Various studies have shown that too tight (tighter than in the image above) nosebands/cavessons will compromise horse welfare. Tight nosebands also press the cheeks into the sharp edges of the teeth, often causing discomfort and sores inside the mouth. Be smart. Check your nosebands. And it’s not the crank noseband (as in the picture) that is the problem, it’s how tight it’s fastened.
McGreevy, Paul, Amanda Warren-Smith, and Yann Guisard. “The effect of double bridles and jaw-clamping crank nosebands on temperature of eyes and facial skin of horses.” Journal of Veterinary Behavior: Clinical Applications and Research 7.3 (2012): 142-148.