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Diabetes-associated hyperglycemia reshapes the oral microenvironment, aggravates biofilm-driven inflammation, and compromises the safety and efficacy of orthodontic treatment. Here, we develop a heat treatment-programmed bioactive orthodontic alloy, named NiTi-5Cu (AH), which combines structural functionality with microenvironment-responsive biological activity. By applying a solution-quench-aging process to NiTi-5Cu, we induce near-surface Cu enrichment and a more uniformly active electrochemical state, thereby enabling sustained Cu release. The resulting alloy maintains functional recoverability while exhibiting robust antibacterial and antibiofilm activities against Escherichia coli, Staphylococcus aureus, and Streptococcus mutans. In parallel, NiTi-5Cu (AH) exhibited no cytotoxicity toward human oral epithelial cells, vascular endothelial cells, and macrophages. Moreover, it induced M2-like macrophage polarization, shows favorable hemocompatibility isn both healthy and diabetic rabbits, and does not induce overt developmental or inflammatory toxicity in zebrafish assays. In a type 2 diabetic periodontitis rat model, intraoral placement of the alloy alleviates alveolar bone loss, inflammatory infiltration, and osteoclast activation. Moreover, 16S rRNA sequencing showed treatment-associated differences in oral-swab microbiota composition, while transcriptomic and metabolomic analyses revealed associative changes in inflammatory and metabolic pathways. Collectively, this work establishes a bioactive platform in which heat-treatment-engineered Cu release enables simultaneous antibiofilm regulation and periodontal protection, offering a promising metallic biomaterial strategy for diabetic oral care.