The rarest type of smile is the complex smile.
This smile is unique because it involves the near-simultaneous contraction of three distinct muscle groups: the levator muscle (raising the upper lip and corners of the mouth), and the depressors of the lower lip. This coordinated muscle action results in the exposure of both the upper and lower teeth. It's considered rare, with only an estimated 2% of the population exhibiting this specific smile pattern. [1, 2, 3]
Several sources describe the complex smile and its rarity:
- Simultaneous Muscle Activation: The complex smile stands out due to the simultaneous activation of the levator muscles of the upper lip and the depressor muscles of the lower lip. This coordinated movement is what distinguishes it from other smile types. [1]
- Low Prevalence: The low prevalence rate of only 2% in the population underscores the rarity of this specific smile pattern. [1, 2, 3]
- Unique Aesthetic: The simultaneous exposure of both upper and lower teeth contributes to the unique aesthetic quality of this smile type.
While other smiles might be considered unusual or uncommon based on individual features, the complex smile’s distinct musculature and low prevalence firmly establish it as the rarest among smile classifications.
