Introduction: Dentin hypersensitivity (DH) is a major dental problem that is manifested as sharp pain of short duration. The cause of DH is controversial; however, the most accepted theory is the hydrodynamic theory. Attempts were made for the treatment of DH as fluoride containing-toothpastes and mouthwashes. Recently, it was found that nanoparticles maybe used for the treatment of DH as they are biocompatible and bioactive materials.
Objectives: To investigate the efficacy of hydroxyapatite nanoparticles in occluding dentinal tubules and resisting erosive wear.
Methodology: Twenty-seven teeth, extracted for orthodontic purpose were used in the present study to obtain 27 dentin discs. Dentin discs were prepared by slicing the teeth from the mid-coronal part. Dentin discs were etched with 37% orthophosphoric acid for 20 seconds then washed with distilled water for 1 minute. Afterwards, they were randomly divided into 2 groups: Group I (Etched control), Group II (Hydroxyapatite nanoparticles): the etched dentin discs were treated with hydroxyapatite nanoparticles. After 7 days, Group II was divided into 2 subgroups; subgroup A: stored in artificial saliva and subgroup B: subjected to erosive challenge by 0.3% citric acid. Finally, dentin discs were analyzed by scanning electron microscope (SEM) and energy dispersive x-ray (EDX).
Results: Group II-A showed more occluded dentinal tubules compared to group I and group II-B. The results of the EDX showed increase in calcium and phosphorous percentage in Group II-A than groups I and II-B.
Conclusion: Hydroxyapatite nanoparticles may be a promising treatment for dentin hypersensitivity.

Keywords: dentin hypersensitivity, hydroxyapatite nanoparticles, dentin.