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[The use of botulinum toxin type A in masseter muscle hypertrophy: long-term effects and lasting improvement].

OBJECTIVES
In this study, we aimed to evaluate the long-term efficacy of botulinum toxin A injection in reducing the masseter muscle thickness.


PATIENTS AND METHODS
Between 2007 and June 2008, we retrospectively analyzed the data from 28 patients (21 females, 7 males; mean age: 25.5±4.5 years; range 20 to 46 years) with benign masseter hypertrophy treated with botulinum toxin A injections. All patients were diagnosed by the morphometric analysis of the masseter muscle. The injections were repeated intermittently every six months and totally for six times. The patients were recalled and the last measurement was performed at a mean follow-up of 13.2 months.


RESULTS
The values obtained following consecutive injections were compared and a statistically significant reduction in thickness of masseter muscle thickness after every single injection was found (p<0.001). The final measurement following treatment discontinuation revealed that this reduction was long-lasting.


CONCLUSION
Botulinum toxin A injection is a safe and long-term effective therapy for the masseter muscle hypertrophy.