Effect of Different Bleaching Protocols on Flexural Strength and Surface Hardness of Two Ceramic Materials (In Vitro Study)

Abstract

In recent years, trends for aesthetic dentistry surprisingly increased. The demands of patients for tooth-coloured restorations and the availability of new types of dental ceramics have driven increased use of ceramic materials in a variety of restorative situations. Many studies are highlighting the effect of bleaching on the clinical success of different restorative materials, and how it can affect their flexural strength & hardness. The present in vitro study was carried out to analyse the effect of different bleaching protocols on biaxial flexural strength and micro-hardness of two ceramic materials. A total of 112 discs, 56 discs of each material, were prepared from Celtra® Duo and VITA ENAMIC®. Each material was divided into 4 groups (n=14) according to the bleaching protocol done: Group 1 Control group “no bleaching”, Group 2 home bleaching “Carbamide Peroxide 22%”, Group 3 home bleaching “Hydrogen Peroxide 14%” and Group 4 In-office bleaching using diode Laser For each material, half the number of discs in each group (n=7) were subjected to Biaxial Flexural Test, while the other half was subjected to Micro-Hardness Test. Biaxial Flexural Test was performed using Universal Testing Machine Instron-3345 together with Instron BlueHill® universal software. While for Micro-Hardness Test, Tukon™ 1102 Wilson® Hardness Tester was used. Numerical data were explored for normality by checking the data distribution, calculating the mean and median values and using Kolmogorov- Smirnov and Shapiro-Wilk tests. Data showed parametric distribution so; it was represented by mean and standard deviation (SD) values. Two-way ANOVA was used to study the effect of different tested variables and their interaction on biaxial flexural strength (Mpa) and micro-hardness.