## 1 Introduction  
Bone defect is defined by the lack of bone tissue in the specific part of the body that may emerge as a result of injury, infection, inflammation, congenital, or traumatic processes [1; 2; 3]. In some cases, it can also occur as a consequence of ongoing diseases or surgical procedures [4; 5]. When the regeneration process in bone loss is hampered or even stopped, bone reconstruction via surgical implantation of materials is often required to increase bone regeneration [6; 7; 8]. During recent decades, materials used for bone reconstruction have mostly been acquired from autograft materials owing to their superior bone conduction, inducibility, and osteogenesis [9; 10]. In terms of bone healing, an autologous bone graft remains the treatment of choice in clinical practice [11; 12]. However, complications related to the harvesting procedure and the limited quantity of donor bone confine the clinical application of this technique [13; 14; 15]. Due to this fact, the necessity of other bone substitutes as alternative graft materials is indispensable for successful bone reconstructions [16; 17; 18].  
An ideal bone substitute should satisfy criteria such as being osteoinductive, osteoconductive, and bioresorbable [13; 14; 15]. It should also not have any risk of immunological rejection and should be thermally nonconductive [3; 5; 11]. In recent years, a number of alloplastic materials for new bone substitutes such as ceramic and ceramic composites, hydroxyapatite, tri-calcium phosphate, calcium phosphate cement, calcium sulfate, and bone morphogenetic protein have been extensively studied [9; 11; 19; 20]. Although there is no material to completely replace autologous bone, an outstanding bone substitute, \(\alpha\)-calcium sulfate hemihydrate (\(\alpha\)-CSH), can be used instead of autologous bone grafts thanks to its excellent biocompatibility, osteoconductivity, easy availability, and biodegradability [2; 4; 9]. The \(\alpha\)-CSH is regarded as a prime type of bone substitute that plays a crucial role in bone formation by facilitating the ingrowth of bone [13; 21; 22]. A growing body of evidence indicates that \(\alpha\)-CSH has been clinically used to treat various bone defects like resorbed maxilla [23; 24], post extraction-socket preservation [25; 26], and large segmental bone defect [21] due to its similar properties to the autologous bone. For this reason, the biomedical field is showing a vast interest in the development of \(\alpha\)-CSH as a potential booster for bone regeneration [19; 27]. While this bone substitute has shown superior biological properties, there remains a need to improve the performance of the current \(\alpha\)-CSH for clinical practice [2; 13; 28].  
In our previous study, we developed an innovative \(\alpha\)-CSH bioceramic synthesized from green processing technology (microwave-irradiation treatment) with superior blood wettability and biocompatibility [27]. Histopathological evaluation from an in vivo test of chick chorioallantoic membrane confirmed that the innovative \(\alpha\)-CSH bioceramic not only induces angiogenesis formation but also enables osteogenesis potential [27]. In the present study, we further use the innovative \(\alpha\)-CSH bioceramic as a bone graft substitute in artificially-created defects of rabbit models to analyze new bone formation and material degradation. It is believed that the innovative \(\alpha\)-CSH bioceramic possesses the ability to regenerate a new bone with good in vivo biocompatibility for clinical applications especially for bone repair and reconstruction in dental and orthopedic fields.