Surface alteration of human tooth enamel subjected to acidic and neutral 30% hydrogen peroxide.

OBJECTIVES

To investigate the effects of acidic and neutral 30% hydrogen peroxide (HP) on human tooth enamel in terms of chemical structure, mechanical property, surface morphology and tooth colour.

METHODS

Twenty-seven human dental blocks were obtained from premolars and randomly divided into three groups (n=9): Group acidic HP (30% HP, pH≈3.6), Group neutral HP (30% HP, pH≈7.0) and Group DW (distilled water, pH≈6.8). Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, atomic force microscopy (AFM) investigation, microhardness test and colour measurements were carried out before and after treatments. ATR-FTIR and Raman spectroscopy were analysed and then the carbonate:mineral ratio (C:M), Raman absolute intensity (RAI), Raman relative intensity (RRI), and laser-induced fluorescence intensity (FI) were obtained for evaluation.

RESULTS

The C:M, percentage microhardness and percentage RRI of group acidic HP decreased more significantly than those of group neutral HP (P=0.02, P=0.001, P<0.001, respectively) and group DW (P=0.01, P=0.008, P<0.001, respectively). Whilst group neutral HP and group DW had no statistical difference in above terms (P=0.818, P=0.528, P=0.158, respectively). Significant morphological alterations were observed in group acidic HP. Group acidic HP and neutral HP had no significant difference in percentage FI (P=0.652) and ΔE (P=0.906).

CONCLUSIONS

This study suggested that neutral 30% HP had the same efficiency in tooth bleaching and it caused less deleterious effects on enamel than acidic 30% HP.