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Evaluation of the Effect of Thickness on the Translucency of Super-high Translucent Zirconia &amp; Zirconia Reinforced Lithium Disilicate

This in vitro study demonstrates that zirconia-reinforced lithium disilicate exhibits superior translucency compared to super-high-translucent zirconia at both 0.9 mm and 1.3 mm thicknesses, despite both materials showing reduced translucency as thickness increases.

Original authors: Rajesh Shetty, Faseela Thenukutty, Shrimaa Kateel, Sanath Kumar Shetty, Mohammed Zahid

Published 2026-07-01

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CC BY 4.0

Original authors: Rajesh Shetty, Faseela Thenukutty, Shrimaa Kateel, Sanath Kumar Shetty, Mohammed Zahid

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are trying to build a window out of two different types of glass. Your goal is to make the window look as invisible as possible, letting light pass through just like a clear pane of glass, rather than looking like a cloudy piece of plastic.

This research paper is essentially a "transparency test" for two high-tech materials used to make dental crowns (the caps that go over damaged teeth). The researchers wanted to see which material looks more like a natural tooth and how the thickness of the material changes its "see-through" quality.

Here is the breakdown of the study in simple terms:

The Two Contenders

Think of the two materials as different types of "glass":

The "Super-Zirconia" (Zolid Fx): This is a very strong, modern ceramic. It's like a thick, high-tech safety glass. It's known for being tough, but the researchers wanted to see if its new "super-translucent" version could look clear enough to be invisible.
The "Glass-Metal Mix" (LDS / Vita Suprinity): This is a mix of glass and a tiny bit of zirconia. Think of it as a very clear, delicate glass that has been reinforced with a little bit of steel wire to make it stronger.

The Experiment: The "Window Pane" Test

The researchers didn't test these on real teeth. Instead, they made 40 perfect, square "panes" (10mm x 10mm) in a lab. They cut them into two sizes to test how thickness affects the view:

The Thin Slice: 0.9 mm thick (about the thickness of a credit card).
The Thick Slice: 1.3 mm thick (a bit thicker, like a stack of two credit cards).

They put these "panes" over black and white backgrounds and used a special light meter (a spectrophotometer) to measure exactly how much light passed through. The higher the score, the clearer and more "see-through" the material is.

The Results: Who Won the Transparency Contest?

The study found two main things:

1. The "Glass-Metal Mix" (LDS) was the clear winner.
No matter how thick they cut it, the LDS material let more light through than the Super-Zirconia.

The Analogy: Imagine holding up a thin sheet of clear plastic wrap (LDS) versus a thin sheet of frosted glass (Zirconia). Even if the frosted glass is very thin, the plastic wrap still looks clearer. The LDS material simply has a "clearer" natural look.

2. Thickness is the "Light Blocker."
For both materials, making the slice thicker made it look less clear.

The Analogy: Think of looking through a single pane of window glass. It's very clear. Now, imagine stacking two panes of that same glass on top of each other. It's still glass, but it looks slightly darker and less transparent because the light has to travel through more material.
The Twist: The LDS material lost more of its clarity when it got thicker compared to the Zirconia. However, even with this drop, the thick LDS piece was still clearer than the thin Zirconia piece.

The Big Takeaway

The researchers concluded that if your main goal is to make a dental crown that looks as much like a natural, see-through tooth as possible, the LDS material (Vita Suprinity) is the better choice.

Even though the Zirconia material is famous for being strong, the study showed that the LDS material is naturally more "see-through." The only catch is that if you make the LDS crown too thick, it starts to lose some of that magic clarity. So, for the best look, you want the LDS material to be as thin as safely possible (around 0.9 mm).

In short: If you want the most natural-looking, invisible tooth crown, this study suggests using the glass-reinforced material (LDS) and keeping it thin, rather than the super-strong Zirconia.

Technical Summary: Evaluation of the Effect of Thickness on the Translucency of Super-high Translucent Zirconia & Zirconia Reinforced Lithium Disilicate

Problem Statement
The increasing patient demand for high-quality esthetic restorations has driven the evolution of all-ceramic materials. While zirconia offers superior flexural strength and chemical stability, it has historically demonstrated inferior esthetic performance and translucency compared to glass ceramics like lithium disilicate. Although recent advancements have introduced super-high translucent zirconia (Zolid Fx) and zirconia-reinforced lithium disilicate (LDS, e.g., Vita Suprinity) to balance mechanical and optical properties, direct comparisons of their translucency at varying clinically relevant thicknesses remain limited. This study addresses the need to evaluate how thickness influences the translucency of these two specific materials to guide clinical material selection.

Methodology
This in vitro experimental study utilized a non-randomized sampling method to fabricate 40 ceramic specimens (10 mm × 10 mm) using CAD/CAM technology (Ceramill® Mind and Motion 2). The specimens were divided into four groups (n=10 per group) based on material and thickness:

ZrSH-1: Super-high translucent zirconia (Zolid Fx) at 0.9 mm thickness.
ZrSH-2: Super-high translucent zirconia (Zolid Fx) at 1.3 mm thickness.
LDS-1: Zirconia-reinforced lithium disilicate (Vita Suprinity) at 0.9 mm thickness.
LDS-2: Zirconia-reinforced lithium disilicate (Vita Suprinity) at 1.3 mm thickness.

All specimens were fabricated in A2 pre-shaded blocks. Zirconia specimens underwent dry milling, sintering, and glazing, while LDS specimens underwent wet milling and glazing. Translucency was measured using a spectrophotometer to determine the Translucency Parameter (TP). The TP was calculated as the color difference ( $\Delta E$ ) between measurements taken over white and black backgrounds using the CIE $L^*a^*b^*$ color system. Statistical analysis was performed using one-way ANOVA and Bonferroni post-hoc tests with a significance level of $p < 0.05$ .

Key Results
The study yielded statistically significant differences in TP values across all four groups ( $p < 0.001$ ).

Material Comparison: Zirconia-reinforced lithium disilicate (LDS) demonstrated significantly higher translucency than super-high translucent zirconia (ZrSH) at both thicknesses.
- At 0.9 mm: LDS-1 (Mean TP: 11.09) was significantly more translucent than ZrSH-1 (Mean TP: 6.52).
- At 1.3 mm: LDS-2 (Mean TP: 8.14) was significantly more translucent than ZrSH-2 (Mean TP: 4.60).
Thickness Effect: For both materials, translucency decreased as thickness increased.
- ZrSH showed a reduction from 6.52 (0.9 mm) to 4.60 (1.3 mm).
- LDS showed a reduction from 11.09 (0.9 mm) to 8.14 (1.3 mm).
Comparative Observation: Notably, the LDS specimens at 1.3 mm thickness exhibited higher translucency than the ZrSH specimens at the thinner 0.9 mm thickness.

Key Contributions
The primary contribution of this research is the direct quantitative comparison of two modern high-translucency ceramic systems at clinically relevant thicknesses. The study confirms that material composition (glass-ceramic matrix vs. polycrystalline zirconia) is a dominant factor in optical performance, often outweighing the influence of thickness alone. Specifically, it establishes that zirconia-reinforced lithium disilicate maintains superior translucency even when compared to super-high translucent zirconia at reduced thicknesses.

Significance and Claims
The authors conclude that within the limitations of this in vitro study, zirconia-reinforced lithium disilicate (Vita Suprinity) exhibits superior translucency compared to super-high translucent zirconia (Zolid Fx), regardless of the thickness tested (0.9 mm or 1.3 mm).

The study claims that these findings suggest LDS may be the preferable material when maximizing esthetic translucency is the primary clinical consideration, particularly for anterior restorations where blending with natural enamel is critical. The authors note that while increasing thickness compromises translucency for both materials, the inherent composition of LDS allows for better optical outcomes. Consequently, the null hypothesis was rejected, confirming that thickness significantly influences translucency in both materials, but material selection remains the critical determinant for achieving optimal esthetics. The authors advise that clinical decisions must still balance these optical findings with functional demands, as zirconia-based ceramics may remain indicated for situations requiring enhanced mechanical strength.

The Two Contenders

The Experiment: The "Window Pane" Test

The Results: Who Won the Transparency Contest?

The Big Takeaway

Technical Summary: Evaluation of the Effect of Thickness on the Translucency of Super-high Translucent Zirconia & Zirconia Reinforced Lithium Disilicate

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