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.