Maxillofacial Prosthetics – Use of Splints & Stents during Radiation Therapy
Splints and stents can be used to shield, displace and position tissues in an effort to minimize postradiation morbidity. These devices are usually made of acrylic resin and are fabricated prior to the radiation simulation appointment to ensure that the calculated dosimetry take into account the position of the tissues when the patient is wearing the device. This program describes the common devices used and the methods used in their fabrication
Maxillofacial Prosthetics – Use of Splints and Stents during Radiation Therapy — Course Transcript
- 1. 2. Use of Prosthodontic Splints and Stents during Therapy Harold Gulbransen, DDS John Beumer III, DDS, MS Division of Advanced Prosthodontics, Biomaterials and Hospital Dentistry UCLA School of DentistryAll rights reserved. This program of instruction is covered by copyright ©. Nopart of this program of instruction may be reproduced, recorded, or transmitted,by any means, electronic, digital, photographic, mechanical, etc., or by anyinformation storage or retrieval system, without prior permission of the authors.
- 2. Use of Prosthodontic Splints and Stents During Radiation Therapy Table of Contentsv Positioning stentsv Shieldingv Recontouring tissues to simplify dosimetryv Positioning radioactive sourcesv Tissue bolus devices
- 3. Positioning StentsCombination bite opening and tongue positioning stents Controlled depression of the tongue allows the radiation to better focus on the clinical tumor volume thereby reducing the dose delivered to adjacent normal tissues Master casts are made and are mounted on an articulator with a record made with the mandible separated from the maxilla by about 25 mm. Begin fabrication by blocking out undercuts
- 4. Positioning StentsCombination bite opening and tongue positioning stents Extension used to depress the tongue For ease of insertion opening should not exceed 25 mmTip of the tonguefits in this hole 25 mm
- 5. Combination bite opening and tongue positioning stents v This patient was treated with CRT. The tongue is limited superiorly to the level of the occlusal plane. v The radiation field can be lowered sparing significant parotid tissue and the palatal glands. If IMRT is used the radiations can be better confined to the clinical tumor volume Result: More salivaTip of the tongue placed here output postradiation.
- 6. Direct technique These positioners can be fabricated using a direct technique. Softened baseplate wax is used and the resultant wax pattern is invested and processed into acrylic resin.
- 7. Lingual stents Useful in patients with carcinomas of the oral tongue that do not extend into the floor of the mouth where the dose is boosted locally with interstitial brachytherapy.The lingual stent displaces thetongue away from theradioactive sources imbedded inthe tongue, significantly reducingthe dose to the lingual surface of One cm thickness of acrylicthe mandible. resin reduces the dose by 50%.
- 8. Shieldingv Only useful when electron beam is usedv Primarily used when treating tumors of the buccal mucosa, lip and skin. Purpose: a) Reduce radiation dose to normal tissues medial to the tumor b) Simplify the dosimetry by flattening out the cheek
- 9. Shielding A shield for a patient presenting with a squamous carcinoma of the buccal mucosa. Note that the shield separates the mandible from the maxilla. This serves to flatten the buccal mucosa and simplify the dosimetric calculation.
- 10. Shielding v Only useful when electron beam is used v Primarily used when treating tumors of the buccal mucosa, lip and skin. Combination bite opener shield for squamous ca of lower lipPurpose:a) Reduce radiation dose to normal tissues medial to the tumorb) Simplify the dosimetry by flattening out the cheek
- 11. Shielding Another shield for a patient being treated for a lymphoma of the mandibular gingiva Cast of overextended Shield impression Shield in mouthShield oncast withcerrobendalloy
- 12. Positioning a Radioactive Source This patient developed a recurrence of a previously irradiated squamous carcinoma. The patient was not a candidate for surgery. After the stent is positioned the iridium seeds which areMaster cast with acrylic resin stent. incorporated within a smaller diameterpolyethylene tubing isThe tubing is then incorporated loaded.within the stent and a cerrobendshield is added.Stent with polyethylene tubing
- 13. Positioning a Radioactive SourceThis patient presented with a superficial squamouscarcinoma of the right alveolar ridge extending into thefloor of the mouth. The position of the radioactivesources are outlined on the cast. The stent is fabricated with polyethylene tubing imbedded at the prescribed distances from the mucosal surfaces. The stent is loaded with radioactive sources after it has been positioned.
- 14. Positioning a Radioactive Source Following radical maxillectomy, the patient developed a recurrence on the posterior wall of the defect. She had previously received 5000 cGy postoperatively. An impression was made and a cast fabricated. Occlusal ramps were added, the radium needles loaded and the patient wore the appliance until another 3500 cGy had beenAn acrylic resin administered.stent was madeand channelswere developedto receiveradium needles.
- 15. Positioning a radioactive source Patient presented with severe trismus, so the radiation carrier was made of a flexible silicone materialThe radioactivesources are insertedafter the patient insertsthe carrier.
- 16. Positioning a radioactive sourcev This patient presented with a new superficial lesion (squamous carcinoma) on the posterior lateral surface of a maxillectomy defect. She had previously received Note the implants in the postoperative residual premaxilla. They had radiation following a been placed following her radical maxillectomy. initial radiation therapy.
- 17. Positioning a radioactive sourceTubing is imbedded within the device at prescribedintervals which will later receive the iridium seeds. The radioactive sources are inserted after the carrier is positioned introrally.
- 18. Positioning a radioactive sourceThe radiation carrier is placed introrally andloaded with the radioactive iridium.The device was retained with the implant retained tissuebar connected to the osseointegrated implants. Occlusalstops are incorporated within the device to help maintainconsist positioning of the stent.
- 19. Tissue bolus devicesv Problem – Irrregular tissue contours create uneven radiation dose distributionsv Bolus – a tissue equivalent material placed directly onto or into irregular tissue contoursv Result – More homogenous dose distributionMaterials used: v Wax v Saline v Acrylic resin
- 20. Tissue bolus devices In this patient a saline filled bladder was used to fill a radical maxillectomy defect with a tissue equivalent material.
- 21. Tissue Bolus DevicesIrregular tissue contours of external structures This patient presented with a squamous carcinoma of the tip of the nose. Overlaying the nose and cheek with a tissue equivalent material will result in more homogenous dosimetry. A cerrobend nasal stent was designed and fabricated to shield the nasal mucosa. The surface bolus of acrylic resin and the cerrobend nasal stent in position.
- 22. Tissue BolusThis tissue bolus is made of dentalcompound. Patient is to be irradiated for asquamous carcinoma of the nasal vestibule.
- 23. Tissue Bolus This tissue bolus is made of acrylic resin. Patient is 3 weeks S/P partial palatectomy and is to receive postoperative radiation therapy. The appliance fills the defect with acrylic resin and is made of two pieces to allow for easy insertion and removal.The device also separates the mandible from the maxillaand keeps the tongue below primary treatment volume.
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