There's no more natural-looking type of crown.
Due to the life-like translucency of the materials from which they're made, all-ceramics can be the most aesthetically pleasing of all of the different types of dental crowns. And for this reason, they often make an excellent choice for restoring front teeth.
Not all all-ceramics can make this claim.
It's important to know that some types of all-ceramic crowns are much better than others in their ability to closely mimic the look and luster of natural teeth. This is due to both the type of ceramic and fabrication method used in their construction.
- At one end of the spectrum lies those crowns whose full thickness has been crafted by hand by combining multiple layers of porcelain.
- Since each one can be different in terms of shade or level of translucency, the restoration can be given a very life-like appearance. (Unfortunately, due to both the technique involved and the materials used, these types of crowns are comparatively brittle.)
- At the other end of the range lies those crowns milled from a single homogeneous cube of ceramic. In this case, the result is one where the restoration just has one uniform color. And that means it really can't mimic the normal shade and translucency variations found in natural teeth.
The solution.
As a compromise, nowadays all-ceramics for front teeth are typically constructed in a fashion where those portions of the crown that aren't readily visible are premade (milled, pressed or cast), using ceramics that are generally less natural-looking but have better physical properties. The front surface of the restoration is then crafted by hand, by adding on individual layers of porcelain.
Doing things this way provides a way where the crown can be given great characterization, and also better mechanical properties (such as greater strength). But you can't just assume that this is the way the crown for your front tooth will be constructed. You absolutely have to ask.
DISADVANTAGE
Concerns about strength and longevity.
Generally speaking, porcelain-fused-to-metal and especially all-metal crowns can be considered to be stronger types of restorations.
That means in the back of the mouth where substantial chewing forces are routinely generated, placing an all-ceramic might not make the best choice. (Your dentist's judgment will be required on this point.)
In the front of the mouth, crown strength is less of an issue and easily out weighed by the superior aesthetics that an all-ceramic restoration can typically provide.