What characterizes an aphthous ulcer?

An aphthous ulcer is characterized as a shallow ulcer that is not associated with any infection. These ulcers are typically small, painful lesions that occur on the soft tissues of the mouth, such as the inner cheeks, tongue, and the base of the gums. Unlike deep, infectious ulcers, aphthous ulcers are usually self-limiting and do not result from an underlying infectious process. They may be triggered by factors such as stress, hormonal changes, or certain dietary items, but they are not caused by bacteria or viruses, which differentiates them from infections. Their shallow nature and the absence of infection are key hallmarks that define aphthous ulcers, making option B the correct characterization.