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ePaper created 2017-05-10, 16:12:25 | version 1.38.0
restoration of the edentulous maxilla case report | not vary performance. The metal abutments demon- strated considerable wear as well (Fig. 2). Relining the lower denture did not improve the performance of the anchor system. At the subsequent appointment, the patient was presented with the Atlantis Conus concept as a potential solution to her ongoing dilemma. Treatment options were presented as well including a fixed hybrid prosthesis and a 2-in-1 bar overdenture. These were rejected as interarch space was less than optimal, re- quiring compromise to the strength of the design. The patient also expressed a desire for a removable design as she was concerned with having adequate facial support and wished to be able to remove the prosthe- sis for proper hygiene and maintenance. It was agreed that a new maxillary and mandibular complete den- ture would be fabricated, and Atlantis Conus Abut- ments would be made to secure the lower restoration. Clinical and laboratory procedures Because the existing dentures were made within the last five years and were acceptable with regard to tooth position and vertical dimension, it was decided that clear, acrylic resin duplicates of each denture would be made to serve as custom trays.7 Double- sided impressions of each denture were made and delivered to the dental laboratory for fabrication of the duplicates. Once processed, the copy denture bor- ders were shortened by 2 mm to allow border mould- ing. The duplicate of the mandibular denture clearly showed the position of each Locator housing and therefore the position of the dental implants. Holes of adequate diameter to allow the duplicate denture to be placed in the patient’s mouth over impression cop- ings were prepared (Fig. 3). The intaglio surface of both the upper and lower duplicate denture were relieved to allow for a wash impression. The patient returned for final impressions, and the Locator abutments were removed and kept in appro- priate order to avoid confusion when reseating them at the appointment completion. Open tray impression copings were connected to each of the four dental implants to be restored and tightened into place; one implant with greater bone loss and placed sig- nificantly more shallowly than the rest was omitted (Fig. 4). Light-body polyvinyl siloxane (PVS) was in- jected around the base of each impression coping and medium-body PVS was placed in the custom tray. The tray was seated, ensuring that the impression copings were completely accessible through the holes previously prepared. The patient was instructed in facial and tongue movement to achieve proper pe- ripheral border extension. Regisil Rigid (Dentsply Sirona) bite registration material was injected around each impression coping to rigidly adhere them to the impression tray. This step is critical as reliance on flex- ible impression material may allow transfer error when constructing the working cast. Once the impression materials were fully set, the screws retaining the impression copings were re- moved and the final impression and tray were with- drawn from the patient (Figs. 5 & 6). All Locator abut- ments were reseated and tightened. Final impression of the maxilla was completed with border moulding using modelling plastic and a wash impression with light-body PVS. Upon completion, the patient was dismissed. In the dental laboratory, implant analogues were secured to the impression posts, gingival moulage was injected around the analogues to an adequate depth to completely cover the coping-analogue in- terface. The impressions were boxed with wax and Fig. 8 Fig. 8: Atlantis Conus Abutments on the working cast. Each abutment has the tooth number location scribed on the buccal-facing surface. Fig. 9: SynCone caps seated on the abutments on the working cast. An impression of this arrangement is made to fabricate a cast metal frame Fig. 9 to reinforce the final restoration. Fig. 10: Completed laboratory restoration; note the termination the arch at the first molar to avoid excessive cantilever length. The chrome frame is opaqued on the functional side to prevent gray show-through. Fig. 11: Completed laboratory restoration showing the metal frame and recessed area to receive the Fig. 10 Fig. 11 SynCone caps. CAD/CAM 2 2017 13