# Bone Substitutes Scaffold in Human Bone: Comparative Evaluation by 3D Micro-CT Technique
###### Abstract  
The main purpose of the study is to assess a selection of commercially available bone biomaterials substitutes used as scaffolds for tissue engineering applications in dentistry, performing a clinical study on human subjects and using the microcomputed tomography (micro-CT) analysis to investigate the main morphological and critical parameters of bone and biomaterials structures. Micro-CT was performed in both the phases, preclinical and clinical. In addition, it was combined with histology to analyze the extracted bone four months after implantation. Quantitative analysis of the main morphological parameters as the porosity, the bone volume fraction (BV/TV) and the trabecular thickness (Tb.Th) evidenced the main difference among the biomaterials properties and their influence on the bone tissue regeneration. Qualitative observations by the three-dimensional (3D) reconstruction of the microstructure, contributed to the visualization of the mineralized areas. The analyses conducted on the bone substitutes before and after the implantation allowed quantifying the main biomaterials morphological parameters and the characterization of the human bone tissue regeneration. Thus, micro-CT and its combined application with histology demonstrated as a powerful approach for the microstructural investigation and for the final assessment of the efficacy and effectiveness of the various treatments and implants. biomaterials; bone substitute; human bone; scaffold; microcomputed tomography 2020 accepted: 14 May 2020; Published: 16 May 2020 accepted: 15 April 20  
of new bone through the mechanisms of osteogenesis, osteoinduction and osteoconduction is another important aspect. As evidenced in a recent review [4], the requirements in terms of scaffold composition, characteristics, and design, should be defined considering many aspects, like the specific clinical bone deficiency, the patient characteristics, the defect and the desired outcome. Furthermore, it is underlined that scaffolds structures need to be controlled not only on a macroscopic level but also microscopically, to improve the main features. In the last years, many studies were elaborated considering in vitro and in vivo applications and scaffolds of various compositions looking for the best reasonable solution [5]. The manufacturing technologies for scaffolds are numerous from the conventional ones like solvent casting and particle leaching [6], freeze-drying [7], freeze-gel casting [8], powder-forming [9], sol-gel [10; 11] and electrospinning [10], to the emerging ones as bioprinting [12] and three dimensional (3D) printing [13; 14; 15; 16]. The design and the characterization of scaffolds benefit from the advantages offered by microcomputed tomography (micro-CT) analysis in particular in relation to the morphometric structural investigation, to quantify scaffold porosity, surface area, pore size, pore distribution and structural thickness, allowing a precise measurement of bone growth [2; 17; 18]. Unsintered hydroxyapatite/poly-D/L-lactide (3D-HA/PDLLA) with beta-tricalcium phosphate (b-TCP) [19] or with mesenchymal stem cell [20], dental pulp stem cells [21], amniotic epithelial cells loaded on a calcium-phosphate synthetic bone substitute [22] and polycaprolactone-tricalcium phosphate (PCL-TCP) [23], are some examples of bone grafts compositions studied by the application of microtomographic analysis. Moreover, studies were carried out on bioactive composite 3D scaffolds [24] and degradable hybrid polymer biomaterials with controlled properties for highly efficient biomedical applications [25]. The micro-CT is a consolidated 3D nondestructive imaging technology used for various applications and specifically for the analysis of bone structures and mineralized tissue [26; 27]. Dentistry, maxillofacial surgery and orthopedics are the main fields of interest, and in the last years, more are emerging regarding new manufacturing processes and quality controls for medical applications [16; 28].