Pulpitis is the word that we use to describe the pain that originates from the inflamed inside tissues in the tooth. If bacteria invades the pulp (commonly called the nerve) tissues they become inflamed, and normally painful. The problem with this is that the blood supply of the pulp tissues is quite small and if compromised results in death of the pulp tissue. Before this happens the pulp becomes sensitive to cold and/or hot and often throbs uncontrollably. It can also be sensitive to sweet, but this is normally only during the early stages of cavity formation. At this stage there are many proprietary pain killers on the market that can help remove the pain, but it is sensible to see the dentist as soon as possible.