Prosthodontic outcomes of mandibular overdenture treatment with one or two implants: 4-year results of a randomized clinical trial.

OBJECTIVE: To assess the incidence of prosthodontic maintenance events and complications during 4 years of follow-up after mandibular overdenture treatment with one or two implants. METHODS: Participants received one or two implants inserted in the midline (1-IOD group) or the lateral incisor-canine area bilaterally (2-IOD group). Implants were loaded with an early loading protocol after 3 weeks. Programmed recall visits were scheduled at the 6-, 12-, 36-, and 48-month follow-ups and nonprogrammed visits in case of prosthodontic complaints. The type of maintenance was registered, and the final treatment outcome was classified as successful, surviving, unknown, dead, repair, or retreatment. RESULTS: Forty-seven participants, mean age 65.4 ± 8.6, 74.5% female, were included (1-IOD = 23; 2-IOD = 24) and 44 completed the 4-year follow-up. A total of 159 prosthodontic maintenance events occurred and 89 in unscheduled visits. The most common event was the need for minor modifications of the denture base due to sore spots in the oral mucosa (n = 56 in 31 patients), matrix activation (n = 54 in 34 patients), and overdenture fracture (n = 25 in 18 patients). A "successful" or "surviving" outcome could be attributed to 57.5% of cases, whereas 38.3% needed repair. No significant differences in the incidence of prosthodontic events or treatment outcomes were found between the two groups. CONCLUSIONS: Findings show that 1-IODs perform similar to 2-IODs when considering the incidence of fractures and the need for prosthodontic maintenance, including adjustments of the overdenture and the attachment system.

A prospective cohort on the incidence of fractures in single-implant mandibular overdentures.

OBJECTIVE: Denture fracture is one of the most common complications in prosthodontics and implant overdentures are reported to be at higher risk of fractures. Therefore, the aim of this study was to assess the incidence and factors associated with the occurrence of fractures in patients treated with a single implant mandibular overdenture (SIMO) opposed by a conventional maxillary complete denture. METHODS: A cohort of 152 patients, 65.1% female and 34.9% male, mean age 65.4 ± 8.5 years, were prospectively followed-up for a minimum of 1 year and up to 6.7 years. Patients received a single midline mandibular implant with a retention system incorporated in the overdenture: Straumann ball abutment and gold elliptical matrix (n = 37), Neodent ball/nylon matrix (n = 83), or Neodent Equator/nylon matrix (n = 32). Fracture was defined as a complete separation of denture parts and classified as midline fracture (over the implant region), or elsewhere. No metal reinforcement was incorporated into the overdenture. Incidence rates, life table analysis, Kaplan-Meier, and Cox regression were used for data analysis. RESULTS: Overdenture fractures occurred in 49 patients (32.2% incidence), with repeated fractures in 16 patients. The majority of fractures were associated with function (42.6%) or due to the overdenture being dropped (36.8%). Overall incidence density was 0.14 fracture/patient/year. The risk of fracture was associated with the duration of the overdenture use (HR = 0.84; 95%CI = 0.71-0.99). CONCLUSION: Midline denture fracture was a common complication in patients receiving SIMO treatment regardless of the implant / retention system. The use of metal reinforcement may be considered to reduce the risk of recurrent fractures. CLINICAL SIGNIFICANCE: This clinical prospective study showed that single-implant mandibular overdentures are at high risk of midline fractures. Proper post-insertion monitoring and the identification and management of patient's individual risk factors are essential for the successful treatment in the long-term.