When assessing an aesthetic smile, the size of the teeth, their proportions to one another, gum levels and their relationship with the lips matter as much as tooth colour. The "golden proportion" is one of the concepts often referred to in this assessment; however, it is not a rule on its own but a guiding measure.
What is the golden proportion?
The golden proportion is a ratio of roughly 1.618 that is considered harmonious in nature, art and architecture. In smile aesthetics it has been used to describe the relationship between the visible widths of the central incisors, lateral incisors and canines when seen from the front. Current approaches, however, accept that this ratio does not suit every face and that it should be applied flexibly according to the person's facial structure.
Other criteria used in smile assessment
- Midline: Whether the midline of the upper front teeth matches the midline of the face
- Tooth length-to-width ratio: The ratio of width to length of the central incisors
- Smile line: Whether the biting edges of the upper teeth follow the curve of the lower lip
- Buccal corridors: The space beside the teeth at the corners of the mouth when smiling
- Gum levels: Symmetry of the gum margins on the front teeth
Gum appearance
How much gum shows when smiling varies from person to person. A smile in which the gums show prominently is called a "gummy smile". Causes include a short or very mobile upper lip, teeth covered too much by the gum, excessive vertical growth of the upper jaw and over-erupted front teeth. Treatment is planned according to the cause, with orthodontic treatment, gum contouring or other methods.
Tooth colour and a natural look
Natural teeth are not a single colour; they are more translucent at the biting edges and darker near the gumline. Very white, uniform teeth can look unnatural. Skin tone, eye colour and age are also taken into account when choosing a shade.
The role of orthodontics
The position of the teeth directly affects gum levels and the smile line. For example, when a deep bite or over-erupted front teeth are corrected orthodontically, the appearance of the gums can also change. This is why aesthetic assessment is often done together with orthodontic assessment.
Digital planning
Digital smile design makes it possible to assess these criteria on photos and digital models. For details, see our article what is digital smile design?
