Abstract
The aim of the present review was to summarize the current knowledge about (i) the dimensional alterations that occur in the alveolar ridge following tooth extraction and (ii) the available clinical procedures to preserve the ridge dimension. Several studies in human and in dogs demonstrated that the healing of the edentulous site is characterized by a marked reduction of the height of the buccal bone crest and shrinkage of the alveolar ridge. Further reports also observed that flapless tooth extraction and immediate implant installation after tooth extraction failed to prevent the dimensional alteration of ridge. The graft of a fresh socket with a virtually non-resorbable and highly osteoconductive biomaterial was, however, found to compensate for the buccal bone loss and maintain most of the pristine volume of the alveolar process. In conclusion, the graft of the alveolar socket after tooth extraction with a biomaterial may be performed to preserve the dimensional of the alveolar ridge.
Tooth extraction has been widely performed in Dentistry mainly due to caries and periodontal infections. However, little attention has been paid to the subsequent loss of ridge bone volume that inevitably follows. Now, that implant-support restorations are so frequently performed, such a bone loss becomes increasingly relevant. Indeed, it may not only preclude implant placement but also the achievement of optimal esthetics. Thus, the aim of the present paper is to summarize the current knowledge about the bone loss that occurs following tooth extraction and the clinical procedures that are available to compensate for it.
The alveolar process with its corresponding volume is the anatomical feature that we want to preserve following tooth extraction. Thus, a brief description of tissues to be preserved is provided below (for a more detailed description, see Schoroeder 1986). The alveolar process may be defined as the bone tissue that surrounds a fully erupted tooth (Figure 1). It is limited coronally by the bone margins of the socket walls while an imaginary line that cuts the bottom of the socket in a perpendicular direction to the long axis of the root limits it apically. Beyond such line, the basal bone of the mandible or the maxilla can be found. Furthermore, the socket walls are named alveolar bone proper (bundle bone) and the remaining hard structure is named alveolar bone. In the bundle bone, the Sharpey’s fibers are invested in such way to connect the periodontal ligament to the alveolar bone and skeleton. Likewise and on the contralateral side of the periodontal ligament, the dental cementum invested with Sharpey’s fibers connects the periodontal ligament to the dentin. Just like the dental cementum, the bundle bone is a dento-dependent structure and, therefore, following tooth extraction it is gradually lost.
In order to understand why the buccal bone plate is lost after tooth extraction, it is important to recognize that the alveolar bone at the buccal aspect is thinner than its lingual counterpart (Figure 2). Indeed, the average width of the buccal bone plate in the anterior region of the maxilla is about 0.5 mm while the bundle bone width may reach up to 0.4 mm (Schroeder 1986). Thus, the buccal bone plate is frequently made of only bundle bone and, consequently, gradually disappears following extraction.
Finally, one more aspect is important before the beginning of a discussion about ridge preservation: the wound healing process. The socket wound healing can be divided into three different phases: (i) inflammatory, (ii) proliferative and (iii) remodeling and modeling (Cardaropoli et al. 2005). For the purpose of the this paper, it is sufficient to say that after tooth extraction the shape of the alveolar ridge is the result of the bone modeling that takes place in the last phase of the socket healing (Araújo & Lindhe 2005). The bone modeling is equally distinct in both buccal and lingual walls but it will be at the thin buccal wall that a vertical bone loss is more evident and frequent (Fig. 3). Thus, healing of the edentulous site is characterized by a marked reduction of the height of the buccal bone crest. These observations are supported by retrospective and prospective studies in man and animal studies (Pietrokovski & Massler 1967, Schropp et al. 2003, Araújo & Lindhe 2005, Araújo et al. 2008, 2009, Pietrokovski et al. 2007).
The first step to preserve the volume of the alveolar ridge after tooth removal is to perform the extraction in a manner that preserves the integrity of the bone walls. Forceps and luxator should be used in a way that the root is not forced buccally in order to avoid wall to fracture. On the other hand, different animal and clinical studies failed to support the common belief that a flapless tooth extraction (Fig. 4) may prevent ridge alterations (Fick et al. 2008, Chen et al. 2009, Araújo & Lindhe 2009). These studies demonstrated that the benefit of flapless tooth extraction is time-dependent and in the long-term fades away.
Another wide spread concept between dental professionals is that the placement of an implant immediately after tooth extraction will avoid ridge atrophy (Fig. 5). Well-designed experimental studies in the dog model demonstrated, however, that the placement of an implant in fresh extraction sockets failed to prevent bone modeling and a substantial vertical bone loss of the buccal walls occurred (Araújo et al. 2005 and Araújo et al 2006a, b). Several clinical studies have confirmed that such implant installation procedure is unable to prevent bone loss (Botticcelli et al. 2004, Chen et al. 2008, Evans & Chen 2009, Tomasi et al. 2010). Thus, immediate implant is a risky procedure as ridge alterations including periimplant soft tissue recession may occur and lead to undesirable esthetic outcome.
Recently, several clinical and animal experiments were performed to evaluate the hypothesis that grafting of the socket immediately after tooth removal may represent a suitable ridge preservation procedure (Figures 6 a-f). Randomized clinical trials designed to address this question demonstrated that the use of biomaterials in the socket contributed significantly to preserve the ridge volume after tooth extraction (Barone et al 2008, Mardas et al 2010). In a sequence of histological studies in dogs (Araújo & Lindhe 2009, Araújo et al 2008, 2009b, 2010) the socket healing with a xenogenic graft comprised of anorganic bovine bone (Bio-Oss Collagen, Giestlich, Wolhusen, Switzerland) was evaluated. The authors inserted the biomaterial in the socket immediately after tooth extraction and retrieved tissues samples representing from 1 to 180 days of healing. Histological sections were prepared for histological examination. The authors found that (i) the biomaterial was mainly non-resorbable but highly osteoconductive and (ii) it compensated for ridge resorption in the marginal compartment of the extraction socket. Other preclinical studies on ridge preservation using biphasic calcium phosphate ceramic or surgical-grade calcium sulfate with platelet-rich plasma as graft material have also showed to compensate for alveolar ridge resorption following tooth extraction (Boix et al 2006, Shi et al 2007).
In summary, (i) during socket healing processes of modeling and remodeling will result in qualitative and quantitative changes at the edentulous site and, as a result, the dimension of the ridge is reduced, (ii) flapless and flap tooth extraction appears to exhibit a similar amount of ridge reduction, (iii) immediate implant installation fails to prevent bone modeling and (iv) socket graft with a virtually non-resorbable and highly osteoconductive biomaterial compensates for the ridge reduction that occurs after tooth extrac
tion. Thus, whenever a tooth extraction is planed, ridge preservation with a grafting material may be performed if the volume occupied by the alveolar process is needed for implant installation or for providing optimal esthetics.
Mauricio G. Araújo, Cleverson Oliveira e Silva, Flavia Sukekava, Department of Dentistry, State University of Maringá, Parana, Brazil.
Oral Health welcomes this original article.
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