# The Use of Autogenous Teeth for Alveolar Ridge Preservation: A Literature Review
## 3 Autogenous Teeth as a Bone Graft Material  
### Biological Plausibility  
In order to understand the use of human teeth as a bone graft material, we must bear in mind the chemical composition of human teeth and alveolar bone. The ratio inorganic/organic/water of the various components of the teeth goes as follows: enamel (95%/0.6%/4%), dentin (70-75%/20%/10%) and cementum (45-55%/50-55%) [12; 16]. When comparing with the alveolar bone ratio, (65%/35%/0%), the similarity between bone and especially dentin becomes clear [16].  
Considering this potential, researches started looking for the different hard tissues present in teeth. [PERSON] and [PERSON] pioneer study on the potential bone-inducing properties of dentin opened up new boundaries on graft materials [27]. [PERSON] and [PERSON] firstly reported the bone induction capacity of autogenous demineralized dentin matrix [27]. In the same year, [PERSON] and [PERSON] also referred the similarity between dentin collagenous matrix and bone matrix in terms of osteoinductive capacity [28]. Only in 2009, the Korean Tooth Bank, in Seoul, Korea, developed an autogenous tooth bone graft material, which lead to a significant increase of studies in this field regarding the clinical performance of this material [29].  
Given the role and highly percentage of dentin in autogenous tooth [30], several studies have focused on different methods of treating dentin matrix towards the optimization of the procedure clinical effectiveness [14].  
In the inorganic component of dentin, X-ray diffraction analysis showed that, unlike enamel hydroxyapatite, dentin hydroxyapatite (which consists of 70% of the dentin in its weight volume) is structured with low-crystalline calcium phosphate, which in turn, allows the osteoclasts to easily decompose this mineral, promoting an effective bone remodeling [15; 30]. This property is not only similar to bone tissue, also mainly composed by low-crystalline calcium phosphate, but also essential in alveolar ridge regeneration, ensuring osteoconductive capacity [12; 16; 29]. Besides hydroxyapatite, there are other three biological calcium phosphates such as: tricalcium phosphate, octacalcium phosphate and amorphous calcium phosphate [31]. All these forms interact with each other, playing a positive role in bone remodeling [15].  
In the organic component of the dentin matrix, a dense network of type 1 collagen fibrils represents 90% of its content [12]. The other 10% is formed by the so-called non-collagenous proteins such as: osteocalcin, osteonectin, sialoprotein and phosphoprotein, which are known to be involved in bone calcification [15]. Additionally, growth factors are also present, including bone morphogenetic proteins (BMP), LIM mineralization protein 1, transforming growth factor-\(\beta\) among others [12; 14]. [PERSON] et al. compared the dentin-matrix derived BMP with the bone-matrix derived BMP, concluding that although they are not identical, both induce bone formation [32]. Similarly, [PERSON] et al. demonstrated that LIM mineralization protein 1 is a positive regulator of the osteoblast differentiation [33]. These growth factors, alongside other non-collagenous proteins have a proven osteoinductive capacity [12; 15; 16; 29; 32; 33; 34; 35].  
One important aspect that can be beneficial in terms of implant placement is the healing period. In the literature, this period usually varies from 4 to 6 months [36; 37], although in some cases, dental implants may be placed 2 to 3 months after alveolar ridge preservation [38]. Several authors compared the use of autogenous tooth graft versus a xenograft [17; 39; 40]. While some studies assess the performance of the implants immediately placed after graft [17; 40], one study compared the two grafts after a healing period of 6 months [39]. Regarding this matter, thanks to the reduced resorption rate of the autogenous tooth graft (4 to 6 months) an earlier placement of the implant can be done, reducing the healing period [38; 41].