Are intraoral customized stents still necessary in the era of Highly Conformal Radiotherapy for Head & Neck cancer? Case series and literature review

3D printing technology to produce intraoral stents for head and neck radiotherapy: A scoping review

INTRODUCTION

Radiotherapy remains one of the main treatments for head and neck cancer; however, it is accompanied by acute and chronic adverse effects. Use of three-dimensional (3D) oral stents to modulate radiation intensity to specific target areas have been developed to minimize these adverse effects. This study aimed to present a scoping review of studies published on 3D printing of oral stents and their clinical applicability.

METHODS

MEDLINE/Pubmed, Scopus, Web of Science and CENTRAL Cochrane data bases were searched, studies selected, and data collected by three independent reviewers up to December 2022. The review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis-Extension for Scoping Reviews (PRISMA-ScR).

RESULTS

The search resulted in 404 studies and 5 articles fulfilled the eligibility criteria and were considered for this review. Three-dimensional printed intraoral stents were produced for 56 patients with indication for radiotherapy. 3D-printed stents were well-tolerated by all tested patients and demonstrated great reproducibility of maxillomandibular relation, required less time for production and lower cost to manufacture. Two studies showed great protection of healthy tissues with 3D-printed stents during radiotherapy.

CONCLUSIONS

Three-dimensional printing is promising for production of intraoral stents, however, more studies are needed to improve the technique and further investigate the safety and prevention of oral toxicities from radiotherapy.

Effectiveness of intraoral stents in reducing oral adverse events during radiotherapy for maxillary or nasal cavity malignant tumors

PURPOSE

Many patients experience oral adverse events during head and neck cancer radiotherapy (RT). The methods of management of such events are under debate. One such technique is the intraoral stent (IOS) technique, which removes normal tissue from the irradiation field. This retrospective study examined the factors associated with the occurrence of oral mucositis (OM) and dysgeusia and the efficacy of IOSs in preventing them.

METHODS

Twenty-nine patients who underwent RT in the maxilla or nasal cavity between 2016 and 2022 were included. They were investigated for background characteristics, treatment factors (IOS and dose-volume histogram), and oral adverse events (OM and dysgeusia).

RESULTS

Significant risk factors for the incidence of grade ≥ 2 (Common Terminology Criteria for Adverse Events v5.0) OM were the non-use of IOSs (p = 0.004) and diabetes (p = 0.025). A significant risk factor for the incidence of grade ≥ 1 dysgeusia was concomitant chemotherapy (p = 0.019). The radiation dose to the tongue was significantly lower in the IOS group than in the non-IOS group.

CONCLUSION

Our findings suggest that the use of an IOS during RT reduces the severity of OM by reducing irradiation to the tongue. Therefore, the use of an IOS is recommended during RT performed in the maxilla or nasal cavity.

Assessment of mouth opening before and after head and neck radiotherapy in patients with intraoral stents

Background

We evaluated the evolution of mouth opening before and after radiotherapy of the head and neck in patients using intraoral stents.

Materials and methods

Twenty-one patients with head and neck cancer who were indicated for radiotherapy participated in this study. Maximum interincisal opening measurements were performed before and after radiotherapy. Paired analyses of the pre- and post-radiotherapy groups were performed using paired samples t-tests and correlation analyses using Spearman's correlation test, with p < 0.05 considered statistically significant.

Results

Paired analyses of the pre- and post-radiotherapy groups revealed a statistically significant reduction in post-radiotherapy maximum interincisal opening (p < 0.001). However, only four individuals were diagnosed with trismus after radiotherapy. Regarding the correlation tests, no statistically significant differences were observed between the differences in pre- and post-radiotherapy maximum interincisal opening values and the study variables.

Conclusion

The use of prosthetic devices during head and neck radiotherapy can reduce radiation doses in areas of no interest, thereby preventing the acute and late toxicities associated with cancer therapy.

Radiation attenuation properties of materials used to fabricate radiotherapy prostheses in vitro study

PURPOSE

This study investigates the attenuation of radiation doses by four materials, heat-polymerized, and self-polymerized polymethyl methacrylate (PMMA), putty-type, and injection-type polyvinyl siloxane (PVS) impression material. This in vitro study should aid in the selection of dental materials for radiotherapy prostheses, thereby minimizing the possibility of radiotherapy side effects.

METHODS

Specimens of each type were fabricated as a 5 × 5 cm squares with a thickness of 10 mm. Heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS impression material, and injection-type PVS impression material were selected. A calibration curve was created to determine the association of radiation doses and grayscale value. A linear accelerator was used to irradiate the specimens. The radiation doses above and below the materials were measured using radiochromic film dosimetry. After film irradiation, the pixel scale of color change was used to determine the radiation dose based on the created calibration curve. The results were exported to find average doses to calculate the percentage of the attenuated dose for a comparison of the four materials.

RESULTS

The average attenuated doses of heat-polymerizing PMMA, self-polymerizing PMMA, putty-type PVS, and injection-type PVS were 10.8%, 6.2%, 17.2%, and 14.2% respectively.

CONCLUSION

PVS showed higher attenuating radiation exposure compared with PMMA.

Radiotherapy of tongue cancer using an intraoral stent: a pilot study

Aim:

The aim was to evaluate the feasibility of an intraoral stent (10 and 20 mm thickness) in radiotherapy of tongue cancer, and to measure the reduction in acute mucositis in the palate.

Materials and method:

There were six patients in the intervention group, and seven patients in the control group. Target coverage was measured by the minimum dose covering 98% of the clinical target volume (CTV). Data were collected from the planning CT and daily cone-beam computer tomography (CBCT).

Results:

The 10 and 20 mm stent yielded a mean distance of 26 and 36 mm, respectively, between the tongue and the hard palate. We found comparable dose coverage of the CTV in the treatment plan, and on the CBCT. The stent reduced mean dose to the hard palate by 61.0% (p = 0.002). Dose to the soft palate was not reduced (p = 0.18). Average Common Terminology Criteria for Adverse Events (CTCAE) mucositis scores of the hard palate were 0 and 0.8 in the intervention and control group, respectively. The mucositis scores of the soft palate were 1.2 and 1.8.

Findings:

Use of an intraoral stent substantially reduced the dose to the hard palate. CTV coverage was maintained. We did not find any significant reduction in visually scored radiation-induced mucositis.

Development of a customisable 3D-printed intra-oral stent for head-and-neck radiotherapy

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Advanced radiotherapy techniques have improved head-and-neck treatments.

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More improvements are possible with intra-oral stents stabilising sensitive anatomy.

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MRI imaging shows new modular 3D printed stents provide stable displacement.

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Modular stents achieve positive outcomes within standard treatment workflow.

Intra-oral stents (including mouth-pieces and bite blocks) can be used to displace adjacent non-involved oral tissue and reduce radiation side effects from radiotherapy treatments for head-and-neck cancer. In this study, a modular and customisable 3D printed intra-oral stent was designed, fabricated and evaluated, to utilise the advantages of the 3D printing process without the interruption of clinical workflow associated with printing time. The stent design used a central mouth-opening and tongue-depressing main piece, with optional cheek displacement pieces in three different sizes, plus an anchor point for moulding silicone to fit individual patients’ teeth. A magnetic resonance imaging (MRI) study of one healthy participant demonstrated the tissue displacement effects of the stent, while providing a best-case indication of its comfort.

Intraoral radiation stents-Primer for clinical use in head and neck cancer therapy

Intraoral radiation stents (IRS) are prosthetic devices that assist in the effective delivery of radiation to tumor tissues and aim to avoid unnecessary radiation to adjacent healthy tissues, thus limiting postradiotherapy toxicities. They are used to protect or displace vital structures, assist in positioning of the treatment beam for effective administration of radiotherapy, carry a radioactive material, shield healthy tissues of the oral cavity, and/or maintain the desired mouth opening during radiotherapy. With close collaboration between radiation oncologist and oral health care provider, several IRS can be fabricated by the latter for appropriate targeting and delivery of planned radiation dose and optimized treatment results. Modification of these IRS based on individual patient need is recommended to maximize prosthesis utility. The purpose of this review is to discuss the various types of IRS and highlight their clinical utility and benefits in patients receiving radiation therapy in the head and neck cancers.

Are intraoral stents effective in reducing oral toxicities caused by radiotherapy? A systematic review and meta-analysis

STATEMENT OF PROBLEM

Intraoral stents have been provided to minimize acute and chronic toxicities induced by radiotherapy, including oral mucositis, salivary changes, trismus, radiation-related caries, and osteoradionecrosis. However, a systematic review and meta-analysis is necessary to determine their effectiveness.

PURPOSE

The purpose of this systematic review and meta-analysis was to determine the effectiveness of intraoral stent use and determine whether these prosthetic devices can reduce radiation dosage to nontargeted oral tissues and adverse effects related to head and neck radiation.

MATERIAL AND METHODS

Two independent reviewers made a systematic search for articles published from January 2010 to March 2020 in 3 databases, supplemented by a manual search. Studies were included if they were clinical trials (randomized controlled trials, both prospective and retrospective), published in English, and evaluated radiation dose and oral adverse side effects (acute or chronic) induced by radiotherapy of participants with and without intraoral stents.

RESULTS

The search strategy identified 201 studies; of which, 9 were included. A total of 251 participants were evaluated; of whom, 168 (77.3%) used intraoral stents and 57 (22.7%) were treated with radiotherapy without a prosthetic device. A statistically significant difference was found regarding the use of intraoral stents for preventing oral mucositis (P<.001), salivary changes (P=.003), and trismus (P<.02). A funnel plot showed asymmetry among the differences of means in all selected studies.

CONCLUSIONS

Intraoral stents have a positive effect on preventing oral mucositis. Further clinical trials are needed to address the flaws identified in the present systematic review.

Benefits of intraoral stents in patients with head and neck cancer undergoing radiotherapy: Systematic review

Intraoral stents aim to reduce the oral complications associated with head and neck cancers radiotherapy. The aim of this study is to determine the benefits associated with these devices. A systematic review was conducted in PubMed, Web of Science, and Scopus databases selecting full articles published in English, Portuguese, or Spanish until June 6, 2020 (PROSPERO registration: CRD42020185065). The studies were evaluated by Hadorn and Somerfield criteria and guidelines were established. Nineteen studies were identified suggesting the use of intraoral stent for radiotherapy for patients with cancer on/near the mandible to reduce oral mucositis, trismus, xerostomia (LoE III), and dose in healthy structures (LoE IV) and for cancer on/near the maxilla to reduce oral mucositis and dose in healthy structures (LoE IV). Despite the limited scientific evidence, several benefits associated with the use of intraoral stent for radiotherapy of the head and neck neoplasia have been reported.

Radiation-Induced Salivary Gland Dysfunction: Mechanisms, Therapeutics and Future Directions

Salivary glands sustain collateral damage following radiotherapy (RT) to treat cancers of the head and neck, leading to complications, including mucositis, xerostomia and hyposalivation. Despite salivary gland-sparing techniques and modified dosing strategies, long-term hypofunction remains a significant problem. Current therapeutic interventions provide temporary symptom relief, but do not address irreversible glandular damage. In this review, we summarize the current understanding of mechanisms involved in RT-induced hyposalivation and provide a framework for future mechanistic studies. One glaring gap in published studies investigating RT-induced mechanisms of salivary gland dysfunction concerns the effect of irradiation on adjacent non-irradiated tissue via paracrine, autocrine and direct cell-cell interactions, coined the bystander effect in other models of RT-induced damage. We hypothesize that purinergic receptor signaling involving P2 nucleotide receptors may play a key role in mediating the bystander effect. We also discuss promising new therapeutic approaches to prevent salivary gland damage due to RT.