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Objective: To assess the relative position of mini‐implants to retain a mandibular overdenture, according to the surgical protocol, technical and anatomical factors. Methods: Mandibular cone‐beam computed tomography (CBCT) scans were analyzed for 73 patients who received four one‐piece titanium‐zirconium mini‐implants. Drilling was performed using a 1.6 mm needle drill and a 2.2 mm Pilot Drill, according to the bone density with a surgical stent. Post‐insertion CBCT images in DICOM format were analyzed using the E‐Vol‐DX software with BAR filters. Divergence angle between implants and between implants and the overdenture path of insertion was measured using CliniView 10.2.6 software. Results: Divergence between implants ranged from 0° to 22.3° (mean = 4.2; SD = 3.7) in the lateral and from 0° to 26.2° (mean = 5.3; SD = 4.1) in the frontal projections (p <.001). Only 1 (0.2%) and 3 (0.7%) of the measurements were higher than 20° in the lateral and frontal views, respectively. The mean angulations between the implant and the path of insertion for the overdenture were 9.3° (SD = 7.5) and 4.0° (SD = 2.9) for the lateral and frontal views, respectively (p <.001). Regression analyses showed a significant association between the divergence of implants and the frontal view projection (p <.001), greater distance between the paired implants (p =.017), the flapped surgical protocol (p =.002), higher final insertion torque (p =.011), and deeper preparation with the needle drill (p <.001). Conclusions: The mini‐implants were placed with low divergence angles and satisfactory parallelism. Factors including shorter distances between the implants, higher density bone, and a flapless surgical approach all contributed positively to improved parallelism of the mini‐implants. [ABSTRACT FROM AUTHOR]

Objective: This prospective study is part of a randomised clinical trial and reports the changes in masticatory performance (MP) and bite force, and explores their influential factors, 1 year after the provision of mandibular overdentures retained by four titanium–zirconium mini implants. Methods: Edentulous patients received conventional complete dentures, followed by placement of four mini implants (Straumann® Mini Implant System) in the anterior mandible and converting the conventional prosthesis into a mandibular overdenture. Treatment protocols were randomised using a 2×2 factorial design combining different surgical (flapped vs. flapless) and loading (immediate vs. delayed) protocols. MP was assessed using a two‐colour mixing ability test and a colorimetric analysis to measure the level of colour mixing (Variance of Hue–VoH). Maximum voluntary bite force (MBF) was measured by a digital gnathodynamometer in the posterior and anterior regions. Sex, age, surgical and loading protocols and ridge morphology were tested as independent variables. MP and MBF tests were performed at baseline (pre‐treatment) and the 3‐, 6‐ and 12‐month after implant loading. Descriptive statistics, independent t‐test, and linear mixed‐effect model (LMM) regression were used for data analysis. Results: Seventy‐four participants were assessed and 73 completed the 1‐year follow‐up. Statistically significant improvements in functional parameters were observed in all follow‐up periods compared to baseline (p <.001). The flapless protocol was associated with higher improvement in MP at the 3‐month follow‐up (p =.004), while less resorbed ridges were associated with better MP (p =.038) and higher MBF (p <.001). Conclusion: The mandibular overdenture protocol using four titanium–zirconium mini implants was effective in improving MP and MBF of edentulous patients, compared to pre‐treatment values. The findings also suggest that improvements in chewing function and bite force are impacted by clinical factors since better outcomes were observed for flapless surgeries and less resorbed edentulous ridges. CLINICAL TRIAL REGISTRATION: ClinicalTrials.Gov ID NCT04760457. [ABSTRACT FROM AUTHOR]