Longitudinal changes in implant stability assessed by resonance frequency analysis and marginal bone remodeling around immediate implants: A retrospective cohort study

Resonance frequency analysis (RFA) provides a non-invasive and reproducible method for quantifying implant stability using the implant stability quotient (ISQ). Evidence on the influence of prosthetic configuration and anatomical location on ISQ changes during healing remains limited. This retrospective cohort study evaluated longitudinal changes in implant stability and investigated the influence of different implant collar configurations.

Sixty-five patients (431 implants) treated with immediate implant placement and fixed prosthetic rehabilitation were included. Implant stability was assessed using ISQ values at placement and before definitive restoration. Implants were classified into four collar design groups, including an anodized collar configuration. Patient-level transition analyses were conducted using ISQ stability classes (red<60, yellow 60‒69, green≥70), and implant-level mixed-effects regression models, with patient included as a random effect, accounted for clustering within patients. Secondary outcomes included marginal bone level change, implant survival, prosthetic success, and peri-implant soft tissue indices. Significance was set at P<0.05.

ISQ values increased during healing by approximately six units. Patients rehabilitated with splinted restorations showed a higher rate of improvement in stability class than those receiving non-splinted restorations (46.7% vs. 20.0%; P=0.041); however, prosthetic configuration was not independently associated with baseline or postoperative ISQ values in adjusted mixed-effects analyses. Mixed-effects models identified posterior maxillary location as a significant negative predictor of ISQ, whereas implant diameter was positively associated with stability. Collar design showed no significant independent association with ISQ outcomes.

Longitudinal RFA monitoring detected meaningful changes in implant stability during healing. Although splinted restorations showed more frequent improvements in stability class in unadjusted analyses, prosthetic configuration was not independently associated with ISQ values after multivariable adjustment. Therefore, the present findings do not support a definitive effect of splinting on implant stability. Anatomical location and implant diameter appeared to be the main determinants of ISQ values, whereas prosthetic configuration and collar design showed limited influence on implant stability outcomes.