The short answer: a smile looks natural when the shape, color, translucency and proportions of the teeth suit each other and your face. Whiteness is only one of these, and the brightest shade is not always the most natural.

Shape

The outline of each tooth, rounder or squarer, the corners at the biting edge and the texture of the surface all affect how light falls on the teeth. Teeth that are all identical tend to look artificial; small differences between neighbors look natural.

Color

Tooth color has three parts: hue (the shade, slightly yellow or gray), value (how light or dark it is) and chroma (how strong the color is). Value is the most noticeable. A shade lighter than the rest of your teeth, or than your features suit, can look out of place. If whitening is planned, it is done first, so new restorations can be matched to the result.

Translucency

Natural front teeth let some light through, especially near the biting edge. A restoration that is too opaque can look flat even when its shade is right; the material and its thickness affect this. The materials are compared in types of veneers.

Proportion

The width and length of each tooth, and how the front teeth relate to each other, shape how a smile reads. Proportion rules, such as the "golden proportion", are guides rather than laws. Tooth sizes and proportions differ from person to person, so a plan starts from your own teeth, lips and face rather than from one ideal ratio. The studies listed in the sources describe the groups they measured; they are not a standard for everyone.

The frame: lips, gums and face

Teeth are seen with the lips and gums around them: how much tooth shows at rest and when you smile, the line of the gums, the center line of the face, and the space at the corners of the smile. A change that looks right on one tooth is judged against all of these.

Comparing photographs

Photographs only compare fairly when the light, the angle and the framing are the same. A photograph alone is not enough to judge the quality of the work or how it functions, and it does not predict a result for someone else.

Questions patients ask

Do I have to change all my teeth? No. A plan can be one change, or several brought together; see bonding or porcelain veneers.

Is whiter always better? No. The most natural result usually matches your other teeth and your features.

Read more about smile design, teeth whitening and gum contouring.

Sources