The aim of this study was to examine changes in human enamel after exposure to 40% hydrogen peroxide with and without light, and to test the effects of amorphous calcium phosphate containing mousse (ACP), using FT-IR spectroscopy. It is hypothesized that infrared spectroscopy is capable of showing alterations in enamel after peroxide treatment and the alteration is proportional to treatment time.
Thirty non-carious human teeth were used in this study. They were divided into 4 groups. Group 1 and 2 were subjected to two treatments with 40% hydrogen peroxide each for duration of 20 minutes. Group 2 was treated with ACP for 5 minutes in between and after the bleaching treatments. Group 3 was treated with 40% hydrogen peroxide and light for a total of 8 minutes and was then subjected to a 5 minute treatment with ACP. Group 4 (control group) was stored in isotonic saline that was kept in a stable 37 ºC and tested after two weeks and four weeks. IR spectra of Groups 1-3 were taken prior to bleaching and immediately after each bleaching treatment. Spectra were taken after each ACP treatment. The spectra of Group 4 were taken at the initiation of experiment and after week one and two.
FT-IR spectrum showed two distinct bands (apatite PO4 ν1 and ν 2) that were capable of describing the alterations in enamel structure. On comparing the infrared spectra of non-treated and treated specimens, structural changes were evident in enamel. ACP containing mousse has shown a significant effect and can possibly partially compensate the effects of bleaching. The numerical analysis of the IR spectra revealed that upon second treatment using hydrogen peroxide solutions, the alterations in the spectra were more pronounced. The spectra taken in 1 week after treatment in the bleached group showed a continuous deterioration of the enamel structure suggesting that 40% hydrogen peroxide might have a long lasting effect.
40% hydrogen peroxide containing bleaching agents are capable of causing alteration in enamel. Changes are directly proportional to the treatment time. ACP has a significant effect and can possibly partially compensate the structural alterations caused by the bleaching.