Design Matters? Evaluating Implant Macro‐Geometry in Immediate Implants: A Randomized Clinical Trial With Six‐Month Interim Analysis

Objectives

To compare the early stability trajectories of two tissue‐level implant macro‐designs after immediate placement, using monthly resonance frequency analysis (ISQ) over 6 months.

Materials and Methods

Single‐center randomized clinical trial in adults requiring immediate implant placement in posterior sites. ISQ was recorded at implant placement and monthly for 6 months. A linear mixed‐effects model (subject‐level random intercept; fixed effects for group, visit, their interaction, and baseline ISQ) was fitted, with the group × visit interaction as the primary inferential term. The 6‐month endpoint was assessed by baseline‐adjusted ANCOVA, with equivalence tested against a ±3 ISQ margin (2 one‐sided tests).

Results

Thirty implants were placed in 30 patients (aggressive self‐tapping, n  = 15; conservative uniform‐thread, n  = 15). ISQ increased significantly over time in both groups ( p  < 0.001). The group × visit interaction was significant (χ ²  = 43.25, df = 5, p  < 0.001); baseline‐adjusted differences favored the aggressive design at t1 (+3.84 ISQ, 95% CI 1.64 to 6.03; p  = 0.004) and t2 (+3.70, 95% CI 1.51 to 5.90; p  = 0.005), and were no longer detectable from t3. At 6 months, the baseline‐adjusted difference was −0.73 ISQ (95% CI −2.91 to 1.46; p  = 0.500), and equivalence within ±3 ISQ was supported (TOST p  = 0.021). All aggressive‐design implants reached ISQ ≥ 70 by 3 months versus 33% in the conservative group ( p  = 0.001).

Conclusions

Within the limitations of this trial, the more aggressive macro‐design showed significantly higher stability during the first 2 months of healing, with significantly different trajectories over time, whereas at 6 months, no between‐group difference was demonstrated and equivalence within the pre‐specified ±3 ISQ margin was supported. Macro‐design therefore influenced the timing of stability acquisition rather than stability at 6 months, supporting its relevance for early loading protocols.

Trial registration: ClinicalTrials.gov identifier: NCT06711744; Date of registration: 21 November 2024; EC Protocol ID: 6271 (Ethics Committee Lazio 3).