The shape and orientation of the tip are influenced by the alar cartilage. Its movement is influenced by the depressor muscle of the nasal septum, and the lifting muscle shared between the upper lip and the nose.
– Tip projection, radix depth, length of the nose
Several rules can be used to calculate the right projection for the tip.
1) The 1 :2 :3 ratio
The tip’s projection (2 on the picture), defined by the distance between the alogenian groove and the cartilage domes, should be two-thirds of the length of the nose (3 on the picture) and should be double the distance between the nasion (the most recessed part of the dip between the nose and forehead) and the inner canthus (1 on the picture).
2) The projection is adequate when 50-60% of the tip is in front of the vertical line from the upper lip, and if it is equal to 60-65% of the nose length.
3) Crumley’s triangle rule: the ideal projection allows us to draw a right-angled triangle where the sides respect the 3: 4: 5 ratios of Crumley’s triangle.
– The rotation
Rotation is defined by the angle of the naso-labial opening which should be between 90°-100° for men, and 95°-110° for women.
For the tip’s rotation-projection, visual illusions should be taken into account: The dorsum’s convexity gives the impression of a plunging tip, even though the naso-labial angle is normal; an exaggeratedly concave dorsum will give the impression of excessive rotation.
– Definition rests on characteristics which don’t always fit well together.
1) Visualisation of the cartilaginous alar reliefs when the skin is insufficiently thick to hide them.
2) Subtle depression of the upper-tip, automatization of the tip when its projections goes slightly beyond that of the dorsum.
3) Double lobulo-columella break which makes the apical lobule a clearly distinct element of the columella.