# Profilometric and scanning electron microscopy analysis comparing hydroxyapatite and zinc oxide nanoparticles for erosion resistance

## TL;DR

This study compares hydroxyapatite and zinc oxide nanoparticles in reducing dentin hypersensitivity by evaluating their effectiveness in occluding dentinal tubules and resisting erosion.

## Contribution

The study introduces a novel comparison of hydroxyapatite and zinc oxide nanoparticles in treating dentin hypersensitivity using experimental and microscopic analysis.

## Key findings

- Zinc oxide nanoparticles showed superior effectiveness in resisting erosive wear compared to hydroxyapatite nanoparticles.
- Both nanoparticle treatments occluded dentinal tubules, but zinc oxide provided better protection against erosion.
- Scanning electron microscopy confirmed higher dentinal tubule occlusion in zinc oxide-treated samples.

## Abstract

Dentin hypersensitivity (DH) is a prevalent dental issue characterized by sharp pain of short duration. Although the exact cause of DH remains debated, the hydrodynamic theory explains its mechanism. Furthermore, various methods, such as potassium-containing toothpaste, mouthwash, and chewing gum, have been attempted to address DH. However, recent research has explored the potential of nanoparticles (NPs) for DH treatment due to their biocompatibility and bioactive properties.

Twenty-seven sound premolars extracted for orthodontic purposes were utilized in the present study to obtain 27 mid-coronal dentin discs. These discs were then etched with 37% orthophosphoric acid for 20 s to expose dentinal tubules (DTs) and simulate DH. Subsequently, dentin discs were rinsed with distilled water for 1 min. These dentin discs were randomly allocated into 3 groups: Group I (etched control), Group II (the etched dentin discs were treated with a carboxymethyl cellulose (CMC) dental hydrogel scaffold loaded with 20% HANPs), and Group III (the etched dentin discs were treated with a CMC dental hydrogel scaffold loaded with 20% ZnO NPs). After 7 days, Group II and III underwent erosive challenge to evaluate the protective effect of the nanoparticle treatments. Finally, the dentin discs were analyzed using profilometric analysis to measure surface roughness (SRa), scanning electron microscopy (SEM) to evaluate DT occlusion, computer-assisted SEM image analysis using Image J.

Among the groups, Group I exhibited the highest SRa following the DH simulation. Group II showed lower SRa compared to group III. SEM analysis indicated that Group III displayed more occluded DTs compared to Group II. Group I showed the most unoccluded DTs. The SEM analysis results were further quantitatively confirmed using Image J.

The results indicated that both HANPs and ZnO NPs exhibited promising outcomes; however, ZnO NPs demonstrated superior effectiveness in resisting erosive wear compared to HANPs.

The online version contains supplementary material available at 10.1186/s12903-025-06299-2.

The inclusion of ZnO NPs is anticipated to enhance clinical outcome in reducing dentine hypersensitivity by occluding dentinal tubules and resist erosive challenges.

All authors agree with the submission.

The work has not been published or submitted for publication elsewhere, either completely or in part, or in another form or language.

No conflict of interest with the authors in this work.

The online version contains supplementary material available at 10.1186/s12903-025-06299-2.