Autogenous and Allogeneic Bone Grafts in Periodontal Therapy

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localized juvenile periodontitis (Yukna and Sepe, 1981; Evans et al, 1989). A study that compared FDB A with and without tetracycline to a nongraft procedure in 12 juvenile periodontitis patients demonstrated significantly greater bone fill and resolution of osseous defects in grafted as opposed to control sites (Mabry et al, 1985). 3. Decalcified Freeze-Dried Bone Allograft Urist and co-workers showed through numerous animal experiments that demineralization of a cortical bone graft induces new bone formation and greatly enhances its osteogenic potential (Urist, 1965; Urist etal, 1967; Urist and Dowell, 1968; Urist etal, 1968 and 1975). The work of Urist has been confirmed by others (Koskinen et al, 1972; Chalmers et al., 1975; Oikarien and Korhonen, 1979; Mellonig et al., 1981a and b). Demineralization with hydrochloric acid exposes the bone inductive proteins located in the bone matrix (Urist and Strates, 1970). These proteins are collectively called bone morphogenetic protein (BMP) (Urist and Strates, 1971). They are composed of a group of acidic polypeptides that have been cloned and sequenced (Urist et al., 1983a and b; Wozney et al., 1988). In addition, there appears to be homology among bone inductive proteins between mammalian species (Sampath and Reddi, 1987). BMP stimulates the formation of new bone by osteoinduction (Urist et al, 1970). That is, the demineralized graft induces host cells to differentiate into osteoblasts (Harakas, 1984), whereas an undemineralized allograft is felt to function by osteoconduction as it affords a scaffold for new bone formation (Goldberg and Stevenson, 1987). The sequence of bone induction with a demineralized bone graft is believed to follow a bone induction cascade (Reddi et al, 1987; Bowers and Reddi, 1991). At day 1, there is chemotaxis of fibroblasts and cell attachment to the implanted demineralized bone matrix. At day 5, there is continued cell proliferation and differentiation of chrondroblasts. At day 7, chrondrocytes synthesize and secrete matrix. From days 10 to 12, there is vascular invasion, differentiation of osteoblasts and bone formation, and mi- neralization. By day 21, there is bone marrow differentiation. This cascade for the induction of endochondral bone has been shown to occur in heterotopic sites of animals grafted with demineralized bone matrix (Reddi et al., 1987). It has not been demonstrated to occur following implantation of this material in a periodontal osseous defect. A more likely scenario for the periodontal defect is the induction of new bone through the intermembranous route (Mellonig et al, 1981b). Libin et al (1975) were the first to report the use of cortical and cancellous decalcified FDB A (DFDBA) in humans. The three grafted sites responded with 4 to 10 mm of new bone formation. Cortical DFDBA was evaluated in 27 intraosseous periodontal defects and yielded a mean of 2.4 mm of bone fill (Quintero et al, 1982). In six cases, Werbitt (1987) showed bone fill ranging from 75 to 95% of the original defect. The results of a radiographic analysis of cancellous DFDBA in 16 patients demonstrated a mean bone fill of 1.38 mm, whereas six control sites showed 0.33 mm (Pearson et al, 1981). The reason for this meager bone fill after a graft of cancellous DFDBA may lie in the fact that the bone inductive proteins are located in the bone matrix (Urist and Iwata, 1973). Because the mass of bone matrix is lower in cancellous bone than that in cortical bone, the yield of new bone could be expected to be lower with cancellous than cortical bone (Urist et al, 1970). Another controlled study in 47 periodontal osseous defects demonstrated a mean bone fill of 2.6 mm (65% defect fill) in sites treated with cortical DFDBA in comparison with 1.3 mm (38% defect fill) in sites treated without DFDBA. Rummelhart et al (1989) clinically compared DFDBA and FDB A in 11 paired sites. No statistical difference in probing depth reduction, clinical attachment gain, or bone fill was reported, which might have been reflective of insufficient inductive bone protein in DFDBA or the types and depths of the grafted lesions. Additional factors might also have influenced the decision to use a mineralized or demineralized preparation. The processing of both preparations included multiple immersions in absolute ethanol. The DFDBA underwent further processing that included immersion in 0.6 N HC1 (Mellonig, Downloaded from cro.sagepub.com by guest on January 10, 2013 For personal use only. No other uses without permission. 339
1991). Each of these chemical processes was thought to inactivate HIV (Martin et al, 1985; Resnick et al, 1986; Quinnan et al, 1986). 4. Allografts Compared with Alloplasts Both FDBA and DFDBA have been compared to porous particulate hydroxyapatite, a synthetic or alloplastic bone graft material. Studies by Burnett et al. (1989) and Bowen et al (1989) suggest that there is little difference in posttreatment clinical parameters between allograft and the hydroxyapatite graft sites. Another study suggests a slight difference in favor of the alloplast (Oreamuno et al, 1990). Histologically, grafts of DFDBA heal with regeneration of the periodontium (Bowers et al., 1989c), whereas grafts of synthetic bone heal by repair (Baldock et al., 1985; Froum et al, 1982; Stahl et al, 1986; Kenney et al, 1986; Carranza et al, 1987). Therefore, the choice of material will depend in part on the objectives of the clinician. V. WOUND HEALING WITH PERIODONTAL BONE GRAFTS The objectives of the clinician who uses bone grafts are (1) probing depth reduction; (2) clinical attachment gain; (3) bone fill of the osseous defect; and (4) regeneration of new bone, cementum, and periodontal ligament (Schallhorn, 1977). Case reports and controlled clinical trials provide valuable information with respect to the first three objectives. They do not reveal the type of wound healing adjacent to the postgrafting root surface. Therefore, histologic analysis of the nature of the attachment apparatus is needed to determine true regeneration of the periodontium. A. Animal Studies Histologic evaluations in animals are of interest because they indicate the potential of a graft material to produce favorable results. In a review of the studies performed over the past several decades comparing graft and nongraft procedures in artificially created defects in animals, 75% of 340 the studies indicated that more favorable results might be obtained following the placement of a bone graft (Table 2). None of the nongraft control sites were found to be superior to grafted sites. The results of animal experimentation must be viewed with caution, and the tendency to extrapolate this information directly to the human situation should be duly tempered. B. Human Studies Only in clinical trials can the true potential of any graft material to regenerate the periodontium be analyzed. To date, approximately 159 human periodontal bone grafts have been removed en bloc and processed for histologic evaluation (Dragoo and Sullivan, 1973; Ross and Cohen, 1968; Nabers et al, 1972; (Hiatt and Schallhorn, 1973; Hawley and Miller, 1973; Froum et al., 1975; Moomaw, 1978; Hiatt et al, 1978; Listgarten and Rosenberg, 1979; Moskow et al, 1979; Langer et al, 1981; Evans, 1981; Froum et al, 1983; Dragoo and Kaldahl, 1983; Bowers et al, 1982; Bowers, 1989a, b, and c). Most human histologic evaluations have been criticized because they failed to adequately demonstrate that the adjacent root surface was biologically contaminated and devoid of its connective tissue attachment. For example, biopsies were commonly evaluated from the most apical level of root planing (Hawley and Miller, 1975; Hiatt etal, 1978; Moskow et al, 1978), from a notch placed in cementum with a bur at the base of the defect (Nabers et al, 1972; Moomaw, 1978; Listgarten and Rosenberg, 1979), from a notch placed in cementum at the level of the alveolar crest (Dragoo and Sullivan, 1973), or from a naturally occurring notch in the root surface (Ross and Cohen, 1968; Evans, 1981). All of these histologic reference points, although highly suggestive of a root exposed to the oral bacterial contamination, did not prove that the root surface had lost its connective tissue attachment (periodontal ligament). Therefore, reattachment rather than regeneration might have been the result. Using the above cited examples for a histologic reference point, new bone cementum and periodontal ligament have been observed following grafts of cortical bone chips (Nabers et al, 1972), Downloaded from cro.sagepub.com by guest on January 10, 2013 For personal use only. No other uses without permission.
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Autogenous and Allogeneic Bone Grafts in Periodontal Therapy

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