A 34-year-old man has had spontaneous throbbing pain in the lower left quadrant for two days. Tooth 36 has a deep occlusal-distal carious lesion. Cold produces intense pain lasting about 40 seconds after removal of the stimulus. Percussion and palpation are normal and the periapical radiograph shows an intact lamina dura. He is scheduled for full treatment next week. What is the most appropriate emergency treatment today?