BACKGROUND: Marketed toothpastes vary in the extent to how much abrasive wear they cause to dentin. New abrasive particles in a dentifrice should be evaluated since there they can be at risk of abrasion to dentin and root surfaces. AIM: The aim of this in vitro study was to evaluate abrasive dentin wear and surface roughness after brushing with whitening toothpaste containing zirconia at four different concentrations. MATERIAL AND METHOD: This study tested 40 extracted human teeth. After crown removal, root dentin samples were randomly divided into four experimental groups based on zirconia toothpaste concentration: Group A (10 samples) brushed for 5 min with 0.5 % zirconia toothpaste, Group B (10 samples) with 1 %, Group C (10 samples) with 2 %, and the last 10 samples with 5 %.Before brushing, specimens were weighed three times using a precision analytical scale and measured with a Profile Projector. After completing the brushing cycles, surface roughness was measured to evaluate the differences after brushing. RESULTS: The Kruskal-Wallis test showed no significant difference in the weight of samples at 0.5 %, 1 %, and 2 % toothpaste concentrations. However, at the 5 % toothpaste concentration, there was a significant difference in sample weight measurements (P <
0.05). The mean roughness difference in the three lower concentrations indicated no significant statistical difference, but with the 5 % toothpaste, there was an increase in average dentin roughness (P <
0.05). CONCLUSION: Results showed that percentage ≤2.0 % of zirconium powder added in a toothpaste, can lead to dentin minimal wear and better roughness by polishing effect. Toothpaste containing 5 % zirconia showed an abrasive effect on dentin and increased surface roughness.