Purpose: To determine the clinical and radiological outcomes of hybrid-design- (HD) and bone-level (BL) implants for bar-retained mandibular implant-overdentures (IODs).

Methods: For this retrospective study, edentulous patients who had received maxillary complete dentures and mandibular bar-retained IODs were invited for a follow-up assessment. Implant survival, implant success and health of peri-implant tissues were assessed on an implant level-based analysis. Patient-based parameters served to identify risk factors for peri-implant bone loss, presence of peri-implantitis and success.

Results: Eighty patients (median age 72.72 [67.03; 78.81] years, 46 females) with 180 implants (median follow-up 12.01 [10.82; 21.04] years) were assessed. There was no difference concerning the rate of implant failure (p = 0.26), or peri-implantitis (p = 0.97) between HD and BL implants. Solely in one study group, there was the presence of peri-implant pus. Implant success was higher in BL implants with one group being notably higher than the comparing groups (p = 0.045). For bone loss, a width of keratinized mucosa (KM) ≤ 1 mm (p = 0.0006) and the presence of xerostomia (p = 0.09) were identified as risk factors. Smoking (p = 0.013) and a higher body mass index (BMI) (p = 0.03) were a risk factor for peri-implantitis. As risk factors for reduced implant success, a small width of KM (p = 0.003) and the presence of xerostomia (p = 0.007) were identified.

Conclusions: For mandibular bar-retained IODs, both BL and HD implants are mostly successful. A minimum of 1 mm KM around implants and normal salivary flow are relevant factors for implant success and stable peri-implant bone levels. Smoking and a high BMI are potential risk factors for peri-implantitis.