Porcelain veneers are generally regarded as superior to composite ones in terms of performance long term. Both can look extremely lifelike and superb if done well by a skilled dentist, and a composite veneer will only suffer perhaps a slight lack of translucency as compared with a porcelain one when viewed soon after placement. Over time however, the porosity of composite means that it is likely to discolour to some degree and the amount can vary depending on the type and density of the filler used. Abrasion from tooth-brushing can cause damage to composite veneers, especially inappropriate horizontal brushing across the buccal (front), aspect, whereas porcelain withstands abrasion very well and should maintain its smooth glazed surface. Composite will tend to dull and lose its shine within a couple of years in many cases. Plaque adheres to composite surfaces fairly readily, especially once the surface glaze has disappeared, whereas porcelain remains smooth and resists plaque formation very well, often better than natural tooth enamel.
An adequate amount of tooth structure may need to be removed to allow for placement of either type of veneer in order to get the desired shape without adding bulk.
Because porcelain veneers require longer chair side time plus laboratory time they can be considerably more expensive than composite veneers.
One factor that is sometimes overlooked is that composite will adhere quite well to old composite restorations, and this means that if part of a composite veneer fractures off, the veneer may usually be repaired in situ by adding more, and building up as before. In the case where a porcelain veneer fractures this is more of a disaster since it can’t be properly repaired, and a whole new one has to be made; sometimes involving considerable chair side time if remaining fragments of porcelain need to be removed first.
Having said that, porcelain veneers are generally very durable, and, when they are not directly involved in the stresses of biting can last for many years. However, a patient may be cautioned by their dentist to avoid biting into very hard types of food in order to be on the safe side.
There is no doubt that porcelain is more translucent than composite and this can help considerably in achieving a very lifelike, natural appearance. The composite gives a duller, flatter, more solid appearance by comparison, although this is often quite acceptable. It is perhaps wise for the dentist to check first just how translucent are the patient’s natural teeth.
Porcelain is able to achieve a hard, smooth, and impervious surface, making it very resistant to staining and this is one of its most important characteristics. When porcelain veneers are provided in whatever shade or colour, they remain that way virtually for a lifetime whereas composite becomes more porous over time and absorbs stains which may limit its lifetime to 2-5 years in many cases. It can however, be more easily renewed.
Porcelain veneers are generally thinner than those made from composite, often less than 0.5 mm which is difficult to achieve with composite and provide a good appearance. Thus porcelain veneers may require less removal of tooth substance in any given case and be a more conservative method.
The composite veneer is more easily removed than a porcelain one and this might sometimes be a consideration if further treatment options were contemplated in the future because of the condition of other teeth. A composite veneer might be a good temporary solution for example where it is likely that several teeth may need to be crowned eventually, for example.
In short, porcelain veneers are a better long term prospect although more time consuming and expensive to provide.