Comparison surface characteristics and chemical composition of conventional metallic and Nickel-Free brackets

This study aims at comparing conventional and nickel-free metal bracket surface characteristics with elemental composition by scanning electron microscopy (SEM), using energy dispersive spectroscopy (EDS). The sample consisted of 40 lower incisor brackets divided into four groups: ABZ = conventional brackets, Kirium Abzil 3M® (n = 10); RL = conventional brackets, Roth Light Morelli® (n = 10); NF = nickel-free brackets, Nickel-Free Morelli® (n = 10); and RM = nickel-free brackets, Roth Max Morelli® (n = 10). Qualitative evaluation of the bracket surface was performed using SEM, whereby surface features were described and compared. The elemental composition was analyzed by EDS. According to surface analysis,groups ABZ and RL showed a homogeneous surface, with better finishing, whereas the surfaces in groups NF and RM were rougher. The chemical components with the highest percentage were Fe, Cr and C. Groups NF and MR showed no nickel in their composition. In conclusion, the bracket surface of the ABZ and RL groups was more homogeneous, with grooves and pores, whereas the surfaces in groups NF and RM showed numerous flaws, cracks, pores and grooves. The chemical composition analysis confirmed that the nickel-free brackets had no Ni in their composition, as confirmed by the manufacturer’s specifications, and were therefore safe to use in patients with a medical history of allergy to this metal.

本研究旨在借助扫描电子显微镜（Scanning Electron Microscopy, SEM）与能量色散光谱法（Energy Dispersive Spectroscopy, EDS），对比传统正畸托槽与无镍金属正畸托槽的表面特性及元素组成。本研究样本包含40颗下颌切牙正畸托槽，分为四组：ABZ组为传统正畸托槽（Kirium Abzil 3M®，n=10）；RL组为传统正畸托槽（Roth Light Morelli®，n=10）；NF组为无镍正畸托槽（Nickel-Free Morelli®，n=10）；RM组为无镍正畸托槽（Roth Max Morelli®，n=10）。采用扫描电子显微镜对正畸托槽表面进行定性评估，描述并对比其表面特征；同时通过能量色散光谱法分析托槽的元素组成。表面分析结果显示，ABZ组与RL组的托槽表面均一性良好，表面光洁度更优；而NF组与RM组的托槽表面更为粗糙。占比最高的化学成分为铁（Fe）、铬（Cr）与碳（C）。NF组与RM组的托槽成分中未检出镍元素。综上，ABZ组与RL组的托槽表面均一性更强，仅伴随少量沟槽与孔隙；而NF组与RM组的托槽表面则存在大量缺陷、裂纹、孔隙与沟槽。元素组成分析结果证实，无镍正畸托槽的成分中确实不含镍元素，这与生产商的规格说明一致，因此此类托槽可安全用于对该金属有过敏史的患者。