlltion Tle 1. Results of histometric mesurements (men nd SD) descriing the distnce etween the vrious lndmrks SLA-C SLA-B/ C-B/ Buccl Lingul Buccl Lingul Buccl Lingul 4 weeks Premolr 0.7 (0.6) 1.4 (0.2) 0.8 (0.7) 0.2 (0.1) 0.1 (0.4) 1.5 (0.6) Molr 0.2 (0.9) 0.8 (0.9) 1.5 (0.3) 0.6 (0.5) 1.7 (1.5) 1.4 (1.7) 12 weeks Premolr 2.1 (0.5) 0.4 (0.3) 2 (0.5) 0.1 (0.2) 0.1 (0) 0.5 (0.3) Molr 1 (0.7) 0 (0.9) 0.8 (0.8) 0.6 (0.6) 0.2 (0.3) 0.6 (0.6) Negtive vlues indicte tht C or B/ were picl to SLA. For revitions, see Fig. 2. extrction socket... the clinicl outcome nd degree of osseointegrtion does not differ from implnts plced in heled, mture one. This study, however, did not report dt for uccl lingul sites nd did not include informtion on whether loss of crestl one height hd occurred. Findings from experiments in humns nd dogs, however, (Botticelli et l. 2003, 2003; Arújo et l. 2005) demonstrted tht mrked reduction of the height of the lveolr ridge consistently occurred following tooth extrction, nd tht implnt instlltion in the fresh extrction socket did not interfere with the process of one modeling. Further, in clinicl study compring one heling following implnt plcement immeditely fter tooth extrction or fter 6 8 weeks, Covni et l. (2004) oserved tht mrked reduction of the uccl lingul width of the one ridge hd occurred 4 6 months fter implnt plcement nd independent of the timing of implnt plcement. The ojective of the present experiment ws to determine whether modeling of the lveolr ridge tht occurs following tooth extrction nd implnt plcement (i) ws influenced y the size of the hrd tissue wlls of the socket, nd (ii) would continue fter the first 4 weeks of heling, i.e. once most of the effect of the surgicl trum ws overcome. L Fig. 4. Premolr site; 4 weeks. Buccl lingul section. B, uccl one wll; L, lingul one wll;, implnt;, peri-implnt mucos. Ldewig s firin stining; originl mgnifiction 1.6. two components to the vrious dimensions ssessed. Polntonio et l. (2001) included 48 ptients in study to determine the outcome of implnttion in fresh extrction sockets. One implnt ws plced in n extrction socket nd one implnt in fully heled ridge. The implnts, together with surrounding tissues, were removed fter 12 months nd ground sections were prepred. The uthors stted tht when screw-type dentl implnt... is plced into fresh B Mteril nd methods The Ethics Committee for Animl Reserch t the University of Mring, Brzil, pproved the study protocol. Six egle dogs out 1-yer-old were included in the experiment. The nimls were fed pellet diet nd sujected to regulr mechnicl tooth nd implnt clening. During surgicl procedures, the dogs were nesthetized with intrvenously dministered Pentothl Ntrium s (30 mg/ ml; Aot Lortories, Chicgo, L, USA). The third premolrs nd first molrs in oth qudrnts of the mndile ( 3 P 3 nd 1M 1 ) were used s experimentl teeth. The mesil root cnls were remed nd filled with gutt-perch. Mucoperiostl full-thickness flps were elevted to disclose the uccl nd lingul hrd tissue wll of the ridge. The experimentl teeth were hemi-sected nd the distl roots were removed with the use of forceps. The uccl lingul dimension of the entrnce of the fresh extrction socket ws mesured using sliding cliper. mplnts (Strumnn s Stndrd mplnt, 4.1 mm wide nd 6 or 8 mm long; Strumnn, Wldenurg, Switzerlnd) were instlled in the fresh extrction sockets. The recipient sites were prepred for implnt instlltion ccording to the guide- 608 Clin. Orl mpl. Res. 17, 2006 /

4 Aru jo et l. Bone modeling following implnt instlltion NB Fig. 5. Buccl lingul section of premolr site. Higher mgnifiction of the res (squres) outlined in Fig. 4. Lingul () nd uccl () spects of the crest nd mrginl gp regions., lveolr one; NB, new one;, implnt. Ldewig s firin stining; originl mgnifiction 5.0. The dogs were scrificed with n overdose s of Pentothl Ntrium (Aot Lortories, Chicgo, L, USA) nd perfused, through the crotid rteries, with fixtive contining mixture of 5% glutrldehyde nd 4% formldehyde (Krnovsky 1965). The mndiles were dissected. Ech implnt site ws s removed using dimond sw (Exct Apprteeu, Norderstedt, Hmurg, Germny). The iopsies were processed for ground sectioning ccording to the methods descried y Donth & Breuner (1982) nd Donth (1988). The smples were dehydrted in incresing grdes of ethnol, infils trted with methcrylte (Technovit 7200 VLC-resin; Kulzer, Friedrichrsdorf, Germny), polymerized nd sectioned in the uccl lingul plne using cutting grinds ing device (Exkt, Apprteu). From ech iopsy unit, one uccl lingul section representing the centrl re of the site ws prepred. The sections were reduced to thickness of out 20 mm y micro-grinding nd polishing. The sections were stined in Ldewig s firin stin (Donth 1993). Histologicl exmintion The exmintions were mde in Leitz s DM-RBE microscope (Leic, Wetzlr, Germny). n the sections, liner mesurements (mgnifiction 16) were mde etween the following lndmrks (Fig. 2): SLA: the mrginl termintion of the rough surfce; C: the crest of the uccl or lingul one wll; nd B/: the most coronl point of contct etween one nd implnt. L B Fig. 6. Molr site; 4 weeks. Buccl lingul section. B, uccl one wll; L, lingul one wll;, implnt;, peri-implnt mucos. Ldewig s firin stining; originl mgnifiction 1.6. lines provided y the mnufcturer. The mrginl level of the modified, SLA-coted surfce of the implnt ws following plcement consistently locted picl of the uccl one crests (Fig. 1). Heling cps s (Strumnn Dentl mplnt System, Wldenurg, Switzerlnd) were djusted to the implnts. The flps nd the wound mrgins were replced nd secured to llow semi-sumerged heling of the experimentl sites. The sutures were removed fter 2 weeks. The root extrction nd implnt instlltion procedure ws first performed in the right side of the mndile. Two months lter, n identicl procedure ws repeted in the left mndile. The nimls were scrificed 1 month fter the second extrction nd implnttion procedure. The width of the uccl nd lingul one wlls ws determined y mesuring the distnce etween the uccl or lingul surfce of the implnt ody nd the outer surfce of the hrd tissue wll. The ssessments were mde t the SLA level nd 1, 2 nd 3 mm picl of SLA. The men vlues nd stndrd devition mong nimls were clculted for ech vrile nd implnt loction. Results The men uccl lingul width of the entrnce of the extrction socket of the premolr sites ws mm, while 609 Clin. Orl mpl. Res. 17, 2006 /

5 Aru jo et l. Bone modeling following implnt instlltion lr molr regions s well s the peri-implnt mucos t clinicl check-ups fter the first two weeks ws free from overt signs of inflmmtion (Fig. 3). The thickness of the socket wlls t vrious levels long the implnt ws determined in sections representing the centrl portion of the experimentl site. Only sections in which the ody of the implnt ws 43.2 mm were used for the ssessments. For this reson, one out of 30 sites hd to e discrded. CNT CNT NB Histologicl nd histometric oservtions Peri-implnt mucos Fig. 7. Buccl lingul section of molr site. Higher mgnifiction of the res (squres) outlined in Fig. 6. Lingul () nd uccl () spects of the crest nd mrginl gp regions., lveolr one; NB, new one; CNT, provisionl connective tissue;, implnt. The rrows indicte the presence of osteoclsts. Ldewig s firin stining; originl mgnifiction 5.0. Tle 2. Results of histometric mesurements (men nd SD) descriing the width of the uccl nd lingul one wlls t 4 weeks nd 12 weeks in premolr nd molr sites At SLA Buccl 4 weeks Premolr 0 (0) Molr 1.6 (1.3) 12 weeks Premolr 0 (0) Molr 0 (0) At 1 mm At 2 mm At 3 mm Lingul Buccl Lingul Buccl Lingul Buccl Lingul 1.4 (0.8) 1.3 (0.5) 0.4 (0.3) 1.9 (0.8) 1.8 (0.5) 1.7 (0.7) 0.8 (0.2) 2.2 (0.8) 2.1 (0.4) 2.1 (0.2) 1 (0.2) 2.5 (0.8) 2.3 (0.3) 2.2 (0.2) 1.1 (0.8) 0.7 (0.7) 0 (0) 0.9 (0.3) 1.9 (0.7) 1.1 (0.8) 0.3 (0.3) 1.3 (1) 2.2 (0.8) 1.4 (0.6) 0.5 (0.3) 1.7 (0.9) 2.5 (0.8) 1.7 (0.4) For revitions, see Fig. 2. Fig. 8. Buccl lingul section. Lrge numer of osteoclsts resided on the outer surfce of oth the lingul () nd uccl () one wlls. Ldewig s firin stining; originl mgnifiction 10. the corresponding dimension t the molr site ws mm. Heling following 610 Clin. Orl mpl. Res. 17, 2006 / The mucos t the implnt sites ws protected with wide, well-kertinized orl epithelium tht ws continuous with thin rrier epithelium tht fced the implnt surfce. The dense connective tissue tht resided etween the two epithelil comprtments ws devoid of infiltrtes of inflmmtory cells. tooth extrction nd implnt instlltion ws uneventful. The gingiv in the premo- mplnt sites fter 4 weeks of heling (Tle 1) At premolr sites (Fig. 4), the smll mrginl gp etween the implnt nd the one ws occupied y vrious mounts of provisionl connective tissue nd newly formed woven one (Fig. 5, ). The crest of the lingul one wll (Fig. 5) ws locted out 1.4 mm coronl to the SLA order (Tle 1) while the uccl crest (Fig. 5) ws consistently locted t vrying distnce picl of this lndmrk (SLA-C: mm). No residul one defect (C-B/; Tle 1) ws seen t the uccl spect ut t the lingul spect (Fig. 5) mm deep ngulr hrd tissue defect ws present. The center of the uccl nd lingul one wlls ws comprised of lmellr one surrounded y newly formed one. The numer of one multicellulr units (BMUs) ws lrger in the lingul thn in the uccl socket wll. At the molr sites (Fig. 6), the tissue within the wide mrginl gp ws comprised of similr mounts of provisionl connective tissue nd newly formed one (Fig. 7, ). The depth of the residul hrd tissue gp (Fig. 7, ) t the uccl spect ws mm nd mm t the lingul spects (Tle 2). The outer surfce of oth the uccl nd lingul one wlls exhiited the

6 Aru jo et l. Bone modeling following implnt instlltion presence of lrge numer of osteoclsts (Fig. 8, ). mplnt sites fter 12 weeks of heling (Tle 1) At the uccl spect of the premolr sites, no residul hrd tissue gp could e oserved (Figs 9, 10). The crest (C) of the uccl one wll s well s the level of one-to-implnt contct (B/) ws out 2 mm picl of the SLA order (SLA-C: mm, SL/: mm) (Fig. 10). At the lingul spect (Fig. 10), shllow ( mm deep) mrginl defect remined (C-B/; Tle 1). At molr sites (Figs 11 nd 12), the uccl one crest ws locted mm picl of SLA while the mrginl level of one-to-implnt contct ws found on the verge mm picl of the SLA order of the implnt (SLA-B/) (Fig. 12). At the lingul spect (Fig. 12), shllow ( mm deep) ngulr defect (C-B/) remined. L Width of the uccl nd lingul one wlls (Tle 2) B Fig. 9. Premolr site; 12 weeks. Buccl lingul section. B, uccl one wll; L, lingul one wll;, implnt;, peri-implnt mucos. Ldewig s firin stining; originl mgnifiction 1.6. Fig. 10. Buccl lingul section of the premolr site. Higher mgnifiction of the res (squres) outlined in Fig. 9. Lingul () nd uccl () spects of the crest nd mrginl gp regions. Note tht the mrginl level of one-to-implnt contct t the lingul spect is close to the SLA order (dotted line), while t the uccl spect this contct level is out 2 mm picl of SLA. Ldewig s firin stining; originl mgnifiction 5.0. Four weeks of heling. n the premolr sites (Fig. 13, Tle 2), no uccl one ws present t the SLA level, ut the hrd tissue wll ws , , nd mm wide t the reference levels 1, 2, nd 3 mm picl of SLA. The corresponding dimensions for the lingul wll were mm t the level of SLA nd , , nd mm t more piclly locted levels. n the molr sites (Fig. 14, Tle 2), the overll uccl one wll ws thicker thn its counterprt t the premolr sites. At the SLA level, the uccl one ws mm wide nd incresed in thickness (1.9, 2.2, nd 2.5 mm) the further picl of SLA the mesurements were performed. The lingul one of the molr site hd width tht ws similr to tht of the premolr site. Twelve weeks of heling. The mesurements performed t the uccl spect of the premolr sites (Fig. 13, Tle 2) showed tht no one ws present t the SLA nd the 1 mm reference levels. At the 2 nd 3 mm levels, the uccl one wll ws nd mm wide. The lingul one wll hd width tht ws similr to tht oserved t the 4-week intervl. 611 Clin. Orl mpl. Res. 17, 2006 /

7 Aru jo et l. Bone modeling following implnt instlltion disppered s result of one fill nd resorption of the crest regions of the hrd tissue wlls. The modeling in the mrginl defect region ws ccompnied y mrked ttenution of the dimensions of the uccl nd lingul one wlls of the implnt sites. Thus, implnt plcement evidently filed to preserve the hrd tissue dimension of the ridge following tooth extrction. P M P M Size of mrginl defect L B Fig. 11. Molr site; 12 weeks of heling. Buccl lingul section. B, uccl one; L, lingul one;, implnt. The width of the uccl nd lingul one wlls. Ldewig s firin stining; originl mgnifiction 1.6. Fig. 12. Buccl lingul section of the molr site. Higher mgnifiction of the res (squres) outlined in Fig. 11. Lingul () nd uccl () spects of the crest nd mrginl gp regions., lveolr one;, periimplnt mucos;, implnt. Ldewig s firin stining; originl mgnifiction 10. n the molr sites (Fig. 14, Tle 2), there ws no one present t the uccl SLA level, ut t the 1, 2, nd 3 mm reference levels, the uccl one ws , 1.3 1, nd mm thick. The lingul one wll ws mm wide t the SLA level nd , , nd mm t the remining levels. 612 Clin. Orl mpl. Res. 17, 2006 / Discussion The present investigtion demonstrted tht mrked hrd tissue ltertions occurred during heling following tooth extrction nd implnt instlltion in fresh extrction socket. The mrginl gp tht ws present etween the implnt nd the wlls of the socket t implnttion The extrction socket of the distl root of the mndiulr third premolrs nd first molrs ws selected for implnt instlltion s the size of the teeth nd the dimensions of the ridge of the two sites re mrkedly different (Brtley et l. 1970). mplnts of the sme size (dimeter 4.1 mm nd length 8 mm) were plced in sockets of vrying dimensions. As result, the width nd depth of the mrginl defect (gp) etween the implnt nd the wlls of the socket were considerly lrger in the molr thn in the premolr loctions (Fig. 1). n the iopsy mteril, it ws noted tht the smller (o0.3 mm wide) gps t the premolr sites hd een resolved lredy fter 4 weeks of heling while the lrger (1 1.3 mm) horizontl defects in the molr sites were completely resolved first in the 12-week specimens. These findings re in greement with dt presented y Botticelli et l. (2003, 2003) from experiments in the dog. They studied one pposition in 1 mm wide mrginl defects prepred round implnts plced in fully heled ridge. The defects were prtilly heled through ppositionl one formtion fter 1 nd 2 months ut completely resolved with proper one fill nd one-to-implnt contct first fter 4 months. Crestl resorption n the present experiment, it ws oserved tht the process of one pposition in the mrginl gp region ws ccompnied y hrd tissue ltertions in the crestl regions of the uccl nd lingul one wlls. n the premolr sites, these tissue ltertions resulted in mrked reduction (42 mm) of the height of the thin uccl crest nd loss of one-to-implnt contct in the mrginl portion of the implnt. This finding is in greement with dt recently pulished y Botticelli et l. (2006). They studied heling of mrginl defects tht occurred t

8 Arújo et l. Bone modeling following implnt instlltion mm uccl SLA 1 mm 2 mm 3 mm implnts plced in fresh extrction sockets in the premolr regions of the mndile of dogs. The uthors reported tht fter 4 months, some one fill hd occurred in the more picl prt of the mrginl defects ut lso tht this one deposition ws 0 mm lingul 1 month 3 months Fig. 13. Premolr site. Schemtic drwing descriing the dimensions of the uccl nd lingul one wlls t different reference levels (SLA, 1, 2, 3 mm picl of SLA) nd intervls of heling. The lue rs represent 4 weeks nd the purple rs represent 12 weeks of heling. The shded res illustrte the volume of one t the two intervls of heling studied. uccl mm SLA 1 mm 2 mm 3 mm lingul 1 month 3 months Fig. 14. Molr site. Schemtic drwing descriing dimensions of the uccl nd lingul one wlls t different reference levels (SLA, 1, 2, 3 mm picl of SLA) nd intervls of heling. The lue rs represent 4 weeks nd the purple rs represent 12 weeks of heling. The shded res illustrte the volume of one t the two intervls of heling studied. mm ccompnied y mrked loss of one in the mrginl segments of the socket. The molr sites in the current study initilly hd wider mrginl defect thn the premolr sites ut similr width of the uccl one wll (Fig. 1). During the first 4 weeks of heling, the mrginl gp ws filled with newly formed one nd provisionl connective tissue tht ws replced with woven one in the lter phse of heling. The width of the uccl wll in the molr sites ws it herey incresed. Also, this wide hrd tissue wll ws, however, exposed to mrked modeling nd tenution, lthough the ensuing diminution of its height hd less effect on the level of one-to-implnt contct thn ws the cse t the premolr sites ( 0.8 vs. 2 mm). n other words, the wider the comined defect nd one wll dimension ws in the present study, the less the reduction of the one-to-implnt contct. Reduction of the width of the socket wlls One importnt oservtion mde in the present study ws the mrked reduction of the thickness of the uccl one wlls tht occurred etween 4 nd 12 weeks (Tle 2, Figs 13 nd 14). t is ovious from the dt reported tht this decrese ws more pronounced in the thicker uccl one wll t molrs thn in the thinner wll t premolr sites. This finding is in greement with dt reported from mesurements mde on csts from edentulous regions in humns (Johnson 1963; Pietrokovski & Mssler 1967; Schropp et l. 2003). n the studies referred to the mount of uccl resorption ws much more pronounced thn the resorption of the lingul spect, nd the resorption in the molr region ws more sustntil thn tht which occurred in the premolr region. n the present nlysis, it ws noticed tht the width of the lingul wll, t reference levels 1, 2, nd 3 mm picl of SLA of the premolr ut not t the molr sites, remined unchnged etween 4 nd 12 weeks. A further nlysis of the histologicl sections reveled tht new one hd formed on the outer spects of the lingul wll of the premolr sites in this intervl (Fig. 5). Such incrementl one formtion is normlly the result of environmentl influences such s lod (Ruin et l. 1994). n the present experiment, the locl environment, e.g. the mrkedly reduced dimension of the uccl one wll my hve stimulted one formtion t the lingul wll. t is, thus, suggested tht the new one tht formed t the lingul surfce compensted for one loss tht occurred t the uccl surfce. Similr findings were 613 Clin. Orl mpl. Res. 17, 2006 /

9 Arújo et l. Bone modeling following implnt instlltion reported y Crmgnol et l. (1999) from experiments in dogs. Position of implnt in reltion to one wlls The shpe (volume) of the lveolr process is determined y the form (size) of the teeth, their xis of eruption nd inclintion in occlusion (Schroeder 1986). This mens tht t dentte sites, the size of the socket s well s its hrd tissue wlls my vry considerly. This fct must e considered when tretment plnning clls for the plcement of implnts in fresh extrction sockets. Thus, the findings of the present experiment clerly showed tht the thinner one wllofsuchsitendtheclosertothis wll the implnt is plced, the higher the risk of compromised heling nd occurrence of one dehiscence. References Arújo, M.G., Sukekv, F., Wennström, J.L. & Lindhe, J. (2005) Ridge ltertions following implnt plcement in fresh extrction sockets: n experimentl study in the dog. Journl of Clinicl Periodontology 32: Brtley, M.H., Tylor, G.N. & Jee, W.S.S. (1970) Teeth nd Mndile n: Andersson, A., ed. The Begle s n Experimentl Dog, Ames, A, USA: The ow Stte University Press. Botticelli, D., Berglundh, T., Buser, D. & Lindhe, J. (2003) Appositionl one formtion in mrginl defects t implnts. An experimentl study in the dog. Clinicl Orl mplnts Reserch 14: 1 9. Botticelli, D., Berglundh, T., Buser, D. & Lindhe, J. (2003) The jumping distnce revisited. An experimentl study in the dog. Clinicl Orl mplnts Reserch 14: Botticelli, D., Persson, L.G., Lindhe, J. & Berglundh, T. (2006) Bone tissue formtion djcent to implnts plced in fresh extrction sockets. An experimentl study in dogs. Clinicl Orl mplnts Reserch 17: Crmgnol, D., Arújo, M., Berglundh, T., Alrektsson, T. & Lindhe, J. (1999) Bone tissue rection round implnts plced in compromised jw. Journl of Clinicl Periodontology 26: Covni, U., Bortoli, C., Brone, A. & Sordone, L. (2004) Bucco-lingul crestl one jw. Chnges fter immedite nd delyed implnt plcement. Journl of Periodontology 75: Donth, K. (1988) Die Trenn-Dünnschliff-Technik zur Herstellung histologischer Präprten von nicht schneidren Geween und Mterilen. Der Präprtor 34: Donth, K. (1993) Preprtion of Histologic Sections (y Cutting Grinding Technique for Hrd Tissue nd other Mteril not Suitle to e Sectioned y Routine Methods) Equipment nd Methodicl Performnce. Norderstedt: EXACT Kulzer-Puliction. Donth, K. & Breuner, G.-A. (1982) A method for the study of undeclcified ones nd teeth with ttched soft tissues. The Säge Schliff (swing nd grinding) technique. Journl of Orl Pthology 11: Johnson, K. (1963) A study of the dimensionl chnges occurring in the mxill fter tooth extrction Prt. Norml heling. Austrlin Dentl Journl 8: Johnson, K. (1969) A study of the dimensionl chnges occurring in the mxill following tooth extrction. Austrlin Dentl Journl 14: Krnovsky, M.J. (1965) A formldehyde glutrldehyde fixtive of high osmolrity for use in electron microscopy. Journl of Cell Biology 27: Polntonio, M., Dolci, M., Scrno, A., d Archivio, D., Plcido, G., Tumini, V. & Pitelli, A. (2001) mmedite implnttion in fresh extrction sockets. A controlled clinicl nd histologicl study in mn. Journl of Periodontology 72: Pietrokovski, J. & Mssler, M. (1967) Alveolr ridge resorption following tooth extrction. Journl of Prosthetic Dentistry 17: Rogers, W. & Appleum, E. (1941) Chnges in the mndile following closure of the ite with prticulr reference to edentulous ptients. Journl of Americn Dentl Assocition 28: Ruin, C., Gross, T., Donhue, H., Guilk, F. & McLeod, K. (1994) Physicl nd environmentl influences on one formtion. n: Brighton, C.T., Friedlender, G. & Lne, J.M., eds. Bone Formtion nd Repir. 1st edition, Rosemont: Americn Acdemy of Orthopedic surgeons. Schroeder, H.E. (1986) The Periodontium. Berlin: Springer-Verlg, p Schropp, L., Wenzel, A., Kostopoulos, L. & Krring, T. (2003) Bone heling nd soft tissue contour chnges following single-tooth extrction: clinicl nd rdiogrphic 12-month prospective study. The nterntionl Journl of Periodontics nd Restortive Dentistry 23: Tylmn, S.D. & Tylmn, S.G. (1960) Theory nd Prctice of Crown nd Bridge Prosthodontics.4th edition, St. Louis: The C.V. Mosy Compny. 614 Clin. Orl mpl. Res. 17, 2006 /