implants international magazine of oral implantology

research I I 11implants2_2012 denture or a bar- and clip-retained overdenture instead. The patient opted for the bar and clip overdenture. The first step was to remove the damaged ball abutments and seat the appropriate implant adapters on each implant (H1 adapters of 1mminlength;Figs.4a&b).Thetubebarwasthen 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 adaptersandtorquedintoplace.Theuniversalna- ture of the ball joint allows the tube bar to be lo- cated in the horizontal plane in a truly stress-free alignment (Figs. 2a–c & 7b–c). Theimplantadapterswerechosensothatwhen the bar is seated it is parallel to the occlusal plane, withatleast1.0mmclearancebetweentheunder- side of the bar and the mucosal tissues (Fig. 7b). Thisallowsaccessforeffectiveoralhygieneproce- dures around the dental implants and reduces theriskoftissuehyperplasiaaroundthe bar when the denture is seated. From a surgical perspective, ridge reduction procedures may be required firstly to aid idealimplantplacementandsec- ondly to ensure there is enough spacetofabricatethefinaldenturetobeseatedon the bar assembly. If multiple implants are used, adapters with a range of lengths should be used. Multipleimplantsaremoredifficulttoplaceparal- lel to each other, but the ball joints can accommo- date up to 15° of implant divergence. Surgical complications are seen more commonly in bar and clip overdentures than stud-attachment overden- tures. Clinically, the whole procedure took six minutes, from removing the 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 was being fabricated. A custom tray was used to make a border-moulded final im- pression with Impregum (3M ESPE), after blocking outthebarassembly(Fig.10).Awaxocclusalrimwas thenusedtodeterminetheverticaldimensionofthe occlusionandobtainaCRrecord.Thiswasfollowed by a full wax try-in to ensure that all the aesthetic, phonetic and occlusal parameters were correct. At this point, the denture was ready to be processed. The denture is processed in one of two ways: – In the laboratory technique, the female part T (made from pure Grade 4 titanium) is integrated into the denture and a complete prosthesis is re- turned to the clinic. Part T is contra-indicated for use on two implant bars (Figs. 11a & b). – In the chairside technique, the denture is processed and a window is cut in the denture, throughwhichthedentistcanpickupthefemale part E (made from Elitor—68.6% gold alloy), us- ing self-curing acrylic resin in the patient’s mouth after seating the spacer and blocking out all undercuts (Fig. 10). The total width of the bar with the E clip seated is4.3mm(Fig.12)and3.6mmwiththeTclipseated (Fig.11a).Thisisrelevantfortreatmentplanning,as ridge reduction may be indicated to provide space for the denture. In the laboratory method, the denture is com- pleted with the female part T integrated into the denture. The dentist then chooses the level of re- tentionrequiredbyselectingtheappropriateplas- tic inserts and seating them in part T (Fig. 11b). The plastic inserts are designed to compensate for transfer inaccuracies during the impression, mas- ter cast fabrication and post-processing stages. The presence of a laboratory technician is recom- mended for the chairside technique. A spacer is Fig. 12Fig. 11b Fig. 11a