Maxillary and mandibular overdentures retained by two unsplinted narrow-diameter titanium-zirconium implants - A clinical pilot study

ObjectivesTo evaluate the survival rates and marginal bone loss of narrow-diameter titanium-zirconium implants supporting complete maxillary and mandibular overdentures up to 3 years after loading.Materials and MethodsTen completely edentulous patients who were dissatisfied with their complete dentures were enrolled. Two narrow-diameter implants were placed in the canine region of the maxilla and mandible. After second-stage surgery, implant-supported overdentures (palatal-free) attached by parallel alignable stud-attachments were placed. Patients were followed periodically for up to 36 months. Standardized radiographs were taken at baseline, 12 and 36 months to analyze mean marginal bone level changes around the implants.ResultsThe Kaplan-Meier survival rates were 100% for mandibular and 68.0% (SE +/- 10.9%) for maxillary implants at 36 months (p = .008). Six maxillary implants failed after loading; no mandibular implants were lost. Five implants failed due to loss of osseointegration. One implant fractured. The mean marginal bone level changes around the analyzed implants (n = 28, 9 patients) were -0.71 +/- 0.82 mm in the mandible and -2.08 +/- 1.52 mm in the maxilla at the 36-month follow-up. The difference in marginal bone level changes between the maxilla and mandible was significant (p = .019) at the 12- and 36-month follow-ups.ConclusionTwo narrow-diameter titanium-zirconium implants with stud-attachments showed a highly satisfactory outcome in the mandible. The maxillary implants showed a high failure rate and significantly more bone loss over time than the mandibular implants. The minimal concept of two implants and an overdenture should be limited to the edentulous mandible.