Enamel Surface and Elemental Changes Following In Vitro Bleaching: A SEM-EDS Approach

<b>Background and Objectives:</b> Chairside bleaching can alter enamel morphology and mineral content. This in vitro study compared surface changes and elemental shifts after three in-office protocols using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). <b>Materials and Methods:</b> Forty-two human premolars/molars were sectioned; matched halves served as control or received Opalescence Quick 45% carbamide peroxide (CP), Opalescence Boost 40% hydrogen peroxide (HP), or BlancOne Ultra+ 35% HP with light activation. Gels were applied per manufacturers' instructions. SEM assessed topography (×500-×1100); EDS quantified atomic percent of O, Ca, P, C and trace elements. One-way ANOVA compared Ca and P between bleached groups (α = 0.05). <b>Results:</b> Controls showed compact surfaces with preserved Ca and P. After Quick, SEM revealed roughness, fissures and microcracks; Ca fell from 11.5 to 12.5 to 9.53-11.73 at% and P from 7.5 to 8.9 to 7.41-8.59 at%. Boost produced mild superficial restructuring and granular deposits with variable Ca 13.80-27.94 at% and P 7.32-14.65 at%. BlancOne Ultra+ caused diffuse erosion and loss of prismatic clarity with marked demineralization (Ca 1.42-7.85 at%, P 1.22-6.71 at%); C rose locally to 46.61 at%. Across bleached groups, Ca and P differed significantly (both <i>p</i> < 0.001). Oxygen remained dominant (~39-50 at%) in all spectra; occasional Al/Si/Cl/K likely reflected residues or preparation artifacts. <b>Conclusions:</b> All protocols produced surface and compositional alterations, with a severity gradient: BlancOne Ultra+ > Boost > Quick. High-concentration, light-activated HP yielded the largest Ca/P losses. Clinically, neutral-pH, non-activated or chemically activated regimens and immediate post-bleach remineralization should ideally be used when feasible, particularly before adhesive procedures.