# Ten Years of Micro-CT in Density and Maxillofacial Surgery: A Literature Overview
## 3 Micro-CT Studies: In Vitro and In/Ex Vivo Applications
### Biomaterials and Bone Tissue Regeneration  
3D micro-CT scans were usually conducted to evaluate bone reformation, bone mineral density, remodeling, the scaffold morphology, and the biomaterial structure performing in vitro and in/ex vivo studies. The use of animal models seems to be a required step in testing new bone regeneration materials [96]. The in vivo applicability of bioengineered 3D constructs [97] and bone graft substitutes is usually evaluated in animals models as rats, rabbits, mini pigs bone defects, and applications are recorded in dentistry [98; 99; 100; 101; 102] as in MFS [103; 104; 105]. Mainly, the biomaterials and bone grafts investigated for tissue engineering applications are:  
* Uncalcined and unsintered hydroxyapatite/poly-D/L-lactide with beta-tricalcium phosphate (b-TCP) [104] or with human mesenchymal stem cell [103]. * Granular deproteinized bovine bone and b-TCP alone or with dental pulp stem cells [62]. * Polycaprolactone-tricalcium phosphate (PCL-TCP) [102]. * Nano-hydroxyapatite/collagen composite [106]. * Nanofibrous bone graft coupled with osteoinductive proteins/peptides--poly(D,L-lactide-co -glycolide)/collagen/gelatin [99]. * Bioresorbable collagen membranes [96; 107]. * Silk fibroin scaffolds [108]. * Injectable scaffold based on oxidized alginate microbeads encapsulating periodontal ligament stem cells and gingival mesenchymal stem cells [109]. The in vitro applicability of bone graft substitutes is usually evaluated on extracted teeth in dentistry as in the studies conducted on polylactic acid (PLA)-based mineral-doped scaffolds [110] and in MFS [105]. [PERSON] et al. performed a comparison of the biological, chemical, and structural features of four different commercially available bone substitutes derived from an animal or a synthetic source, analyzing the biomaterials structures by micro-CT [111]. A common problem in clinical dentistry is the significant and rapid bone loss that occurs after tooth extraction, traumatic events, and surgery. The possibility to have a fast repair of bone defects is a challenge [112] and research has been conducted to investigate the various treatments. Micro-CT quantification of histomorphometric data was applied in animal studies to evaluate the effect of injected protein on alveolar bone [113], high-frequency acceleration, and the rate of bone formation after tooth extraction [114]. The osseointegration is another main aspect investigated performing a microtomographic analysis. Structural parameters of bone as, volume, trabecular thickness, trabecular number, trabecular separation, and total porosity, are the more significant parameters usually assessed and evaluable by micro-CT for the bone characterization, under various conditions, in studies conducted on patients [115]. In vitro experiments were carried out on coatings and correlated to micro-CT information about bone morphology to examine osseointegration [116]. Micro-CT allowed to demonstrate that a bisphosphonate treatment for osteoporosis, can invert the negative effect of osteoporosis on osseointegration, promote osseointegration itself and, the fixation of dental implants in autologous bone grafts under osteoporotic condition [117]. Furthermore, bone tissue response and osseointegration were investigated in experimental animal protocols, in relation to a bioactive silicate coating [118], lightweight implants [119], and poly-\(\varepsilon\)-caprolactone-coated and previtalized magnesium implants, manufactured by selective laser melting technology [120], alternative to traditional implants in MFS and new implants with modified surfaces, in comparison with commercially available dental implants [121]. Titanium implants were microtomographic observed and induced osteolysis was addressed [122], as well as newly formed bone in bioactive coated implants [118].