Computer Guided Surgery for Implant Placement and Dental Rehabilitation in a Patient Undergoing Sub-Total Mandibulectomy and Microvascular Free Flap Reconstruction
A 58-year-old patient presented with an extensive, destructive, recurrent pleomorphic adenoma occupying the mandibular body and the soft tissues of the mouth and neck. Resection of the mandible from right ramus to left condylar process, and implant rehabilitation in both jaws with fixed bridgework was planned. Comprehensive presurgical prosthetic work up was carried out to record the existing dental relationship and guide all stages of the reconstruction. The jaw was first grafted with a segmented, fibular microvascular free-flap, which was fixed in place with a fixation plate prebent on a Rapid Prototype Anatomical Model of the jaw. Reconstruction with implant supported fixed partial dentures took place to the dental scheme planned preresection, using a computer guided approach to implant placement in the complex and unfamiliar anatomy of the extensively grafted mandible. This approach facilitated and expedited implant surgery such that treatment could take place using a minimally invasive approach relatively soon after surgery, prior to commencement of radiotherapy, and highlights the importance of a multidisciplinary approach to treatment for patients having extensive surgery to the jaws. The patient's personal assessment 2 years post surgery was recorded using 1999 University of Washington Quality of Life Questionnaire.
Figure 1. The patient at presentation. Figure 2. (a) Panoramic radiograph showing expansive lesion to mandibular body. (b) Three-dimensional rendered computerized tomography (CT) scan of the mandible showing expansive lesion to mandibular body. Figure 3. Stereolithographic model of the mandible. Figure 4. Altered stereolithographic model of the mandible. Figure 5. The anterior maxillary teeth were extracted and the cyst simply enucleated. Figure 6. The resected specimen. Figure 7. The fibula flap raised and still in situ. Figure 8. The resin mandibular try-in extended and marked with gutta-percha markers to create a radiographic stent. The resin addition facilitates anchorage of the drill guide, which will be based upon the geometry of the try-in.
Figure 9. The 3D virtual environment showing the reconstructed mandible, radiographic stent, and planned implant positions. Figure 10. The 3D virtual environment showing the reconstructed mandible, radiographic stent, and planned implant positions. Figure 11. The stereolithographic drill guide. Note that it has been reinforced with a clear resin (shiny material) in view of its relatively fragile configuration. Figure 12. Computer-guided surgery in progress. Figure 13. Fixtures in place postoperatively. Healing abutments have been buried where skin is overlying so as to facilitate access to the fixture heads; they emerge through oral mucosa. Figure 14. The bulky skin and fat overlying the graft is trimmed to thin the tissues. Figure 15. Three fixtures/abutments emerge through the thinned-down overlying skin covering the neomandible. Figure 16. Intraoral indexing of the lower set-up to the upper denture prior to conversion of the removable prostheses to simple resin bridgework.
Figure 17. The prosthesis is indexed to the working model and adapted to form a simple resin bridge. Figure 18. Resin bridges in place 3 months post insertion. Figure 19. The patient 3 months post insertion of fixed bridgework. Figure 20. (a) Postoperative panoramic radiograph showing implants within bony envelope. (b,c) Postoperative 3-dimensional rendered cone-beam computerized tomography scan of the region showing implants within bony envelope. Compare with Figures 9 and 10.
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