Comparative analysis of enamel mineral content and surface morphology alterations after bleaching: a study using colorimetric spectrophotometry and scanning electron microscopy

Background: Bleaching agents are widely used for aesthetic dental enhancement, but concerns remain regarding their effects on enamel mineral content and surface morphology. This study aimed to evaluate the alterations in calcium and phosphorus levels and enamel microstructure following the application of three different bleaching protocols. Methods: Ninety extracted human premolars were randomly divided into three groups (n = 30): Group 1 – McInnes solution, Group 2 – modified McInnes solution, and Group 3 – Pola Office bleach. Each group was subdivided for calcium, phosphorus, and scanning electron microscopy (SEM) analyses. Enamel samples were collected via microbiopsy at five time points. Calcium and phosphorus were quantified using spectrophotometric analysis, and surface changes were observed using SEM. Results: All three bleaching agents resulted in measurable mineral loss. The McInnes solution group exhibited the greatest decrease in calcium concentration, particularly at T2 (P = 0.001) and T4 (P = 0.04). SEM revealed pronounced surface alterations in this group compared to modified McInnes and Pola Office groups. Remineralization was observed after storage in artificial saliva, with partial recovery of mineral levels over 14 days. Conclusion: All bleaching protocols induced varying degrees of mineral loss and surface changes, with the McInnes solution causing the most significant effects. Modified McInnes showed relatively milder alterations, suggesting a potentially safer alternative. Post-bleaching remineralization in artificial saliva showed beneficial effects.