Dental News - Dental clinicians could soon click “print” before they head to surgery

Dental Tribune International

Sun. 24. December 2023

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CHENGDU, China: Though modern treatments for periodontal disease can offer some solutions for dental tissue restoration, they often fail to reproduce the original complex anatomical structure of tissue. 3D bioprinting has revolutionised care by offering precision in tissue regeneration. A team in China has published a review of the currently available 3D-printing methods for collagen-based biomaterials and their application for regeneration of oral tissue such as pulpal nerve and blood vessels, cartilage and periodontal tissue.

Background

3D printing, initiated by Charles Hull in 1986, employs digital models to construct objects layer by layer using bondable materials, facilitating design flexibility, reduced production costs and enhanced functionality. In dentistry, 3D bioprinting targets oral tissue regeneration and has shifted dental surgery towards more accurate and digitised approaches.

Collagen, a primary component of extracellular matrix, is often employed in tissue engineering owing to its structural and chemical resemblances to the extracellular matrix of oral tissue. However, its rapid degradation limits its direct application in tissue scaffolds. To enhance its effectiveness, collagen is typically combined with other materials. For example, for biomimetic structures, researchers have combined bioactive glass with modified collagen to improve human mesenchymal stem cell viability.

Collagen-based bioinks offer excellent printability for various 3D-printing methods. Collagen’s printability depends on bioink formulation and the printing technique. 3D-printed collagen scaffolds can provide an environment for cell growth, either by attracting stem cells or by hosting cells directly.

Bioprinting methods

Bioprinting technologies are broadly categorised into inkjet, pressure-assisted and light-assisted bioprinting. Originating from traditional inkjet printing, inkjet-based bioprinting deposits ink droplets layer by layer. It offers precise cell placement in 2D and 3D structures, suitable for tissue engineering. Yet, it faces challenges with high-density cell printing owing to nozzle clogs.

Extrusion-based bioprinting employs pressure, either pneumatic or mechanical, to push bioink through a nozzle. It is scalable and handles high-viscosity bioinks well. However, factors like nozzle diameter can affect cell viability.

First introduced for 2D cell patterning, light-assisted bioprinting uses lasers to solidify bioink, ensuring minimal mechanical stress and allowing for high-resolution structures. Techniques include laser-induced forward transfer, stereolithography and digital light processing. These methods create scaffolds with high structural fidelity and good cell viability.

Applications

Research exploring 3D bioprinting of cartilage with collagen bioinks showed that high-density collagen hydrogels, when heated, enhanced the geometric precision of printed structures, improving structural fidelity and mechanical strength. Another study provided a comparison between different bioinks for cartilage printing, finding that alginate–agarose and alginate–collagen combinations offered superior compressive and tensile strengths over alginate only. Additionally, alginate–collagen promoted better cell survival and maintained chondrocyte phenotype effectively.

3D printing has also been beneficial in recreating the nanofibre structures of the extracellular matrix of cartilage. These scaffolds have been found to support cell adhesion, proliferation and differentiation and to demonstrate osteochondral regeneration potential. There have also been initiatives to use 3D printing for temporomandibular joint repair. Scaffolds created from gelatine exhibited the potential for cartilage differentiation of human bone marrow-derived mesenchymal stem cells. The team noted in the review that research has also emphasised the efficacy of the use of two cross-linking methods together in scaffolding, finding that such structures favour bone and cartilage growth.

Collagen extraction

There are a number of methods of collagen extraction. A means of extracting with high efficiency and in a manner that is environmentally friendly is enzymatic extraction, which cleaves covalent bonds in collagen under acidic conditions, preserving collagen’s physical and biochemical properties. Commonly used enzymes include pepsin, pancreatic protease, papain and ficin. Factors affecting extraction include temperature, pH, time and enzyme concentration. Beyond this, complex extraction methods have been developed in order to obtain efficient and rapid collagen extraction without compromising structure.

The review, titled “3D bioprinting of collagen-based materials for oral medicine”, was published online on 31 August 2023 in Collagen and Leather.