Background: Surgical removal of the third molar impaction is the most routine procedure done in Oral & Maxillofacial Surgery. "How to reduce the postoperative swelling, pain, and trismus?" is the most frequently asked question by surgeons. Aim: To evaluate the effect of the submucosal injection of 4mg dexamethasone on postoperative trismus and pain after third molar surgery.

Method: This study was conducted at the University College of Dentistry, University of Lahore, from January 2019 to December 2019. One hundred and fifty patients presented for the extraction of impacted third molar teeth were divided by using a random number into two groups. Group A received nothing while group B received submucosal 4mg dexamethasone soon after local anesthesia administration for extraction of the impacted third molar. The postoperative pain was assessed using the visual analog scale and trismus measured by interincisal distance on the third postoperative day. Statistical analysis was done through SPSS version 21.

Result: In group A, pain score varied from 4 to 9 on a visual analog scale (0=minimum to 10=maximum). The mean pain score was 6.5. While in group B, mean pain varied from 1 to 6 on a visual analog scale. The mean value of the pain score was 3.5 (P-value 0.000). In group A, the maximum mouth opening measured was 16mm and the minimum was 6mm with a range of 10mm. In group B, the maximum mouth opening measured was 26mm and a minimum of 12mm with a range of 14mm (P-value 0.000).

Conclusion: The submucosal injection of 4 mg dexamethasone injection effectively reduces trismus and pain after third molar surgery.

Keywords: third molar, submucosal dexamethasone, trismus