Porcelain Laminate Veneers - What are they? / How do they work? / When won't they work? / Advantages & Disadvantages.
- Details about how porcelain veneers work and what makes them so special, and times when they don't make the right choice.
What are they?
Porcelain veneers (also referred to as dental laminates), are wafer-thin shells made out of dental ceramic 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 function of veneers is improving the appearance of teeth.
Porcelain laminates are routinely used as a way of making changes for teeth that are discolored, worn, chipped, malformed, have spaces between them or are slightly misaligned.
[See our Uses and Applications (before & after pics) page for examples.]
Veneers are usually an elective procedure.
In most cases laminates are placed at the patient's discretion solely to enhance the appearance of their teeth, as opposed to improving them structurally or to prevent their further deterioration.
Why do they work?
You might 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 these two facts:
- Although porcelain is inherently brittle and is easily fractured if dropped or flexed, when it's firmly bonded to a sturdy substructure (its tooth) it's supported in a manner that avoids these weaknesses. (Minimal flexure occurs. Forces directed to it are passed onto and withstood by the strong, rigid tooth structure underneath.)
- The hard, ceramic (glass-like) nature of a veneer creates a very durable surface. (It's impervious to the compounds it is exposed to and resists wear well.)
How do they work?
The way porcelain laminates are attached to teeth is really just an extension of the science of tooth bonding.
- With that process, a series of steps are used to create a strong bond between dental composite (tooth-colored filling material) and a tooth's enamel.
- When veneers are placed, similar steps and materials are used but this time establishing a strong bond between enamel and porcelain.
The net result is one where the bonding acts as a layer of cement sandwiched between the veneer and its tooth, thus anchoring the restoration firmly in place.
What advantages do porcelain veneers offer?
As we detail below, there are three characteristics that make porcelain laminates especially unique. They are:
- Placing veneers is a relatively conservative process. - As compared to placing dental crowns, much less tooth trimming is required.
- The way they handle light is similar to natural teeth. - When taken advantage of, this property can result in laminates that give an exceedingly life-like appearance. And one unsurpassed by any other type of dental restoration.
- Due to their ceramic surface, they offer superior stain resistance.
a) Placing veneers is a comparatively conservative process.
Dental crowns and veneers can both be used to create the same cosmetic end result. But they differ greatly in scope.
A veneer just covers the front side of a tooth.
- A veneer just covers the front side of its tooth.
- A crown fully cups over all sides of the tooth on which it is placed.
That's a really big difference. And it dictates how much tooth trimming is required when each of these respective types of restorations are made.
With veneers ...
In their most conservative form, porcelain laminates usually have a thickness that runs on the order of .5 to .6mm. (That's less than the thickness of a credit card.)
So when one is made, the side of the tooth it is placed on (the front side) only needs to be trimmed back by about that much.
With dental crowns ...
The required thickness for a porcelain crown typically runs on the order of around 2mm, which is about 4 times thicker than a veneer.
And when one is made its tooth needs to be trimmed by that much. Keep in mind however that that means on all of its sides, not just the front one. That's because a crown fully encases the tooth on which it is placed.
Overall, that's a very significant difference. (The Edelhoff study mentioned above determined that preparing a tooth for a crown typically involves removing 63% to 76% of its structure vs. 3% to 30% for porcelain veneers).
And since it's usually the goal of a dentist to preserve as much of a tooth's structure as possible, veneers are typically their preferred choice for making changes if the patient's situation allows.
(This page shows examples and explains differences between crowns and veneers in greater detail.)
b) Veneers 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.
3) In comparison, when dental bonding is used ...
Just so you know, laminates for teeth can also be made out of dental composite (tooth bonding). And there's a big difference between it and porcelain. It's only semi-translucent.
That means when light strikes the surface of a composite veneer it's mostly reflected off it's front surface (there's much less light penetration as compared to what's possible with various types of porcelain). And for that reason, this kind of laminate typically has difficulty in creating a truly life-like appearance.
(We compare this and other aspects of porcelain vs. composite veneers on this page.
c) A porcelain veneer's surface resists staining well.
Another advantage that ceramic veneers offer is that their impervious glass-like surface resists staining well.
This is in comparison to veneers made using materials such as bonding (dental composite). These laminates typically will stain or discolor over time (see bonding link above).
(It does bear mentioning that the cement used to hold a porcelain veneer in place may tend to stain, thus spoiling its appearance. Use the link for more detailed discussion about this potential complication.)
How natural your veneer appears will depend on its construction method.
Specifically how lifelike a porcelain veneer can or will look will in part depend on the way it's been fabricated.
There are generally 3 different processes that can be used, and especially in the case where the appearance of your veneer is critically important, you should quiz your dentist about which one will be used and how this choice might affect how natural the results of your case will end up looking.
Methods of veneer construction:
1) 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.
2) Heat-pressed ceramic. -
With this process, the porcelain is melted and then pressed into a mold.
As a shortcoming of this technique, only one color of porcelain can be used. And this is a problem because the shade and degree of translucency of different regions of a tooth typically varies.
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 the latter technique is used, the end result can be quite life-like.
3) Milled (CAD/CAM) ceramics. -
This is a process where CAD/CAM technology is used to grind the veneer out of a single, uniform-color block of synthetic porcelain.
Like above, the uniformity of color 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.
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 for porcelain laminates.
That's because veneers do not strengthen teeth, they only improve their appearance. And as mentioned above, if the tooth on which one has been placed is not rigid enough to prevent flexure, it may ultimately crack or break.
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.
- 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.
- 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: 1) Tooth wear or trauma. 2) The placement of previous dental restorations. 3) Erosion - Tooth wear caused by an exposure to acidic foods and beverages, regurgitation of gastric acid, etc...
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 for porcelain veneers.
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 veneers by a factor of 8.
As a measure against fracture, construction using a comparatively stronger type of "porcelain" can help (such as: aluminium oxide, lithium disilicate, zirconia). The trade-off is that restorations made using these ceramics characteristically have a comparatively less lifelike appearance (similar to our description of dental bonding above).
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