Results with Overdentures Retained by One or Two Implants

Objectives: This randomized clinical trial tested the hypothesis that there is no difference in patient satisfaction with mandibular overdentures retained by one or two implants. We also compared component costs, treatment time and maintenance time.

Methods: The study was supported by CIHR (Grant #58954), ITI Foundation (Grant #222) and Straumann Canada. Subjects wearing complete dentures were randomly assigned to receive either a single midline implant or two implants (Solid Screw, SLA surface, Straumann Canada) in the anterior mandible. They indicated satisfaction with their dentures on visual analogue scales (VAS) at baseline and one year after their lower dentures were relined to incorporate implant retention (Straumann ITI Gold Matrix). We recorded surgical and prosthodontic times, as well as component costs.

Results: We enrolled 86 subjects (39 women and 37 men, mean age 67), one of whom withdrew after receiving two implants. At one-year follow-up, median satisfaction was 93 in the single-implant group (VAS max=100) and 94 with two implants (Wilcoxon-Mann-Whitney test, p > 0.5 ). Median improvement in satisfaction in both groups was similar (about 44 points) and significant (signed-rank test, p < 0.001). Time for prosthodontic maintenance was also similar for both groups (p > 0.1). On the other hand, the single-implant group had lower component costs, and lower mean and median times for surgery, post-surgical denture maintenance, and denture reline for implants; these differences were statistically significant (each p < 0.02) and clinically important (post-surgical maintenance time averaged 186 vs. 268 minutes). Three implants failed, all before denture reline and all in the two-implant group.

Conclusion: One-year results indicate comparable satisfaction and maintenance time, with lower component costs and treatment times, when mandibular overdentures are retained by a single implant. This procedure should be considered as an alternative to the standard two-implant overdenture for maladaptive denture patients.