Timing Matters: Denture Use for Cognitive Protection is Most Effective Before Major Tooth Loss

Background Tooth loss is a potential risk factor for cognitive decline, but the longitudinal evidence on the protective role of dentures and the intervention timing remains limited. This study aimed to investigate the associations of tooth loss, denture use, and their changes with distinct cognitive trajectories among older adults. Methods We conducted a prospective cohort study of 2,188 community-dwelling older adults from the Chinese Longitudinal Healthy Longevity Survey (2008-2014). Group-based trajectory modeling (GBTM) identified heterogeneous cognitive pathways. Multinomial logistic regression was used to estimate risk ratios (RRs) for the associations of baseline tooth number, denture use, and longitudinal tooth loss with cognitive trajectory membership. Results GBTM identified two cognitive trajectories: maintained-high (57.4%) and low-declining (42.6%). Baseline tooth loss (0-4 vs. ≥21 teeth: RR = 1.20, 95% CI : 1.02-1.41) and progression to having 0-4 teeth (RR = 1.76, 95% CI : 1.55-2.00) significantly increased the risk of the low-declining trajectory. Denture use was associated with a 13% lower risk (RR = 0.87, 95% CI : 0.78-0.96). Critically, a gradient effect was observed: the protective association was strongest in participants with ≥21 teeth (RR = 0.27, 95% CI : 0.08-0.86, corresponding to a 73% risk reduction) but attenuated with greater tooth loss. Conclusions Tooth loss is a significant risk factor for adverse cognitive trajectories, while denture use is associated with a mitigated risk. The effectiveness of dentures is highly dependent on timing, with the greatest cognitive benefit achieved when used early, before major tooth loss occurs. These findings underscore the importance of timely prosthodontic intervention as a potential strategy for cognitive preservation in older adults.