Characterization of a Lithium Disilicate CAD/CAM Material with Firing Temperature-Controlled Translucency

Lithium disilicates are widely used in restorative dentistry due to their aesthetics, strength, and durability. Increased strength can be achieved by increasing crystal fraction, but this modification also reduces translucency. Recently developed lithium disilicates like Amber Mill claim to offer customizable translucency via firing protocols without changes in flexural strength. This study evaluated whether Amber Mill's firing protocols produce significant differences in translucency without changing flexural strength. Forty specimens (n = 10) were assessed for translucency using Contrast Ratio (CR) and Translucency Parameter (TP) tests under four firing protocols designed to obtain high translucency (HT), medium translucency (MT), low translucency (LT), and medium opacity (MO). Using the three-point bending test, sixty specimens (n = 15) were tested for flexural strength with the same four firing protocols. The Weibull modulus and characteristic strength were also calculated, and SEM observation was performed. The CR and TP tests revealed statistically significant translucency differences only between MO and LT/MT/HT. Flexural strength ranked as MO > LT > MT > HT, with significant differences observed between MO vs. MT/HT and LT vs. HT. The findings indicate that the recommended firing protocols for the same shaded blocks resulted in limited differences in translucency. Additionally, higher translucencies were associated with reduced flexural strength, highlighting a trade-off between aesthetic and mechanical properties for Amber Mill.