Table 1 Aesthetic variables examined

Gingival smile

The amount of gingival shows above the central incisor crowns when smiling. More than 3mm is generally considered unattractive.

Maxillary arch midline discrepancy

The relationship of the maxillary dental midline (measured between the central incisors) to the midline of the face, defined by the center of the philtrum. By definition, the ideal was considered to be 0 for this variable.

Buccal corridor fill

The amount of dark space displayed between the facial surfaces of the posterior teeth and the corners of the mouth calculated as the total dark space on both sides of the mouth as a percentage of the total smile width. It can be absent (0 %), normal (1-13 %), wide (14-26 %).

Gingival margin discrepancy

The difference in the vertical height of the gingival zenith of the central incisor to the lateral incisor. The gingival margins of the maxillary central incisors and canines should be symmetric and in a more apical position compared to those of the lateral incisors.

Hygiene

Poor oral hygiene (dental plaque on the teeth). Plaque is a yellow sticky film that forms on the teeth and gums and can be seen at gum margins of teeth with a food dye.

Gum recession

The exposure in the roots of the teeth caused by a loss of gum tissue and/or retraction of the gingival margin from the crown of the teeth.

Diastema

Open spaces between the upper incisors.

Dental crowding

The dental arch length is less than the mesial distal width of the teeth intended to occupy it. Dental crowding occurs when the space required for the correct alignment of the teeth exceeds the space available in the dental arch. Crowding is classified to mild (2 – 3 mm), moderate (4 – 6 mm), severe (7 – 10 mm) and extreme (>10 mm).

Protrusion of anterior teeth

Increased incisal profile in the anteroposterior direction. 2-3 mm is the normal horizontal overlap of the incisors.

Incisor midline discrepancy

The relationship of the maxillary central embrasure to the mandibular central embrasure. By definition, the ideal was considered to be 0 for this variable.

Hypodontia

A usually congenital condition of having fewer than the normal number of teeth. It is the developmental absence of 1 or more teeth.

Anterior teeth colour

Abnormal tooth color, hue or translucency. External discoloration is accumulation of stains on the tooth surface. Internal discoloration is due to absorption of pigment particles into tooth structure.

“Golden proportion”

A ratio of front teeth crown width and height. According to the golden proportion, the relationship between the maxillary central and lateral incisors and the canine should be as follows:1,62:1:0,62.

Occlusal cant

The divergence of the occlusal plane from the horizontal axis, as seen when smiling. By definition, the ideal is considered to be 0° for this variable.

Convex occlusal plane

Relationship between the curvature of the incisal edges of the maxillary anterior teeth and the curvature of upper border of the lower lip. As a rule, the incisal plane, when observed from the front, has a convex curve that follows the natural concavity of the lower lip during smiling.

Flat occlusal plane

Relationship between the curvature of the incisal edges of the maxillary anterior teeth and the curvature of upper border of the lower lip is not parallel with flat maxillary incisal curvature to the upper border of lower lip.

Reversed curvature of occlusal plane

Relationship between the curvature of the incisal edges of the maxillary anterior teeth and the curvature of upper border of the lower lip is not parallel with reverse maxillary incisal curvature to the upper border of lower lip.