Veneers are porcelain or ceramic layers that replace external layer of the teeth. They allow you to correct irregularities in the shape and color of tooth, and protect your teeth (for example, when playing wind instruments). As a result, the restored tooth becomes strong and looks the like the rest of the teeth. Veneers are made according to the shape, color and wishes of the patient’s teeth.
Veneer is a 0.2 mm thick plate that is glued to the labial, that is, the lip side of tooth and has aesthetic, restorative, camouflaging, phonetic and alimentary functions. Composite plate is an organic resin filled with ceramic or glass micro-particles. An example of ceramic plate is lithium-disilicate glass-ceramic.
Generally veneers do not require any aggressive preparation of the tooth enamel; in some cases (microdontia or abrasion) veneers can be made without any preparation of tooth substance. If the occlusal and gnathological principles are followed in the clinic by the operator and if the laboratory engineer follows all the procedural steps, this method of restoration has a long term perspective and can be widely recommended.
Materials and technology
There are different types of veneers — composite and ceramic. Composite veneers can be made directly (in the dentist’s chair in one visit) and indirectly (in a dental laboratory).
Ceramic veneers
Ceramic veneers are made from different types of ceramics. The most common types are porcelain feldspar and IPS Emax glass-ceramic, but ceramic veneers are more rarely made of zirconium dioxide blocks. Ceramic veneers are only made in the laboratory. The doctor prepares (grinds down) the tooth, then takes an records of the teeth and sends it to a dental laboratory where permanent ceramic veneer will be made for the patient within two weeks. To avoid the patient having to walk around with their teeth grinded, a temporary veneer made of plastic is placed on the tooth while they are waiting. The main types of ceramic veneers are described below.
Feldspathic (porcelain) veneers
First ceramic veneers were made from porcelain, because this type of ceramic allows to perfectly copy the optical properties of the tooth (shade and translucency of enamel). Porcelain veneers show very good esthetics — even no worse than E.max glass-ceramic veneers. Porcelain veneers are made using three laboratory techniques. First, the porcelain mass is applied layer by layer, and each layer is sintered in a porcelain sintering furnace at high temperature. Second, the method of pressing porcelain under high pressure and temperature. The third method, which is relatively new, is the milling of feldspar ceramic blocks (for example, Vita Mark 2 blocks) on CEREC machines (CAD/CAM technology).
When using porcelain, the best of these three methods will be pressed ceramic, because the veneers made of it have significantly greater strength. The flexural strength of the porcelain layering method is only 50-75 MPa. The bending strength of the press or CAD/CAM method is about 150 MPa. The latter is sufficient if you have a correct bite and no bad habits, but the next type of ceramic has even greater strength.
IPS Emax glass-ceramic veneers
- IPS Emax glass-ceramic (manufacturer — Ivoclar Vivadent) consists of lithium disilicate crystals that have the same coefficient of transparency as real tooth enamel, so veneers made from this material look very similar to real teeth. There are two types of IPS Emax material. First, there is the Emax PRESS material, which is designed for making veneers using pressing technique. The veneers made from this material are the strongest — they have a bending strength of approximately 400 MPa, which almost completely eliminates the risk of chipping. The so-called «thin veneers» are made from Emax PRESS, which are only 0.3-0.4 mm thick (standard ceramic veneers are 0.6-1.0 mm thick).
- Second version of the IPS Emax glass-ceramic is the E.max CAD material, which is produced as special blocks for milling on a CEREC-type CAD/CAM machine (CAD/CAM technology). The same manufacturing method is used for the next type of ceramic veneers — zirconia veneers. The strength of E.max CAD veneers is also very high — about 360 MPa, but no thinner than 0.6 mm can be made out of this material.
Zirconia veneers
These veneers are made of zirconium dioxide blocks by milling (CAD/CAM technology). The strength of these veneers is highly dependent on the type of zirconia blocks. If so-called raw, soft zirconia blocks are used, the bending strength of the veneers is around 900 MPa, but the aesthetics are lower due to the opacity of the material and its milky white color. If zirconia blocks with yttrium are used, the zirconia veneers are translucent and have good aesthetics, but their bending strength is lower (about 550 MPa).
In terms of aesthetics porcelain (feldspar) and IPS Emax veneers are significantly better than veneers made of zirconium dioxide. According to clinical studies (source), Katana UTML (Japan) is the closest to IPS Emax glass-ceramic by aesthetics, followed by Katana STML (Japan), BruxZir Anterior or Prettau Anterior (Germany).
Composite veneers
In order to install composite veneers, doctor grinds down thin layer of enamel, then, using adhesive systems, layers composite filling material. These veneers are made in the oral cavity and last for 3 to 5 years. The most common purpose of these veneers is to use them when one or two teeth in row are to be improved, or they are made in the laboratory: after making an impression, a model is made, the veneer is modeled and polymerized in special polymerization oven. At the clinic the veneer is fixed with liquid composite. The advantage of this method compared to direct veneers is that the composite is more completely polymerized, resulting in increased strength.
Lumineers
Ultra-thin ceramic veneers manufacturing technique patented by Cerinate (USA) is called Lumineers. This type of veneers is made exclusively in the laboratory of Cerinate, located in California (USA). The advantages of this type of veneers over classic veneers are:
- Non-invasive: no grinding of hard dental tissues is required;
- higher aesthetics in «Hollywood smile» style;
- possibility of removing and replacing installed veneers without damaging the dental tissue.
It is not recommended for use in cases of «stained» or colored enamel, as lumineers are transparent.