CTSK as a Collagen Degradation Marker Induces Gingival Recession During High-Force Orthodontic Tooth Movement.

INTRODUCTION AND AIMS: Gingival recession is a common complication of orthodontic treatment that affects both aesthetics and periodontal health. While traditionally associated with bone resorption, recent research suggests that Cathepsin K (CTSK) play a significant role in collagen fibre degradation within periodontal connective tissues. This study combines animal experiments and clinical research to investigate whether CTSK plays a role in the process of gingival recession during orthodontic tooth movement (OTM). METHODS: An OTM model was created using the maxillary first molar in mice. Differences in gingival tissue thickness and height between experimental and control groups were statistically analysed. Additionally, in the clinical study, CTSK expression in gingival crevicular fluid (GCF) was assessed. CTSK mRNA expression in gingival crevicular fluid was evaluated in orthodontic patients, comparing healthy and gingival recession groups. RESULTS: High-force OTM significantly decreased the thickness and height of mesial gingival tissues (P < .005). In the gingival recession group, the number of cells within the region of interest (ROI) decreased, while the number of CTSK+ cells increased significantly (P < .0005). RT-qPCR analysis showed that CTSK mRNA expression in GCF of gingival recession patients was significantly higher than in the control group (P < .05). CONCLUSION: High-force orthodontic tooth movement induced gingival recession in mice. The results of the animal experiment suggested that CTSK contributes to collagen fibre degradation in gingival connective tissue, leading to recession. Studies of human GCF have further supported the role of CTSK as a marker of collagen degradation in gingival recession. CLINICAL RELEVANCE: These findings may offer new insights for the clinical management of complications such as "black triangles" following orthodontic treatment.