Based on this year’s Cancer statistics in the United States, it is estimated that the incidence of Head and neck cancers (HNC) will reach 58,450 cases, with deaths estimated to be around 12,2301. Most of tese cases constitute oral, pharyngeal, and laryngeal squamous cell carcinoma (SCC)2. The treatment and management of HNC remain the same, utilizing a combination of Radiotherapy, surgery, and chemotherapy. Despite advances in high-dose and precise radiation beams (i.e., Proton therapy and image-guide intensity-modulated radiotherapy (IG-IMRT), patients are left with a very poor quality of life due to radiation-induced oral mucositis (RIOM)3, characterized by the inflammation and ulceration of the oral cavity. In this blog, we want to introduce the benefits and challenges in using 3D-printed stents to reduce radiation-induced complications.
Role of positioning oral stents in HNC radiotherapy in mitigating RIOM:
HNC patients receiving radiotherapy will typically develop RIOM within 2-4 weeks after initiation of their treatment. They can be characterized by (1) pain, sores, or redness of the oral cavity, (2) hoarseness, (3) change of taste, (4) dry mouth, and (5) sensitive teeth. Duration of these side effects varies from 6-8 weeks to as long as two or more years, with swallowing difficulties being the most common long-term effect4.
‘Oral stents’ for HNC radiotherapy vary in terms of designs depending on their clinical utility. Singh et al. (2021) provide a great summary of such nuances involving stents with dose shielding, radiation carrier, and positioning/immobilization capabilities5. This article focuses on positioning oral stents, of which are utilized by clinicians to immobilize the patient’s teeth and tongue to achieve accurate patient positioning and prevent the irradiation of healthy tissues and thus, minimizing the effects of RIOM5, 6. These devices are used by patients intraorally and are used throughout the course of the patient’s treatment and vary from simple popsicle-like devices to patient-specific designs (see Fig. 1).
Manual fabrication vs. Digital 3D-printing
Patient-specific positioning stents commonly used in the clinic are often fabricated with an acrylic resin due to its biocompatibility, durability, and free-forming capabilities7. The manual fabrication workflow, which remains the standard of care for HNC radiotherapy, involves the acquisition of the patient’s dental impression, followed by creating a stone model and a wax pattern for modeling the acrylic stent. Often, these stent models undergo further verification and modification to ensure that the final stent model received by the patient fits correctly. Here, we are looking at an estimated 3-4 days’ worth of effort for a single stent device, involving labor-intensive processes to fabricate the final acrylic stent, and numerous patient visits and long appointments to manually acquire stone models, perform stent verifications, and modifications.
Computer-aided design (CAD) and 3D printing’s customization capabilities allow for the fabrication of complex structures and the streamlined production of customizable stents tailored to patients8-11. A prospective trial by Zaid et al. (2020) demonstrated these advantages, showing: the non-inferiority of 3D-printed stents in terms of patient-reported outcomes, their comparable reproducibility in intraoral positioning, their low-cost production (average of 12 USD per stent) and reduced fabrication time (average of 8 hours per stent)(see Fig. 2)12. Compared to the manual fabrication process, it is easy to see how digital 3D printing provides a cost-effective option for clinicians and patients!
Limitations of 3D Printed Oral Stents:
Despite promising results, there exist challenges limiting the integration of 3D-printed oral stents into clinical practice:
- The quality of 3D-printed oral stents and post-processing time depend on the imaging quality of the oral anatomy — oral stent designs for 3D-printing can be generated using (a) CT imaging data, (b) surface scans of stone models, or (c) intraoral scanning. Segmentation of dental data from CT comes with numerous disadvantages due to presence of imaging artefacts, leading to a poor reconstruction of the dental anatomy with under/overestimation of tissue boundaries. Surface scanning method11 provides a more accurate dental anatomy, however, requires the manual fabrication of the patient’s stone model, which are not readily available. Lastly, intraoral scanning offers a superior advantage in terms of quality and efficiency compared to (a) and (b), however, are expensive and requires more resources and the proper training of clinical personnels10.
- Inter- and intra- variabilities of 3D-printed devices — there exists a wide range of biocompatible 3D-printing materials, technologies and parameters which offers users great flexibility in their design and manufacturing objectives. Unfortunately, this high number of variables opens up myriad of uncertainties concerning safety, durability, and compatibility13, 14. As a general rule, users must utilize the same vendor material, 3D printing machine, as well as vendor-recommended 3D printing parameters. Furthermore, it is advised that users perform their own in-house testing and analysis to ensure that errors/uncertainties are properly accounted for. Common technologies utilized for fabricating oral stents includes stereolithography with biocompatible resin materials8, 10-12. Some have utilized material extrusion technologies, using Polylactic Acid (PLA) filaments9, 15.
- The steep learning curve for cancer centers adopting this technology — most HNC centers offering oral stents still utilize manual processes which involves a hefty number of tools and equipment. In comparison to a digital dental lab involving 3D-printers, we can start to observe a stark difference in terms of space, techniques, personnels, equipment, and workflows. For existing point-of-care facilities, transitioning between two different methods requires the proper education and training of key stakeholders such as technicians and clinicians. To facilities aiming to provide stent devices to other domestic facilities, the proper coordination with teams across sterilization and logistics further plays an important role in its successful implementation in the clinic. On the other hand, companies offering 3D-printed oral stents enables an easier and straightforward process, requiring minimal training of technicians and clinical personnels.
What lies ahead is the intricate landscape of regulations and reimbursem*nts. The successful integration of a medical device into clinical practice relies on securing approvals from regulatory bodies and garnering acceptance within the broader cancer care community. Despite limited clinical data in the current literature, our hope is that generation of robust and reliable clinical data from randomized trials will effectively demonstrate the safety, efficacy, and feasibility of 3D-printed oral stents compared to the standard of care treatment. Until such clinical data becomes available, the adoption of this technology in clinical settings is likely to be limited, predominantly confined to a few well-resourced cancer research institutions.
For reimbursem*nts, I suggest readers to read on the article titled “Financial Issues of 3D Printing in Hospitals – Guide”, which explores the complexity of finance and how key stakeholders may tackle issues concerning Category I, II, and III CPT codes, of which all plays a key role towards the proper reimbursem*nt of medical devices fabricated via 3D printing technologies.
Below are recent developments in the areas of 3D-printed oral stents for HNC radiotherapy:
- A 3D-printed positioning oral stent device, ‘Stentra™’, developed by Kallisio has received its FDA 510(k) clearance, and is ready to be utilized in HNC patients receiving radiotherapy. This technology was licensed by an existing patent developed by researchers at MD Anderson Cancer Center, Cancer Physics and Engineering Laboratory.
- The National Cancer Institute is currently sponsoring a clinical trial evaluating the use of customized 3D printed oral stents during head and neck radiotherapy. The goal is to assess the effectiveness of these personalized stents in reducing radiation exposure to normal tissues.
- Adaptiiv, a Canadian medtech firm, partnered with HP and Varian to create 3D-printed personalized devices for radiation oncology. Its FDA-cleared Simple Bolus software designs custom bolus accessories conforming to patient anatomy, shielding healthy tissues from unnecessary radiation exposure during radiotherapy treatments.
- Similarly, 3D Systems developed their own 3D medical image processing software DICOM-to-PRINT (D2P®), offering clinicians an efficient workflow to create 3D-printable models from diagnostic patient imaging data. Leveraging this technology, 3D Systems introduced their VSP® Bolus solution, receiving its FDA 510(k) clearance in 2022, aiming to reduce tissue toxicities from Radiotherapy.
Conclusion:
3D-printed oral stents stand as a testament to progress in the interface of design, engineering, and healthcare, offering hope in mitigating the debilitating effects of RIOM. Intraoral scanners, CAD, and 3D printing are now becoming common in modern dental clinics around the globe due to their synergistic features involving the efficient and accurate acquisition of oral anatomy and the rapid prototyping capabilities of CAD and 3D printing technologies. Unsurprisingly, these state-of-the-art technologies will continue to advance oral cancer care for HNC radiotherapy and are well-positioned to transform manual fabrication processes into the digital realm.
Acknowledgements:
I want to acknowledge the mentorship and guidance of my mentor, Dr. Eugene Koay, at MD Anderson Cancer Centre and the continuous support of our patients and collaborators!
Author information:
Rance Tino, PhD., is a postdoctoral fellow at the Cancer Physics and Engineering Lab at MD Anderson Cancer Center, utilizing CAD, 3D printing and computational modeling technologies for applications in Radiation Oncology.
If you are interested to read more about the amazing applications of 3D printing in Dentistry, go check-out this article “Dental 3D printing – The Ultimate Guide”!
Check out the following courses below:
Dental 3D Printing: Pioneers and Rulebreakers
Additive Manufacturing in Dentistry
References:
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