Buccal corridor
-an intermediate buccal corridor is considered as most esthetic. -a narrow buccal corridor is considered as more esthetic than a wide buccal corridor (higher than 16% (13,44,45).
Maxillary central incisors width/height ratio and assymetry
-the esthetic ratio width/height of the central maxillary incisor varies between 75 and 85% (26). -a smile is considered as unesthetic if the central incisors have assymetrical incisal edges (4).
Midline and tooth angulation
-a midline deviation greater than 2mm is considered as unesthetic (46) -an angulation greater than 3,5° is notable to laypeople (47)
Gingival exposure -according to various studies, a smile is considered as unesthetic if the gingival margin exposure exceeds 2 to 3 mm (39,48).
Gingival margin
-gingival margin difference between the central incisors and the maxillary canines varies between 0 and 1mm(49). -lateral incisors have a gingival margin of 0.5mm below the central incisor (50).
Smile arc
-depends on the vertical positioning of the maxillary incisors. -a smile is considered as esthetic if the incisal edges of the maxillary incisors are below the cuspid tip of the canines (41,51).
Lips and teeth positionning
-voluminous lips are considered as most esthetic (26) -maxillary incisal edges must touch the lower vermilion of the lip (52).
Tooth color and anatomical shape (see text above)
Anterosuperior teeth ratio (see text above)
Diastema (see text above)