Bar versus ball attachments for maxillary four-implant retained overdentures: A randomized controlled trial

To compare the clinical treatment outcomes of maxillary four-implant retained overdentures with either splinted (bar) attachments or non-splinted (ball) attachments.

Forty participants who were dissatisfied with their existing conventional maxillary complete dentures were included in this randomized controlled trial. Six months after implant placement, a definitive prosthesis was inserted. Implant success, condition of peri-implant tissue, prosthodontic maintenance and complications, and patient satisfaction were assessed. Outcomes were recorded at baseline, prosthesis delivery, and at 3 and 12 months following prosthesis delivery, and a statistical analysis was performed.

Thirty-two of the forty patients completed the 1-year follow-up and had their treatment outcomes evaluated. The mean marginal bone loss after 1 year of loading was 0.34 ± 0.88 mm, and there were no significant differences between the two groups. Plaque index, gingival index and bleeding on probing were significantly higher in the bar group (p<.001), and the implant success rate of the bar group was significantly lower than that of the ball group (p=.028). The most frequent prosthodontic maintenance and complication issue was the need to change the bar clip or O-ring as a result of retention loss. Patient satisfaction did not differ between the two groups except for aesthetics at 3 months.

Within the limitations of this study, the maxillary 4-implant retained overdenture exhibited predictable results regardless of the attachment systems (ball or bar) in the 1-year follow-up period. The bar group was more vulnerable than the ball group with respect to maintaining peri-implant tissue health.