CATEGORY 70 AUSTRALASIAN DENTIST Mandibular reconstruction is used to rebuild a missing lower jaw following significant bone loss due to cancer, trauma, infection and benign pathology. Since the turn of the century, little progress has been made in mandibular reconstruction techniques that still largely rely on composite microvascular free flaps that involves complex, lengthy surgery with high morbidity and a not insignificant failure rate (1). Furthermore, the ability to replicate the complex anatomy of the natural mandible is almost impossible with existing free flaps which often leaves the patient without teeth to chew and consequently a reduced quality of life. The aim of this article is to present an example of 21st century digital technology which was used to rebuild a human jaw that was significantly destroyed by chronic osteomyelitis following a mandibular osteotomy that became infected. Case report A 65yo lady (Fig. 1) presented to the author in 2018 complaining of significant jaw deformity and compromised oral function following ongoing chronic infections of the mandible over a 20 year period. The patient had undergone a bilateral mandibular sagittal split osteotomy some 20 years previously to correct a class 2 skeletal base mandibular hypoplasia. Unfortunately, the osteotomy sites became infected and despite repeated surgical procedures to clean up the infection, the bone developed chronic destructive osteomyelitis. The progressive bone loss was further exacerbated by multiple attempts to replace the missing bone with autogenous bone grafts that failed. Microvascular reconstruction was offered but the patient declined because of the poor contours that fibula bone offered as well as the complexity and high morbidity involved. By the time she saw the author in mid 2018, the right side of her mandible had virtually disappeared with only a small fragment of rudimentary condyle. On the left side, there was severe resorption of the ramus and angle of the mandible, including the mandibular condyle (Fig. 2). This resulted in a severe class 2 crossbite of her remaining teeth with significant depression deformities at both angles of her mandible and limited oral opening (Fig. 1). Furthermore, the significant jaw deformity made the patient a virtual recluse as she feared people staring at her severe jaw deformity whenever she ventured outside. The patient was seeking a much simpler alloplastic solution with significantly less morbidity than the microvascular flap reconstruction that had been previously offered to her. Hence, she came to the author because of his experience in 3D titanium prosthetic technology. Initial scans showed multiple plates and screws in her remaining mandible (fig. 2) which needed to be surgically removed before a new mandibular prosthesis could be designed. She was taken to the operating theatre in late 2018 where the plates and screws were removed and bone samples were taken for microbiological investigations to check if there was still any active infection present. She was then sent to Infectious diseases specialists who managed her with 6 months of antibiotic therapy to ensure that any traces of infection were completely eliminated before she had her mandibular prostheses placed. Further bone scans were taken and her remaining mandible was reformatted in 3D to assess the nature of the deformity (Fig. 3). Using Materialize software, the engineers at MaxoniQ were able to design 2 hemimandibular components that stretched from the condyles to the remaining body/symphysis segment of her mandible (Fig. 4). These were 3D printed in titanium. Furthermore, a brand new temporomandibular anchor device made entirely of ultra-high molecular weight polyethylene (UHMWPE) was developed to help functionally secure the titanium mandibular condyles to the base of skull. In effect, the temporomandibular anchors Mandibular Reconstruction using 3D Print Technology By George Dimitroulis, Consultant Oral & Maxillofacial Surgeon, Epworth-Freemasons Hospital, East Melbourne Vic Fig. 1 – Shows the patient at her initial presentation to the author. Note the significant jaw defect at the angle of the mandible. Fig. 3 – A 3D render of the patient’s jaws and facial skeleton based on DICOM CT-Scan images. Note the missing right mandible and rudimentary right condylar process which was subsequently removed at the time of placement of the new mandibular prostheses and anchors. Fig. 2 – An OPG X-ray showing the missing right posterior mandible and the severely deformed left side of the mandible. The plates and screws shown on this x-ray were removed in a separate procedure prior to planning the mandibular prostheses. Fig. 4 – A 3D render of the planned bilateral titanium prostheses attached to the remaining mandible anteriorly, and posteriorly to the skull base via a Temporomandibular anchor made of polyethylene (UHMWPE). LINICAL
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