# The Use of Autogenous Teeth for Alveolar Ridge Preservation: A Literature Review
## 2 Alveolar Ridge Preservation in Extraction Sockets
### Alveolar Ridge Preservation: Concept and Bone Graft Materials Used  
The biological effect subsequent to a tooth extraction might have a devastating impact on the rehabilitation treatment, affecting both hard and soft tissues [3]. While bone availability might decrease, which is a key factor in the implant placement, the aesthetic result may also be compromised, by damaging the soft tissue [8; 19]. Under the rationale of ARP, filling a socket with grafting materials might reduce alveolar ridge resorption comparing to natural healing via blood clot [19]. Overall, ARP comprises three essential goals: (1) the maintenance of the existing soft and hard tissue envelope; (2) the preservation of a stable alveolar ridge in order to maximize the functional and aesthetic outcome; and (3) the simplification of the treatment procedures following the alveolar ridge regeneration [20]. When considering ridge resorption in this procedure, one must not only analyze the socket graft material and the surgical protocol but also the systemic and local characteristics that can play a role in this clinical procedure [1]. Among the factors that might affect ARP are number of adjacent teeth to be extracted, socket morphology (single versus multirooted teeth), integrity of the socket walls, periodontal biotype (assessing its thickness), smoking status, systemic factors (e.g., bone metabolic disorders, uncontrolled diabetes) and patient compliance [1; 3; 8]. Regarding the numerous biomaterials used for socket grafting, many approaches have been described in the literature [2; 6; 21]. Examples of these approaches are: using only bone grafting alone, including autografts (e.g., autogenous bone), allografts (including cortical mineralized freeze-dried bone and cortical demineralized freeze-dried bone) xenografts (derived from bovine bone), alloplasts (including medical-grade calcium sulfate, hydroxyapatite and beta-tricalcium phosphate (\(\beta\)-TCP)) [2; 6; 21]. Finally, it has been also described the application of a membrane alone (resorbable or non-resorbable), or combined with a grafting material [2; 6; 21]. Several systematic reviews have addressed ARP effectiveness. While some of these reviews points out to a rather scarce evidence with no significant conclusions [2; 19; 20], more recent systematic reviews showed more promising results [1; 3; 4; 6; 8; 10; 11; 21; 22; 23]. Comprehensively, there is general consensus that ARP does not avoid completely the inevitable dimensional loss that exists [1; 3; 4]. While xenogenic or allogenic materials have been associated with better results when compared with alloplastic grafts [1; 3; 4], others highlight the positive influence of the use of barrier membranes, resorbable and non-resorbable [8; 10; 21] or the combined use of a bone graft with a resorbable membrane [6]. Nonetheless, other studies advocate that although the benefit of this procedure exists, the evidence available is insufficient to state which method is best in reducing the dimensional changes addressed before [8; 11; 23]. The reason behind this limited evidence can be explained by the high heterogeneity present in the existing systematic reviews [1; 2; 3; 4; 6; 8; 10; 11; 19; 20; 21; 22; 23]. This heterogeneity is dependent on the broad definition of alveolar ridge regeneration, where many aspects enter the equation. Some examples are: type of graft material used, with or without resolvable or non-resorbable membrane, use of growth factors, with or without raising a flap when extracting the tooth, achieving primary or secondary intention closure, with damaged or intact sockets, multi rooted teeth or single rooted teeth, mandible or maxilla, among other patient related factors mentioned before [3; 10; 19; 21; 22]. Another technique that has also been described with promising results is the socket-shield [24]. The hypothesis behind this technique is that by retaining a section of the buccal side of the root during implant placement the extensive bone loss that occurs on the buccal side of the bone will be reduced [24; 25; 26].