The most common labiodental sounds are the fricatives, [f] and [v]:
The labiodental nasal [ɱ] seems never to be used as a contrastive sound in any language, but it is used as an allophone of /m/ in many, including English.
Labiodental plosives can sometimes be found as a result of assimilation. For example, the b in English obvious can sometimes assimilate to the labiodental POA of the following [v]. But in general, labiodental stops are not used in the world's languages.
In some dialects known as "Estuary English" (spoken by some people living near estuaries of the Thames River in south-east England), the labiodental approximant [ʋ] is often used as a version of r. The result is subtly different from Bugs Bunny's nemesis, Elmer Fudd.
|[ju wæskəli wæbɪt]||Elmer Fudd|
|[ju ʋæskəli ʋæbɪt]||Estuary English|
Labiodentals have the lower lip as the active articulator and the upper teeth as the passive articulator. It is more awkward, but still physically possible, to touch to lower teeth with the upper lip, resulting in a sound with almost identical acoustics. These "dentolabial" sounds are completely absent from normal adult language, but they are common enough in some disordered child speech that they have a diacritic in the extended IPA.