Researchers have found in a new study that white spot lesions (WSLs) on enamel allow greater penetration of hydrogen peroxide and yield less favorable optical outcomes—especially after in-office bleaching—suggesting that at-home bleaching may be a safer, more esthetically favorable option for managing these lesions. In this in-vitro study published inClinical Oral Investigations, forty premolars were divided into four groups: sound and artificially demineralized (WSLs), each subjected to in-office (35 % hydrogen peroxide) or at-home (16 % carbamide peroxide) bleaching. Analysts measured HP permeability into the pulp chamber and tracked color change using spectrophotometry. The results confirmed that WSLs significantly increased HP diffusion with in-office bleaching (p < .05), indicating heightened sensitivity risk. Moreover, the optical outcomes were consistently poorer: WSL-teeth showed lower lightness (L*) and whitening index (WI_D) values compared to sound teeth across treatments. Notably, differences remained regardless of bleaching method, although at-home bleaching avoided excessive HP penetration and produced marginally better esthetic results. These findings raise concern about the safety and effectiveness of aggressive bleaching in teeth with WSLs, which are already structurally compromised. The authors propose that gentler, home-based bleaching protocols combined with remineralization strategies may preserve enamel integrity while improving appearance safely. For clinicians, this means evaluating lesion type before choosing a bleaching method and advising conservative options when WSLs are present. Further clinical trials are needed to verify long-term outcomes and guide tailored bleaching protocols for patients with enamel hypomineralization. Barbosa, L.M.M., Baracco, B., Carneiro, T.S. et al. Impact of bleaching on white spot lesions: hydrogen peroxide permeability and color alteration. Clin Oral Invest 29, 401 (2025). https://doi.org/10.1007/s00784-025-06490-3 Keywords:white spot lesions, hydrogen peroxide penetration, tooth bleaching, in-office bleaching, at-home bleaching, optical outcome, peroxide diffusion, enamel demineralization, Clinical Oral Investigations, Barbosa, L.M.M., Baracco, B., Carneiro, T.S.