Also known as abduction gingival space, it is usually filled by gingival papilla, which can protect alveolar bone and prevent horizontal food impaction.

There is a gap around the contact area between two teeth, which is called gingival interproximal space. It is like a triangular gap with the alveolar ridge as the bottom and the adjacent surfaces of two teeth as the waist. The midline of upper central incisor: the midline of face; Midpoint of nasal root; The labial arch is higher. The midline of the upper central incisor coincides with or is parallel to the midline of the face. The inclination of the midline of the upper central incisor is one of the main problems. Note: when taking a head photo, the head and neck must be perpendicular to the horizontal line of the shoulder.

Smile line: the smile line is perpendicular to the midline of the face; The smile line is lower than the corner line and bends downward parallel to the curve of the lower lip; The anti-smile line (wear) shows that the position of the upper central incisors in the elderly is "M", and the rest position shows1~ 3 mm; E-position, the position display of the smiling edge >; 8mm, can expose part of the gingival margin and gingival papilla. When the cutting edge is relaxed, it should be about 1mm just behind the wet-dry boundary of the lower lip, which can best reflect the beauty and function when designing the cutting edge.

Long axis inclination: each tooth inclines to the midline; The inclination of the long axis of central incisor, lateral incisor and canine gradually increases. Abduction gap of incisors: the abduction gap between central incisors near central incisors and distal incisors of canines gradually increases; Increasing the abduction gap of distal incisors can reduce the fracture probability of porcelain veneers (especially distal incisors)

Contact point (area) of adjacent surface of incisors: adjust the tooth shape according to the contact area; 50/40/30 standard: the height of the contact area of the central incisor is 50% of the height of the central incisor; The height of the contact area between central incisors and lateral incisors is 40% of the height of central incisors. The height of the contact area between lateral incisors and canine teeth is 30% of the height of central incisors; . Naturally, a gradually increasing abduction gap is formed.