Bidental consonants are consonants articulated with both the lower and upper teeth. They are normally found only in speech pathology, and are distinct from interdental consonants such as [n̪͆], which involve the tongue articulated between the teeth rather than the teeth themselves. The diacritic for bidental consonants in the extensions to the IPA is the same superscript plus subscript bridge, ⟨◌̪͆⟩. This is used for sounds most commonly found in disordered speech:
People with hypoglossia (abnormally small tongue) may use bidental fricatives for target /s/ and /z/.
There is at least one confirmed attestation of a bidental consonant in normal language. The Black Sea sub-dialect of the Shapsug dialect of Adyghe has a voiceless bidental fricative where other dialects have [x], as in хы [xə] (help·info) "six" and дахэ [daːxa] (help·info) "beautiful". It has been transcribed as ⟨x̪͆⟩, reflecting its value in other dialects, but there is no frication at the velum. The teeth themselves are the only constriction: "The lips [are] fully open, the teeth clenched and the tongue flat, the air passing between the teeth; the sound is intermediate between [ʃ] and [f]". This is better transcribed phonetically as ⟨h̪͆⟩, since [h] has no place of articulation of its own.