Bar type attachments are often used to connect abutment teeth or implants and provide retention for removable dentures and overdentures. Retention is achieved by using riders/clips, retention sleeves, O-rings, etc. There are several bar type attachments that are available commercially, including the Dolder Bar System, the Hader Bar System, the Acherman Clip, and others. Any type of bar attachment can be referred to as a primary or meso bar. In this case report, a mesobar using O-rings was used to connect two endosteal implants and provide retention for a maxillary removable implant-retained overdenture.

After osseointegration, the healing collars were removed and prepable permanent abutments inserted. The abutments were prepared with high-speed diamonds and water coolant. A polyvinyl siloxane impression Aquasil (Dentsply, Lakewood, Colo), bite registration, and opposing impression were taken and sent to the laboratory. Two abutment copings were waxed in the lab and connected by a wax mesobar. One male O-ring attachment (ball shaped) was waxed on top of the mesobar between abutments and another mesial to the anterior abutment. The mesobar had an ovate pontic appearance proximal to the tissue. It was cast with type IV gold alloy and tried-in over the implant abutments (Figure 13). The passive fit of the mesobar was confirmed clinically and radiographically. Two female gold-plated retainer rings (metal housings) with rubber O-rings inside were placed onto the male protruded components. The acrylic portion of the existing maxillary RPD in the implant area was hollowed out to allow enough room to receive the framework and check the occlusion. The existing partial denture was placed back and had a passive fit without occlusal interferences. A cold cure acrylic was then added inside the hollowed area of the prosthesis. It was then placed back in the mouth to re-check the occlusion again, and the acrylic was allowed to set in the mouth. Once the acrylic was set, the prosthesis was removed together with the metal framework. The mesobar was then separated from the prosthesis and placed back on implant abutments, leaving two O-ring female housings still remaining in the partial denture. The partial denture was then cleaned and tried-in the mouth once more. All denture determinants, including a group function occlusion bilaterally, centric relation, midline, vertical dimensions, esthetics, and patient's comfort were found satisfactory. The partial implant overdenture was then removed and the mesobar was cemented to implant abutments with permanent cement (Panavia F 2.0, Kuraray Dental, Japan) (Figures 14 and 15). At the completion of the restorative stage, the modified maxillary implant overdenture had a bilateral retention provided on the right side by 2 new O-ring attachments and on the left side by an already existing O-ring attachment on the mesial end of the bridge No. 12-13-14 and clasps (Figure 16). An implant-retained partial overdenture helped to support patient's upper lip and provided harmonious lower facial proportions (Figure 17). Once the procedure was completed, the patient received instructions for function and hygiene. Patient's expectations for the improved retention of her upper partial denture were met and she was satisfied with the final result.