Impact of gastric acid challenge on the optical properties of monolithic zirconia

Objectives: This study was set out to investigate the impact of simulated gastric acid on the surface gloss and translucency parameter of monolithic zirconia materials.
Methods: -Four partially stabilized zirconia, a fully stabilized zirconia and IPS e.maxCAD as a control (10×10×1.2mm) were investigated.
-Each specimen was polished at a constant speed, under constant pressure, standard time, single directed motion and then ultrasonically cleaned.
-All specimens were immersed in 5 ml of simulated gastric acid [Hydrochloric acid (HCl) 0.06 M (0.113% solution in deionized water) pH 1.2] polished surface facing up, for 96 hours in 37°C incubator, pH monitored every 24 hours.
-A reflection spectrophotometer was used to estimate specular component (gloss) and translucency parameter (TP) values before and after acid immersion utilizing the respective formulas:
ΔE*SCE-SCI = [(ΔL*SCE-SCI)² + (Δa* SCE-SCI)² + (Δb* SCE-SCI)²]^1/2
TP= [(Lb* - Lw*)² + (ab* - aw*)² + (bb* - bw*)²]^1/2
Results: Acid immersion had no effect on the TP value of KATANA, PRETTAU ANTERIOR and BRUXZIR. The TP value increased significantly for PRETTAU, ZENOSTAR and IPS e.maxCAD.
Acid immersion had no effect on the specular component (gloss) of KATANA, PRETTAU ANTERIOR AND BRUXZIR. The specular component (gloss) of ZENOSTAR, PRETTAU and IPS e.maxCAD increased.
Conclusions: Based on the findings of this study it can be concluded that the optical properties of monolithic zirconia material displayed signs of resistance to major changes in its translucency and gloss. Some brands were affected more than others, but the change may be very minimum and not perceivable by the human eye.