Abstract

The specimens retrieved from the experimental animals and described grossly in Part I were evaluated histologically. The disappointing results were more fully realized after microscopic examination that revealed far more critical information than was available from the purely clinical data obtained in Part I.

ORAL IMPLANTOLOGYFriday May 09 2003 10:28 PMAllen Press x DTPro SystemA COMPARISON OF ALLOGENEIC ANDAUTOGENOUS ILIAC MONOCORTICAL GRAFTSTO AUGMENT THE DEFICIENT ALVEOLARRIDGE IN A CANINE MODEL.II. HISTOLOGIC STUDYCLINICALA. Norman Cranin, DDS, DEngKEY WORDSHistologyBone graftNonviableInterfaceFibrousOsseousA. Norman Cranin, DDS, DEng, is a clinicalprofessor of Oral and Maxillofacial Surgeryand Implant Dentistry, NYU College ofDentistry, New York, NY, and is editor-in-chiefof the Journal of Oral Implantology. Addresscorrespondence to Dr Cranin, 232 KellyBoulevard, Staten Island, NY 10314 (e-mail:ncranin@optonline.net).132 Vol. XXIX/No. Three/2003posterior iliac crests. Clinical evaluationalone was not considered to be de-finitive. Therefore, each of the 20 quadrantswas evaluated histologically usinghematoxylin and eosin stain aftersectioning.METHODS AND MATERIALSThe specimens retrieved from the experimental animals and described grosslyin Part I were evaluated histologically. The disappointing results were more fullyrealized after microscopic examination that revealed far more critical informationthan was available from the purely clinical data obtained in Part I.Pthat had been harvested from the dogs'q autogenous contributions fied by the animal number ands w e d sli c Ea slips. co b with pared m a ts grafallogeneics coalveolar bone myountedveron glass slihdes, andaprotectedaiduaentiedto evaluate the success of into 5- to 6-mm thick sections, staine e w , ose ul ll ed e ogs d o use thIarNTRODUCTIONe tI of thisf 5study describedin orderThmbedde resultingin nitrocespecimens, afterrbeingcdut,orim 29_302 Mp_132File # 02emrant code. An average of 25 cross-sectionswere made of each quadrant. Thetechnician was unaware of how each ofthe specimens had been treated duringthe clinical phase.The 20 slide boxes were returned tothe author, who then employed 2 pathologiststo independently assess thestatus of each quadrant. The examiners,like the histotechnician, were unawareof the manner in which eachquadrant had been treated. Each wasasked to read the investigational protocolprior to undertaking his or herexaminations so that the informationAfter sacrifice and fixation, as describedin Part I, the 4 quadrants fromeach animal were resected using a reciprocatingsaw and sent to the PacificCoast Tissue Bank for decalcification,embedding, staining, and sectioning.*Order of treatment began with dog 5 and proceeded in reverse order. UR indicates upper right; UL, upper left; LL, lower left, LR,lower right; fib/os, fibrous/osseous; oss/fib, osseous/fibrous.Rating: good 5 50%-80% osseous integration; fair 5 20%-49% osseous integration; poor 5 no osseous tissue present; failed 5 nopoor section, lost during processingnormalsignificant resorption, beyond original host levelfibrous, all viablemostly fibrous, some crest resorption, few bony spursorim 29_302 Mp_133File # 02emA. Norman CraninRatingfairfailedgoodpoorgoodfailedfailedgoodpoorfailedfailedpoorpoorfailedfailedfailedin maxillae. This may be attributed tobetter vascularity. In contradiction,however, of the 8 poor/failed results, 4were found in each jaw. Since these last2 findings were inconclusive, other factorscould have been responsible forthe lack of predictability of the histologicresults. Among them might havebeen the surgical learning curve: dognumber 5 was the first dog treated,dog number 1 was the last. It is notsurprising, then, that the dogs treatedlast yielded the better results. The Tableindicates these findings. Of interestas well is a review of the 5 failed quadrants.Three (or 60%) occurred on theleft side, and the remainder on rightquadrants. One might assume, despitethe low n, that the operator's accessibilityto operative sites played no role.A variety of outcomes was reported:(1) osseous graft with osseous interface(good), (2) osseous graft withfibrous interface (fair), (3) fibrous graft(poor), and (4) nonviable scars (failed).In some cases, the results revealed actualbone loss as compared with theinitial dimensions.Considerations of the validity of thisJournal of Oral Implantology 133ORAL IMPLANTOLOGYFriday May 09 2003 10:28 PMAllen Press x DTPro SystemDogNumber Quadrant Graft Type11112222333344445555viable tissues, dimensional loss.being sought was understood. Thecodes, however, were not broken untilthe results had been registered. Eachquadrant was viewed using no fewerthan 8 of the most relevant sections.The examiners were asked to commenton whether a graft was present; whetherit was viable; and, if so, whether itwas osseous, fibrous, or a combinationof both. The interfaces were analyzedas well regarding their nature and viability.There was surprisingly littledisagreement between the 2 evaluators,and these few disputes were adjudicatedby conference. Finally, with the collaborationof 1 evaluator, Dr Dong SKim, histologic results were analyzed(the Table).The Table indicates that all 5 dogswho supplied the 20 quadrants wereevaluated. There were 2 control quadrants,which demonstrated the expectedslight change that occurs from mucoperiostealreflection (Figure 1a andb). There were 9 quadrants that receivedallogeneic grafts and 9 that hadbeen grafted with autogenous bone.Corroboration with the clinical resultswas not always consistent. AlthoughURULLLLRautogenousallogeneicallogeneicautogenousautogenousallogeneicURULLLLRURULautogenousallogeneicallogeneicallogeneicautogenousautogenousLLLRUR controlallogeneicallogeneicautogenousautogenousallogeneicULLLLRURULLL controlautogenous LRHistologic results*Interface Ridgeoss/fibnoneosseousosseousnonviableosseousfibrousoss/fibnonenoneosseousfibrousfibrousosseousnonviablenonviableosseousfib/osfibrous fibrousfibrousfibrousfibrousfibrousfibrousnonviablefib/osfib/osfibrousfib/osfibrous fibrous10 of the 18 quadrants appeared to beclinically improved, histologic assessmentsindicated that only 4 were ratedas successful (''good''). Of these, 3were allogeneic and 1 was autogenous(Figures 2a and b and 3). Of the remainder,2 were processed poorly andcould not be interpreted; 9 sections (3allogeneic, 6 autogenous) were adjudgedas partially resorbed (Figures 4and 5), and 5 were declared to be completelyresorbed (3 allogeneic, 2 autogenous;Figures 6 through 10). However,it should be noted that after soft tissuereflection, clinical evaluation of the extremes(the best and the worst results)was demonstrated clearly by histologiccorroboration. Descriptions of some ofthe more revelatory specimens will befound beneath their photomicrographs.DISCUSSIONAlthough 20 quadrants were completed,2 were lost because of poor processing.None of the sections revealedsalutary findings. The majority werefailures, and even the more satisfactorysites yielded disappointing results.Three of the 4 good results were foundTABLEHistologybony protuberance, well mineralizedslight fibrous haze, total loss of graftsolid, bony graft, well ossifiedpoor section, lost during processingfibrous, poorly organized, avascularsolid bony graft, lacunae, osteoblastsbone loss beyond graft, fibrosis over hostdebris and scar at crest, nonviable scarviable bony knob, good histo sizeviable fibrosseos graftviable, all fibrous, no mineralizationall fibrous, viable, no ossification50% viable fibrous, remainder scarnormalcrestal bone loss, all fibrous, osteoclastsorim 29_302 Mp_134File # 02emproject are subject to speculation. Sincethere have been no reports on the histologicor even clinical success ratescomparing autogenous to allogeneicgrafts in humans, these results, althoughseemingly disappointing,might indeed be similar to those foundin humans. Clinically, prior to reflectingthe mucoperiosteum of the dogs,detection of the nature of the graftsand their interfaces was rarely possible.The ridges appeared to be well-formedin all but 3 quadrants; broad at thecrest; and covered with pink, healthy,keratinized mucosae. The subsequentclinical (after soft-tissue elevation) andhistologic analyses were required inorder to demonstrate the less attractivefindings that are indicated in the Tablesof Parts I and II.Nonetheless, with the exception ofthe specimens that were shown to havesuffered clinical dimensional loss,mostof them would have provided successfulbearing areas for partial denturesaddles. Their service as implant sites,which was limited to 4 quadrants,would have been dependent on the levelsof bone apposition. The dilemmafaced by clinicians is that they are rarelypresented with opportunities toevaluate the results of their bone graftingusing histologic methods, and assuch might undertake endosteal implantationin less than optimal sites.eralized freeze-dried bone (DFDB) graft.There is a similarity between this sectionand the control seen in Figure 1a. The graft,which is delineated by the arrows, is wellmineralized, and its interface with the hostridge is well ossified (original magnification310). (b) Higher magnification of the sectionseen in Figure 2a. This view is centeredon the interface. There is some osteoid, butthe majority of the junction is mature bone(original magnification 340). FIGURE 3.Maxilla with successful autogenous bonegraft. The graft, which is of good size, isviable and well mineralized. The interfacereveals a combined fibrous and bony union(original magnification 310). FIGURE 4.Mandible with a partially resorbed ridge.There are some fibrous wisps at the site ofthe graft, a DFDB block. All of the tissuesat the operative site are viable (originalmagnification 310).ORAL IMPLANTOLOGYFriday May 09 2003 10:28 PMAllen Press x DTPro SystemCOMPARISON OF GRAFTS. II. HISTOLOGIC STUDYFIGURES 1-4. FIGURE 1. (a) Normal mandible. This is a control quadrant. The cortical surfaceirregularities might have been caused by the elevation of the mucoperiosteum. Of note isthe large fatty marrow space and the well-formed zone of cortex (original magnification310). (b) Normal maxilla. This is a control quadrant. There are smooth cortical surfacesand a very small marrow space. The large void is the nasal cavity and is lined with intactnasal mucosa (original magnification 310). FIGURE 2. (a) Mandible with successful demin-134 Vol. XXIX/No. Three/2003ORAL IMPLANTOLOGYFriday May 09 2003 10:28 PMAllen Press x DTPro SystemFIGURES 5-10. FIGURE 5. Maxilla with a partially resorbed DFDB graft and some viablebone adjacent to it (original magnification 310). FIGURE 6. Maxillary failure with totallyresorbed host site and no viable tissue in the area. Graft was autogenous bone (originalmagnification 310). FIGURE 7. Mandibular failure with much resorbed host site and littleviable tissue in the area. Graft material was autogenous bone (original magnification 310).FIGURE 8. Higher magnification of the section seen in Figure 7. At the resorbed bone surface(b), a reactive, thickened cortex is seen with some adjacent viable fibrous strands (originalorim 29_302 Mp_135File # 02emA. Norman CraninSUMMARY AND CONCLUSIONSFive dogs were partially edentulated(premolar areas, maxillae, and mandibles).They contributed 20 quadrantsfor the study of autogenous and allogeneicblock grafts for ridge augmentation.The results revealed an unsatisfactorysuccess rate, which appeared to belower than that found clinically in humans.The results regarding whichmaterialautogenous (from the animals'posterior iliac crests) or allogeneic(from dog demineralized, freezedriedbone)yielded better resultswere equivocal. This was disappointing,because considerable questions remainunanswered regarding how the 2materials can be compared as comparedwith human grafting. Possiblythe research model that had been selectedwas inappropriate. Alternatively,it might be that human results wouldbe similar if similar analyses could beperformed.ACKNOWLEDGMENTSHistologic sections were prepared byThe Pacific Coast Bone Bank. Gratitudeis extended to Eli Gendler, MD, for hisadvice and generous underwriting ofthe color photographs throughout. Theauthor is grateful for the constructivesuggestions made by Jack Lemons,PhD, for Parts I and II.magnification 340). FIGURE 9. Maxilla witha completely nonviable graft. There hasbeen very little change to the underlyinghost site except for minimal resorption(original magnification 340). FIGURE 10.Mandible with failed autogenous bonegraft. There is no repair or alteration at thesite of the resorption beneath the graft site(original magnification 340).Journal of Oral Implantology 135