Impact of Endodontic Treatment on CRP Levels in Apical Periodontitis: A Prospective Observational Cohort Study

<b>Background/Objectives:</b> Apical periodontitis is a prevalent dental condition associated with systemic inflammation. C-reactive protein (CRP) is a sensitive biomarker of inflammatory status. While previous studies have examined CRP changes after endodontic treatment, limited evidence exists on short-term systemic effects following clinically indicated endodontic therapy in healthy individuals. This prospective observational cohort study aimed to evaluate the impact of endodontic treatment or retreatment on serum CRP levels in patients with symptomatic and asymptomatic apical periodontitis and assess demographic influences. No control group was included. <b>Methods:</b> A prospective observational cohort study was conducted in a private endodontic clinic in Jeddah, Saudi Arabia (2021-2023). Three hundred ASA I patients were enrolled and categorized into symptomatic apical periodontitis (SAP) and asymptomatic apical periodontitis (AAP) groups. Blood samples were collected before treatment and two weeks post-treatment. CRP levels were measured using a high-sensitivity assay. Statistical analyses included paired <i>t</i>-tests, Mann-Whitney U tests, and multiple regression. Laboratory personnel were blinded to patient grouping. <b>Results:</b> CRP levels significantly decreased after treatment in both groups (SAP: 6.99 to 2.01 mg/L; AAP: 5.40 to 1.64 mg/L; <i>p</i> < 0.001). Reduction was greater in SAP (mean difference = 4.98 mg/L) than AAP (3.76 mg/L; <i>p</i> < 0.001). Paired <i>t</i>-test showed a very large effect size (Cohen's d = 3.51). Age and sex were not significant predictors of CRP changes (R² < 0.02). <b>Conclusions:</b> Endodontic treatment or retreatment significantly reduces systemic inflammation in patients with apical periodontitis. These findings reinforce the oral-systemic health link and highlight the clinical relevance of managing apical infections. Longer-term studies and inclusion of additional biomarkers are recommended.