3D Printing Has Come of Age But How Safe Are the Devices Going Into Our Mouth?

Introduction

I commenced experimental research into the safety of 3D-printed devices at the time 3D Printing (3DP) was largely considered to be at a “proof of concept stage” in dentistry. I vividly remember how the technology was relatively unknown in my discipline when I arrived on the splendorous Gold Coast, 7 years ago to take up a lecturing position at Griffith University. It is against these backdrops that I would describe the recent hype and the desperate attempt by companies to diversify and innovate competitively as another milestone or perhaps a watershed in the dental specialism concerned with the design and manufacture of devices such as orthodontic splints (Fig.1), surgical guides, and dentures. While it is seemingly laudable that polymers and metals, which form the bulk of dental devices, can now be processed by 3DP, limited scientific evidence exists on their biological safety. It is, therefore, my intention to highlight some pertinent findings from my doctoral study that examined medically-approved photopolymers using the innovative zebrafish embryo model and analytical spectrometry.

Findings

  1. All 3D-printed devices will display a varying degree of toxicity subject to physicochemical characteristics of the materials and postprocessing techniques that include disinfection protocols.
  2. Resin formulations on the market are constantly evolving, and hence there is a need to independently verify their biological safety as per intended use.
  3. New preclinical standards are required for 3D-printed devices bearing in mind the materials and additive processes differ considerably from traditional counterparts.

Recommendations

Since the different materials and additive processes make it nearly impracticable to achieve a consensus, it is recommended that users engaged in biomedically-related 3DP activities adopt the three-tiered approach that may together guarantee optimal results i.e., approved materials, apposite manufacturing parameters and postprocessing. Likewise, caution is required in the use of third-party materials in “open” 3DP systems without approved certifications. To guarantee patient safety, it is high time manufacturers are compelled by legislation to make available to the general public test results for scrutiny and academic reflection. While standards for preclinical testing are bound to lag behind evolving materials and emerging technologies, the gap can be narrowed considerably if urgent steps are taken to revise those in circulation to reflect the trends toward non-traditional medical devices. For instance, it will be preposterous to evaluate dental devices solely on ISO 20795 guidelines when evidence suggests that they may contain other potentially toxic acrylic esters apart from the recommended residual methyl methacrylate. In this regard, qualitative and quantitative analyses of the chemical composition of the printed devices will be more useful for predicting biological safety. Furthermore, dental devices that are likely to leach toxic substances could be scrutinized for acute toxicity using zebrafish, which has a high genetic similarity to humans, and offers economy and ease of quantifying multiple toxicity endpoints (Fig. 2).

Figure 1 3D-printed orthodontic appliance
Figure 2: Normal zebrafish (A) versus coagulated counterpart exposed to toxic 3D-photopolymer (B). Image Source: Alifui-Segbaya, F. 2018. Toxicological assessment of photopolymers in additive manufacturing using the innovative zebrafish embryo model. Ph.D. Doctorate, Griffith University.

Further Reading

Alifui-Segbaya, F. 2018. Toxicological assessment of photopolymers in additive manufacturing using the innovative zebrafish embryo model. PhD Doctorate, Griffith University.

Alifui-Segbaya, F., Bowman, J., White, A. R., Varma, S., Lieschke, G. J. & George, R. 2018a. Toxicological assessment of additively manufactured methacrylates for medical devices in dentistry. Acta Biomaterialia, 78, 64-77.

Alifui-Segbaya, F. & George, R. 2018. Biocompatibility of 3D-Printed Methacrylate for Hearing Devices. Inventions, 3, 52.

Alifui-Segbaya, F., Varma, S., Lieschke, G. J. & George, R. 2017a. Biocompatibility of Photopolymers in 3D Printing. 3D Printing and Additive Manufacturing, 4, 185-191.

Alifui-Segbaya, F., White, A. R. & George, R. 2018b. Zebrafish as a model organism for biological assessment of esters and degradation products in additive manufactured dental photopolymers. Griffith University: School of Dentistry and Oral Health Research Grant.

Alifui-Segbaya, F., Williams, R. J. & George, R. 2017b. Additive Manufacturing: A Novel Method for Fabricating Cobalt-Chromium Removable Partial Denture Frameworks. European Journal of Prosthodontics and Restorative Dentistry, 25, 73-78.Hitzler, L., Alifui-Segbaya, F., Williams, P., Heine, B., Heitzmann, M., Hall, W., Merkel, M. & Ochsner, A. 2018. Additive Manufacturing of Cobalt-Based Dental Alloys: Analysis of Microstructure and Physicomechanical Properties Journal of Advances in Materials Science and Engineering, 2018, 12.

Biographical Note

Dr. Frank Alifui-Segbaya has been a lecturer at the School of Dentistry and Oral Health, Griffith University since 2012. He graduated from the University of Wales Institute, Cardiff (now Cardiff Metropolitan University) with a BSc in Dental Technology with First Class Honours, completed an MPhil at the same university, and a PhD at Griffith University. Frank qualified as a dental technologist in 2005 and has served in other capacities: as an academic, a scientist and researcher in Ghana, Germany, Wales, England, and Australia. His research interests include biomaterials, zebrafish toxicology, 3D printing, and the application of CAD/CAM to dentistry.

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