## 3 New GTR and GBR Using Tissue Engineering
### Three-Dimensional (3D) Scaffold Fabrication Techniques  
Previously, conventional methods including particle leaching, gas foaming, freeze drying, phase separation, fiber bonding, melt molding, and solution casting were employed for 3D scaffold fabrication [109]. As those methods revealed heterogeneities in pore size, porosity, and architecture, a new technique called solid-freeform fabrication (SFF), which is known as rapid prototyping (RP), was developed. SFF can fabricate scaffolds with precise external shape, internal morphology, and reproducible 3D architecture [110]. Several additive manufacture processes can be applied to build a complex structure by 3D printing. Those include laser-assisted printing (e.g., selective laser sintering (SLS) and stereolithography (SLA)), inkjet printing, and extrusion-based printing (e.g., fused deposition modeling (FDM)). Each procedure has their indications according to the different features and viscosity of biomaterials; materials with low viscosity can be adapted to inkjet printing, while only thermoplastic biomaterials can be used in extrusion-based printing, and a wide range of viscosities can be printed by laser-assisted printing [111]. Also, they can utilize living cells in printing, and the printed cells can be kept in a hydrogel scaffold made with natural or synthetic polymers [81; 94; 111]. All of these technologies use the computer-aided design (CAD) and computer-aided manufacturing (CAM) software or digital images for the design [112; 113]. CAD models are produced using direct computed tomography (CT) scans of patient-specific bone defects, which could help in regenerating extensive or complex forms [113]. Few studies using image-based 3D-printed scaffolds showed promising results in practice [72; 114; 115]. Extrusion-based printing is the most widely used method in periodontal regeneration. This technique includes the controlled extrusion of a material through a printer head onto the collector, and the dimension of the filament is adjusted by controlling printing conditions such as temperature, extrusion rate, and velocity of the collector [112; 114]. Its features include \begin{table}
\begin{tabular}{l l l} \hline \hline
**Types of Grafts** & **Advantage** & **Disadvantage** \\ \hline
**Natural polymers** & High biocompatibility & \\ Collagen & Enhanced cellular & Lack of bioactivity \\ Alginate & Interaction & Rapid degradation rate \\ Chitosan & Hydrophilicity & Low mechanical strength \\ Hyaluronic acid & Antibacterial effect & Cell/drug containing \\ \hline
**Synthetic polymers** & & Slow degradation rate \\ Polycaprolactone (PCL) & Mechanical strength & Hydrophobic (PCL) \\ Polyethylene glycol (PEG) & Can be processed variously & Low cell affinity \\ PolyAlactic acid (PLA) & Able to seed mesenchymal & Poor cellular response \\ Polyglycolic acid (PGA) & cells/growth factors & Not suitable for a drug-delivery system \\ Poly(lactic-co-glycolic) acid (PLGA) & & Acidic byproducts \\ \hline  & Easy to handle & \\  & Bioactivity & \\  & Good biocompatibility & Very brittle \\  & Hydrophilicity & High stiffness \\  & Similar inorganic components & Low flexibility \\  & Osteoconductivity & \\  & Potential osteoinductivity & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Advantages and disadvantages according to biomaterials for the scaffold. temperature-controlled material handling, a dispensing system, and an optional light source and piezoelectric humidifier [113]. FDM is a common extrusion method and thermoplastic material is fed from the filament coil and inserted into the heated nozzle head for deposition of semi-molten state polymer [115]. Another scaffold fabrication technique introduced in periodontal regeneration is electrospinning which consists of a polymer syringe, a syringe pump, a high-voltage supply, and a collector plate [113]. It can be classified into solution electrospinning (SE), which uses polymer solution, and melt electrospinning (ME), which uses polymer melts [116].