A clinical trial of patient satisfaction and prosthodontic needs with ball and bar attachments for implant-retained complete overdentures: Three-year results

Abstract

Few prospective trials of implant-retained mandibular dentures have evaluated the increase and duration of patient satisfaction, costs of denture maintenance in relation to different methods of attaching overdentures to implants, or the use of a reinforced framework. This report evaluates subjects' satisfaction and prosthodontic maintenance during a 3-year randomized clinical trial of implant-retained mandibular complete dentures, whether reinforced or not with a cast framework, and attached by bar-clip or 2.25-mm ball-spring matrices to endosteal dental implants. One hundred edentulous subjects, each having at least 1 year's experience with conventional complete dentures, were selected from respondents to a university dental clinic's request for volunteers. Candidates were examined to verify adequate mandibular bone and medical suitability for implants. Subjects then received 2 implants in the anterior mandible before being stratified by mandibular bone height and gender and assigned randomly to 1 of 4 treatment groups. Every subject received a new maxillary complete denture in addition to an implant-supported mandibular complete denture, with or without a reinforcing framework, connected to implants by either a bar-clip or a ball-spring patrix and matrix. The dentures were adjusted and repaired as needed. Subjects indicated on a visual analogue scale (VAS) satisfaction with conventional dentures prior to the study and then with new dentures at 1 month, 1 year, and 2 years. The results reported here are from the first 68 subjects observed for 3 years after receiving new dentures (19 subjects received new dentures less than 3 years before this analysis, and another 13 subjects were lost to follow-up). VAS scores are presented in simple tables and graphs, and results for different groups were compared using 2-sided nonparametric rank tests and repeated measures ANOVA. With respect to costs and maintenance, t tests were used to compare group means. Sample size and other design considerations used a .05 significance level. After receiving new dentures with mandibular implant supports, improved satisfaction "within subject" was prompt, durable, substantial, and statistically significant, regardless of the attachment mechanism, and with or without a reinforcing framework. In contrast, there were no notable satisfaction differences between the 2 attachment mechanisms, or with the presence or absence of a reinforcing framework, either at specific intervals after receiving the new dentures, or in repeated measures ANOVA. For both attachment groups, most denture adjustments occurred during the first year. This accounted for 81% of total adjustments during 3 years, when the 34 subjects in the ball-spring group and the 34 in the bar-clip group were combined. The mean numbers of adjustments per subject and associated clinical times did not differ significantly between the 2 groups. Conversely, denture repairs declined more slowly than adjustments. Almost all repairs (90%) occurred in the ball-spring group to correct problems with the attachments, 39% in the first year, and tapering off only slightly in the following 2 years. Over 3 years of follow-up, mean numbers of repairs per subject differed significantly between groups: 6.7 repairs per person in the ball-spring group, compared to 0.8 in the bar-clip group ( P<.001), and mean time per appointment was greater for repairs in the ball-spring group: 18.9 minutes compared to 16.9 ( P<.01). The cast framework had no influence on the satisfaction expressed or on adjustments and repairs. Subjects were very satisfied with the new dentures, although the ball-spring attachment tested in this trial required substantially more repairs.