Computerised Design for Fabrication of an Oral Stent

Introduction: Advanced oral cancer often requires radical ablative surgery, resulting in defects that affect patient's speech, mastication, swallowing and quality of life. Ideally a stent should be fitted at the time of surgery that will cover the defect and restore function during the healing phase. However impression taking is often difficult due to pain, swelling, bleeding, infection, and limited mouth opening. Objectives: The study aimed to fabricate a post-surgical stent by rapid prototyping methodology using optical images obtained by computer tomography to build a three dimensional virtual model of a patient's maxilla. This would be compared with a stent created by traditional impression techniques. Methods: CT scans of a volunteer's maxilla were taken using 0.5mm cuts, and the information was downloaded to a computer where a virtual model was created. This was refined and manipulated using the Freeform modelling software with a phantom haptic device. Thereafter, a wax stent was produced by rapid prototyping using a Thermojet printer. For the traditional method, an impression of the patients mouth was taken, a plaster cast poured, and a wax stent was prepared on this. Both wax stents were then processed into acrylic resin using conventional dental methods. Stents were polished and fitted on the original casts and the volunteer's mouth to test for accuracy and comfort. Results: Both processes produced accurate, well fitting and comfortable stents. Conclusion: Computer generated prostheses have many advantages over traditional fabrication methods in that that no impressions are needed; the digital models can be manipulated to simulate the surgical resection prior to prosthesis fabrication; the data can be sent directly from the hospital to outside laboratories for processing without the patient needing to go there; and it can be stored for later usage.