CAD/CAM international magazine of digital dentistry

research _ SFI-Bar I I 17CAD/CAM 3_2012 ters had been corrected in the wax denture try-in. Two 4.1mmRNconnectiondental implants (Straumann), each 8 mm in length, were placed in sites #32 and #42 (Figs. 7a & 9b). These were allowed to integrate for three months priortotheprovisionofaball- abutment-retained overden- ture. This denture functioned without surgical or prosthetic issues for a five-year period. Unfortunately, the patient revisited her denturist and complications arose after an attempted intra-oral relining procedure. On examination, it was determined that the ball abutments were damaged and needed to be replaced. The fe- male housings needed to be replaced, as they were no longer seated properly on the ball abutments. The patient was then given the option of having either another ball-abutment-retained overdenture or a bar- and clip-retained overdenture instead. The patient opted for the bar and clip overdenture. The firststepwastoremovethedamagedballabutments and seat the appropriate implant adapters on each implant(H1adaptersof1mminlength;Figs.4a&b). The tube bar was then inserted into the cutting tool and cut to correct length using the cutting disc (Figs. 6a–c). The bar assembly was then connected to the implant adapters and torqued into place. The universal nature of the ball joint allows the tube bar tobelocatedinthehorizontalplaneinatrulystress- free alignment (Figs. 2a–c & 7b–c). The implant adapters were chosen so that when the bar is seated it is parallel to the occlusal plane, with at least 1.0 mm clearance between the under- side of the bar and the mucosal tissues (Fig. 7b). This allows access for effective oral hygiene procedures around the dental implants and reduces the risk of tissue hyperplasia around the bar when the denture is seated. From a surgical per- spective, ridge reduction pro- ceduresmayberequiredfirstly to aid ideal implant placement and secondly to ensure there is enough space to fabricate the final denture to be seated onthebarassembly.Ifmultiple implants are used, adapters with a range of lengths should be used. Multiple implants are more difficult to place parallel toeachother,buttheballjointscanaccommodateup to 15° of implant divergence. Surgical complications areseenmorecommonlyinbarandclipoverdentures than stud-attachment overdentures. Clinically, the wholeproceduretooksixminutes,fromremovingthe ball abutments to torquing the bar assembly into place. The ball-abutment- retained denture was then hollowed out so that it could be seated over the bar assembly and used as a provisional while the new definitive denture wasbeingfabricated.Acustomtraywasusedtomake a border-moulded final impression with Impregum (3MESPE),afterblockingoutthebarassembly(Fig.10). A wax occlusal rim was then used to determine the vertical dimension of the occlusion and obtain a CR record. This was followed by a full wax try-in to ensure that all the aesthetic, phonetic and occlusal parameters were correct. At this point, the denture Fig. 9a Fig. 9b Fig. 9c Fig. 10 Fig. 11a Fig. 12Fig. 11b