Purpose: The purpose of the present study is to assess the effect of different hydrofluoric acid etching durations on the translucency, flexural strength and surface topography of a lithium silicate-based glass ceramic (LS). Materials and Methods: Forty LS (Obsidian) samples will were constructed and divided into four groups (n=10 each) according the duration of hydrofluoric acid (HF) application including group (I); (control) as received samples without surface treatment, group (II); ceramic surfaces etched with HF for 10 seconds; following the manufacturer's recommendations, group (III); ceramic surfaces etched with HF for 30 seconds and group (IV); ceramic surfaces etched with HF for 60 seconds. All treated samples were evaluated for translucency (TP) using spectrophotometer, flexural strength using universal testing machine and surface topographic analysis using SEM and profilometer. Obtained values were statistically analyzed. Results: The highest mean value of translucency and biaxial flexural strength were recorded at the control group. Values then gradually decreased in the subsequent etching times to reach its lowest level after 60 seconds. While the lowest mean value of surface roughness (Ra) was recorded at control group. The mean Ra value gradually increased with the subsequent increase in etching times to reach its highest level after 60 seconds. Conclusions: Increasing HF acid etching duration negatively affects the translucency of lithium silicate based glass ceramic; while it has no effect on its biaxial flexural strength or its surface roughness (Ra).
Key Words
Biaxial flexural strength (FS), LS (Obsidian), surface roughness, translucency.