Genetic predisposition to caries, poor oral health and aesthetic needs, as well as the desire to have a perfect smile, have led to a series of breakthroughs. Recently, dental material manufacturers all over the world have introduced many new materials and dental materials to the market, supported by this global need. Among these materials, zirconia has surpassed the methods and materials previously used in the dental sector with its strong structure and ability to adequately respond to aesthetic requirements. However, each treatment has its suitability, advantages and disadvantages in certain situations. These treatment options can be affected by many variable factors such as the patient’s age, gum health, whether the tooth has root canal treatment or not, the healthy remaining part of the tooth if an existing decay on the tooth has been cleaned, and the relationship of the teeth during chewing or closing.
What is a Zirconia Veneer?
Zirconia is a metal oxide derived from zirconium, a metal in the titanium family in the periodic table. Zirconium-oxide has been used in healthcare since the 1970s, and in the early 2000s it began to be used in the dental sector, first as a substrate material for other dental ceramics and later as the base material for veneers made entirely of zirconia materials. Due to its natural strength and durability, zirconia crowns are an ideal material for patients who need posterior group dental crowns that require strength to chew food. Zirconia has gained tremendous popularity for many clinical applications due to its mechanical and aesthetic properties as well as its biocompatibility. In addition to being a strong crown and bridge material, zirconia has been used as implant abutments, intramucosal attachments, intra-osseous implant material and most recently as a framework for bone grafts.
What are Porcelain Veneers?
Metal-backed porcelain (MDP) veneers have been used in dentistry since the 1950s. Porcelain veneers are multi-layered restorations made by layering (stacking) ceramic material on a metal substructure. Metal-backed porcelain veneers gain durability and longevity thanks to their metal substructure and have a sufficient aesthetic and natural appearance acceptable to the patient thanks to the porcelain layer stacked on them.
Although metal-backed porcelain veneers are an excellent choice of material for those looking for a less costly restorative solution, as mentioned earlier, they have several disadvantages such as gum discoloration, possible allergic reactions and the need for an additional metal frame to support the porcelain superstructure. These restorations consist of two main structures: a metal substructure and a porcelain layer. This main material structure significantly influences the final performance of the restoration made and placed in the patient’s mouth. If we briefly evaluate the success rate and survival rate of metal-supported porcelain veneers historically; it has been observed that the ceramic layered by stacking on metal exhibits high chipping, fracture and breakage rates. There are two main reasons for these failures; first, the ceramic layer layered on the metal support is too thin, making the material less durable. Second, there is a difference between the thermal expansion properties of the substrate metal and the physical properties of the layered ceramic in response to heat. This means that the layers expand and contract at different rates during manufacturing. Due to the differences in these physical properties, defects and weaknesses are created for the final restoration, especially at the junction of metal and ceramic. However, this disadvantage does not apply to zirconia veneers.
This situation is different for zirconia restorations. Zirconia veneers are sintered from a solid block of zirconia using the subtractive method to produce full-shaped restorations. Thanks to the monolithic and fully anatomical structure of the material, the restoration has a more robust structure as it has the same material properties in all areas. The disadvantages of metal-supported porcelain veneers described above are eliminated in zirconia restorations thanks to this solid structure.
In the light of all these evaluations, although zirconia is statistically significantly stronger than ceramics used for MDP veneers as a dental material, there are areas where the monolithic material is also weak. The clinical limitations of monolithic material are mouths with insufficient distance, and situations where bridge connections cannot be made with sufficient thickness due to distance. MDP veneers are recommended by our clinic because they provide a longer lasting solution in such limited areas.
Why are Zirconia Restorations More Preferred?
Reliability and Durability
Natural Appearance
Variety of materials according to the patient
Biocompatibility
Reliability and Durability
Zirconium material offers superior strength and durability for dental veneers. This strength and durability is at least 3 times stronger than the porcelain layer compared to metal-backed porcelain restorations. In a metal-backed porcelain restoration, the layer of porcelain stacked on top of the metal is very thin, which reduces the bond strength between the two materials and makes porcelain less durable in the oral environment. Unlike dental porcelain, zirconia material can withstand wear and tear without chipping, so zirconia restorations better tolerate the forces of chewing and bruxism (teeth clenching problem). Monolithic zirconia (single, solid blocks of zirconia), developed thanks to new technologies, is much stronger, almost unbreakable, and is made to withstand difficult areas where the chewing force reaches its maximum, especially in the posterior group of teeth. This is due to the fact that the zirconia material contains much more stabilizers than dental porcelain. This makes it durable and resistant to strong chewing and grinding, and has the capacity to last a lifetime as long as patients perform proper care and cleaning.
Natural Appearance
Since zirconium does not contain any gray metal support, it does not form a gray halo or line on the gingival edge. Metal-supported porcelain veneers have a metal reinforcement under the porcelain layer in the part of the veneer close to the gum. Although this metal support is usually not visible at the gingival margin, it may cause gray discoloration and reflections on the gingiva over time. Since zirconia has a much less opaque structure compared to metal-supported porcelain, it meets the color characteristics of the tooth better. In this way, the light incident on the veneers is partially absorbed, partially reflected and partially filtered by the zirconia material. This transparent, translucent and reflective property gives the material its basic color characteristics. Since there is no gray metal layer in zirconia restorations, they mimic the physical characteristics of color more similar to natural teeth. As a result, if we ask our question “zirconia or porcelain?” again in terms of naturalness, zirconia veneers offer a more natural appearance to patients compared to metal-supported porcelain.
Material Variety According to the Patient
With the developing technology, many different types of zirconia used in dentistry today have been put on the market under many brand names and this has led to serious confusion in patients. When our patients come to the clinic, one of the first questions they ask us physicians is which zirconia or which brand do you use. When we exclude zirconia brands that are produced under very simplified stairs; Regardless of the name and brand, most dental zirconia materials have a similar chemical composition. Regardless of their content, the two main physical properties of dental zirconia, strength and transparency, can be changed according to the differences in production processes. These customizations, especially in the transparency of the zirconia material, minimize the margin of error and allow us to choose blocks with different aesthetic properties for each region.
Biocompatibility
Biocompatibility is the medical suitability and acceptability of the reaction of living tissue in terms of any inflammatory, allergic, immune, carcinogenic effects of the biomaterial used in the patient. Zirconia is currently used in veneers and bridges, dental implants, orthopedics, as a skeleton for bone grafts. Thanks to its high biocompatibility, zirconia does not cause allergic reactions that may occur against alloys in metal-supported porcelain restorations. At the same time, it has become the safest harbor for clinical use in veneers and bridges with its excellent compatibility with tissues. Metal-backed porcelains can cause undesirable reactions in the soft tissues of the patients due to the metal and ceramics in their content and can disrupt gum health. Therefore, our clinical answer to the question “zirconia or porcelain?” in patients with allergic phenotype will definitely be zirconia.
Conclusion
In conclusion, metal-supported porcelain restorations have been used in dental practice for more than 60 years and have gained an important place. With the continuous development of technology, modern dental materials such as zirconia have replaced previous materials and indications used in dentistry. Numerous studies are being carried out in the fields of science and technology to meet the aesthetic and functional expectations of patients. An excellent material for dental practice today may become a mediocre material in the future. Therefore, it is very important to follow the developing materials and to establish the application practice in the clinic in terms of current patient approach.
