Internal Characteristics of Ceramics — Translucency, Structure, and Strength

Why the internal structure of ceramics matters

Laboratory technicians know that ceramics are not a homogenous mass. The problem begins when dentists choose a material based solely on its name — "e.max for aesthetics, zirconia for posteriors" — without considering that the internal structure determines the aesthetic outcome, reliability, and behavior during cementation.

Four key internal parameters of ceramics:

• Translucency — how much light passes through the material
• Crystalline structure — how atoms are arranged in a lattice
• Grain size — affects light scattering and opacity
• Residual stress — whether and how the material "lives" after firing

Translucency — what translucency truly measures

Translucency in ceramics is a measurable parameter, not a "feeling."

Material	Translucency	Practical Implications
E.max Press / IPS	60–70%	Abutment shade influences final outcome
Standard Zirconia (YTZ)	0–2%	Masks abutment shade — independence from substrate
Reinforced Zirconia (ZTA)	20–30%	Intermediate translucency, a compromise

How translucency affects color matching and cementation

E.max scenario (high translucency): A1 specification on e.max + B2 abutment shade (yellowish) = final shade similar to A2/A3 in the mouth. Translucency allows to "read" the dark tooth underneath. A darker or lighter cement selected compensates for this difference.

Zirconia scenario (low translucency): Zirconia masks the abutment shade — final shade ≈ pure selected shade. Easier matching, but lack of corrective flexibility after firing.

Dentists say: "I sent A1, the crown came out too dark." Often the problem is underestimating the effect of translucency on the final result.

E.max vs. Zirconia vs. Reinforced Zirconia

E.max — high translucency, many decisions

• Translucency: 60–70%, strength: 360–400 MPa
• Best aesthetics for anterior region (1–2)
• Requires precise preparation and awareness of cement influence
• Not recommended for extensive posterior bridges

Zirconia — low translucency, predictability

• Translucency: 0–2%, strength: 900–1200 MPa
• Versatile — works everywhere (regions 1–8, implants, bridges)
• Independent of abutment shade
• Requires precise color matching at the prescription stage — post-firing corrections are limited

Reinforced Zirconia (ZTA, YTZ) — a hybrid compromise

• Translucency: 20–30%, strength: 1000–1200 MPa
• Half the translucency of e.max, half the opacity of standard zirconia
• Ability to "read" the abutment with reduced influence
• Reliable for implants and bridges with aesthetic requirements

Crystalline structure and strength

Medical zirconia is YTZ (Yttria-Stabilized Zirconia) — yttrium ions stabilize the tetragonal structure. Upon microfracture, the tetragonal phase transforms into a monoclinic phase, leading to volume expansion and "closing" of the crack. This is transformational toughening — the reason why zirconia is so reliable.

E.max does not have this mechanism — small cracks can grow. Therefore, every e.max crown at deltalabs. undergoes PID (Penetrant Inspection Dye) control before shipment. A colored liquid penetrates every crevice — a crack < 0.1 mm is detectable. If the test reveals a crack, the crown is not shipped.

deltalabs. protocol — from material to quality control

Every order begins with an analysis of clinical conditions:

• Region: anterior (1–2), buccal (3–5), posterior (6–8)
• Abutment shade: lighter or darker than standard
• Cementation type: clear or opaque cement
• Loads: bruxism, parafunction, antagonist

Based on this data, we choose: e.max (anterior region 1–2, natural abutment shade), zirconia (regions 3–8, implants, bridges), ZTA (regions 1–3 with aesthetic and reliability requirements).

Frequently Asked Questions

Why does zirconia look "artificial" compared to e.max?

Zirconia does not "read" the abutment shade — this is an advantage (predictability), but it requires precise color selection during the design phase. E.max is more "lively" due to its translucency.

Can e.max be used for bridges in the 1–2 region?

Possible, with conditions: no parafunction, good retention, minimal lateral forces. We recommend reinforced zirconia (ZTA) as a safer choice for most bridge work.

How long does ceramic firing take?

E.max: ~30 min. Zirconia: ~90–120 min (higher melting temperature 2700°C vs 920°C for e.max).

Does shading change the material's strength?

Minimally — shading is a dedicated layer of pigment. It changes light propagation, not mechanical parameters.

Do you have doubts about material selection for a specific case? Contact us — we will analyze the clinical conditions and propose the optimal option. Also, check out the article e.max vs zirconia for a full comparison.