Bidirectional influences and clinical implications of psychological factors and oral health during orthodontic treatment.

INTRODUCTION: Psychological factors such as anxiety and stress frequently affect orthodontic treatment outcomes, but the underlying mechanisms remain unclear. To review evidence on how psychological factors influence orthodontic outcomes and to describe the biological pathways involved. METHODS: We conducted a narrative review of Web of Science and PubMed up to January 2025, including 102 peer-reviewed studies on orthodontics, psychology, oral microbiota, taste, and inflammatory markers. RESULTS: Psychological factors affect orthodontic treatment through three pathways: First, nervous system activation (HPA axis and autonomic nervous system); Second, alterations in oral microbiota and salivary biomarkers (cortisol, α-amylase, s-IgA), and third, modulation of alveolar bone remodeling via pro-inflammatory cytokines (IL-1β, IL-6, IL-8). Taste changes under stress may indirectly alter dietary habits and oral microbial ecology. Most evidence is cross-sectional, limiting causal inference. CONCLUSION: Psychological factors significantly influence orthodontic outcomes via measurable biological mechanisms. Routine psychological assessment and patient education should be integrated into orthodontic practice.