# In Vivo Evaluation of Decellularized Human Tooth Scaffold for Dental Tissue Regeneration
## 4 Discussion
Vascularization is an important part of tissue regeneration because blood vessels supply essential elements for the process. Angiogenesis was observed to have occurred through the expression of VEGF shown by IHC and the expression of CD31 and CD34 shown by qPCR. VEGF is a marker for angiogenesis, which accompanies osteogenesis. The generation of blood vessels facilitates the supply of nutrients, oxygen, and minerals essential for mineralization and bone-forming progenitors. Osteogenic factors, such as BMP2, promote osteoblast differentiation and mineralization and are secreted from blood vessels [59; 60]. Matter osteoblasts generate mature angiogenic factors, such as VEGF, which also promote angiogenesis. Thus, the presence of these factors indicate that processes are occurring which promote tissue regeneration. Furthermore, when endothelial cells are co-seeded with stem cells on scaffolds, the roles of factors that can positively affect osteogenesis and vascularization can be expected [61]. Teeth are complex organs made up of various cells and structures, thus it is difficult to repair once damaged PDL and pulp, which play an important role in teeth's physical, formative, nutritional, and sensory functions and affect tooth vitality [62; 63]. PDL is a soft connective tissue that connects the root of the tooth and the inner wall of the alveolar socket [62]. PDL can be damaged by local factors, such as plaque, dental calculus, and traumatic occlusion, and destroyed by systemic or external factors, such as smoking. PDL can also be damaged by external force, more so by avulsion than luxation. Damage to PDL can cause early tooth loss or root resorption, thus recovery of damaged PDL is essential for tooth recovery [64; 65]. Pulp can become necrotized due to caries, trauma, and anatomic variations, such as dens evaginatus and dens invaginatus [66]. The traditional treatment for necrotized pulp is to remove and replace it with dental material, which can harm the tooth vitality. The loss of vitality can disrupt the development of immature teeth, resulting in a poor clinical prognosis. REP development has made a significant progress in recent years, becoming an alternative treatment for damaged pulp that can preserve tooth vitality [36]. Although REP promotes continuous tooth growth and development of immature teeth, and it guides endodontic repair through cell-homing rather than the true regeneration of the pulp tissue [67]. Contemporary dental treatment processes simply replace missing tooth structures or entire missing teeth through various methods, including direct restoration and the insertion of inert dental materials, fixed prostheses, and dental implants. The development of osseointegrated dental implants was a revolutionary advance in dental treatment, making it possible to recover a missing tooth without affecting surrounding healthy teeth [68]. However, even biologically advanced materials and mechanically advanced implants still suffer structural limitations and cannot mimic biological functions. Dental tissue therapiesare transitioning from traditional methods to working with patient biology, which is increasing treatment success rates [69]. The goal of traditional dental treatments is to restore the function and morphological integrity of the damaged tooth. However, the goal of cutting-edge dental treatments is to maintain tooth vitality and regenerate tissue. To overcome these limitations, research is being conducted to develop regenerative clinical treatments [70]. The ultimate goal of this line of research is to regenerate entire teeth. A study on the manipulation of a bioengineered incisor tooth germ using single cells isolated from the epithelium and mesenchyme of the dental germ produced the successful eruption of a bioengineered tooth germ. Bioengineered teeth exhibit masticatory properties and respond to harmful stimuli [71,72]. Previous studies on the use of stem cells in tooth regeneration have only used specific epithelial and mesenchymal stem cells.