To compare the effectiveness of different oral analgesics for relieving pain and distress in adults following the extraction of teeth and deep cavity preparations under local anesthesia. Methods: This randomized controlled study was conducted between November 2015 and May 2016. One hundred and twenty patients were randomly allocated to 3 groups. Forty patients were in the paracetamol (1 gram) group, 40 in the ibuprofen (400 mg) group and 40 in the diclofenac potassium (50 mg) group. Evaluation of the post extraction and deep cavity preparations pain was made by patients immediately postoperatively, 2, 4 and 6 hours postoperatively on standard 100 mm visual analogue scales (VAS). Furthermore, each patient was observed preoperatively and immediately postoperatively for signs of distress by using a 5 point face scale. Results: There were significant decreases in mean pain VAS scores for diclofenac potassium group compared to paracetamol and ibuprofen groups at 4 hours postoperatively (one-way Analysis of Variance: p=0.0001, p=0.001) and 6 hours postoperatively (p=0.04, p=0.005). Changes in distress scores from the preoperative score to the postoperative score were made using the paired sample t-test. There were significant decreases in distress scores between the preoperative and postoperative scores (p=0.0001). Conclusions: Diclofenac potassium was more effective than paracetamol or ibuprofen for reducing postoperative pain associated with tooth extraction and deep cavity preparation. Patients' distress levels can be alleviated by using preemptive analgesics.