Like a round pentagon, incisal diameter > mesio-distal diameter

The neck edge is curved and convex toward the root apex Mesial edge (long, abducted) > Distal edge (short, rounded, oblique to the neck) Mesial oblique edge < distal oblique edge

Cusp: long and mesial, accounting for about 1/3 of the crown length The mesial oblique edge and the distal oblique edge intersect at about 90°

Sharp mesial angle The distal incisal angle is blunt and skewed towards the lingual side

Labial axis ridge is obvious Divide the labial surface into sublabial slopes (small and protruding) Distal labial slope (large, flat, sloping distally and lingually)

Developmental groove: There is a longitudinal development groove on each of the mesiodistal and distal labial slopes, which is longer and more significant than the central incisor.

High point of appearance: on the labial axial ridge at the junction of middle 1/3 and cervical 1/3

Like labial surface, slightly smaller, like rhombus

Mesial marginal ridge (narrow, long and straight) > distal marginal ridge (wide and short process) Mesial cusp ridge (shorter) < distal cusp ridge (longer)

The lingual protuberance is obvious (most of the front teeth) - the high point of the appearance

The lingual axis ridge divides the lingual fossa into two parts: distal lingual fossa > mesial lingual fossa

Like a triangle, smaller and more protruding than the incisors

The mesial contact area is close to the mesial incisal angle The distal contact area is slightly farther from the distal incisal angle and is lingual

The crown and root lips are connected without an arc

The cusp is located on the labial side of the long axis of the tooth

Composed of 4 ridges and 4 slopes

Labial view: apical deviation mesial; proximal view: apical deviation labial side of the long axis of the tooth

long narrow pentagon

The mesial edge is long and straight, nearly parallel to the long axis of the tooth, and approximately in a straight line with the mesial edge of the tooth root. Distal margin short and protruding The mesial oblique edge is short and the distal oblique edge is long (1:2)

The cusp is obviously mesial, with an angle greater than 90°

The mesial incisal angle is sharp and the distal incisal angle is blunt. The mesial contact point is high and the distal contact point is low The labial axial ridge, labial cervical ridge, and developmental groove are not as obvious as those of the maxillary canines. High point of appearance: Labial cervical ridge

The lingual axis ridge is not as obvious as the maxillary canines (the fossa is shallow and the ridge is low) Mesiodistal lingual fossa: long, narrow and rounded triangle High point of appearance: lingual protuberance

Like a triangle, The mesial surface is long and flat, contact area: cut 1/3 of the mesial angle, The distal surface is short and protruding, the contact area: the cut 1/3 is slightly far away from the incisal angle, and is biased towards the lingual side The crown and root lips are connected in an arc The cusp is on the long axis of the tooth or on the lingual side

Not as obvious as maxillary canines The cusp of the tooth is obviously more mesial The cusp is located on the long axis of the tooth or on the lingual side distal tongue tilt