A dental consonant is a consonant articulated with the tongue against the upper teeth, such as /t/, /d/, /n/, and /l/ in some languages. Dentals are primarily distinguished from sounds in which contact is made with the tongue and the gum ridge.
Dental - Learning to speak with the teeth
The dental is a form of consonant that is characterized by the fact that when one make the sound in one's speech, one's tongue moves up to touch the upper teeth.
This is an easy way to remember what the dental is: after all, most people know that "dental" itself ordinarily refers to the teeth, as in when one goes to get a dental check-up.
The dental is part of a larger set of concepts used by linguists, including the coronal and the alveolar, in order to describe how the tongue moves when a given sound is made within a given language.
Speaking properly using dental intonations
The main rule for the dental consonant is that the tongue rises up to touch the upper teeth and gum ridge when a speaker makes the relevant sound. Whenever this is the case, one can rest assured that one is in the presence of a dental consonant.
The dental consonants within the English language include l, t, d, and n. If you try making this sounds, you will see that the your tongue automatically touches your upper teeth. Again, this is the way to define a dental consonant.
The dental would seem to be subset of the category of consonants known as the coronal. This is because like the dental, the coronal involves the tongue being raised when pronouncing a sound. The dental, though, specifically involves the tongue touching the upper teeth; some coronal consonants can be pronounced further back in the mouth.
How accents change pronunciation
Interestingly, it would seem that one's accent could influence whether one pronounces a given letter in a dental way or not. For example, a speaker of an Indian language may pronounce consonants that are ordinarily further back in the mouth in English in a more dental way; and this itself would be a characteristic part of his accent as a whole. This is usually not enough to make the speaker incomprehensible, although the difference in dental enunciation is in fact noticeable at the level of accent.
Dental consonants are related to the dental stop, which involves the speaker pressing his tongue against his upper teeth in such a way that the airflow is actually blocked, thereby creating a pause within the context of a given spoken statement. This is more common in some languages than in others. Likewise, the significance of dental enunciations in general is greater in some languages than it is in others.
Whether a given consonant is dental or not is first and foremost of interest to linguists, and not as much to layspeakers of languages, who often just produce the relevant dental sounds in an instinctive way without consciously thinking about it. This kind of technical awareness of the dental, though, may also be useful when one is trying to learn how to pronounce a dental within a foreign language. At first the sound may seem mysterious; but then, once one learns how to technically move one's tongue in order to produce the dental sound, it may become simple enough.