Rectangular faces can be caused by:
1) enlarged muscle at the temple areas. (You may feel the muscle buldge at both sides of your forehead when clenching your teeth.)
2) enlarged muscle at both sides of the jawline area
To improve the aesthetics towards the oval face shape, muscle relaxation treatment can reduce their width nd produce a narrower face shape, while cheek augmentation with fillers can be done to increase overall forward projection to reduce the “appearance of widening effect of the rectangle shape appearance.