## 4 Application of DDM in Bone Regeneration  
Extensive studies have been conducted on DDM with its osteoinductivity and osteoconductivity in vitro and in vivo [17; 18; 48; 49; 50; 51]. In animal studies, DDM enhanced the bone healing process of tooth sockets, and promoted new bone formation in rat calvaria defects, rabbit parietal defects, minipig crania defects, sheep iliac defects, and porcine sinus [17; 18; 47; 48; 49; 52]. Besides bone, DDM was employed in osteochondral regeneration [20]. DDM was implanted in rabbit keens with articular cartilage defects, while the control group was left untreated. Samples were collected in pre-determined timepoints and examined histologically and radiographically. The DDM group had statistically more new bone formation inside the defect, compared with control group at week three. Hyaline-like cartilage appeared in the peripheral area of the defect at week six, while the control group had none. The sample surface was covered with hyaline-like cartilage with a similar thickness to that of normal cartilage at week nine. Besides animal experiments, clinical trials were also launched. The Korea Tooth Bank and Hospital Tooth Bank (HTB) established a system to store teeth, then process them into DDM as bone substitutes [8]. One clinical study examined the safety and efficacy of autogenous DDM prepared immediately after extraction, for clinical applications in bone regeneration related to dental implantation, including: (1) socket preservation, (2) maxillary sinus floor augmentation, and (3) alveolar ridge augmentation. Sixteen patients underwent dental implant placement using  
Figure 2: The dentin matrix-induced bone formation depended on the degree of demineralization and particle size. (**A**) Micro-CT analysis. New bone formation was enhanced in all particle sizes in PDDM groups, more than in CDDM groups. The results of 1000 μm PDDM were especially noteworthy. In contrast, in UDD groups, much less new bone formed, and defects were occupied by dentin particles. (**B**) Newly formed bone (n-Bone%) were quantitatively evaluated. At 4 weeks, there is significant difference of n-Bone% between the PDDM and other groups in each particle size. At 8 weeks, there is a significant difference of the n-Bone% between the PDDM and the other groups in the 200 and 500 μm samples. (From [PERSON] [17] in _PLOS ONE_, with permission.)DDM transplantation. The results showed that: (1) in the socket preservation group, the height and width of the alveolar ridge were clinically preserved in all cases. (2) In the maxillary sinus floor augmentation group, the vertical height from the top of the alveolar crest to the sinus floor was increased after autogenous implantation, from 3.4 mm to 9.5 mm before surgery to 14.7 mm to 17.1 mm 3 months post-operation. The height of the augmentation area maintained for at least 1 year. (3) In the alveolar ridge augmentation group with implant placement, the autogenous DDM was replaced by bone-like tissue 3 months after dental implant placement. In all three groups, the graft sites healed without any notable complications. No implants were lost over 2 years of observation. This report showed that the clinical application of autogenous DDM was safe and efficient as a bone substitute in implant dentistry [42]. Another clinical study compared the efficacy of autogenous DDM and Bio-Oss (inorganic bovine bone) in alveolar bone augmentation and found that the autogenous DDM was as effective as Bio-Oss [53]. A long-term follow up of guided bone regeneration using DDM reported five cases which were followed for 3 to 6 months after DDM grafting. The results showed that the corticocancellous bone which formed after implantation was maintained for an average of 5 years [12]. The results of these clinical researches on DDM were consistent and promising. However, the number of cases was relatively small, and more randomized control trial clinical studies are needed.