Sustainable orthodontics: direct environmental, material, and implementation evidence from a systematic review

Orthodontic care generates environmental burdens through polymer and metal consumption, single-use products, manufacturing, transport, energy use, and end-of-life disposal. This systematic review evaluated primary orthodontic evidence that directly measured environmental outcomes or examined implementation behavior explicitly related to environmental sustainability. PubMed/MEDLINE, Scopus, Web of Science Core Collection, EMBASE, and the Cochrane Library were searched from January 2010 through October 2025, with supplementary Google Scholar and reference-list screening. The corrected search used two reproducible concept blocks-orthodontics and environmental sustainability-without a human-subject filter so that laboratory and life-cycle studies remained eligible. Five primary studies met the revised PICOS criteria: two laboratory/material studies, one comparative life-cycle assessment, and two cross-sectional surveys. Incineration of used clear-aligner polymers produced measurable hazardous emissions; a comparative life-cycle assessment indicated that retainer selection was sensitive to product lifespan and system-boundary assumptions; and a shape-memory aligner material showed potential to reduce the number of appliances, although a complete life-cycle assessment was not performed. Survey evidence showed inadequate disposal knowledge and a persistent gap between favorable attitudes and routine sustainable practice. The evidence remains sparse, heterogeneous, and at some risk of selection, modeling, and self-report bias. Current findings support targeted action on aligner and retainer life cycles, disposal guidance, and implementation barriers, but stronger orthodontic-specific life-cycle studies and standardized environmental outcomes are required. Because eligibility was intentionally restricted to primary orthodontic studies with direct environmental outcomes or explicit sustainability-related implementation outcomes, the five included studies represent a highly selected evidence base rather than a comprehensive survey of all sustainability-related orthodontic literature. The 4D-printing finding is interpreted only as a potential appliance/material-reduction pathway; no net environmental benefit has yet been demonstrated. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251250285, identifier CRD420251250285.