Hello,
I've been wanting to write about this for a long time, but I haven't been able to find the time. I'd like to share my insights on choosing between e.max, zirconia, and monolithic zirconia materials, which have caused a lot of confusion among you.
- In this article, I'll explain what is zirconia, monolithic zirconia, and e.max are,
- Which is more durable and why,
- Which is more aesthetic and why,
- Which material should I choose where and why, I will try to briefly address these questions without confusing you too much.
The increasing demand for materials with the best aesthetics has led to the use of metal-free ceramic systems as an alternative to metal-ceramic restorations. To achieve optimal aesthetic results in restorations such as crowns and bridges, the optical properties of the materials used must match those of natural teeth. The most important factor here is translucency, i.e., the material's ability to partially transmit light; a translucent material allows some light to pass through while reflecting some and absorbing some.
The success of a dental restoration depends on many factors related to the selected material, such as its mechanical properties, anatomical form, surface texture, translucency, and color.
What is zirconia?
Zirconium is a material found in nature as an element. Zirconia is the name given to the material that has been strengthened through various mechanical and chemical processes. Among dental ceramics, the zirconia dental framework material, known as Y-TZP, is the most durable and hardest material. However, traditional zirconia material is optically opaque and has poor color aesthetics for direct use in the mouth because it is a material with very low light transmittance. It lacks the properties of light transmission, reflection, and absorption that create the character of the restoration color. In traditional zirconia, porcelain veneers can be applied to zirconia crowns and bridges to achieve this type of color aesthetics, but this can cause chipping over time.
As an alternative to this situation, monolithic zirconia material has been produced with very little or no ceramic veneer on zirconia.
Monolithic Zirconia
Recently, as an alternative to the method mentioned above, there has been a trend toward producing full-contour zirconia (monolithic zirconia, full-contour zirconia) restorations to prevent failures in crowns and bridges, particularly those caused by chipping of layered porcelain. To enhance the translucency and aesthetics of full-contour zirconia, certain modifications have been implemented, such as sintering temperature, production processes, and the addition of coloring liquids. The most significant clinical advantages of monolithic zirconia are:
- Very little or no layered porcelain is applied to the monolithic structure,
- Compared to veneered crowns, this full-contour structure is much more biocompatible.
- Another advantage of monolithic zirconia is that its fracture resistance is significantly higher than that of layered or monolithic (full-contour) lithium disilicates.
- Monolithic zirconia ceramics have been found to have much better resistance to chipping and flexural fracture than lithium disilicate (e.max), glass-infiltrated zirconia, and veneering porcelain.
- Studies have also shown that a well-polished monolithic zirconia ceramic restoration causes much less wear on the enamel of the opposing tooth compared to a glazed veneering porcelain. Therefore, well-polished monolithic zirconia ceramics have a much more friendly approach to contact with tooth tissue during chewing.
- In addition, monolithic zirconia ceramic has performed similarly to or better than natural enamel in terms of toothbrush abrasion.
- With advancing technology, monolithic zirconia ceramics have been pressed in layers to increase their light transmittance, i.e., translucency values.
- Retrospective clinical follow-ups in patients have shown that monolithic zirconia ceramic restorations have good marginal adaptation and gingival adaptation.
- At the same time, monolithic zirconia ceramics have a very high survival rate and success rate in implant-supported restorations.
Lithium Disilicate glass ceramic (E.max)
In recent years, rapid developments have been recorded in both the properties of materials and production techniques, particularly in the field of dental ceramics. Glass ceramics have become the preferred materials due to their high aesthetic properties and acceptable mechanical properties under oral conditions. These types of glass ceramic materials come in two forms: as millable blocks compatible with CAD/CAM systems or as ingots that can be pressed using the lost wax technique.
The most important and significant clinical advantages of lithium disilicate glass ceramics are:
- Although their mechanical properties are not as excellent as monolithic zirconia, they are suitable for use in single-unit restorations in the oral cavity.
- The color and optical properties of lithium disilicate glass ceramics (e.max) are much better than those of monolithic zirconia materials. They allow for near-perfect restorations in aesthetic areas within the mouth.
- Since the optical properties of glass ceramics are very close to those of natural teeth, they are the materials that show the closest color and light properties to teeth in single tooth restorations.
- Clinic studies show that full ceramic systems have a very good success rate and survival rate in single-tooth anterior restorations.
- Another good feature is that they do not cause any allergic reactions.
- Due to all these good features I have mentioned, lithium disilicate glass ceramics such as E.max stand out as an expensive material in the dental field.
In conclusion;
• E.max lithium disilicate glass ceramics are more expensive than monolithic zirconia but offer more aesthetic solutions.
• Monolithic zirconia is slightly cheaper and a much stronger restorative material. It can be used in the fabrication of much more complex restorations such as implant-supported restorations.
