If you have an infection of the pulp, you may not feel any pain at first. But if it is not treated, the infection will cause pain and swelling. In some cases, an abscess will form. Your tooth might need a root canal if:
• It hurts when you bite down on it, touch it or push on it
• It is sensitive to heat
• It is sensitive to cold for more than a couple of seconds
• There is swelling near the tooth
• It is discolored (whether it hurts or not)
• It is broken
• It has long term decay leading to chronic irritation of dental nerves.