## 4 Discussion
However, several studies have reported that PRP alone does not accelerate bone regeneration [3; 6; 9; 35]. Using PRP alone in the treatment of defects is unfixed, caused difficulty to adapt in defect areas, and degrades very quickly [3; 24]. Therefore, PRP needs to be combined with a graft material to make it more rigid. Platelet concentration and growth factor as a result of the preparation procedure are also factors that influence the effectiveness of PRP [6]. In the current study, a double centrifugation method was performed to produce optimal platelets to regenerate the bone at a concentration of 5 times higher than whole blood, while even higher concentrations could reduce osteoblast cell proliferation [6]. One of the osteeconductive properties of the graft material owns the resorption rate similar to bone formation [12]. Our previous study using \(\alpha\)-CSH on a rabbit's artificial femur defect revealed that the graft material began to absorb, and there was an increase in bone volume at eight weeks post-implantation [12]. Another previous study also used \(\alpha\)-CSH on rat's artificial hind leg bones defect presented the complete absorbing of graft material at seven weeks after implantation [24]. Referring to the biological process of fractured bone repairing, bone remodeling will begin with the formation of granulation tissue and soft callus, which in animal models occurs seven to nine days after injury, while in humans it occurs at two to four weeks post-trauma [51; 52]. In the current study, granulation tissue is more pronounced at two weeks in defects treated with \(\alpha\)-CSH/PRP. At the same time, angiogenesis is seen, which is a crucial part promote bone regeneration [51]. Other studies have shown that the combination of PRP and autogenous bone graft can increase the absorption of bone graft material, which is related to the new bone formation [6]. The absorption of \(\alpha\)-CSH bone graft allow the defect to absorb bioactive component such as calcium, which responsible for re-mineralizing the defect [12; 24]. The rapid regeneration of bone as a result of the combination of PRP and \(\alpha\)-CSH provides the advantage of a single-stage dental implant clinical procedure that has the potential to fail due to the lack of osseointegration during the healing period, especially in the installation of dental implants in the maxilla region, which have a lower bone density than the mandible leading to implant instability [8; 53]. Moreover, various factors that affect wound healing in the maxillary sinus such as low vascularity, low oxygen pressure, and intra-antral pressure make the use of PRP useful due to accelerating revascularization [6; 33]. Several studies also have reported the use of synthetic bone grafts to be ineffective in extensive segmental defects or areas requiring load-bearing resistance due to their weak mechanical strength [54; 55]. Although mechanical strength is required when restoring a defect in the jaw for chewing purposes, the use of \(\alpha\)-CSH bone graft is successful in treating large bone loss before implant placement, which is evident six months after implant placement, radiographs show osseointegration in the defect area, and the implant remains in a stable state [24]. As discussed above, we suggest that the combination of PRP and \(\alpha\)-CSH can have a synergistic effect in rapid bone regeneration for clinical application. Nevertheless, the limitations of the present study are performed on small sample size, were conducted on animal samples, and have a short evaluation period. Hence, further study with a larger sample size, long-term evaluation period, and tested in clinical application is needed to support the current findings of the effectiveness \(\alpha\)-CSH in combination with PRP.