Crusty scabs on female dogs ear

Could this be because of ear mites or ear margin hyperkeratosis?

Hello - this does indeed look as though it could be ear margain hyperkeratosis, which is a symptom and not a disease.  Other examples of symptoms might include a rash or a squinty eye or a limp, or not getting up, or not eating.  A symptom is a sign that you can see, which could have any number of causes (to take the limp; it could be arthritis, a broken bone in the foot, a sprained tendon or ligament, skin disease, a wound, a corn, a foreign body or an ingrowing toe-nail).   This probably all sounds quite obvious as you are reading it, so let's get back to the point. The reason I'm making a meal of this difference is, that hyperkeratosis also has a long list of possible causes, so even if it turns out to be hyperkeratosis, identifying the symptom tells you nothing about the cause.   Your vet has some detective work to do.....   more to follow

What can cause thickening at ear margins?  Always be aware of public health concerns when dealing with ear-tip disease, for example Ringworm.  Another parasite might be Scabies or even Demodex mites.  However, causes of hyperkeratosis specifically might include a heretidary tendency not to shed skin cells but to cling on to them at the ear margins.  As well as genes, this can be caused by the hormonal environment and I would worry about changes to the ovaries in cycling females, or early signs of Cushings disease or Addisons disease.  These last three reasons can become serious, even life-threatening and crusty ears is an early-warning sign of them.  Therefore, although it often seems very innocuous at the outset, we would strongly recommend letting your vet triage (assess the urgency of) and then assess the patient in context.