Smile Designing in

Orthodontics

Introduction

The smile is formed in 2 stages:

a) Raising the lip to the nasolabial fold.

b) More raising of the lip and the fold by

the lip elevator muscles.

The smile is framed by the soft tissue

drape (lip curtain).

The display zone of the smile:

- The area of the smile framed by the

upper and the lower lip.

- Composed of teeth and gingival

scaffold.

The display zone

Types of smile

1) Social (Posed) & Enjoyment (Unposed)Smile:

A) Social (Posed) smile:- Used as greating.- Voluntary, unstrained, static.- Moderate contraction of lip elevator

muscles.- Lips are apart. Teeth and gingival scaffold

are displayed.

B) Enjoyment (Unposed) smile:

- Elicited by laughing or great pleasure .

- Involuntary, dynamic.

- Maximum contraction of lip elevator &

depressor muscles.

- Full expansion of lips. Maximum display of

anterior teeth and gingiva.

2) Commissure, cuspid and complex smile:

A) Commissure (Monalisa) smile:

-Action of zigomaticus major muscles.

- Outer commissures are drawn outward and

upward then the upper lip is gradually

elevated.

B) Cuspid smile:

* Action of all upper lip elevator muscles

* The lip is elevated uniformly

C) Complex smile:

* Action of upper lip elevators & lower lip

depressors

* Upper lip is elevated, lower lip is lowered

3) High, average and low smile:

A) High smile:

Complete display of upper incisors& gingival

tissue.

B) Average smile:

75-100% display of upper incisors ( the most

attractive).

C) Low smile:

Less than 75% display of upper incisors.

Smile capture methods

1) Photography:

* Difficult to standardize.

* Difficult to repeat social smile exactly.

2) Digital videography:

* Allows capture of speech, oral and

pharyngeal function and smile at the same

time.

Macroesthetic elements of smile design

1- Facial midline

* The most important aspect of smile design.

* How to locate the facial midline?

Nasion Base of filtrum

* One goal of orthodontic treatment is to achieve

coincident upper and lower midlines, both with

each other and with the facial midline. This serves

both a functional and an esthetic purpose.

Facial midline

* Canted midline:

The dental midline is at angle to the facial midline.

Axial midline angulations of ten degrees or more are

not accepted and should be assessed for orthodontic

treatment.

* Mandibular midline is less important than maxillary

one. The narrowness and uniform sizes of lower

incisors make visualization of their midline more

difficult, especially when seen in relation to soft

tissue landmarks.

Canted midline

2- Incisal embrassures

* The spaces among incisal edges of teeth.

* Increases in size, when progressing away from

midline.

3- Connectors

* The places where adjacent anterior teeth touch.

* 50-40-30 rule:

The ideal connector zone between upper central

incisors should be 50% of the length of the central

incisor.

The ideal connector zone between upper lateral and

central incisor should be 40% of the length of the

central incisor.

The ideal connector zone between upper canine and

lateral incisor should be 30% of the length of the

central incisor.

4- Symmetry

* Regularity in the arrangement of objects.

* Types of symmetry:

A. Horizontal (running) symmetry:

The design shows similar elements from left to

right in a regular sequence.

B. Radiating (bilateral) symmetry:

The design extends from a central point and the left

and right sides are mirror images.

5- Axial inclination of teeth

* The direction of the long axis of anterior teeth.

* Teeth should tip mesially. Tipping increases when

moving progressing away from midline.

6- Shade progression

* Upper centrals are the lightest& brightest teeth in

smile.

* The shade of the upper teeth follows a progressive

pattern based on the distance from the midline.

7- Tooth shape& harmony

* Tooth shape: rectangular, triangular or ovoid.

* Frush& Fisher (SPA factors):

Women round delicate teeth.

Men Square angular teeth.

8- Teeth displayed in the smile

* From upper second premolar on one side to the

contralateral one.

9- Upper lip curvature

* According to the relation of the corner of the

mouth to the center of the lower border of the upper

lip, the curvature can be upward, straight or

downward (least esthetic).

10- Lower lip position

* The relation between the lower lip and the incisal

edges of the upper incisors may be:

a. Slightly covering

b. Touching

c. Not touching

11- Smile line (arch)

* The parallism of upper anterior incisal curve with

the lower lip may be parallel, straight or reverse

(least esthetic).

12- Buccal corridor

* The space between the facial surfaces of posterior

teeth and the corners of the lip, when the patient is

smiling.

* Represented by the ratio (the distance from right

upper first premolar to the left one / the

intercommissural width).

* Minimal buccal corridor is a preferred esthetic

feature, as it results in fullness of the smile.

Buccal corridor

Factors affecting smile1) Aging and smile:

* Aging gradually decreases upper and increases

lower incisor exposure.

Causes:

a. The effects of gravity on upper and lower lip

positions.

b. Attrition of incisal edges of upper incisors.

2) Tooth extraction and smile:

* Extraction of premolars results in narrowing of

the arch width and negative spaces lateral to the

buccal segments Poor smile esthetics.

* Several studies determined that smile esthetics

were the same in both extraction and non-

extraction patients.

3) Oral condition and smile:

* Missing or malaligned teeth impair the smile.

4) Personality and smile:

* Low anxiety is correlated with a more attractive

smile, especially in females.

* The esthetic levels of females smiles are more

correlated to personality than males (Kim et al

1995).

Evaluation of smile in frontal dimension

1- Crown lengths of upper and lower incisors:

* Lip coverage of upper incisors increases with age.

* Low smile line is mainly a male characteristic,

while high smile line is mainly a female

characteristic (Tjan et al 1984).

2- incisor curve and lower lip:

* Types of smile lines:

1- Parallel: The most esthetic type.

2- Straight: Less esthetic appearnce.

3- Reverse: The least ethetic one.

3- Arch form:

* Narrow collapsed arch form results in inadequate

transverse characteristics of the smile.

* Arch expansion reduces the size of the buccal

corridor causing improvement of the transverse

smile dimension.

* If the buccal corridor is obliterated, denture like

smile will result.

4- Transverse cant of maxillary occlusal plane:

* Causes:

1- Differential position and eruption of anterior teeth.

2- Skeletal asymmetry of the mandible, resulting in

compensatory maxillary cant.

3- Differential elevation of the upper lip during smile,

resulting in illusion of transverse cant of the maxilla.

Transverse cant of maxillary occlusal plane

5- Incisor display at rest and at smile:

* Causes of inadequate crown display during smile:

1- Vertical maxillary deficiency.

2- Limited smile area (Large smile index).

3- Short clinical crown height (Lack of tooth

eruption, gingival encroachment or attrition).

Inadequate incisor display

Clinical implications for low smile types:

* Avoid overintrusion of upper incisors in deep bite

cases (Worsens with age).

* Intrude the lower incisors, or extrude posterior teeth

(in young patients with low facial height).

Deep Bite

Clinical implications for high smile types (Gummy

smile):

* What is gummy smile?

2 mm or more of maxillary gingival exposure in full smile.

* Causes:

a) Vertical maxillary excess

b) Increased muscular capacity of the upper lip

c) Delayed passive eruption

* Correction:

1- Orthodontic therapy:

* Intrusion of upper incisors.

* Selective intrusion &restorative techniques.

2- Periodontal therapy:

* Gingivectomy or surgical crown lengthening with

removal of crestal alveolar bone.

3- Surgical therapy:

* Le Fort I osteotomy.

* Muscle detachment from the underlying bony

structures to bring the lip down.

* Myectomy & partial resection of LLS

.

4- The use of botulinum toxin:

* It blocks the release of acetylcholine from the

motor neurons, so it decreases the contractility of

upper lip elevator muscles.

Gummy smile