Effect of N-acetylcysteine and calcium hydroxide on postinstrumentation pain and matrix metalloproteinase-9 levels: A randomized controlled trial

Objectives: This study investigated the influence of N-acetylcysteine (NAC) and calcium hydroxide (Ca(OH) 2 ) intracanal medications (ICMs) on the pain intensity and levels of matrix metalloproteinase-9 (MMP-9) in apical periodontitis (AP). Subjects and Methods: Thirty patients with necrotic, single-rooted premolars and AP were randomly divided into two groups following cleaning and shaping: NAC and Ca(OH) 2 (n = 15). Postinstrumentation pain was assessed at 6, 12, 24, and 48 h using the Numerical Rating Scale. Periapical samples were collected: postinstrumentation (Ps1) and after 7 days of ICM (Ps2) to assess MMP-9 levels using enzyme-linked immunosorbent assay. Results: The total incidence of postinstrumentation pain was highest at 6 h and least at 48 h in both the groups, with no statistically significant difference seen in these incidences between the two groups at any time interval (P > 0.05). After 1 week, both ICMs significantly decreased MMP-9 levels, with a significantly greater percentage reduction with Ca(OH) 2 than with NAC (P < 0.001). Conclusions: Both NAC and Ca(OH) 2 effectively reduced postinstrumentation pain and decreased MMP-9 levels in periapical tissues. While pain reduction was statistically different only at 6 and 12 h, Ca(OH) 2 showed a greater percentage reduction in MMP-9 compared to NAC after 7 days.