Methods: Sixteen patients who had edentulous mandible with a mean age of 71.3 years (range, 60 to 85 years) at Dental Hospital, Tokyo Medical and Dental University enrolled in this study. For radiographic guides preparation, a newly fabricated removable denture was used. The computer planning followed the design procedure (Procera, Nobel Biocare), and the surgical guides (Nobel Guide, Nobel Biocare) were fabricated for each patient. Flapless surgery was performed with this surgical guide, and two implants, threaded titanium oxide-surface implants (Speedy Groovy, Nobel Biocare) (n = 32 implants) were placed in canine positions. At the operation day, removable overdenture supported with two ball attachments (Ball abutment and Gold cap, Nobel Biocare) was delivered. Subjects were seen for follow-up examinations after 1, 6, and 12 months, during which masticatory function was measured using the color changeable chewing gum (Masticatory Performance Evaluating Gum XYLITOL, Lotte). The survival of each implant was evaluated clinically and radiographically. Surgical and prosthetic complications were recorded. The Tukey HSD post-hoc test was used to evaluate changes in the masticatory function.
Results: Two patients, with one failed implant, dropped out prior to completion of the study. The failed implants were included in the evaluation of cumulative implant survival. The cumulative implant survival rate at 1 year was 94% (30/32). The mean masticatory performance was 32.3±11.4, 35.2±17.4, 39.4±1, and 40.0±17.8 at baseline, 1month, 6month and 12months, respectively. No irreversible surgical and/or prosthetic complications were observed.
Conclusions: In this 1-year pilot prospective study, the immediate loading of two-implants mandibular overdentures with ball attachments resulted in favorable implant survival and masticatory function.