The complex smile is considered the rarest type of smile.
This smile involves the coordinated activation of three distinct muscle groups associated with smiling: the zygomatic major, the orbicularis oculi, and the levator labii superioris.
The zygomatic major muscle pulls the corners of the mouth upward, while the orbicularis oculi muscle contracts to create the characteristic "crinkle" around the eyes, and the levator labii superioris muscle lifts the upper lip.
This complex interplay of muscles creates a genuine, expressive, and visually striking smile that is often associated with genuine happiness and amusement.
The cuspid smile is another uncommon smile, seen in only about 2% of the population. This smile is characterized by the prominence of the canine teeth, creating a more prominent, almost "feline" appearance.
While the cuspid smile is not as rare as the complex smile, it's still significantly less frequent than other smile types, such as the commissure smile, which is the most common.
