Questions & Answers about Estis necese, ke la dentisto eltiru la muelodonton.
Esperanto often uses an impersonal expression where English would use a dummy subject like it.
So English says:
- It was necessary that...
But Esperanto can simply say:
- Estis necese, ke...
There is no need for a word like English it.
Also, necese is used here because the idea is general and impersonal: it was necessary / it was necessary that... If there were a real noun being described, you would normally use necesa instead:
- La operacio estis necesa. = The operation was necessary.
But in your sentence, there is no real subject noun, so the impersonal pattern estis necese is very natural.
The ending -e makes it an adverb, and Esperanto often uses adverbs in expressions like this:
- Estas grave, ke... = It is important that...
- Estis strange, ke... = It was strange that...
- Estis necese, ke... = It was necessary that...
This is a very common Esperanto pattern.
If you used necesa, that would usually describe a noun:
- La eltiro estis necesa. = The extraction was necessary.
So in your sentence, necese does not describe a noun; it helps form an impersonal statement.