Evaluation of the effects of different concentrations of bleaching agents on flexural strength and microhardness of VITA ENAMIC

Abstract

Background: Considering the studies on the effects of bleaching materials on properties of dental
materials, The aims of this in vitro study were to evaluate the effects of two different concentrations
of bleaching agents on flexural strength and microhardness of VITA ENAMIC.
Materials and Methods: In this experimental in vitro study, 30 rectangular‑shaped specimens (2 mm
width × 2 mm height × 12 mm length) for flexural strength and 30 specimens (5 mm width × 5 mm
length × 2 mm height) for microhardness tests were prepared from VITA ENAMIC blocks
12 × 14 × 18 mm. The specimens were polished using silicon‑carbide sandpapers 400, 600, 800,
1200, 2000 under flow of water for 60 s each. The prepared samples for flexural strength and
microhardness were divided into 3 subgroups (n = 10): control group (C), samples bleached using
Opalescence PF 15% (B15), and samples bleached with Opalescence Xtra Boost 40% (B40). Flexural
strength measurement was done using a universal testing machine, and microhardness test was
done using Vickers. Data were analyzed using analysis of variance and post hoc tests and P < 0.05
was considered significant.
Results: The mean microhardness values of C, B15, and B40 groups were 255.46 ± 3.02,
249.86 ± 4.18, and 235.53 ± 4.61 kgf/mm2. Opalescence PF 15% and Opalescence Xtra Boost 40%
affected microhardness of ENAMIC significantly (P < 0.05). The mean flexural strength values of C,
B15, and B40 groups were 155.26 ± 16.13, 142.14 ± 11.52, and 133.39 ± 16.13 MPa. A significant
decrease in flexural strength was found between the C and B40 groups (P = 0.007). However, the
difference between flexural strength of the C and B15 groups was not significant (P > 0.05).
Conclusion: Our study showed that both concentrations of bleaching agents can affect
microhardness of ENAMIC. Moreover, hydrogen peroxide 40% has a negative effect on the flexural
strength of ENAMIC.
Key Words: Bleaching agents, flexural strength, hardness, VITA ENAMIC