Clinical differences between sequential injection and single injection of botulinum toxin type A for curing masseteric hypertrophy

Objective To study the clinical effects of different injection methods of Botulinum toxin type A for curing masseteric hypertrophy. Methods A total number of 36 patients with idiopathic masseter hypertrophy in our hospital between December 2012 to December 2014 were enrolled into this study.15 patients received single injection and 21 patients received sequential injection group.By using the repeated measurement design,the masseter thickness of all subjects were detected and compared at the time of 1,3,6,9,12,18 months after the injection. Results The masseter thicknesses of the two groups were different after the injections,and the differences was statistical significant(F=38.91,P<0.001).For the single injection group,the masseter thicknesses was(14.80±0.18)mm before the injection,and decreased to (11.21±0.18)mm,(10.54±0.19)mm,(9.62±0.18)mm,(10.21±0.22)mm,(12.63±0.18)mm and(13.79±0.35)mm at the time of 1,3,6,9,12,18 months after the injection,respectively,the difference was statistical significant(F=955.59,1 503.4,2 239.03,1 183.99,384.87 and 70.39,respectively,P<0.001).For the sequential injection group,the masseter thicknesses was (14.93±0.18)mm before the treatment,and decreased to (11.41±0.16)mm,(10.62±0.18)mm,(10.00±0.18)mm,(9.50±0.25)mm,(9.33±0.25)mm and (10.44±0.24)mm at the time of 1,3,6,9,12,18 months after the injection,respectively,the difference was(F=2 184.58,3 724.88,1 610.48,3 105.48,3 665.60 and 1 948.86,respectively,P<0.001). Conclusion The sequential injection of Botulinum toxin A for 18 months has better clinical effects than the single injection of Botulinum toxin A in the treatment of masseteric hypertrophy.