How can missing or unusually positioned teeth affect speech articulation?

In the context of medicine, speech disorders resulting from structural defects in oral articulators—such as the lips and teeth—are collectively referred to as dysglossia.1

The teeth serve as essential articulators, acting as rigid structures against which mobile organs like the tongue are positioned to modify the airstream and produce speech sounds. When teeth are missing or unusually positioned, the mechanics of articulation are physically limited, which can reduce the overall quality and intelligibility of a person's speech.21

Specifically, abnormal tooth number or placement is a recognized cause of lisping, a type of articulatory disorder. Lisping occurs when the tongue interacts incorrectly with the teeth or palate, such as when the tongue tip protrudes between the front teeth or exerts excessive pressure against them. Because these structural issues directly interfere with the precise configuration of the vocal tract required for clear articulation, they can lead to persistent speech impediments that may require professional correction.3