Bioprinting and advances in materials make it easier to create collagen structures needed for maxillofacial surgery.
Despite the fact that modern methods of treating periodontal diseases offer enough solutions for restoring dental tissue, they often cannot replicate the original complex anatomical structure of tissues. 3D bioprinting has revolutionized this area by ensuring the accuracy of tissue regeneration. A team of scientists from China has published a review of currently available collagen-based 3D bioprinting methods and their application for oral tissue regeneration. Namely, pulp and blood vessels, cartilage and periodontal tissues.
3D printing, pioneered by Charles Hull in 1986, uses digital models to build objects layer by layer using adhesive materials, allowing for design flexibility, lower manufacturing costs, and increased functionality. In dentistry, 3D bioprinting is aimed at regenerating oral tissue and has changed the direction of dental surgery toward more precise, digitalized approaches.
Collagen, the main component of the extracellular matrix, is often used in tissue engineering due to its structural and chemical similarity to the extracellular matrix of oral tissues. However, its rapid degradation limits its direct application in tissue scaffolds. To improve its effectiveness, collagen is often combined with other materials. For example, to create biomimetic structures, researchers combined bioactive glass with modified collagen to improve the viability of human mesenchymal stem cells (MSCs).
Collagen-based bioinks provide excellent printability across a variety of 3D printing methods. The printability of collagen depends on the bioink composition and the printing technology. 3D printed collagen scaffolds can provide a growth medium for cells, either by recruiting stem cells or by directly hosting cells.
Bioprinting Methods
Bioprinting technologies are broadly classified into inkjet, pressure-assisted bioprinting, and light-assisted bioprinting. Bioprinting, based on traditional inkjet printing, deposits ink droplets layer by layer. It enables precise placement of cells into 2D and 3D structures suitable for tissue engineering. However, when printing high-density cells, nozzle clogging can cause problems.
Extrusion bioprinting uses pneumatic or mechanical pressure to push the biofilm through a nozzle. Printing is scalable and performs well on highly viscous biofilms. However, cell viability can be affected by factors such as nozzle diameter.
First introduced to create 2D cell models, light-based bioprinting uses lasers to cure bioinks, ensuring minimal mechanical stress and allowing the creation of high-resolution structures. Methods include laser-induced direct transfer (LIFT), stereolithography, and digital light processing. These methods allow the creation of scaffolds with high structural accuracy and good cell viability.
Practical application
Studies on 3D bioprinting of cartilage using collagen bioinks have shown that high-density collagen hydrogels, when heated, increase the geometric accuracy of the printed structures, improving structural precision and mechanical strength. Another similar study compared different cartilage-printing biofilms and found that alginate–agarose and alginate–collagen combinations provided superior compressive and tensile strength compared to alginate alone. In addition, alginate–collagen promoted better cell survival and effectively maintained the chondrocyte phenotype.
3D printing has also proven useful in recreating nanofibrous structures of the extracellular matrix of cartilage. These scaffolds have been found to support cell adhesion, proliferation, and differentiation, and show potential for regenerating osteochondrosis. There have also been initiatives to use 3D printing for temporomandibular joint repair. Scaffolds created from gelatin have shown potential for differentiation of human bone marrow-derived MSCs into cartilage. Research has also highlighted the effectiveness of using both methods simultaneously, finding that such structures promote bone and cartilage growth.
Collagen Extraction
There are several methods for extracting collagen. A highly efficient and environmentally friendly means of extraction is enzymatic extraction, which cleaves the covalent bonds in collagen under acidic conditions, preserving its physical and biochemical properties of collagen. Commonly used enzymes include pepsin, pancreatic protease, papain, and ficin. Factors affecting extraction include temperature, pH, time, and enzyme concentration. In addition, sophisticated extraction methods have been developed to allow efficient and rapid extraction of collagen without compromising the structure.