Preparation Shade and the Final Esthetic Outcome

In your practice, you prepare a tooth, I receive the scan, we produce an e.max crown in the chosen shade. The patient is disappointed — the crown looks worse than expected. The reason? The preparation shade.

Ceramics, especially e.max, are not opaque. They are a translucent material — light passes through them and reflects from the dentinal walls of the tooth. If the prepared tooth is dark (gray-brown, discolored), its color shows through the crown, creating a grayish or yellowish tint on the surface.

Problem: Light Crown on a Dark Background

A very common scenario in practice: endodontically treated teeth (discolored by endodontic brown), complete reconstructions (after restoration or poor composite), teeth with amalgam. Their common feature: the prepared tooth is darker than the natural dentin of a healthy tooth.

When you seat a white/light e.max crown on it, without a smoothing base — the crown will appear gray or darkened.

Physics: Ceramic Translucency and Background

E.max translucency:

• HT (High Translucency) — ~90% light transmission
• LT (Low Translucency) — ~75%
• Ultra-thin (~0.4 mm) — almost complete transparency

The thinner the crown, the more the background (substrate) is visible.

Masking Strategies in the Lab

1. Smoothing and Lightening the Preparation

If the prepared tooth is discolored — clean the structure (grinding), apply a whitening resin, cover with white cement.

2. Internal e.max Layers

In the lab during fabrication: opaquer on the internal surface of the crown in the upper 1/3, an intermediate dentin layer, an esthetic glaze on the surface.

3. Choosing an e.max Shade

Light shades (BL, WO, A1) — prefer with a dark background. Universal shades (2M, 3M) — safe, but require advanced masking.

Strategies for Different Types of Abutment Discoloration

Discoloration Type	Problem	Masking Strategy
Light abutment (natural dentin)	Almost none	Standard opacity at the cervical margin
Intermediate (yellow)	Yellow shows through white crown	Opaquer at the cervical margin and half of the crown
Dark (grey-brown, endo)	Gray shows through, strong masking necessary	Strong opacity on the entire cervical margin and internal part
Greenish (amalgam)	Very difficult — need to neutralize green tones	Red-brown pigments, strong opacity, lightening the abutment

Practical Recommendations for the Clinician

1. Before preparation: assess the natural tooth color.
2. After preparation: check if the abutment is significantly darker. If so — inform the technician.
3. When sending impressions: include a photo of a comparative vital tooth.
4. For e.max: lean towards lighter shades, if possible.
5. Sometimes use white cement — it increases background brightness.

Can I cover endodontic discoloration with white resin?

Partially. White resin increases brightness, but if the discoloration extends deep into the dentin — the effect will be limited. A better solution: an opaquer layer within the e.max from the inside.

Does zirconia also show through the abutment shade?

Much less than e.max — zirconia is more opaque. However, with a very dark background, zirconia can appear grayish-white.

How much time does the lab need for more complex masking?

An additional 1–2 hours. Therefore, it's crucial to alert the technician when sending the case.