Cytokine levels in immediate loaded and unloaded mini-screw: A split-mouth randomised clinical trial.

Objective: To compare the levels of interleukin (IL)-1 beta (IL-1β), alpha (IL-1α), receptor antagonist (IL-1Ra), IL-10 and IL-13 in peri-mini-screw crevicular fluid (PMCF) between unloaded and immediately loaded mini-screws during orthodontic treatment.

Design: Single-centre paired split-mouth controlled trial.

Participants: Patients who required at least two mini-screws as a part of their orthodontic treatment at orthodontic clinic of School of Dentistry of Ribeirão Preto, University of São Paulo (USP) were recruited.

Methods: A total of 40 mini-screws were inserted into the interradicular alveolar bone in 16 patients. Using the coin toss method, each mini-screw was randomly allocated into one of two groups: a control group of unloaded (n = 20) and a group of immediately loaded mini-screws (n = 20). Immediately postoperatively, a continuous load in the range of 150-200 cN was applied to the mini-screws allocated to the loaded group. The PMCF was collected in four experimental times: immediately postoperatively (and on load time, to mini-screws allocated into the loaded group) and 7, 14 and 21 days postoperatively. Biomarker levels were measured using Multiplex Microsphere Immunoassays and compared between groups and covariates using statistical tests that accounted for multiple observations per participant (alpha =5%).

Results: No mini-screws were lost. There was a progressive and statistically significant increase of the biomarker's levels in the two groups during the experimental times ( <0.001). The biomarker levels were significantly higher in the immediately loaded group compared to the unloaded group at all time points ( <0.05), except for IL-10 after 7 days postoperatively.

Conclusion: Although all biomarker levels were statistically higher in the immediately loaded group at all experimental time points in comparison with the unloaded group, no mini-screws were lost. This suggests a balanced and normal adaptive bone response to the mechanical stress of immediate loading, with no negative impact on clinical outcomes.