CATEGORY AUSTRALASIAN DENTIST 71 acted like new temporomandibular joints that prevented the alloplastic condyles from displacing out of the fossae during mandibular function. In September 2019, the patient was taken to the operating theatre where she had both hemi-mandibular titanium custom prostheses implanted and attached to the specially designed UHMWPE temporomandibular anchors which engaged the titanium condylar heads in a simple 90o twist motion. The devices were secured to the underlying bony base with multiple titaniumscrews (Fig. 5).The 3 hour operation went smoothly as the custom devices eliminated the need to alter the jaw bone as the devices were a snug fit. Because of the simplicity and speed of the surgery, the patient did not require a tracheostomy and was sent straight to the ward after her surgery rather than ICU which is commonly the case with Microvascular reconstructions. She was discharged from hospital 2 days later and has required no further surgical intervention. At her 18 month follow-up, the patient was extremely pleased with the aesthetic and functional improvement in her facial appearance and chewing respectively (Fig. 6). Updated x-rays show the mandibular prostheses are intact and functioning well (Fig. 7). Discussion While titanium mandibular reconstruction plates have often been used in the past, these are normally based on stock standard off-the-shelf plates that need to be bent at the time of surgery. Unfortunately, the thin nature of these plates means they are liable to fracture and fail to replace the full contour of the missing mandible. Furthermore, even with fibular bone reconstruction, when the condyle is missing, it is often virtually impossible to anchor the superior tip of the bone and/or reconstruction plate to the base of the skull which often results in displacement and jaw dysfunction with significant malocclusion that restricts the patients chewing ability and adversely affects their speech. The fully customized titanium 3D printed mandibular prosthesis not only replicates the exact jawbone dimensions and contours that replace the missing native mandibular bone, but also has the strength to withstand the full functional loads of the mandible. Furthermore, the temporomandibular anchor device clearly has the advantage of securing a fully functional artificial TMJ that allows jaw movements and occlusal stability which cannot be achieved with conventional reconstructive techniques (Fig. 8). The custom devices also speed up the surgery time and lead to quicker recovery times compared to conventional techniques. MaxoniQ engineers are currently working on adding dental implants that are incorporated within the frame of the mandibular prosthesis so that full dental rehabilitation will eventually become a reality. Conclusion Digital technology has opened up a whole new way of dealing with significant jaw defects and deformities with techniques that are vastly simpler than existing surgical techniques. Custom, 3D printed devices that are designed specifically for individual patients have led to improved outcomes in terms of reduced surgical times, reduced mobidity with improved and predictable outcomes (2) that far surpass the current techniques that rely on conventional reconstruction plates and microvascular bone flaps to reconstruct significant defects of the mandible. Acknowledgements: The contribution of biomedical engineers at MAXONIQ (www.maxoniq.com) who helped design, develop and produce the Mandibular Prosthesis is gratefully acknowledged. Declaration: Dr George Dimitroulis is a practicing Oral & Maxillofacial Surgeon and Clinical Director of MAXONIQ (www.maxoniq.com) a Melbourne based Medtech Company which developed and manufactured the Mandibular Prosthesis system described in this article. u REFERENCES 1. Dimitroulis G. Mandibular reconstruction following ablative tumour surgery: an overview of treatment planning. Aust N Z J Surg. 2000 Feb;70(2):120-6. 2. Bender-Heine A, Petrisor D, Wax MK. Advances in Oromandibular Reconstruction withThreeDimensional Printing. Facial Plast Surg. 2020 Dec;36(6):703-710 All Correspondence: Dr George Dimitroulis Suite 1, Ground Floor, 124 Grey Street East Melbourne Vic 3002 Tel: +61 03 9654 3799 Fax: +61 03 9650 3845 Mob: +61 0409 505 146 e-mail: geodim25@gmail.com Fig. 5 – Intraoperative photos showing the temporomandibular anchor (left) secured to the skull base with titanium screws. On the right is the custom 3D printed titanium mandibular prosthesis attached to the remaining mandible anteriorly with titanium screws. The underlying soft tissues are sutured to the frame via the 3 holes at the angle of the prosthesis. Fig. 6 – Before (left) and after (right) profile photos of the patient showing the elimination of the mandibular angle defect and restoration of normal jaw contour after placement of the mandibular prostheses. Fig. 7 – OPG X-ray showing the bilateral mandibular prostheses in situ held in their respective fossae by the invisible polyethylene temporomandibular anchors which only the screws at the base of skull are visible. Fig. 8 – full functional mouth opening being demonstrated 18 months after surgery. LINICAL
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