## 4 Discussion  
The choice of bone graft material can affect the success of healing and bone regeneration during osseointegration in areas experiencing bone loss, which is estimated by BMD parameters, volume defects, and histology of the sample studied. Since BMD is relevant to the HU value [41], in present study, BMD can be accessed via HU value, which is determined from the \(\mu\)-CT imaging system. In the current study, the trend of increasing HU value in \(\alpha\)-CSH bone graft combined with PRP showed an increase in BMD in the sinus area supported by a decrease in sinus defect volume two weeks after implantation. The rise in BMD indicates an improvement in bone quality influenced by the healing period, which has an impact on bone regeneration [42; 43]. Several studies have demonstrated the increased performance of PRP in bone regeneration when combined with an autogenous bone graft or mesenchymal stem cells [2; 6; 8; 14; 44; 45]. Although autogenous bone graft is the gold standard in treating various bone defects, its use causes some specific problems such as limited stock availability, extended surgical time, and complications in the donor area such as pain, easy infection, and prolonged healing time [1; 8; 46; 47]. The \(\alpha\)-CSH bone graft resembles autogenous bone graft in that it promotes osseointegration with superior properties such as high purity, high calcium, quick setting, low temperature, bone booster formation, and ease to handle [12; 24]. However, the \(\alpha\)-CSH bone graft itself exhibited a slow progression in elevating BMD. A similar incident occurred in our previous study, which revealed a better progression of increasing BMD existed at 8 and 12 weeks after \(\alpha\)-CSH implanted in the defect [12]. Nevertheless, the research using the combination of PRP with mesenchymal stem cell or an autogenous bone graft on in vivo sinus floor elevation rabbit seems to be in line with our study that increased bone volume in  
Figure 5: Masson trichrome staining results of \(\alpha\)-CSH and \(\alpha\)-CSH/PRP at 1, 2, and 3 weeks after implantation. (The higher magnification images were taken from the investigated samples in each time point marked as black circular and rectangular areas, respectively). the second week after implantation [8]. Another study that combined PRP and autogenous bone graft in treating rabbit's artificially calvarium defect demonstrated that new bone formation at four weeks after receiving autogenous graft with the combination of PRP was the same as a new bone formation that only obtained autogenous graft without PRP at 12 weeks post grafted [9]. The increase in bone volume and the reduction in defect volume in a short time can be provoked by the property of PRP, which increases the formation of new bone and accelerates wound healing [8]. Therefore, PRP combined with \(\alpha\)-CSH can contribute to favorable conditions to speed up bone regeneration. The histological evaluation of \(\alpha\)-CSH and \(\alpha\)-CSH/PRP indicated the appearance of bone regeneration by the second week. However, \(\alpha\)-CSH/PRP showed better bone regeneration than \(\alpha\)-CSH because both new tissue and osteoblasts were more common in the experimental group. Moreover, in the \(\alpha\)-CSH/PRP group, angiogenesis was seen, which is essential in providing nutrition to the defect area to accelerate healing and lead to bone regeneration [48; 49; 50]. The use of PRP is known to regenerate bone in a short time due to the various bioactive molecules properties along with their physiological functions to induce bone regeneration in the defect area, such as adhesive protein, which services in intercellular interactions, adhesion, and osteoblast migration; growth factors, cytokines, and chemokines that function in adhesion, proliferation, migration, differentiation of osteogenic and osteoblasts, inhibit osteoclasts from occurring in bone resorption, stimulate angiogenesis, and stimulate bone repair in a fast time [9; 13; 34].