The term "asymmetry" is used to make reference to the dissimilarity between homologous elements, altering the balance between structures. Facial asymmetry is common in the overall population and is often presented subclinically. Nevertheless, on occasion, significant facial asymmetry results not only in functional but also esthetic issues. Under these conditions, its aetiology should be carefully investigated in order to achieve an adequate treatment plan. Subsequent asymmetry treatment depends on patient's age, the aetiology of the condition and on the degree of disharmony, and might include from asymmetrical orthodontic mechanics to orthognathic surgery. Whenever the degree of asymmetry is more severe, the condition is typically rendered noticeable, which negatively affects one's facial and smile esthetics. Congenital changes associated with facial asymmetry comprise (among others): 

• facial clefts
• oculo auriculo vertebral spectrum 
• hemifacial microsomia
• neurofibromatosis
• anatomical changes at the base of the skull 
• congenital muscular torticollis.