Abstract

Objectives: Investigating the prevalence of unilateral hypertrophy of the masseter muscle, its effect on the asymmetry of the lower face and the effect of reducing its thickness on the symmetry of the face using botulinum toxin with ultrasound and investigating its consequences with the help of eye tracking in 18 patients Introduction: Asymmetry in the face is one of the things that can have a destructive effect on people's attractiveness. symmetry has been proposed as a ‘‘certificate of health’’ in a mating perspective. Lower face asymmetry can be influenced by factors such as Size of the bony mandible , Mass of the masseter muscle , Volume of subcutaneous fat tissue. The volume and width of masseter muscle is determined especially by the biting force, chewing habits, diet and etc. so far, there has been no study on the prevalence of unilateral hypertrophy of the master muscle among patients. Materials / method: 435 clients of a beauty clinic were randomly examined for bilateral and unilateral hypertrophy of the master muscle with ultrasound. The distance of the mandibular gonion to the oral commissure was investigated before and 4, 8 and 16 weeks after botulonium toxin injection. The effect of asymmetry reduction on eye tracking patterns was evaluated. Results: The prevalence of bilateral and unilateral hypertrophy was 35 and 8%, respectively. The distance between the oral commissure(OC) and the mandibular gonion(MG) was significantly higher on the dominant side than other side. The amount of observer's gaze on the lower face area was significantly reduced in 60% of cases. The noteworthy point is that the decrease in the distance between OC and MG was more than the decrease in muscle thickness, which indicates that the jaw deviates in the direction where there is hypertrophy. Conclusion: This study, by examining the prevalence of bilateral and unilateral hypertrophy of the master muscle, the effect of unilateral muscle hypertrophy on asymmetry, and the change in the fixing eye pattern before and after botulinum toxin injection, provides new evidence to aesthetic doctors in the approach to lower face asymmetry.