Who hath aching teeth, hath ill tenants.

The proverb imagines teeth as occupants of the mouth. When they ache, they become troublesome tenants whose presence is hard to ignore.

Its humor comes from making a private physical discomfort sound like a household problem. The complaint is about the painful teeth, not about actual tenants.

Use it as a wry response to a complaint about toothache when a playful comparison is welcome. The archaic phrasing gives it an old-fashioned tone and would be out of place as medical advice.