Many patients are interested in improving their appearance. One option is porcelain veneers. This involves the removal of less tooth structure than for a crown. In a crown the final appliance covers the entire tooth. A veneer only covers the front portion of the tooth and a small amount of the biting edge. It has advantages and disadvantages. The main advantages are the fact that less tooth structure is removed and they are very aesthetic looking. A disadvantage would be on an individual basis as not all teeth are well suited for veneers. A person should be an adult before a veneer is considered, for example. There have been reported cases where a dentist will place veneers on younger persons. In such cases the teeth may not be fully erupted and in time the margins will be exposed with an unsightly line. As well in many younger patients orthodontics might have a better result. A patient's exaggerated expectations can be a factor that is a warning to a dentist who may not perform the veneer process. Veneers should not be placed on patients who have a heavy under bite. That is the front teeth are always in heavy contact in closing. In such cases the veneers can split or chip readily.
When a person is selected, on good clinical grounds, for veneers the process is actually very satisfying. The teeth are reduced minimally, 1 -1.5 mm in most cases. If a tooth is out of line with the next one to it, the reduction may be more to allow for a final placement of veneers which line up aesthetically. The impression is taken and the case is sent to the laboratory. Due to minimal reduction temporaries are not always indicated.
The laboratory makes the porcelain veneers and the shade is coordinated with the dentist. In some cases the veneers will be masking a dark tooth or teeth so the veneer may be less translucent. In cases where the underlying tooth colour will be normal a more translucent veneer can be produced. When the veneers are returned to the dentist there are several steps which are undertaken. When veneers first were developed in the late 1930's they did not adhere well to tooth structure so were really a temporary measure. In the 1980's new techniques were developed to allow adhesion of the veneer to tooth structure. The inside of the veneer is first 'etched' with hydrofluoric acid. This is a type of acid that can etch glass, of which porcelain is a type. It is etched for about a minute then cleaned off with water. Then a milder acid, orthophosforic acid is used to rinse the etched inside of the veneer. This step neutralizes the strong hydrofluoric acid. At this stage the veneer is rinsed again. Then a drying solution, usually an acetate solution, is used to remove any water in the veneer inside portion. At this stage a relatively new material is used, Propanone, the brand name of the one I use is Den-Mat-s Link Bond. It is painted on the inside of the veneer. It is a polymer chemical with a branch that can bond to the porcelain. This is lightly dried and the veneer is ready to place on the tooth.
The tooth is etched with orthophosphoric acid 4%, this roughens the tooth surface lightly allowing a bonding liquid to adhere to the tooth. The tooth is then painted with a polymer liquid bonding agent. It is a polymer dissolved in acetone. The acetone evaporates quickly leaving the polymer that polymerizes or sets. It becomes the "anchor" for the material we next place in the veneer. A polymer plastic paste is placed on the inside of the veneer. This paste comes in many shades to both match the underlying teeth, or often to mask the discolouration of the tooth. A paste and veneer that are complimented by the colour of the underlying colour of the teeth are manufactured to allow light to shine through, these are called translucent. In some severe cases the underlying tooth may be severely discolored and a non-translucent material is used in both the veneer and the bonding paste.
The veneer is seated on the tooth, the paste can bond to the dried bonding agent and a visible light curing unit (which hardens the polymer) is used to ensure the veneer seats well and for along duration. The material I use has what is called an infinite cure polymer. That is once it has begun to harden the material will continue to set. This is particularly important as the veneer, even when translucent, does block some of the light from the curing unit.
Minor adjustments are made, such as removing the material between the teeth and trimming the margins where some of the polymer bonding material has over flowed. As well the 'bite' is checked to ensure there is not a heavy contact on closing as this will crack a veneer. Veneers are estimated to last about 15 + years.
They are a great option and worth a discussion with your dentist. But, if no negatives are discussed I might seek a second opinion.
Dental Veneers, A Cosmetic Option
Dr Michael Pilon
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