## 3 Results and Discussion  
### Bone Healing Features of the Implanted Materials  
Figure 2 depicts the \(\upmu\)-CT images of the surgical area as well as the healing of bone defects at each time point. As the results show, the blank group (Figure 2a) demonstrated some new bone formation within the defects, but to a lesser degree than that observed in the control material (Figure 2b) and the \(\upalpha\)-CSH (Figure 2c). New bone was more rapidly formed in the \(\upalpha\)-CSH group (Figure 2c) compared to the blank group (Figure 2a). Overall, there was not much difference in the newly-formed bone between the \(\upalpha\)-CSH group (Figure 2c) and the control group (Figure 2b). However, when we looked into the progress of bone healing from time to time, the sites implanted with \(\upalpha\)-CSH demonstrated a tendency to have better progress of tissue remodeling in the defect area. In this study, the innovative \(\upalpha\)-CSH was prepared through the microwave-irradiation treatment since it possesses several pros over the commercially-available medical-grade \(\upalpha\)-CSH (mostly fabricated by the traditional dehydration method) in terms of purity control [27; 29]. The dehydration method is prone to creating certain impurities like \(\upbeta\)-calcium sulfate hemihydrate and anhydrite as the byproduct since this method is unable to control the variations in temperature and pressure [30]. These impurities will affect the crystal size and morphology with elongated crystals that eventually reduce the mechanical and biological properties [31; 32]. On the other hand, the microwave-irradiation treatment can synthesize high-purity bone graft substitute without sacrificing any useful mechanical or biological properties with controllable temperature and pressure, a great heating rate, and a homogeneous reaction temperature of volume [33]. Besides, this method resulted in \(\upalpha\)-CSH with uniform short column crystals (approximately 10 \(\upmu\)m in length) that can render high hydrophilic properties for setting in the dehydrated state [27]. It is known that the crystal size and crystalline structure influence the setting characteristics of bone graft materials [34; 35], while the water absorption ability and setting time of material influence the number of proteins and growth factors absorbed in the blood which in turn affect osteoconduction, angiogenesis, and bone regeneration after the implantation [36]. Figure 2: Micro-computed tomographic (\(\mu\)-CT images) showing the surgical area and the healing area of (**a**) blank, (**b**) control, and (**c**) \(\alpha\)-CSH samples at each time point. Figure 3 represents the BMD in the defect calculated by \(\mu\)-CT scanning. It was seen that the density was equally increased with healing duration in each group. Apparently, the mineral density did not reveal any abnormality. Thus, the mineral can be deposited well in every animal after different applications. Figure 4 displays new bone volume in the defects measured from \(\mu\)-CT scanning. At an early stage, in weeks 2 and 4, the new bone volume was lower than 10% in all treatment groups. Further, after 8 weeks, the new bone volume in defects increased more in the \(\alpha\)-CSH group than other groups. At the final observation at 12 weeks, the tissue remodeling by \(\alpha\)-CSH group had decreased the new bone volume, yet in other groups this increased at the same time as regular mineral density (Figure 3). This unique phenomenon could be explained due to the tissue remodeling process that caused the dense callus to be withdrawn in \(\alpha\)-CSH but not in blank and control material. The general concept of fracture healing can be described in four overlapping stages including hematoma formation, bone repair, which is divided into fibro-cartilaginous callus formation and bony callus formation, and bone remodeling. These stages occur at different times, with different cellular involvement, and different meanings [37; 38].