Effects of Bleaching on Properties of Human Enamel

Objectives: Objectives: The long and short term effects of tooth whitening products on human hard dental tissues have not been thoroughly investigated. Conflicting reports have been published regarding effects on enamel. Three commonly used over-the-counter products; Luster Pro Light by Dentovations Inc. (40 min), Crest 3D Whitestrips Professional Effects (3 days) and Opalescence Tooth Whitening Gel (multiple applications) were selected. The purpose of this in vitro investigation was to compare the immediate short term bleaching effects on enamel properties, namely; elastic modulus-E, nanohardness-H, viscosity, and brittleness-E/H.
Methods: Methods: 30 extracted human incisor teeth were invested into acrylic resin blocks exposing the clinical crowns. Bleaching agents were applied directly on the facial surfaces of teeth according to the manufacturer’s instructions. The lingual surfaces served as control and were not subjected to treatment. Teeth specimens were sectioned and subjected to nanoindentation in a wet environment using a Berkovich tip at a rate of 10 nm/sec up to 500 nm. A total of 341 indents were performed on facial and lingual enamel 10 µm from the outer surface. Indentation values were normalized by dividing facial value by averaged lingual values for each test group, then statistically analyzed, ANOVA (P<0.05).
Results: Results: Absolute Mean±SD values are shown below:
Conclusions: Conclusion: Statistically significant differences were found between the 3 tested materials. The current findings indicate that enamel physical properties are influenced differentially by various whitening agents. Luster Pro Light seemed to have lesser effects on enamel elastic modulus as well as viscosity and brittleness followed by Crest Whitestrips and finally Opalescence gel.