A 26 year old male presents to the local emergency room with a constant sharp pain radiating from the mandibular left second molar up to the left temporal region. The pain has been present off and on for 2 weeks but is now constant and severe. He begs to have the tooth extracted. Intra-oral exam reveals a severly decayed mandibular left second molar. There is some tenderness to extra-oral palpation and intra-oral plapation. There is a very slight degree of swelling in the buccal vestibule adjacent to this tooth. There is no limit to mandibular opening and a radiograph reveals no periapical pathology. The correct treatment is: