Porcelain Veneers -
What are they? / Advantages & Disadvantages. / Applications.
- An overview of what porcelain veneers are, how they work and examples of when they do and don't make the right choice.
What are they?
Porcelain veneers (also referred to as dental laminates), are wafer-thin shells of porcelain that are bonded onto the front side of teeth.
They're generally about .5 to .6 mm thick. That's about 1/2 the thickness of a dime or twice the thickness of an eggshell.
(Some types of laminates, like Lumineers®, can be even thinner. We discuss
ultra-thin veneers here.) What are they used for?
The primary purpose for placing veneers is to improve the appearance of teeth.
They're routinely use as a way of making changes for those that are discolored, worn, chipped or malformed, have spaces between them or are slightly misaligned. (See applications section below.)
In most cases, placing them is an elective procedure.
How do they work?
The way porcelain veneers are attached to teeth is really just an extension of the
science of tooth bonding.
With it, a series of steps are used to create a strong bond between dental composite (white filling material) and tooth enamel.
With this procedure, similar materials are used to create a bond with both enamel and porcelain.
The net result is a situation where the bonding acts as cement sandwiched between the veneer and tooth, holding everything together.
Why do they work?
You may wonder how a wafer-thin shell of porcelain can successfully withstand all of the wear and tear that it's ultimately exposed too.
The answer lies in the fact that although porcelain is inherently brittle, when it's firmly bonded to and supported by a sturdy substructure (a tooth in this case), it creates a very strong and durable surface.
How do veneers differ from dental crowns?
While both of these restorations give the same cosmetic end result, a crown completely encases a tooth and involves far more tooth trimming when it's placed. (
This page explains the differences in greater detail.) What advantages do porcelain veneers offer? A) They can create a very natural-looking appearance.
Due to their ability to closely mimic the way natural teeth reflect light, well-crafted porcelain laminates can look astoundingly lifelike. Here's why:
Light penetrates the enamel and then reflects back out.
1) How teeth handle light.
Tooth enamel is translucent. And because of this ...
1) ...when light strikes it, it penetrates through it ...
2) ... then, once the light has passed through the full thickness of the enamel, it reflects off the opaque (non-translucent) tooth dentin that lies underneath ...
3) ... and then back out of the tooth.
This penetration in and reflection back out is what gives a tooth its characteristic glass-like lustrous appearance.
2) How porcelain veneers handle light.
Light penetrates the veneer and then reflects back out.
When light strikes the surface of a veneer ...
1) ... it penetrates into it ...
2) ... and then either ... traverses the thickness of the porcelain and then gets reflected off the opaque cement that's been used to bond the veneer in place ...
(This is the case where an opaque cement has been needed to help to mask the dark color of the tooth underneath.)
or else traverses the thickness of the porcelain/cement combination and then gets reflected off the opaque tooth structure that lies beneath them ...
(This is the situation where only a minor color change was needed for the tooth and it was possible to use a very translucent cement.)
3) ... the light then passes on back out of the tooth.
Either way, this "penetration in and then reflection back out" method of handling light is similar to enamel. And this is why a well designed and well crafted porcelain laminate (see Takeaways box) can give such a natural, life-like appearance.
Takeaways from this section.
How life-like a porcelain veneer can/will look will, in part, depend on the way it's made. There are 3 processes that can be used:
a) Conventional ceramic (feldspathic porcelain). -
This is a technique where different types of porcelain (each having their own unique color and translucency characteristics) are hand layered to construct the veneer.
When well crafted, the look and characterization possible with this type of restoration is hard to beat.
b) Heat-pressed ceramic. -
Using this process, the porcelain is first melted and then pressed into a mold.
One difficulty with this technique is that only one color of porcelain can be used. This is a problem because the shade and translucency of different regions of a tooth typically vary.
There are 2 processes that can be used to add characterization to this type of veneer (make it look more life-like).
Stains (colored glazes) can be painted on and then fused to its surface.
Small portions of the veneer (usually right at its biting edge) can be trimmed back and then replaced with tinted porcelains.
Especially when this latter technique is used, the end result can be quite life-like.
Milled (CAD/CAM) ceramics. -
This is a process where CAD/CAM technology is used to grind the veneer out of a single block of synthetic porcelain.
Like above, the color uniformity of this type of veneer creates a challenge. Characterization can be added by staining the veneer with glazes. But of the three processes, this is the one with which it's most difficult to get an exceedingly natural-looking end result.
3) In comparison ...
Dental bonding, which can also be used to make laminates for teeth, is only semi-translucent.
That means when light strikes it, it's mostly reflected off the veneer's front surface (there's much less light penetration). We compare this and other aspects of porcelain vs. bonding
on this page. B) They resist staining.
Another advantage that porcelain veneers offer is that their impervious glass-like surface resists staining well. (However,
issues associated with the cement used to hold them in place do exist.)
In comparison, materials like dental bonding typically will stain or discolor over time (see bonding link above).
Applications and uses.
Porcelain veneers can be used to overhaul the appearance of teeth that are chipped, worn, discolored, or even crooked.
They can make a good choice for cases where the extent of change that's needed, and the circumstances under which the veneers will function, are fairly routine and normal. Beyond that, other types of restorations (usually
dental crowns) make the wiser choice.
a) Repairing minor tooth imperfections and defects.
Teeth that have worn or have small chips, surface imperfections (dimples, pits) or relatively minor developmental abnormalities (pegged lateral incisors) frequently make good candidates for porcelain veneers.
In situations where the affected area is just very small,
dental bonding often makes the better choice (it's a simpler, less invasive procedure).
But if a substantial portion of the front side of the tooth could benefit from resurfacing, the durability, stain resistance and life-like appearance that porcelain laminates can offer can make them an excellent solution.
b) Concealing stained fillings.
The process that's used to cement a veneer to a tooth will create a bond with existing white filling material (dental composite) too.
Since composite restorations tends to discolor over time, the ceramic surface of a porcelain veneer offers a more durable, long-lasting result.
c) Making color changes for teeth.
Porcelain laminates can be used to lighten the color of teeth. This includes those that have tetracycline or fluorosis staining, or have darkened in response to trauma or having had root canal treatment.
The situation needs to be one where the teeth are structurally sound; they just need a simple color change.
Veneers don't make a good choice for treating teeth that are exceptionally dark. Using this technique with them can result in over trimming, bulky/poorly contoured laminates or needing to use very opaque porcelain (which sacrifices the translucency effect described above).
(As a solution for this type of situation, bleaching treatments are performed first, so to lighten the teeth somewhat. Then veneers are placed.)
d) Instant orthodontics.
1) Porcelain veneers can be used to close spaces between a person's teeth. In fact, they are ideally suited for this purpose.
With very small gaps, however, dental bonding usually makes the better choice.
2) If a person's misalignment isn't too severe, veneers can be used to give their smile a more even appearance.
When veneers shouldn't be used.
There can be situations where certain teeth, or even certain people, are not good candidates for this procedure. Some areas of concern are:
Veneers aren't the right choice for teeth that need strengthening.
a) Teeth that need strengthening.
Teeth that have lost a significant amount of structure due to wear, decay or fracture, and those that have large fillings don't make good candidates. That's because porcelain veneers do not strengthen teeth, they only improve their appearance.
In this type of situation, dental crown placement makes the more appropriate choice.
b) Teeth with little enamel.
A porcelain veneer won't stay in place well unless it's primarily bonded to tooth enamel. Here's why.
1) When it's bonded onto enamel, the enamel is the more rigid of the two and it tends to absorb most of the forces applied to the tooth.
2) When bonded directly to dentin (the layer underneath enamel), the laminate is the stiffer object and any forces directed to the tooth tend to become focused in it. This can lead to veneer fracture or debonding.
Some teeth may have little or no enamel remaining on their front surface due to wear, erosion, trauma, or previously placed dental restorations. If so, they don't make good candidates. A dental crown would make the more appropriate choice for these teeth.
c) Excessive forces are involved.
People who clench and grind their teeth (referred to as bruxism by dentists), or have a bite where their front teeth come together edge-to-edge, don't make good candidates.
The level of forces generated by these conditions can be substantial and can cause laminates to chip, break or debond. One study (
Beier 2012) found that a habit of bruxism increased the failure rate of a subject's porcelain veneers by a factor of 8.
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