Biological and prosthodontic outcomes of conventional and mini-implants immediately loaded with overdentures : results of a five-year prospective cohort study

Abstract

Objectives: The aims of this study are to report on an ongoing prospective study evaluating the biological and prosthodontic outcomes of patients treated with immediately loaded mandibular overdentures using two conventional or two mini-implants for up to five years.

Methods: Two groups of edentulous patients with functional complete dentures had the lower prostheses converted into an overdenture using either two conventional (4.0mm) or mini-implants (<3.0mm) using unsplinted attachments (Locators) and followed up. Implant survival, peri-implant bone profile and prosthodontic events were assessed. Statistics to compare between baseline, one and five years and between groups were performed using Mann-Whitney U Test. Chi-square test was used to analyze prosthetic maintenance and complication interventions between groups.

Results: 30 patients were followed–9 deaths were reported (5 in CI group and 4 in MI group). 11 patients were lost to follow-up (4 in CI group and 7 in MI Group). In CI group, 16 patients age (70.8±6.7yrs) and MI group, 14 patients (73.8±7.7yrs) were analysed. The mean observation period was 56.1 months (S.D.±22.48) for CI group and 51.35 months (S.D.±21.12) for the MI group and was equal in both groups (MW Test, p>0.05). Implant success rate was 96.8% in the CI group and 89.3% for MI group (Fisher’s exact test, p=0.34). There was no difference in cumulative survival rates of implants in both groups (Log Rank Mantel-Cox, p=0.65). Mean±S.E. bone loss differences between CI (0.41±0.08mm) & MI (0.81±0.13mm) groups were significant (MW Test, p=0.022). With regards to prosthodontic outcomes, significant differences were observed for fractures of the overdenture and antagonist, and debonding of the matrices (p<0.05).

Conclusion: Bone loss was still significantly higher among the MI group. The two-implant mandibular overdenture required regular maintenance which was significantly higher in the CI group.

Clinical Relevance: Further modifications to the prosthodontic protocol are required to further improve the clinical effectiveness of treatment.