1. The development of prominent nasolabial folds
2. Flaring of the nostrils
3. Inferior movement of the nasal tip
4. Display of the teeth
5. Pronounced lip movement
6. Squinting of the eyes
The method of smile measurement described by Ackerman et al (1998)
It depends on drawing vertical and horizontal lines on a photograph of an
unstrained posed smile. The vertical lines correspond to the commissures of the
lips, the distal embrasure of the upper canines and the dental midline. The
horizontal lines correspond to the upper border of the upper lip, the lower border
of the upper lip, the incisal edge of the right central incisor, the upper border of
the lower lip and the lower border of the lower lip. The following measurements
can then be obtained:
A. maximum upper incisor exposure
B. upper lip drape
C. lower lip to upper incisor
D. interlabial gap at rest and smiling
E. commissure (smile) width
F. smile index: The smile index was described by Ackerman et al (1998). It is
defined as follows:
Smile index =Intercommisure width/Interlabial gapon smiling*100. The lower the
smile index, the less youthful the smile appears (because there is relatively less
G. frontal intercanine width the intercanine width as measured from a full-face
H. right and left buccal corridor: the buccal corridor is measured from the mesial line
angle of the maxillary first premolars to the inner aspect of the commissure
I. Buccal corridor ratio:
Smiling component factors
1. Lip factors
The lip line
The smile arc
2. Dental factors
Teeth proportion and symmetry
3. Gingival factors
1. Lip factors
A. The lip line
• It is the vertical relationship between the upper lip and the maxillary dentition
• Females, on average, show 1 mm of gingival smile line and males show –1 mm.
• A number of factors can influence the lip line :
1. The type of smile. posed smile or spontaneous smile
2. Activity of the upper lip. Excessive elevation, also termed hypermobility,
3. Vertical maxillary height.
4. Vertical dental height.
5. Incisor inclination retroclination increases tooth display.
6. Gingival height
Botulinum toxin type A (Botox): Many patients with excessive gingival display
have excessive muscle contraction.
The use of Botulinum toxin A (BTX-A) to reduce gingival display is described by
BTX-A blocks neuromuscular transmission by binding to receptor sites on motor
or sympathetic nerves,
It therefore produces partial chemical denervation of the muscle . Also it has a
filler action to increase the intramatrix space and muscle size.
The muscles injected were the elevators of the upper lip –levator labii superioris,
alaeque nasi, and zygomaticus minor.
B. Buccal corridors
The buccal corridor is the space between the buccal surface of the premolars and
molars and the angle of the mouth during smiling.
Ideally, this should be minimal
Buccal corridor ratio:
The buccal corridor is dependent on a number of factors:
1. Anteroposterior maxillary position.
2. Arch width and arch form
3. The vertical dimension. There is a reported inverse relationship between the
vertical dimension and the buccal corridor area.
4. Molar inclination.
5. Inter-commissure distance during smiling. The greater this distance, the greater
the buccal corridor width.
C. The smile arc
The smile arc was first described by Frush and Fisher in 1958.
It is the relationship between the curvature of the maxillary incisal edges and the
curvature of the lower lip in the posed smile.
A number of factors are important in determining an ideal smile arc relationship
1. The maxillary occlusal plane angle,
2. The curvature of the lower lip
3. Tooth length.
4. Age that cause flattening of the incisal edge and in-consonant smile arc
5. Poor orthodontic treatment,
Parekh et al (2006) investigated the attractiveness of smile arc and buccal corridor
width and found that excessive buccal corridors and smile arcs were rated less
attractive by both orthodontists and lay persons. In addition, flat smile arcs
decreased attractiveness regardless of the buccal corridor width.
Smile arc can be achieved by differential bracket positioning.
2. Dental factors
A. Teeth color
B. Teeth proportion and symmetry
The width of the central incisor should be approximately 80% of its length.
Lateral incisor where the space created is 0.618 of the width of the central incisor.
C. The midlines
The facial midline is constructed by joining a line between soft tissue nasion and
the midpoint of the upper lip. Ideally, the maxillary dental centreline should be
coincident and parallel to this.
Midline discrepancies are not readily noticed unless they are 4 mm off.
D. Tooth angulation
Where teeth have tilted and are at an abnormal angulation, the level of the incisal
edge may not be at the correct relationship to the facial axis of the clinical crown
due to incisal edge wear. Kokich (1993).
Mesiodistal angulation of the midline is more noticeable than absolute
E. Tooth inclination
The inclination of the upper canines and premolars should be upright (zero
inclination). Canines with either positive or negative buccal root torque look
unattractive. When viewed from a sagittal direction, increased tooth inclination
may decrease the amount of incisor display; conversely, decreased inclination
may increase incisor display due to lengthening of the tooth as the crown is
3. Gingival factors
Embrasures, connectors and contacts
A. Embrasures are the spaces between the incisal edges of adjacent teeth above
the contact pint.
Ideally, embrasures should gradually increase in size from the maxillary central
incisors to more distally in the arch
Toothwear can result in elimination of embrasures, which contributes to an aged
B. Connectors are the areas between adjacent teeth where they appear to meet
below the contact point.
Between the central incisors the connector should measure 50% of the height of
the central incisor crown, between the central incisor and lateral incisor it should
measure 40% of the height of the central incisor and between the lateral incisor
and canine it should measure 30% of the height of the central incisor. This has
been terms the 50–40–30 rule.
A poor connector relationship can result from incorrect angulation of adjacent
teeth and/or a triangular tooth shape. The latter can be corrected by interproximal
enamel reduction followed by orthodontic space closure.
C. Gingival contour
Kokich and Spear (1997) give four criteria to evaluate during orthodontic
• the gingival levels on contralateral teeth (e.g.: right lateral incisor and left lateral
incisor) should be the same
• the height of the gingival contour on the lateral incisors should be very slightly
lower than on the central incisors and canines
• the height of the gingival contour of the central incisors and the canines should be
D. Gingival levels
Ideally, the gingival margins of the maxillary central incisors and canines should
be level while those of the lateral incisors should lie 1 mm more incisal
A number of factors can produce gingival marginal discrepancies:
1. Periodontal disease
3. Ankylosis in a growing patient
4. Severe crowding
5. Delayed maturation of the gingival margin.
Treatment of gummy smile