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Published on: February 23, 2017
Comparative effects of integrated and post-applied nano-hydroxyapatite on enamel properties following
Elif E Devrimci1, Hande Kemaloğlu1, İdil Gönüllü1
1Department of Restorative Dentistry, Ege University Faculty of Dentistry.
Purpose:
This study investigated whether nano-hydroxyapatite (nHAp) can reduce the adverse effects of high-concentration hydrogen peroxide (HP) bleaching - such as mineral loss and surface softening - while maintaining whitening efficacy. Incorporation of nHAp into the bleaching gel was also compared with its application after bleaching.
Methods:
Sixty bovine enamel specimens were randomly assigned to six groups and treated with different HP-based protocols with or without nHAp. Color change (ΔE) was measured using spectrophotometry, microhardness with the Vickers test, and surface morphology and elemental composition using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).
Results:
All HP-treated groups showed significant color improvement (ΔE > 3.3, P < 0.05). Post-bleaching nHAp application produced higher ΔE values than bleaching alone, though not to a significant degree. The highest ΔE was observed in the group receiving HP followed by nHAp. Post-bleaching nHAp significantly improved microhardness and calcium content in the Opalescence group, while effects in the BioWhiten group were limited and not significant. SEM analysis revealed superficial granular deposits and partial surface coverage in nHAp-treated specimens, particularly after post-bleaching application.
Conclusion:
Incorporation of nHAp during or after HP bleaching can reduce enamel alterations while preserving whitening efficacy, particularly when applied after bleaching in systems lacking intrinsic remineralizing components.
