At rest, she brings her head into a “swan” position (very similar to the horse in the picture) to compensate for her limited field of vision underneath her chin.
In this head position, the lower jaw slides forward, misaligning the upper and lower teeth arcades. This affects the horse’s ability to chew and grind its feed. Consequently, the filly was not eating well, and she had difficulties gaining weight and condition.
A dental examination showed that her first lower premolars were overgrown and had long hooks, which were digging into the upper premolars and had wore them down to the gum. The hooks were starting to penetrate the soft tissue.
To make the filly more comfortable, the hooks were filed down, and the lower premolars reduced to allow the upper permanent teeth to erupt. I recommended a check every four months to assess the condition of the mouth.