Objectives:The aim of this clinical trial was to evaluate postoperative pain scores related by patients submitted to periodontal surgical procedures receiving different preoperative anti-inflammatory drugs. Methods: A blind, randomized split mouth design was used, since each patient was submitted to at least three periodontal surgical procedures for open flap debridement, under local anesthesia, with a three-week interval apart from each surgery. Before the surgery, the patient was assigned to receive one of the following anti-inflammatory drug regimen: 1) placebo; 2) dexamethasone 4 mg; 3) celecoxib 200 mg, 01 hour before the surgery. After the surgery, the patients were instructed to take paracetamol 750mg as support medication if necessary. The patients were asked to write their postoperative pain scores in an appropriate file, using three different pain scales: 1) visual analogue scale (VAS); 2) 101-point numerical rating scale (101P); 3) four-point verbal rating scale (VRS-4). The amount of anesthetic tubes, the time duration of the procedure, and the number of tablets of support medication used were also registered. The Friedman non-parametric test (p<0,05) was used. Results: There were significant statistical differences in the pain scores between the placebo and celecoxib groups in the periods of 1, 2, 3 and 4 hours when the VAS was used, and for the periods of 1, 2, 3, 4, 6 and 7 hours when the 101P scale was used. No statistically significant differences could be found between placebo and dexamethasone, or between dexamethasone and celecoxib. Conclusions: Within the limits of this study, it can be concluded that the use of celecoxib 200mg as a preoperative anti-inflammatory drug resulted in lower postoperative pain scores in comparison to the placebo group in the first hours after periodontal surgical procedures.