Influences of Light-emitting Diode Illumination Bleaching Technique on Nanohardness of Computer-aided Design and Computer-aided Manufacturing Ceramic Restorative Materials

Abstract

Aim: This study evaluated the effect of light-emitting diode (LED) illumination bleaching technique on the surface nanohardness of various computer-aided design and computer-aided manufacturing (CAD/CAM) ceramic materials. Materials and methods:Twenty disk-shaped samples (width, length, and thickness = 10, 15, and 2 mm) were prepared from each of the ceramic materials for CAD/CAM, including Lava™ Ultimate (L V ), Vita Enamic ® (E n ) IPS e.max ® CAD (M e ), inCoris ® TZI (I C ), and Prettau ® zirconia (P r ). The samples from each type of ceramic were randomly divided into two groups based on the different bleaching techniques to be used on them, using 35% hydrogen peroxide with and without LED illumination. The ceramic disk samples were bleached according to the manufacturer's instruction. Surface hardness test was performed before and after bleaching using nanohardness tester with a Berkovich diamond indenter. Results Conclusion:Bleaching resulted in a diminution of the surface hardness of dental ceramic for CAD/CAM. Using 35% hydrogen peroxide bleaching agent with LED illumination exhibited more reduction in surface hardness of dental ceramic than what was observed without LED illumination.Clinical significance: Clinicians should consider protection of the existing restoration while bleaching.

Effect of Different Beaching Protocols on Biaxial Flexural Strength and Micro Hardness of Two Ceramic Materials

“…Thus, the cleavage effect that hydrogen peroxide has on the resin matrix of these resin polymers is responsible for the decrease in surface hardness. These results were in agreement with Juntavee N et al in 2018 (23) whom conducted an in vitro study to evaluate the effect of light-emitting diode (LED) illumination bleaching technique (35% hydrogen peroxide) on the surface nano-hardness of various (CAD/CAM) ceramic materials (Lava™ Ultimate, Vita Enamic®, IPS e.max® CAD, inCoris® TZI, and Prettau® zirconia), with and without LED illumination. Results denoted that using 35% hydrogen peroxide bleaching agent with LED illumination exhibited more reduction in surface hardness of dental ceramic than what was observed without LED illumination.…”

Color Stability and Staining Susceptibility of Direct Resin-Based Composites after Light-Activated In-Office Bleaching

“…The higher the HP concentration, the greater the de-pigmentation process, resulting in stain removal, and the color changes of RBCs [ 20 ]. Although the effects of HP on the color change of RBCs remain contentious, it is generally agreed that different types of resin-based composites reveal different resistances to bleaching [ 21 , 22 , 23 , 24 ].…”

The effect of bleaching gel application on the physical properties of different CAD/CAM restorative materials

“…The literature lacks consensus regarding surface alterations for restorative materials after bleaching regimens, both with carbamide and hydrogen peroxides. 17,[20][21][22][23] The increase in microhardness of direct composites after the application of bleaching agents is seldom reported in literature. 20 Mainly, it is attributed to the dissociation of the polymeric chain by the free radicals released from the hydrogen peroxide, which brakes the double bonds from the cross linked chains, fomenting physical and chemical degradation.…”

“…Literature has no consensus regarding this topic. Bleaching is reported not to affect microhardness 14 and roughness, 15 as to decrease hardness in feldspathic ceramics, 16 lithium disilicate and zirconia, 17 and increase in roughness in leucite glass ceramic. 18 Time of exposition to bleaching agent, 19 bleaching protocol and type of restorative material 5 may influence the effects of bleaching in materials surface.…”