Dental Asia May/Jun 2018

59 DENTAL ASIA MAY / JUNE 2018 Behind the Scenes increase the accuracy of the restoration and to decrease the di ƥ culty of implementation and the necessary time of processing. Clinical case A 54-year-old, male patient, non-smoker with no major clinical diseases, came to the clinician with an upper edentulous arch with some lower teeth present (from 34 to 45). The upper total prosthesis was incongruous, and caused some di ƥ culties in chewing and phonation. The patient manifested a psychological discomfort due the prosthesis condition in relation to his age, which hindered his speech when socialising with his co-workers. He also expressed the wish to replace the removable upper dentures with implants, quoting his own words, “something that will stay Ƥxed in the mouth and without palate.” The clinician started constructing the upper jaw with a new provisional but still entirely removable prosthesis for diagnostic purposes, and with the periodontal treatment of the lower arch, with a provisional and removable partial denture. Once the aesthetics and correct occlusal plane was restored, it is fundamental to maintain the buccal flange to support the upper lip. Some diagnostic tests were performed to study the placement of implants with a panoramic radiography and a computed tomography. In accordance to the patient’s approval, the clinician proceedswith the following treatment plan: insertion of four implants, in 14, 12, 22 and 24 areas and the construction of an implant - mucosal supported prosthesis with amilled bar on the upper arch; and the lower jaw was maintained healthy and restored with a removable partial denture. Once the implants were placed, the position was established according to the availability of the bone and the prosthetic requirements, the patient waited for the successful osseointegration with the total temporary prosthesis, suitably modiƤed. In this period, the patient was subjected to periodontal maintenance therapy. The same prosthesis was used as a base for the Ƥnal restoration. Implementation of the transparent acrylic resin replica The provisional prosthesis was positioned with a precision silicone with a hardness of 70 Shore-A. The prosthesis and model silicone obtained were placed in a ƪask and then an insulator (insulating silicone spray, Transformer) was applied. Another silicone was placed between the replica and the cover of the ƪask, which was closed and held in place until the full curing of the silicone. The prosthesis was removed from the ƪask and two holes through the upper silicon (a 0.5 cm diameter for the input channel along with a 0.3 cm for the output channel) to allow the injection of the transparent acrylic resin. The resin was mixed and injected inside the ƪask, which was maintained at 50°C for 25 minutes at a pressure of 2.5 bars. Once cured, the ƪask was opened and the replica was Ƥnished with rotary instruments mounted on a laboratory handpiece and delivered to the clinician. Impressionwith the prosthesis replica The transparent resin replica was used in a single chairside appointment, as customised tray, as a reference of the teeth set-up (control of the vertical dimension, the masticatory plane and the relationship with the antagonist), and as a Ƥrst test of the aesthetics (smile line, midline, etc). The clinician proceeded with the insertion of the replica in the oral cavity, checking the occlusion and removing thewrong occlusal contacts. The precise occlusion was then recorded using an additional fast-curing silicone. The replica had been perforated in correspondence with the emergence of the implants and daubed with adhesive. For the impression an addition silicone has been used and the replica was maintained in position by the patient with his bite until the complete polymerisation occurs; before its removal, a face bowwas recorded. After removing the replica from the oral cavity, the silicone inside the holes was removed with a scalpel to allow the insertion of the pick-up transfers. The replica was placed back into the oral cavity and the transfers were screwed on the implants. Keeping the prosthesis in place, the transfers were blocked on the replica using light curing resin with low shrinkage. The Ƥxing screws were removed from the transfers and the impression was delivered to the laboratory after the disinfection protocol (Fig. 1). Fabrication of themastermodel and aesthetic try-in A silicone reproducing the soft tissues was placed at the area around the transfers then a proper insulation was daubed (Fig. 2). The master model was poured by developing the impression obtained with the replica with a class IV plaster; according to the manufacturer’sinstructions(Fig.3-4). Once hardened, the transfers were removed and themaster model was positioned on the articulator using the replica and the face bow. The antagonist model was placed on the articulator with the silicone bite. Fig. 1: Impression obtained with the prosthesis replica Fig. 2: Placing of the laboratory analogues and the artiƤcial gingiva