"Kindern", dative plural - What other words reflect that flexion in the plural form

Question

I practice German cases sentences to learn by heart, but I have stumbled across a form that I don't think it is so common.

Ich sprach mit den kleinen Kindern.

In this sentence, the plural form of Kind reflects the case with an n. I don't think I have seen so many n at the end of words in plural dative.

But if it is to happen with a limited set of words, could you you give me some kind of rule to know which words get an n at the dative plural?

What I guess more or less, it's that plural in er should append and n. Is it all?

Answer 1

All plural nouns that do not end in -n or -s gain an -n ending in the dative case.

Answer 2

Look at german wikipedia:

Dativ-n
Bei Wörtern, die im Nominativ Plural auf -e, -el und -er enden, wird im Dativ Plural ein -n angehängt. Diese Konstruktion ist im Hochdeutschen üblich, in manchen deutschen Mundarten und in der dialektnahen Umgangssprache fällt es allerdings oft weg.

http://de.wikipedia.org/wiki/Dativ#Dativ-n