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28 Implant Tribune Italian Edition - Maggio 2016 Speciale Regeneration SR < < pagina 27 After four months, it was 4.6 ± 0.8 mm, showing an increase of 1.8 ± 0.7 mm, which was statistically significant (p = 0.0001). The thickness of the buccal bone was measured at baseline and rangedfrom1.0to3.0mm,withamean of2.1±0.7mm(Table1).Themeanwidth ofthealveolarcrestatbaselinewas9.2± 1.3mm,andafterfourmonths,itwas7.6 ± 1.2 mm; therefore, the mean width of the alveolar crest showed a decrease of 1.6 ± 0.5 mm (p < 0.0001). The compari- sonbetweenthethicknessofthebuccal bone wall and the width of the alveolar crest indicated that the correlation be- tween the two values was statistically significant (Table 2). Four months after the ridge preservation procedure, the vertical bone loss was 0.2 ± 0.7 mm for mesialsites,1.1±0.9mmforbuccalsites, 0.2 ± 0.8 mm for distal sites and 0.9 ± 0.9 mm for palatal/lingual sites. The dimensional changes were statistically significant for all of the sites (Table 2). The histological analysis performed on the retrieved bone cores found that the granulesofgraftedbonewerestillpres- ent, even though new trabecular bone could be observed in all of the speci- mens.Osteocyticlacunaecouldbeseen on the particles’ surfaces, and newly formedbonewasobservedinsidesome of the resorption areas of the biomate- rial. Vascular growth close to the newly formed bone was also evident, and no inflammatory cells or foreign body re- action around the biomaterial granules wasobserved(Fig.13). Discussion Ridge preservation techniques have been proposed in order to reduce the bone volume shrinkage that follows a tooth extraction, since several studies have reported resorption of both verti- 1. Barone A, Aldini NN, Fini M, Giardino R, Calvo Guirado JL, Covani U. Xenograft versus extraction alone for ridge preservation after tooth removal: a clinical and hi- stomorphometricstudy.JPeriodontol.2008Aug;79(8):1370–7. 2. DarbyI,ChenST,BuserD.Ridgepreservationtechniquesforimplanttherapy.IntJ OralMaxillofacImplants.2009;24Suppl:260–71. 3. HämmerleCH,AraújoMG,SimionM;OsteologyConsensusGroup2011.Evidence- based knowledge on the biology and treatment of extraction sockets. Clin Oral Im- plantsRes.2012Feb;23Suppl5:80–2. 4. Barone A, Ricci M, Tonelli P, Santini S, Covani U. Tissue changes of extraction so- ckets in humans: a comparison of spontaneous healing vs. ridge preservation with secondarysofttissuehealing.ClinOralImplantsRes.2013Nov;24(11):1231–7. 5. Vignoletti F, Matesanz P, Rodrigo D, Figuero E, Martin C, Sanz M. Surgical pro- tocols for ridge preservation after tooth extraction. A systematic review. Clin Oral ImplantsRes.2012Feb;23Suppl5:22–38. 6. Araújo MG, Lindhe J. Dimensional ridge alterations following tooth extraction: an experimentalstudyinthedog.JClinPeriodontol.2005Feb;32(2):212–8. 7. SchroppL,WenzelA,KostopoulosL,KarringT.Bonehealingandsofttissuecontour changesfollowingsingle-toothextraction:aclinicalandradiographic12-monthpro- spectivestudy.IntJPeriodonticsRestorativeDent.2003Jul-Aug;23(4):313–23. 8. CovaniU,RicciM,BozzoloG,ManganoF,ZiniA,BaroneA.Analysisofthepattern of the alveolar ridge remodelling following single tooth extraction. Clin Oral Im- plants Res. 2011 Aug;22(8):820–5. 9. Fickl S, Zuhr O, Wachtel H, Stappert CF, Stein JM,HürzelerMB.Dimensionalchangesofthealveolarridgecontourafterdifferent socketpreservationtechniques.JClinPeriodontol.2008Aug;35(10):906–13. 9. Fickl S, Zuhr O, Wachtel H, Stappert CF, Stein JM, Hürzeler MB. Dimensional changes of the alveolar ridge contour after different socket preservation techniques. JClinPeriodontol.2008Aug;35(10):906–13. 10. Barone A, Orlando B, Cingano L, Marconcini S, Derchi G, Covani U. A randomized clinical trial to evaluate and compare implants placed in augmented versus nonau- gmentedextractionsockets:3-yearresults.JPeriodontol.2012Jul;83(7):836–46. 11. OghliAA,StevelingH.Ridgepreservationfollowingtoothextraction:acomparison between atraumatic extraction and socket seal surgery. Quintessence Int. 2010 Jul- Aug;41(7):605–9. 12. FarinaE,MendittiD,DeMariaS,MezzogiornoA,EspositoV,LainoL,CarinciF.A modelofhumanboneregeneration:morphological,cellularandmolecularaspects.J Osseointegration.2009Aug;1(2):42–53. 13. SerinoG,BiancuS,IezziG,PiattelliA.Ridgepreservationfollowingtoothextraction usingapolylactideandpolyglycolidespongeasspacefiller:aclinicalandhistological studyinhumans.ClinOralImplantsRes.2003Oct;14(5):651–8. 14. Barone A, Borgia V, Covani U, Ricci M, Piattelli A, Iezzi G. Flap versus flapless pro- cedure for ridge preservation in alveolar extraction sockets: a histological evaluation in a randomized clinical trial. Clin Oral Implants Res. 2015 Jul;26(7):806–13. Epub 2014Mar1. 15. Barone A, Toti P, Piattelli A, Iezzi G, Derchi G, Covani U. Extraction socket healing in humans after ridge preservation techniques: comparison between flapless and flappedproceduresinarandomizedclinicaltrial.JPeriodontol.2014Jan;85(1):14–23. 16. Engler-HammD,CheungWS,YenA,StarkPC,GriffinT.Ridgepreservationusing a composite bone graft and a bioabsorbable membrane with and without primary woundclosure:acomparativeclinicaltrial.JPeriodontol.2011Mar;82(3):377–87. 17. Novaes AB Jr, Fernandes PG, Suaid FA, de Moraes Grisi MF, Scombatti de Souza SL, Taba M Jr, Palioto DB, Muglia VA. Ridge preservation with acellular dermal matrixandanorganicbonematrixcell-bindingpeptideP-15aftertoothextractionin humans.Ahistologicandmorphometricstudy.JOsseointegration.2012Jun;4(2):23– 30.18. 18. Lekovic V, Kenney EB, Weinlaender M, Han T, lokkevold P, Nedic M, Orsini M. Bone regenerative approach to alveolar ridge maintenance following tooth extrac- tion.Reportof10cases.JPeriodontol.1997Jun;68(6):563–70. 19. LekovicV,CamargoPM,KlokkevoldPR,WeinlaenderM,KenneyEB,Dimitrijevic B, Nedic M. Preservation of alveolar bone in extraction sockets using bioabsorbable membranes.JPeriodontol.1998Sep;69(9):1044–9. 20. Simion M, Maglione M, Iamoni F, Scarano A, Piattelli A, Salvato A. Bacterial pene- trationthroughResolutresorbablemembraneinvitro.Anhistologicalandscanning electronmicroscopicstudy.ClinOralImplantsRes.1997Feb;8(1):23–31. 21. Fickl S, Zuhr O, Wachtel H, Bolz W, Huerzeler MB. Hard tissue alterations after socket preservation: an experimental study in the beagle dog. Clin Oral Implants Res.2008Nov;19(11):1111–8. 22. Araújo MG, Lindhe J. Ridge alteration following tooth extraction with and without flap elevation: an experimental study in the dog. Clin Oral Implants Res. 2009 Mar;20(6):545–9. 23. Van der Weijden F, Dell’Acqua F, Slot DE. Alveolar bone dimensional changes of postextractionsockets in humans: a systematic review. J Clin Periodontol. 2009 Dec;36(12):1048–58. 24. Vittorini Orgeas G, Clementini M, De Risi V, de Sanctis M. Surgical techniques for alveolar socket preservation: a systematic review. Int J Oral Maxillofac Implants. 2013Jul-Aug;28(4):1049–61. 25. NovaesABJr,MartinsdeBarrosRR,PapalexiouV,GonçalvesdeAlmeidaAL.Buc- cal bone loss after immediate implantation can be reduced by the flapless approach. JOsseointegration.2011Oct;3(3):45–55. 26. Cardaropoli D, Cardaropoli G. Preservation of the postextraction alveolar rid- ge: a clinical and histologic study. Int J Periodontics Restorative Dent. 2008 Sep- Oct;28(5):469–77. 27. Morjaria KR, Wilson R, Palmer RM. Bone healing after tooth extraction with or without an intervention: a systematic review of randomized controlled trials. Clin ImplantDentRelatRes.2014Feb;16(1):1–20. 28. Iezzi G, Degidi M, Piattelli A, Mangano C, Scarano A, Shibli JA, Perrotti V. Compa- rativehistologicalresultsofdifferentbiomaterialsusedinsinusaugmentationproce- dures:ahumanstudyat6months.ClinOralImplantsRes.2012Dec;23(12):1369–76. 29. Nannmark U, Sennerby L. The bone tissue responses to prehydrated and collagena- ted cortico-cancellous porcine bone grafts: a study in rabbit maxillary defects. Clin ImplantDentRelatRes.2008Dec;10(4):264–70. references Age (years) 40.5 ± 13.5 (20 ←→ 61) -14.8 (7.1) Males 15 Females 22 Experimental sites 37v Molars 25 Premolars 12 Mean buccal bone thickness at baseline (mm) 2.1 ± 0.7 (1 pp 3) Clinical parameters Site Baseline (mm) 4 months (mm) Difference (mm) P-value (baseline vs. 4 months) Vertical bone changes Mesial 11.4 ± 1.1 (10 <—> 14) 11.6 ± 1.3 (10 <—> 15) -0.2 ± 0.7 (-2 <—> +1) 0.0367 Buccal 12.8 ± 1.2 (10 <—> 15) 13.9 ± 1.1 (11 <—> 16) -1.1 ± 0.9 (-3 <—> +1) 0.000000145 (1.45 * 10-7 ) Distal 11.2 ± 1.1 (10 <—> 15) 11.5 ± 1.1 (10 <—> 14) -0.2 ± 0.8 (-2 <—> +1) 0.071 Lingual/ palatal 2.0 ± 1.4 (9 <—> 14) 12.9 ± 1.4 (10 <—> 15) -0.9 ± 0.9 (-3 <—> +1) 0.00000843 (8.43 * 10-6 ) Horizontal bone changes 9.2 ± 1.3 (7 <—> 12) 7.6 ± 1.2 (5 <—> 10) -1.6 ± 0.5 (-3 <—> -1) < 0.0001 (4.5 * 10-20 ) Width of keratinized gingiva 2.8 ± 0.9 (1 <—> 5) 4.6 ± 0.8 (3 <—> 6) 1.8 ± 0.7 (1 <—> 4) < 0.0001 (5.7 * 10-17 ) Tab. 1 - Demographic data. Tab. 2 - Dimensional changes four months after the ridge preservation procedure. Fig. 13 - Newly formed bone around the grafting material. No inflammatory cells or foreign body reaction was observed. cal and horizontal dimensions1,6,7,23. The use of various biomaterials and techniques has been proposed over time, but there is still no evidence to indicate the best choice. In the present study37, single-tooth extractions and the subsequent flapless ridge preser- vation procedures were performed. Cortico-cancellous porcine bone and a resorbable collagen membrane were usedinallofthecases,andseveralclin- ical parameters were measured at the toothextractionandafterfourmonths, including width of keratinized gingiva, thickness of the buccal bone wall, and changes to the vertical and horizontal dimensions. A minimally invasive tooth extraction technique, with preservation of the socket walls during the surgery, helps to maintain the architecture of the al- veolar crest1,4 even if bone remodeling is not completely avoidable9. A flapless surgical technique was chosen in our studybecause,eventhoughsomestud- ies have not reported any significant differences between a flapped and a flapless surgical technique5,24, Van der Weijden et al. assert that the elevation of a full-thickness flap is believed to compromise the blood supply, limiting the future regenerative potential23. Furthermore, the use of a flapless tech- niquehasbeendemonstratedtobeless traumatic for both hard tissue – avoid- inginterruptionofthebloodflow–and soft tissue – preserving the keratinized gingiva25,15,26. The exposure of the collagen membrane and the soft-tissue closurebysecondaryintentionseemed not to jeopardize the bone healing, and 100% of the ridge preservation proce- dures were successful. The width of the keratinizedgingivagained1.8±0.7mm after four months. These results cor- respond to those of other studies that usedasimilarsurgicalprotocol14. The evaluation of the clinical param- eters in this study confirmed the ef- ficacy of this surgical procedure in counteracting the soft- and hard-tissue shrinkageafteratoothextraction:both the vertical and horizontal dimensions showed a minimal decrease. In par- ticular, the vertical dimension lost 0.2 ± 0.7 mm at the mesial sites, 1.1 ± 0.9 mm at the buccal sites, 0.2 ± 0.8 mm at the distal sites and 0.9 ± 0.9mm at the palatal/lingual sites after four months. These results are in keeping with those reported in a recent systematic review that compared the outcomes after tooth extractions with and without ridge preservation procedures27. In the case of the ridge preservation proce- dures,theverticalbonechangesranged from a gain of 1.3 ± 2.0 mm to a loss of 0.62 ± 0.51 mm, with follow-up times ranging from three to nine months27. In the current study, the ridge preser- vation procedures in all of the exper- imental sites were successful, and im- plants were placed after four months, with further augmentation procedures being necessary only in 7% of the cas- es at the time of implant placement. Moreover, bone cores were harvested for the histological analysis at the time of implant placement. Corroborating the findings of other studies28,29. this studyfoundthatthecortico-cancellous porcine bone was effective in main- taining the architecture of post-extrac- tion sockets and demonstrated signs of active resorption at the same time. Iezzi et al. examined the use of various biomaterials and performed histolog- ical and histomorphometric analyses after six months28. Among the differ- ent grafting materials, cortico-cancel- lous porcine bone gave rise to a rim of osteoblasts with signs of active bone matrix deposition; in some areas, bone apposition was observed directly on the particles’ surfaces28. Similarly, the biomaterial used in this study showed a great percentage of newly formed bone. No inflammatory cells or foreign bodyreactionwasobservedinthebone samples,butnewbonetissueandblood vessel growth. Active resorption signs were evident, since osteocytic lacunae were observed at the surface of the bio- material granules. As found by another study29, collagenated porcine bone was demonstrated to be resorbable, showing active resorption signs on the surface of the particles. Another study investigated the effect of the exposure of the resorbable membrane to the oral cavity on bone healing, comparing a flapped and a flapless approach14. The percentages of newly formed bone, residual graft particles and marrow spaces were similar for the two groups, suggestingthattheexposureofthecol- lagen membrane had no detrimental effect on the regenerative process14. Similarly, in our study, the secondary intention healing seemed not to affect the bone quality, as seen in the bone cores. The findings of this study sup- port the hypothesis that secondary intention healing and exposure of the collagen membrane do not jeopard- ize bone regeneration, but improve the amount of keratinized gingiva. The ridge preservation technique was demonstrated to be effective in main- taining an adequate bone architecture, allowingthesubsequentimplantplace- ment without adjunctive augmenta- tion procedures in the majority of the cases Further studies are necessary to evaluate the influence of early expo- sure of the membrane on the forma- tion of new bone and on the integra- tion of the grafting material over time. Furthermore, a longer follow-up period could be useful in order o monitor the successofthebiomaterialandthequal- ityofthenewlyformedbone. Conclusion Withinthelimitsofthisprospectiveco- hort study, ridge preservation showed adequate regeneration of the bone and stability of the facial soft-tissue level. The flapless ridge preservation proce- dure maintained the horizontal and vertical bone dimensions, improving the amount of keratinized tissue. The exposure of the resorbable collagen membrane to the oral cavity seemed nottojeopardizethehealingprocessor thequalityofthenewlyformedbone. Competing interests: the authors declare that they have no competing interests related to this study. L’articolo è stato pubblicato su Journal of Oral Science & Rehabilitation No. 1, 2016