How does anesthetic drugs which block the Na+ channels in neurons prevent pain during tooth extraction?

How does anesthetic drugs used by dentists, which block the Na+ channels in neurons prevent a patient from feeling pain during a tooth extraction?

P.S.: Could you give like a chronology of events that are taking place in the channels?
Update: Thanks alot BP-LO.
I also couldn't find any information relating to the action of mechanism when I googled.
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