Immediate vs. Delayed Loading of Mandibular Mini-Implant Overdentures: A 12-Month Comparative Randomized Controlled Trial

Abstract

Background and Aim: While mini-dental implants (MDIs) provide a minimally invasive surgical solution for prosthesis stabilization, the optimal timing for functional loading remains highly contested in the scientific literature. This clinical trial sought to evaluate the effects of immediate versus delayed loading protocols on marginal bone level (MBL) changes and peri-implant mucosal health around MDIs supporting mandibular overdentures.

Methods: Twenty completely edentulous patients experiencing mandibular atrophy were randomly allocated (1:1 ratio) to either an Immediate Loading Group (n=10) or a Delayed Loading Group (n=10). Each participant received four one-piece mini-implants in the interforaminal region utilizing a flapless surgical approach. Implants in the immediate cohort were functionally loaded on the day of surgery via O-ring attachments. The delayed cohort received functional loading after a stringent three-month unloaded healing period. The primary outcome measure was MBL change, quantified via standardized digital periapical radiographs. Secondary outcomes included the Gingival Index (GI) and Probing Depth (PD). Statistical analysis was executed using repeated measures ANOVA and independent t-tests with a significance threshold set at α=0.05.

Results: A total of 80 implants were placed, achieving a 100% cumulative survival rate at the twelve-month follow-up. Both groups exhibited progressive, physiological crestal bone remodeling. At twelve months, the Immediate Loading Group demonstrated a mean MBL of 0.87 ± 0.22 mm (95% CI: 0.79, 0.95), whereas the Delayed Loading Group exhibited a mean MBL of 1.01 ± 0.25 mm (95% CI: 0.92, 1.10). While this 0.14 mm variance was statistically significant (p = 0.042), it remains clinically negligible. GI scores were transiently lower in the immediate group at three and six months (p < 0.05) but converged completely by twelve months (Immediate: 1.88 ± 0.41; Delayed: 2.13 ± 0.52; p = 0.18). PD showed no statistically significant divergence between the cohorts across any observation interval.

Conclusions: The immediate functional loading of 1.8 mm MDIs for the stabilization of mandibular overdentures resulted in highly comparable and predictable twelve-month clinical and radiographic outcomes when juxtaposed against a conventional delayed protocol. The immediate application of controlled functional forces did not precipitate adverse peri-implant tissue responses or pathological osteolysis, thereby validating the protocol as a predictable and patient-centric clinical modality.