Abstract

The surface characteristics of dental implants play an important role in their clinical success. One of the most important surface characteristics of implants is their surface topography or roughness. Many techniques for preparing dental implant surfaces are in clinical use: turning, plasma spraying, coating, abrasive blasting, acid etching, and electropolishing. The Osseotite surface is prepared by a process of thermal dual etching with hydrochloric and sulfuric acid, which results in a clean, highly detailed surface texture devoid of entrapped foreign material and impurities. This seems to enhance fibrin attachment to the implant surface during the clotting process. The authors retrieved 2 Osseotite implants after 6 months to repair damage to the inferior alveolar nerve. Histologically, both implants appeared to be surrounded by newly formed bone. No gaps or fibrous tissues were present at the interface. The mean bone-implant contact percentage was 61.3% (±3.8%).

BONE CONTACT AROUND ACID-ETCHEDIMPLANTS: A HISTOLOGICAL ANDHISTOMORPHOMETRICAL EVALUATION OF TWOHUMAN-RETRIEVED IMPLANTSRESEARCHMarco Degidi, MD, DDSGiovanna Petrone, DDS, PhDGiovanna Iezzi, DDSAdriano Piattelli, MD, DDSKEY WORDSAcid etchingBone contactOsseotiteImplant surfaceMarco Degidi, MD, DDS, is a visitingprofessor in the Dental School at theUniversity of Chieti, Italy, and is in privatepractice in Bologna, Italy.Giovanna Petrone, DDS, PhD, is apostdoctoral fellow in the Dental School,University of Chieti, Italy.Giovanna Iezzi, DDS, is a research fellow inthe Dental School, University of Chieti, Italy.Adriano Piattelli, MD, DDS, is a professorof Oral Medicine and Pathology and dean anddirector of studies and research at the DentalSchool, University of Chieti, Italy. Addresscorrespondence to Dr Piattelli at Via F.Sciucchi 63, Chieti, Italy 66100 (e-mail:apiattelli@unich.it).The surface characteristics of dental implants play an important role in theirclinical success. One of the most important surface characteristics of implants istheir surface topography or roughness. Many techniques for preparing dentalimplant surfaces are in clinical use: turning, plasma spraying, coating, abrasiveblasting, acid etching, and electropolishing. The Osseotite surface is prepared bya process of thermal dual etching with hydrochloric and sulfuric acid, whichresults in a clean, highly detailed surface texture devoid of entrapped foreignmaterial and impurities. This seems to enhance fibrin attachment to the implantsurface during the clotting process. The authors retrieved 2 Osseotite implantsafter 6 months to repair damage to the inferior alveolar nerve. Histologically,both implants appeared to be surrounded by newly formed bone. No gaps orfibrous tissues were present at the interface. The mean bone-implant contactpercentage was 61.3% (63.8%).INTRODUCTIONnitial stability of an implant isimportant for successful tissueintegration, and early osseointegrationis important for longtermimplant stability.1,2 Improvedsurvival of dental implantsin areas of poor bone qualityand quantity is important, and this factinspired a search for an improved surfacethat could enhance bone-implantcontact percentages.3 These implantsurface features have been demonstratedto be the only ones that influencethe amount of bone-implant contactpercentage and interface shearstrength.3,4 Modifications of the implantsurface features produce an increaseof the retention between the implantand the bone by enlarging thecontact surface, increasing the biomechanicalinterlocking between implantand bone, and by enhancing osteoblastactivity with an earlier formation ofbone at the interface.3-5An increase of the bone-implantcontact percentages with increasingroughness of the implant surface hasbeen reported.6-10 Greater surfaceJournal of Oral Implantology 13EVALUATION OF BONE CONTACT AROUND TWO RETRIEVED HUMAN IMPLANTSFIGURES 1-3. FIGURE 1. The implants have been inserted in the left mandible. FIGURE 2. CT scan. The implants are near to the inferioralveolar nerve. FIGURE 3. One of the retrieved implants.roughness increases the implant surfacearea and increases the potentialfor interlocking of bone into the implantsurface.11,12 However, surfaceroughness is not the only aspect of surfacetopography affecting osseointegrationof dental implants; for example,the increased surface roughness doesnot explain the differences observedwhen comparing sandblasted and titaniumplasma-sprayed surfaces.11Other factors that probably have a roleare ionic charge, surface energy, andsurface tension.7-11Acid etching appears to greatly enhancethe potential for osseointegration,especially in the earliest stages ofperi-implant bone healing. Moreover,with this technique there is no need forexternal agents that could contaminatethe implant surface.11 Acid treatmentproduces a clean, highly detailed surfacetexture that lacks entrapped surfacematerial and impurities.2,11 This14 Vol. XXIX/No. One/2003textured implant surface has been reportedto have a positive affect on thebiologic response of bone in terms ofearly bone apposition, a higher percentageof direct bone-to-implant contact,and strong implant anchorage.2,11Acid etching creates an even distributionof very small (1 to 2 mm) peaksand valleys and large features of 6 to10 mm.2,11Chehroudi et al13 showed that amodification of the implant surface topographyinfluenced the frequencyand the amount of bone deposited adjacentto implants, and the areas ofmineralization were guided by the surfacetopography. Surface roughness altersthe responsiveness of osteoblaststo systemic hormones.14 Only a fewstudies of in situ osseointegrated implantswithout complications and withan intact bone-implant interface havebeen reported in the literature.15-18 Theanalysis of human specimens is extremelyuseful to validate the experimentalresults obtained from animals.The aim of our study was a histologicand histomorphometric report of 2 implantswith an acid-etched surface thatwere removed after 6 months becauseof damage to the inferior alveolarnerve in order to evaluate the healingevents in the peri-implant tissuesaround this type of surface.CASE REPORTIn another clinic, a 56-year-old femalepatient underwent the insertion of 2threaded, acid-etched, titanium, screwshapedimplants (Osseotite, 3i, ImplantInnovations, West Palm Beach, Fla) inthe left mandible (Figure 1). Twomonths after the surgical procedure,the patient started to experience a dullpain in the left mandible; this pain increasedin the following months, and 6months after the surgical procedurethe patient was referred to one of usMarco Degidi et alFIGURES 4-7. FIGURE 4. At low-power magnification, newly formed bone can be observed at the implant-bone interface (Toluidine blueand acid fuchsin, original magnification 312). FIGURE 5. Newly formed bone is present at the bone-implant interface. FIGURE 6. No gapsare present at the interface (Toluidine blue and acid fuchsin, original magnification 3200). FIGURE 7. Newly formed bone and marrowspaces are present at the interface with the implant (Toluidine blue and acid fuchsin, original magnification 3100).plant with a high-precision diamonddisc at about 150 mm and grounddown to about 30 mm.Three slides were obtained for eachimplant and stained with acid fuchsinand toluidine blue. A double stainingwith von Kossa and acid fuchsin wasalso done to evaluate the degree ofbone mineralization, and one slide perimplant, after polishing, was improcessedto obtain thin ground sectionswith the Precise 1 AutomatedSystem (Assing, Rome, Italy).19 Thespecimens were dehydrated in an ascendingseries of alcohol rinses andembedded in a glycolmethacrylate resin(Technovit 7200 VLC, Kulzer, Wehrheim,Germany). After polymerizationthe specimens were sectioned longitudinallyalong the major axis of the im-(M.D.). The patient complained of increasingpain and paresthesia; it wasthen decided to remove both implants.A CT scan showed that the implantswere in close contact with the inferioralveolar nerve (Figure 2). The implantswere retrieved with a 5 mm trephine(Figure 3).The specimens were immediatelystored in 10% buffered formalin andJournal of Oral Implantology 15EVALUATION OF BONE CONTACT AROUND TWO RETRIEVED HUMAN IMPLANTS3 for 30 minutes and surface produce mechanical restric- that the surface characteristics of an mersed in AgNOexposed to sunlight; the slides werethen washed under tap water, driedand immersed in basic fuchsin for 5minutes, and then washed and mounted.The percentage of bone contact wascalculated using a light microscope(Laborlux S, Leitz, Wetzlar, Germany)connected to a high-resolution videocamera (3CCD, JVC KY-F55B, JVC ProfessionalProducts, Milan, Italy) andinterfaced to a monitor and PC (IntelPentium III 1200 MMX, Intel IrelandLtd, Kildare, Ireland). This optical systemwas associated with a digitizingpad (Matrix Vision GmbH, Oppenweiler,Germany) and a histometrysoftware package with image-capturingcapabilities (Image-Pro Plus 4.5,Media Cybernetics Inc, Immagini andComputer Snc, Milan, Italy).RESULTSRadiographically and clinically, bothimplants appeared to be osseointegrated.At low-power magnification bothimplants appeared to be surroundedby newly formed bone (Figures 4 and5). At higher magnification, the bonewas compact and mature with smallmarrow spaces (Figure 6). Remodelingareas were present. In some portions ofthe interface the bone appeared inclose contact with the implant surface,whereas in other areas marrow spaceswere present (Figure 7). The bone-implantcontact percentage for both implantswas a mean 61.3% (63.8%). Noinflammatory or multinucleated cellswere present. No foreign body reactionwas found at the bone-implant interface.The newly formed bone showedmany viable osteocytes. No epithelialdowngrowth was observed at the interface.DISCUSSIONImplant surface modifications are importantbecause direct bone-implantcontact is created between the moleculesof the bone tissue and the titaniumdioxide layer at the implant surface.1 The geometric properties of the16 Vol. XXIX/No. One/2003tions on the cytoskeletal cell components,which are involved in thespreading and locomotion of the cells.20Cellular adhesion is related to surfacefreeenergy of the substratum, and surfaceswith a low surface-free energyare reported to be less adhesive.20 Surfaceroughness seems to have an effecton the osteoblast differentiation andthe formation of a differentiated matrix.21 Surface roughness may be one ofthe most important factors determininglong-term implant success, especiallyin low bone quality and quantityareas.22The proliferation and differentiationof cells has been reported to beenhanced by surface roughness,23,24 andMustafa et al22 demonstrated that DNAsynthesis appeared to be dependent onsurface roughness. Osteoblast matrixformation and mineralization, in amultilayering culture system, is modi-fied by surface topography.21 The Osseotitesurface is created by a processof thermal dual acid etching with hydrochloricand sulfuric acids; this treatmentproduces a clean surface with noembedded materials or impurities onthe surface.251. Ericsson I, Johansson CB, BystedtH, Norton MR. A histomorphometricevaluation of bone-to-implantcontact on machine-prepared androughened titanium dental implants: apilot study in the dog. Clin Oral ImplantRes. 1994;5:201-206.2. Klokkevold PR, Johnson P, Dad-2 production is increased24. 350-357.3. Abrahamsson I, Zitzmann NU,It has been reported that acid etchingenhanced early endosseous integrationto a level similar to that observedaround the more complex titaniumplasma-sprayed surface.2 Theacid treatment seems to have an additionalstimulating influence on boneapposition.6 This acid attack helps inproducing a more stable adhesion ofthe blood clot, and this fact could helpobtain intimate and earlier bone contact.26-28 Osteoblast-like cells respond toincreasing surface roughness with adecreased proliferation and an increaseddifferentiation of the osteoblasts:alkaline phosphatase, osteocalcin,Transforming Growth Factor beta,and PGEAbrahamsson et al3 found that the proportionof mineralized bone betweenthreads and outside the threads wasnearly identical in turned and Osseotiteimplants; this fact could indicateimplant may influence tissue reactionsonly in a narrow area near the implantsurface. Klokkevold et al11 comparedthe resistance to removal torque forcesin the femur of rabbits. They used 2surfaces: acid-etched (Osseotite) andmachined. It was found that after a2-month healing period the force necessaryto remove the acid-etched implantswas 4 times greater than thatneeded in the machined implants. Theosteoconductive nature of the microtexturedOsseotite surface may increasethe rate at which new boneforms on the implant.29-32 The higherand earlier bone contact reported forthermal dual-etched surfaces has beenattributed to the fixation of fibrin to thesurface, to an enhancing of bonegrowth through enhancing levels ofbone growth factors, and to an increasedactivation of platelets thatleads up to an up-regulation of osteogenicresponses.32ACKNOWLEDGMENTSThis work was partially supported bythe National Research Council (CNR)and by the Ministry of Education, University,and Research (MIUR), Rome,Italy.REFERENCESgostari S, Caputo A, Davies JE, NishimuraRD. Early endosseous integrationenhanced by dual acid etching of titanium:a torque removal study in therabbit. 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