Infiltratable zirconia – a technology from yesterday or present?

Based on the material properties, any non-sintered zirconia can be infiltrated. It does not matter whether the zirconia is white, already industrially monochrome pre-colored or in several layers (multilayer).

The translucency of the material also plays no role here. When the dental industry speaks of “infiltratable zirconia”, we usually refer to a white delivered zirconia.

When infiltrating zirconium oxide, dental technicians make use of the capillary forces of the material in the unsintered state. On a micro level, the material can be compared to a sponge.

It sucks the staining liquid quickly and completely into the restoration.

Dyes are dissolved as ions in the staining liquids. The subsequent sintering turns them into oxides.

In order to meet the wishes of patients, manufacturers have developed a wide variety of color palettes. From A, B, C or D shades to liquids in the VITA shades or variants that are used by dental technicians to accentuate.

The accent liquids are, for example, blue or violet colors that make the enamel edge appear more translucent than the material actually is.

The procedure differs depending on whether a coloring liquid is used for accentuation or for general coloring.

When using white zirconia, the primary goal is to achieve the base color for the material. The zirconia framework is dipped for this purpose in a solution. In order to achieve the desired coloration, it is important to work exactly according to the manufacturer’s instructions, to mix the coloring liquid well and to observe the recommended drawing time.

The restoration then has to dry – also according to the instructions – and is finally sintered. There are also differences in the sintering program depending on the manufacturer of zirconia and coloring liquid, which must be taken into account for an optimal shade result.

If the infiltration technique is used to accentuate the restoration, the staining liquid will be only applied to the appropriate areas. When using this technique, industrially pre-colored material is usually used as the basis.

As with coloring in basic shades, a drying time must be allowed for before the restoration can be released for sintering.

In the past, the lower purchase price – compared to pre-colored zirconia – was a compelling argument for using the infiltration technique. Even if the shade results were not always what technicians would have wished for, at that time the basic shades of the pre-colored zirconia were still far from today’s standard, so that no time was saved when painting or veneering with ceramics either. It is different today.

The high level of aesthetics – in terms of shade and translucency – of the pre-colored FAB Zirconia 3D ML material also saves time in finalization. A win in times of a shortage of skilled workers. The weaknesses of the material in the infiltration technique remain unchanged. Almost every restoration has a different shade. Responsible for this are, among other things, the brewing time and stirring of the staining liquid.

Changing the manufacturer of the zirconia can also result in different shades due to the different porosities and the associated receptivity of the zirconia. But the porosity within the material differs not only among different manufacturers. There are small deviations even within a single milling blank. These slight variations are enough to create a “blotchy” appearance.

Edges, such as the enamel or the margin, tend to become darker than the rest with the infiltration technique. During drying, the liquid evaporates more quickly in these areas because they are particularly thin. The remaining infiltrate “wanders” in the material and evaporates again at these particularly thin areas. The dissolved ions are also transported and settle at the points where the liquid evaporates. Since they are concentrated there, they ensure a darker coloration. An inconvenient effect for an enamel edge.

Another disadvantage of the evaporation of the liquid becomes apparent during the sintering process. Despite the drying time, a large amount of liquid remains in the material. This liquid evaporates in the sintering furnace, settles on the fuel rods and causes greater corrosion of the material there.

Despite all these weaknesses, why do we go back to white zirconia and do not use the pre-colored material? There is an economic aspect: the warehousing. There are now numerous shade variants – 16 VITA shades, mono or multi-layer, additional bleach shades and much more. It is uneconomical to have every milling blank in stock in several heights and end up being stuck with the rather rare shades. The staining liquids, on the other hand, are much more space-saving and the white zirconia disks can be used for any color desired by the patient.

While the primary goal when shading white zirconia is to achieve a standardized basic shade, the infiltration of accent shades is about customizing the framework. The advantage of the infiltration technique for accentuating the restorations is that the accent colors are applied before the sintering process and thus create a depth effect. Depending on the treatment and requirements, firing is no longer necessary afterwards, and polishing the restoration is sufficient for an aesthetic result. The work as such is accordingly time-saving and efficient.

Alternatively, stains are used to customize restorations.

In contrast to the infiltration technique, the effect of stains can be seen immediately after the liquid has been applied.

If a satisfactory end result is not achieved, it can be reworked directly. Even if the stains are only superficial effects and thus optical illusions, the result is excellent in terms of its aesthetics. In addition, the staining technique offers an advantage if dental technicians are not satisfied with their shade result. While with the infiltration technique the color is deep in the material and can no longer be removed, the stain can be removed by simply blasting and the process repeated.

There are strengths and weaknesses in both the infiltration of white zirconium dioxide and the infiltration of accent colors. Every laboratory, every ceramics department, every technician decides for itself whether the advantages outweigh the disadvantages and which technique should be applied. The dental technician masters from Labor Rager – the dental laboratory of our group of companies – rely on industrially pre-colored multilayer zirconia and staining technique.

What can be said in any case is that not everything was better in the past and even if the developments focused on industrially pre-colored zirconia and reproducibility –

both the material and the coloring liquids have developed enormously in recent years.

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