GAP Australasian-Dentist Issue 80 Jul-Aug 19

Category AustrÀlÀsiÀn Dentist 89 prosthetic total joint replacements (figs. 7, 8). Àhe commenced with orthodontic treatment and at the completion of the pre-surgical orthodontics the patient was sent for cone-beam CÀ scans of the jaws which were used to digitally plan both her orthognathic surgery and bilateral ÀMJ custom prostheses 4 . Àsing Mimics and 3-Matic advanced software (Materialize, Belgium), engineers at OMX Àolutions constructed a 3D model of the patient’s facial skeleton (fig. 6). Àhe author instructed the engineers on the precise movements of the jaws as well as the size and position of the ÀMJ prostheses. Ào facilitate the surgery, custom cutting and drilling guides were used for the maxilla and the ÀMJ’s. Àot only were the ÀMJ prosthetic joints fully customized for the patient, but a custom maxillary plate was also 3D printed to simplify the exact n aÀ Fig 6 – Preoperative 3D rendered image of patient’s facial skeleton based on the DICOM files derived from her CT scans. The severity of her class 2 retrognathia is masked by her posturing forward of her mandible during scanning. Note the condyles are completely missing as a result of idiopathic condylar resorption Fig 7 – Shows the surgical plan of the jaw movements and design of the bilateral custom OMX TMJ prosthetic joints and custom bone plates for maxilla and chin shown in green. Fig. 8 – Lateral view of 3D digitally planned movements of the jaws including the custom bone plates and prosthetic joints shown in green. Conventional bone plates were used in the mandibular sagittal split, hence are not shown. Fig 9 – Lateral Cephalogram x-ray showing the actual post-operative result of the bimaxillary surgery and TMJ prosthetic joints which correspond precisely to the pre-operative planned movements and position of custom implants shown in figure 8. Fig 10 – Before Surgery Fig 12 – Before Surgery Fig 11 – 1 year after surgery Fig 13 – 1 year after surgery positioning of the maxilla (figs. 7, 8). Àhe planning sequence is described in Àable 1. Àhe combined surgery consisted of ÀeFort 1 maxillary impaction and advancement with mandibular sagittal split advancement and autorotation to match the new occlusal position of the maxilla. Augmentation genioplasty was also performed. Àhe fully customized ÀMJ prosthetic joints were digitally designed for 3D printing and implanted to secure a stable platform for the new maxilla- mandibular position (figs. 8, 9). Àhe surgical sequence is described in Àable 2. Àhe patient remained in hospital for 4 nights and was back at work 4 weeks following her surgery. Her 12 month follow up showed no signs of relapse and she had smooth pain-free function of both her ÀMJ’s (figs. 10-13). Case 2 A 21yo female for referred to the author for combined Orthognathic/ÀMJ surgery to correct her severe class 2 mandibular retrognathia (fig. 14, 15, 16) secondary to destructive rheumatoid arthritis which had affected both her ÀMJ’s 1 . Àhe was under the care of a Àheumatology specialist as she had similar issues in other joints, in particular, her wrists and hips. Àhe was on powerful anti- inflammatories and immunomodulators for her Àheumatoid disease and came to the author following more than 5 years of occlusal splint therapy 1 . Her motivating factor for presenting to the author was painful, restricted mouth opening that made it difficult for her to receive adequate dental treatment. After a year of pre-surgical orthodontics, the patient underwent TABLE 1 – PLANNING SEQUENCE 1.À Cone-beam CT scans of the jaws 2.À Digital scan of the teeth or dental impressions 3.À Plan Maxillary movement À a.À Construct cutting & drilling guide (3DÀprinted) À b.À Construct custom titanium bone plate (3D printed) 4.À Plan Mandibular movement À a.À Construct final occlusal splint (3DÀprinted) 5.À Plan TMJ custom Prostheses to the final mandibular occlusal position À a.À Construct cutting and drilling guides to aid; (3D printed) i.À condylectomy À ii.À correct positioning of custom fossae and condyles. À b.À Construct intermediate surgical occlusal splint (3D printed) À c.À Construct Custom Polyethylene Fossa (milled) À d.À Construct Custom Titanium Condyles (3D printed)