, Volume 103, Issue 3, pp 274–279 | Cite as

Effect of various tooth whitening modalities on microhardness, surface roughness and surface morphology of the enamel

  • So Ran Kwon
  • Steven R. Kurti
  • Udochukwu Oyoyo
  • Yiming Li
Original Article


The purpose of this study was to evaluate the effect of four whitening modalities on surface enamel as assessed with microhardness tester, profilometer, and scanning electron microscopy (SEM). Whitening was performed according to manufacturer’s directions for over-the-counter (OTC), dentist dispensed for home use (HW) and in-office (OW) whitening. Do-it-yourself (DIY) whitening consisted of a strawberry and baking soda mix. Additionally, negative and positive controls were used. A total of 120 enamel specimens were used for microhardness testing at baseline and post-whitening. Following microhardness testing specimens were prepared for SEM observations. A total of 120 enamel specimens were used for surface roughness testing at baseline and post-whitening (n = 20 per group). Rank-based Analysis of Covariance was performed to compare microhardness and surface roughness changes. Tests of hypotheses were two-sided with α = 0.05. There was a significant difference in Knoop hardness changes (ΔKHN) among the groups (Kruskal–Wallis test, p < 0.0001). Significant hardness reduction was observed in the positive control and DIY group (p < 0.0001). Mean surface roughness changes (ΔRa) were significantly different among the groups (Kruskal–Wallis test, p < 0.0001). Surface roughness increased in the OTC group (p = 0.03) and in the positive control (p < 0.0001). The four whitening modalities—DIY, OTC, HW and OW induced minimal surface morphology changes when observed with SEM. It can be concluded that none of the four whitening modalities adversely affected enamel surface morphology. However, caution should be advised when using a DIY regimen as it may affect enamel microhardness and an OTC product as it has the potential to increase surface roughness.


Tooth whitening Enamel Microhardness Surface roughness Scanning electron microscope 



The authors would like to thank Ultradent Products Inc and Philips Oral Healthcare for kindly providing the bleaching materials used in this study.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© The Society of The Nippon Dental University 2014

Authors and Affiliations

  • So Ran Kwon
    • 1
  • Steven R. Kurti
    • 2
  • Udochukwu Oyoyo
    • 2
  • Yiming Li
    • 2
  1. 1.University of Iowa College of Dentistry and Dental ClinicsIowa CityUSA
  2. 2.Loma Linda UniversityLoma LindaUSA

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