7-Year Follow-Up of Maxillary Overdentures Supported by Mini-Dental Implants

Background: Mini dental implants (MDIs) are alternatives to support an overdenture when a standard diameter implant cannot be placed due to lack of bone volume. They reduce the need for invasive bone grafting and lower the barrier for treatment. Aim: This prospective study reports on implant and patient-centered outcomes of flaplessly placed, early loaded MDIs supporting horseshoe-shaped maxillary overdentures after 7 years of function. Materials and Methods: Patients with a CBCT-confirmed thin alveolar crest received 5-6 one-piece MDIs using mentally guided flapless surgery. The conventional denture was relined and MDIs were provisionally loaded within one week. After 6 months the non-splinted MDIs were actively loaded with a horseshoe overdenture. Implant and prosthetic survival, peri-implant health (PPD and BoP) and patient-related outcomes using OHIP-14 and Subjective Masticatory Evaluation were assessed after 7 years. Results: 185 MDIs were placed in 14 females and 17 males. During provisional loading, 32 MDIs were lost, and 17 replacements were required in 16 patients. In total, 170 out of 202 totally placed MDIs were supporting 29 overdentures after 6 months. Cumulative implant failure increased from 15.8% at the moment of active loading to 34.7% at 7 years. After 7 years, 76% of the initially placed overdentures remained functional, mean PPD was 3.48 (SD 0.86), BoP was 0.20 (SD 0.40) and peri-implantitis incidence was 0.9%. The total OHIP-14 was reduced from 21.3/56 (SD: 13.1) preoperatively to 15.6/56 (SD 12.8) at provisional loading (p > 0.1) and 7.3/56 (SD 6.7) at final loading (p = 0.006), and it remained unchanged up to 7 years at 6.57/56 (SD: 8.92) (p > 0.5). Conclusions: Maxillary MDIs provide an acceptable treatment option in patients with deficient bone volume that cannot or refuse to be treated with bone grafting. Despite one third of the MDIs being lost, remaining MDIs had good peri-implant health, prosthetic success was 71% and Oral Health Related Quality of Life was beyond expectations.