May be this doesn't exactly answer the question, but pure dental consonants are cross-linguistically rare. Ladefoged and Maddieson discuss in detail how stops which are generally labeled dental, are actually denti-alveolar, with the bulk of the articulation at the alveolar ridge. They also state that for languages that distinguish different types of coronal stops, the actual difference in articulation is caused by tongue shape (laminal versus apical) as opposed to tongue position (dental versus alveolar). The answer by @user6726 notes the Australian aboriginal languages as having distinct dental consonants. Now, I don't know much about Australian languages, in general, but from this Wikipedia article, it seems they too use a laminal and apical distinction. I can, however, vouch for this fact --- as a native speaker --- about the Indo-Aryan languages which have a similar distinction. The so-called retroflexes actually involve curling the tongue back (retroflexing) only in careful and slow speech, or in artificially learned speech (for example, a lot of people learn this careful retroflexed articulation in school, and therefore may have retroflexes in English --- signature Indo-Pakistani accent --- but completely lack retroflexes in their first languages). At least for me, the "retroflexes" 〈ṭ, ṭh, ḍ, ḍh〉 are always apical alveolar (with zero affrication, so they sound quite different from English) and are post-alveolar only inter-vocalically, while "dental" 〈t〉 and 〈th〉 are laminal denti-alveolar and "dental" 〈d〉 and 〈dh〉 are actually laminal alveolar! My point of saying all this is to point out that "dental" is often a placeholder for laminal, and in this sense, I can't imagine a "dental" trill, because I find laminal trills impossible, even though an apical trill is easy to make (regardless of whether its dental or alveolar).
The other interpretation of dental consonants may be inter-dental, like English 〈th〉, which are also cross-linguistically rare. The hyperlinked Wikipedia page and this page says it occurs in careful pronunciation for plosives in Australian languages. I can make an inter-dental trill, with the tip of my tongue sticking out and trilling against the sharp edge of the upper incisors, but this doesn't seem to be a very natural (for want of a better word) thing to do.
Again (as the other answer mentions), Russian and Hungarian (and Rumanian, which I know very little about) have been claimed to have dental trills (for Russian it is the palatized r), but in both these languages the said trills (at least in my experience) are very often taps, and even then are denti-alveolar.
