Untreated dental infections can become very serious. A few months ago I read about a child who had an untreated dental infection and it spread to his brain and killed him. While such instances of people dying from untreated dental problems are rare, untreated dental problems can more often cause systemic illeness. It is not something that should be ignored.
I found this web page listing free and low cost dental treatment in NYC.

http://www.lacnyc.org/resources/healthlit/dent-vision.htm