Title: 1340 - Bleaching Effects on Enamel Characteristics: A Nano-indentation and FTIR Investigation


fatemah Almaqate (Presenter)
Faculty of Dentistry, Kuwait University

Abrar Mansour, Faculty of Dentistry, Kuwait University
Muawia Qudeimat, Faculty of Dentistry, Kuwait University
Michael Swain, Faculty of Dentistry, Kuwait University
Rashed Al-Azemi, Faculty of Dentistry, Kuwait University


Objectives: The aim was to determine the effect of in-office tooth bleaching with 25% hydrogen peroxide on enamel chemical composition and abrasion resistance using Fourier transform infrared (FTIR) spectroscopy and nano-indentation scratch testing.

Methods: Five non-carious human premolar teeth, extracted for orthodontic reasons, were collected and cleaned from gross debris. Teeth were cut and mounted in self-curing EpoFix resin with the buccal surfaces exposed. Grinding and polishing of the buccal surfaces were done using automated polishing system (Buehler, Illinois, USA) to expose outer regions of enamel. Teeth were then stored in Hank’s balanced salt solution. FTIR, using attenuated total reflection, investigation was performed to identify the chemical bonding structures. Nano-indentation scratch tests were carried out at loads of 250, 500, 1000, and 2000 μN to evaluate abrasion resistance using a sharp Berkovich diamond indenter. Both tests were repeated on the same surfaces after bleaching with Philips Zoom WhiteSpeed chairside kit (Philips Discus Dental, California, USA), containing 25% hydrogen peroxide gel and exposing the samples to light emitting diode (LED) blue light for 45 minutes. Qualitative and quantitative statistical analysis for the FTIR spectra and the nano-indentation scratch tests were conducted.

Results: FTIR spectra of the human enamel displayed bands assigned to water, carbonate, and phosphate groups. All these absorbance peaks became distorted, wider, and decreased in intensity after bleaching. Friction plots were generated from the scratch tests for all samples under each load before and after bleaching. Paired t-tests were performed, and showed no statistically significant difference in the mean friction value before and after bleaching (p>0.05).

Conclusions: In-office tooth bleaching with 25% hydrogen peroxide and LED blue light showed alterations in the chemical bonding of enamel when assessed by FTIR analysis however, no statistical difference of enamel resistance to abrasion was seen before and after bleaching.

Student Presenter

Disclosure Statement:
The submitter must disclose the names of the organizations with which any author have a relationship, the nature of the relationship, and the clinical or research area involved. The following is submitted: NONE