Schematic diagram of the recommended botulinum toxin injection strategy. (A) An example of botulinum toxin injection dose and sites. The red dot represents the most prominent point of masseter, determined by palpation during clenching; 12 to 16 units of botulinum toxin should be injected into this point in total. The blue dots represent the lower injection points, which should form an isosceles triangle with the red dot; 6 to 8 units of botulinum toxin should be injected into these points, respectively. (B) Enter the skin vertically until the needle tip reaches the periosteum. (C) Retract for approximately 0.25 cm; the needle tip should be in the center of the deep belly of the superficial part of masseter. Half of the dose should be injected into this layer. (D) Further retract for approximately 0.65 cm; the needle tip should reach the center of the superficial muscle belly, the other half of the due dose of a point should be injected into this layer.