Related Experiment Video
Updated: Mar 21, 2026

Single-stage Dynamic Reanimation of the Smile in Irreversible Facial Paralysis by Free Functional Muscle Transfer
Published on: March 1, 2015
Dynamic smile evaluation in different skeletal patterns
Objective:
To evaluate dynamic smile in different skeletal patterns and to correlate vertical smile parameters with the underlying causative factors.
Materials And Methods:
A total of 150 participants ranging in age from 16-25 years were selected and divided into one of three groups-horizontal, average, and vertical skeletal pattern-using the following three cephalometric parameters: SN-MP, FMA, and Jarabak ratio. Videographic records of smile were obtained, and measurements were recorded and analyzed at rest, including upper lip length, and during smile, including maxillary incisal display, interlabial gap, intercommisural width, change in upper lip length, and smile arc. Differences among the three groups were subjected to two-way analysis of variance and post hoc and chi-square tests for smile arc. Correlations between vertical smile variables and vertical skeletal (N-ANS, N-Me) and dental cephalometric measurements (U1 to palatal plane) were also investigated.
Results:
Vertical parameters were significantly increased in the vertical pattern when compared with the horizontal pattern, ie, upper lip length (P < .01), maxillary incisal display (P < .001), interlabial gap (P < .001), and change in upper lip length (P < .001), whereas intercommisural width was significantly decreased in vertical pattern when compared with the horizontal pattern (P < .001). Flat smile arc was seen more frequently in the horizontal pattern. Positive correlations were found between the N-Me, U1-PP, and change in upper lip length with vertical smile parameters.
Conclusions:
Different skeletal patterns exhibit their characteristic smile features. Upper lip length is not responsible for increased incisal display during smile. Increased incisal display during smile is more closely associated with upper lip elevation than vertical skeletal and dental factors.
Related Concept Videos
Muscles for Facial Expressions
Assessment of Airway, Skin Color, and Use of Accessory Muscles
Introduction
The initial evaluation of a patient's respiratory system...
Relaxation of Skeletal Muscles
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open....
Tooth Anatomy
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or...
Assessment of the Mouth
Mouth Inspection
The inspection begins with visually examining the mouth for symmetry, color, and size.
Introduction to the Skeletal System
Components of the Skeletal System
Bone, or osseous tissue, is a hard connective tissue that forms an internal support structure for the human body. Bones shield vulnerable organs and soft tissue from external forces. For example, the vertebral bones protect and support the spinal cord.
Cartilage, a semi-rigid connective tissue found in regions such as...

