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.

Mandibular bone characteristics, drilling protocols, and final insertion torque for titanium-zirconium mini-implants for overdentures: A cross-sectional analysis.

OBJECTIVE: The aim of this study was to assess the final insertion torque values achieved using site-specific drilling protocols for a novel mini implant system for removable complete overdentures. Anatomical and technical factors influencing final insertion torque were recorded and analyzed. MATERIAL AND METHODS: Participants were randomized to two surgical protocol groups (flapped or flapless) and all received four mini implants (Straumann® mini implant system; Straumann AG) in the anterior mandible, using a 1.6 mm needle drill and a 2.2 mm pilot drill for the implant bed site preparation. The final insertion torque was recorded as the main outcome variable during surgery. Bone type, radiographical bone density, ridge form, implant length, and the drilling protocol were considered as independent variables. Descriptive statistics, generalized estimating equations (GEE) regression, and heatmap charts were used for data analyses. RESULTS: A total of 296 mini implants were placed in 74 patients (mean age = 64.1 ± 8.0; 64.9% female) using flapless (n = 37) or flapped (n = 37) surgeries. Mean final insertion torque was 55.8 ± 18.4 Ncm (10.5% > 35 Ncm, 48.9% between 35 and 65 Ncm, and 40.6% > 65 Ncm). The needle drill was used in only 43.9% of the implant bed sites. Higher final torque values were observed for higher bone densities (bone type I > II > III, and D1-D2 > D3-D4), highly resorbed ridge forms (5-6 > 3-4), flapped surgeries, and male patients. However, regression models showed that the likelihood of achieving optimal insertion torque (≥35 and ≤65 Ncm) was higher for females (OR = 2.14; 95%CI = 1.14-4.01; p = 0.018), ridge forms 3-4 (OR = 2.87; 95%CI = 1.05-7.85; p = 0.040), and flapless surgeries (OR = 1.96; 95%CI = 1.09-3.51; p = 0.024). CONCLUSIONS: Sufficient primary stability for immediate loading was achieved for the majority of the mini implants placed. Surgical implant bed preparation should be site-specific to achieve optimal primary stability for immediate loading while avoiding excessive insertion torque.