Results - Discussion - References.
RESULTS.Observation by Optic Microscopy.
Optic microscopy reveals bone formation in close contact with the titanium without intervening fibers. There is direct bone apposition in hollow areas in the surface of the implant. Bone tissue appears in the cortical area, completely filling the threads of the implant. In the medullary area, there is progress of bone tissue in relation to the surface of the implant, producing a type of cortical bone of a different thickness based on the degree of progress of the osteogenesis. In the areas closest to the cortical bone, greater thickness is seen than in the more distal areas. In the middle, there is bone marrow in contact with the bone in proliferation. At greater magnification, mature bone of the lamellar type is observed in the cortical area with a configuration of osteons within a clearly identifiable haversian system. There is no evidence of inflammatory cells or fibrous tissue.Scanning Electron Microscopy.
The surface of the RBM implants as seen with a scanning electron microscope appears to be a coarse roughness that does not refract light except on the first three threads on which can be seen the machined titanium without surface treatment. In this area, the striae, characteristic of the implant turning process, can be distinguished. From the third thread onward, the surface of the implant is highly irregular and rough all over not only on the crest of the threads but also in the depressions between them. At higher magnification, the surface appears reticulated, with undermining and deformation of the metal remaining after impaction of the resorbable calcium phosphate material blasted under pressure on the surface of the implant. DISCUSSION.
The surface remaining after calcium phosphate blast application is irregular, extremely rough, and comparable to that obtained with other types of treatments, such as the sand form, the application of acids, or a combination of these two. The roughness of the implant surfaces favors distribution of stress, retention of the implants in the bone, and cellular response. An increase in bone response and in the resistance of the bone-implant interface has been reported with bone trabeculae growing perpendicular to the surface of the roughened implant.
Studies have reported that adequate growth of bone in the interior of the pores or cavities left by the surface treatment requires that these must be approximately 100 mm in size. The growth of bone tissue into cavities of this size allows a mechanical interlocking of the implant with the bone. An increase in reverse torque values occurs in implants with pores between 10 mm and 40 mm. These pores do not allow maximum growth toward the inside of the bone. However, they do strengthen the mechanical union of the bone-implant interface. In vitro studies have also shown that the superficial roughness of the materials can influence cell function, matrix deposition, and mineralization.
In terms of superficial roughness and pore size (2.5–4 mm), the RBM implants analyzed using scanning electron microscopy met the criteria, resulting in an improved boneimplant interface as described by various authors. Studies designed to measure the mechanical resistance of this type of surface appear to be absolutely necessary to support what has been described in relation to its microstructure.
Using optic microscopy, there is evidence of direct apposition of bone tissue over the rough surface of this implant, just as was previously described by the authors in relation to other surfaces, such as commercially pure titanium, titanium plasma spray, and implants with a superficial coating of hydroxyapatite. In the cortical areas of the tibia, there is a complete filling of the implant threads, including anatomical repairs, with bone tissue appearing as mature bone of the lamellar type with haversian systems taking shape. In areas of spongy bone, there is bone apposition over the threads of the implant, surrounding them with a thin cortical bone of no more than 10–12 mm, bone tissue that grows at the expense of cortical areas and contact osteogenesis. This stretches toward the medullary area. This condition has also been described by Albrektsson and Johannsson25 in similar animal models and by Lederman, Schenk, and Buser in humans.
This bone property of growth over different surfaces is directly related to the mechanical rigidity of the substrate, its moistening ability, and the topography of the surface. The substrates with superficial tension greater than 30 dynes show greater bioadhesion; thus developing more points of insertion for cellular union. The property of greater moistening ability has been associated with rough implant surfaces. It is argued that it increases the points of initial fixation of the coagulum; thus avoiding its retraction and allowing greater bone contact with the implant.
Scientific evidence accumulated during the last 10 years conclusively indicates that the rough surfaces of titanium implants offer a significantly improved anchor to the bone than machined titanium surfaces.
Future lines of research in this field are absolutely essential to consolidate the new knowledge and to prepare the way for the development of implants that achieve more effective and lasting osseointegration, even in clinical situations of poor bone quality.REFERENCES.
- Buser D, Schenk R, Steinemann S, et al. Influence of surface characteristics on bone integration of titanium implants: A histomorphogenic study in miniature pigs. J Biomed Mater Res. 1991;25:889–902.
- Gross U, Muller-Mai C, Fritz T, et al. Implant surface roughness and mode of load transmission influence periimplant bone structure. Adv Biomater. 1990;9: 303–308.
- Wilke H, Claes L, Steinemann S. The influence of various titanium surfaces on the interface shear strength between implants and bone. Advances in Biomaterials. 1990;9:309–314.
- Martin J, Schwartz Z, Hummert T, et al. Effect of titanium surface roughness on proliferation, differentiation and protein synthesis of human osteoblast-like cells. J Biomed Mater Res. 1995;29:389–401.
- Ledermann P, Schenk R, Buser D. Long lasting osseointegration of immediately loaded, bar connected TPS screw after 12 years of function: A histologic case report of a 95 year old patient. Int J Periodontics Restorative Dent. 1998;18:552-563.
- Ericsson I, Johansson CB, Bystedt H, et al. A histo-morphometric evaluation of to implant contact on machine-prepared and roughened titanium dental implants. Clinical Oral Implant Res. 1994;5:202–206.
- Gotfredsen K, Nimb L, Horting- Hansen E, et al. Histomorphometric and removal torque analysis for TiO2- blasted Titanium implants. An experimental study in dog. Clin Oral Implants Res. 1992;3:77–84.
- Brunette D. The effects of implant surface topography on the behavior of cells. Int J Oral Maxillofac Implants. 1988;3:231–246.
- Bobyn J, Pilliar R, Cameron H, et al. The optimum pore size for the fixation of porous-surface metal implants by the ingrowth of bone. Clin Orthop. 1980;150: 263–270.
- Hay D, Moreno E. Differential adsorption and chemical affinities for apatitic surfaces. J Dent Res. 1979;58:930–942.
- Lausmaa J, Mattson L, Rolander U, et al. Chemical composition and morphology of titanium surface oxides. In: Williams J, Nichols M, Zingg W, eds. Biomedical Materials. Pittsburgh: Materials Research Society; 1986:351–359.
- Sanz A, Farias D, Diaz I, et al. Estudio experimental de la respuesta osea frente a tres diferentes superficies de implantes de titanio Cp, Ha y Tps. REVISTA DEL Ilustre Consejo General de Odontologos y Estomatologos de Espana. RCOE 1998 Vol. 3;3: 221–226.
- Baier R. Surface properties influencing biological adhesion. In: Manly R, ed. Adhesion in Biological Systems. New York: Academic Press, 1970:115–148.
- Boyan BD, Hummert T, Kieswetter K, et al. Role of material surfaces in regulating bone and cartilage cell response. Biomaterials. 1996;17:137–146.
- Harris A. Tissue culture cells on deformable substrata: Biomechanical implications. J Biomech Eng. 1982;106:19–24.
- Harris A. Traction and its relations to contraction in tissue cell locomotion. In: Bellairs R, Curtis A, Dunn C, eds. Cell Behavior. Cambridge: Cambridge University Press, 1982:109–135.
- Sanz A, Farias D, Diaz I, et al. Estudio experimental de la fuerza de torque de remosion de implantes de Titanio cp, Ha, TPS, y RBM. J Periodoncia y Osteointegracion. (in press)
- Schroder A, Pohjer O, Sutter F. Gewebereaktion auf ein titanholzylinderimplanta mit titanspritzchichtoberflache. Schweitz Moonaatsschhr Zahnheilkd. 1976;86:713–722.
- Babbush C, Kent J, Misiek D. Titanium plasma sprayed (TPS) screw implants for the reconstruction of the edentulouos mandible. J Oral Maxillofacial Surgery. 1986;44:274–282.
- Buser D, Mericske-Stern R, Bernard J, et al. Long-term evaluation of non submerged ITI implants. Part 1: 8-year life table analysis of a prospective multicenter study with 2359 implants. Clin Oral Implants Res. 1997;8:161–172.
- Donath K, Breuner C. A method for the study on undecalcified bones and teeth with attached soft tissue. J Oral Pathol. 1982;11:318–325.
- Wong M, Eulenberger J, Schenk R, et al. Effect of surface topology on the osseointegration of implant materials in trabecular bone. J Biomed Mater Res. 1995;29:1567–1575.
- Martin JY, Schwarttz Z, Hummert TW, et al. Effect of titanium surface roughness on proliferation, differentiation and protein synthesis of human osteoblast-like cells (MG63). J Biomater Res. 1995;29:389–401.
- Breme J, Wadewitz V, Furbacher B. Production and mechanical properties of porous sintered specimens of the implant alloy TiAl5Fe2. Advances in Biomaterials. 1990;9:63–68.
- Albrektsson T, Johanson C. Quantified bone tissue reaction in various metallic materials with reference to the so-called osseointegration concept. In: Davies JE, ed. The Bone Biomaterial Interface. Toronto: Toronto University Press; 1991:357–363.
- Wong M, Eulenberger J, Schenk R, et al. Effect of surface topology on the osseointegration of implant material in trabecular bone. J Biomed Mater Res. 1995;29:1567–1575.