Effects of temperature and in-office bleaching agents on surface and subsurface properties of aesthetic restorative materials

Abstract

Objectives: To investigate the effects of in-office bleaching agents on surface and subsurface properties of dental materials at different environmental temperatures.

Methods: Four composite resins, a compomer, a conventional glass-ionomer cement (CGIC), and an industrially sintered ceramic material were evaluated in the present study. Four groups of each material (n=10) were treated: bleaching with 40% hydrogen peroxide at 25°C and 37°C, stored in artificial saliva at 25°C and 37°C. The specimens from bleaching groups were bleached for two sessions, each of two 20 min application, at respective temperatures. After bleaching, the surface and subsurface (0.1-0.5mm) microhardness were evaluated using a Vickers microhardness tester. The substance loss was determined by surface profilometry. The data were statistically analyzed with ANOVA and the Tukey's post hoc test.

Results: All materials were found to have surface softening after bleaching, and bleaching effects on surface micorhardness increased at 37°C compared with 25°C, except for the ceramic. After being bleached at 37°C, the microhardness values of flowable composite resin significantly reduced at a depth of 0.1mm compared with control specimen stored at 37°C. No significant difference was found between the control and bleached specimens with respect to substance loss for any of the materials.

Conclusion: The influence of environmental temperature on the in-office bleaching effects on surface and subsurface microhardness of dental materials was material-dependent. However, no substance loss was detected due to the tested bleaching regimen.

Clinical significance: Environmental temperature should be considered when evaluating the possible bleaching effects on restorative materials. Moreover, dentists should be aware that there might be a need for polishing of restorative materials in clinical situations in which restorations are accidentally exposed to bleaching gels.

Keywords: Environmental temperature; Hydrogen peroxide; Microhardness; Substance loss; Tooth bleaching.