Evaluation and selecting indications for the treatment of improving facial morphology by masseteric injection of botulinum toxin type A.

Few reports exist on effective methods of evaluating the effects and selecting indications for the treatment of improving facial morphology by masseteric injection of botulinum toxin type A. The method for selecting indicative factors, as determined by the change of masseteric area volume at a standard frontal view when tightly clenching teeth, was used in this study. Patients with varying masseteric area volume were randomly enrolled. Bilateral masseteric muscles were treated with multi-point percutaneous intramuscular injections of botulinum toxin type A, 30-50 u for each side. Changes in facial appearance and satisfaction of patients were observed and standard frontal view photographs were taken pre-treatment and 2-3 months post-treatment. Following this, the anterior facial height(FH), bizygomatic facial width (FWz) and intergonial width (FWg) were measured from the photographs. The indices of FH/FWz and FWg/FWz were calculated and analysed. The results showed that the volume of masseteric area was reduced and the facial morphology was improved at 2-4 weeks post-injection, with maximum reduction at 2-3 months post-injection. All of the 32 patients were satisfied with the clinical effects. The pre-treatment and post-treatment values of FH/FWz were 0.8309±0.0423 and 0.8331±0.0382, respectively, and FWg/FWz values were 0.8281±0.0209 and 0.7925±0.0206 (P<0.01), respectively. In conclusion, the appropriateness of masseteric injection of botulinum toxin type A for improving facial morphology can be determined by the changes in masseteric area volume at a standard frontal view of tightly clenched teeth. In addition, the facial index of FWg/FWz can be used to evaluate the treatment.