Chemical and physical properties of nickel-free brackets: An in vitro and ex vivo controlled clinical trial
Abstract
Objective: To evaluate the chemical and dimensional changes of metallic and nickel-free metallic brackets in vitro and ex vivo, regarding oxidation, tie-wing deformation and surface roughness.
Design: A split-mouth, in vitro and ex vivo controlled clinical trial.
Methods: A total of 34 adult participants, aged 20-35 years, underwent conventional orthodontic treatment. The right upper central incisor carried the metallic bracket and the left upper central incisor carried the nickel-free metallic bracket. At the 120th day of treatment with a 0.018-inch steel alignment wire, the upper central incisor brackets were removed (ex vivo) and compared with unused brackets (in vitro), distributed into four groups (n = 34): group 1 = in vitro metallic brackets; group 2 = ex vivo metallic brackets; group 3 = in vitro nickel-free metallic brackets; and group 4 = ex vivo nickel-free metallic brackets. Analyses were performed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) to assess slot dimensions and surface irregularity (roughness), respectively, and by energy dispersive spectroscopy (EDS) for oxidation. Analyses were performed with a significance level of 5%.
Results: Evaluation of composition showed that ex vivo nickel-free and metallic brackets had higher percentages of oxygen (O) and carbon (C), lower percentages of niobium (Nb) and chromium (Cr) (P P >0.05). Brackets showed no dimensional changes when comparing in vitro and ex vivo conditions.…
How strong is the evidence?
Evidence Hub reads this as a clinical trial, done in people. Its evidence level is 3 of 5 (Moderate · trial / cohort / secondary analysis). Trials without a large randomized design, cohorts and secondary analyses give moderate evidence. Reported size: 34 participants or records.
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