Objectives: Tooth whitening (bleaching) products have become extremely popular because of their relative ease of use and affordability. Several products are available which, to ensure acceptable esthetic results, require multiple applications over extended periods of time involving several days. Prolonged exposure to such products has been shown to cause adverse effects on the physical properties of enamel. A recently introduced product (Luster Premium White by Dentovations Inc.) is recommended to produce desired whitening effect through a full treatment regimen of forty (40) minutes, whereby the bleaching agent is directly applied on the tooth and activated by light. The purpose of this in vitro investigation was to evaluate the immediate after bleaching effects on physical properties of human enamel; particularly nanohardness and elastic modulus. Methods: Extracted human incisor teeth were invested into acrylic resin blocks exposing the clinical crowns. Teeth were bleached for 40 minutes of light treatment per manufacturer's instructions, then sectioned and prepared for nanoindentation. Similarly intact non-bleached incisors were used for control. Indents were done in a wet environment using a Berkovich tip at a rate of 10 nm/sec up to 500 nm. Each specimen was subjected to 7 indents. Enamel nanohardness-H and elastic modulus-E were then calculated. Results: Mean±SD values in GPa and two-way ANOVA with post-hoc Fisher's PLSD comparison test results are shown below:
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Treatment | Control | P-Value | |
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Nanohardness-H | 3.256±1.1 | 2.973±0.5 | 0.3617 |
Elastic Modulus-E | 45.076±16.2 | 47.241±5.1 | 0.6214 |
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Conclusion: Since time and effects on hard tissues are of prime importance for bleaching protocols, the results of this investigation are of particular clinical significance. Immediately following treatment with Luster Premium White, no significant differences were seen between bleached and non-bleached enamel regarding nanohardness and enamel elastic modulus indicating no adverse effects of product usage on human enamel. This study is supported in part by Dentovations Inc., Boston, MA, USA.