Comparative Efficacy of Calcium Hydroxide Combined with Silver Nano-particles and Conventional Calcium Hydroxide as Intra-canal Medications in Reducing Postoperative Pain in Endodontic Retreatment: A Randomized Clinical Tria

Objectives: This research aims to evaluate the comparative efficacy of calcium hydroxide combined with silver nano-particles and conventional calcium hydroxide as intra-canal medications following non-surgical root canal retreatment in reducing post-operative pain. Materials and Methods: A randomized, prospective, parallel, triple-blind clinical trial was conducted with 120 medically healthy patients diagnosed with symptomatic apical periodontitis. All patients had previously undergone endodontic treatment on anterior or premolar teeth and were between 25 years and 50 years old. Participants were randomly and equally assigned to two groups based on the added solution; either nano-silver solution or distilled water. Opaque bottles containing the nano-silver solution or distilled water were covered and coded as either A or B by a dental assistant, who prepared the intra-canal medicament paste by mixing one of the solutions with calcium hydroxide (Ca(OH)₂) powder before providing it to the operators. Both operators and patients were blinded to the group assignments. Patients were assessed pre-operatively and at 6, 12, 24, and 48 hours post-operatively using the Numerical Rating Scale (NRS). Statistical analyses were conducted using the Mann-Whitney U test, Wilcoxon’s rank test, Friedman’s test, and chisquare (χ²) test. Additionally, relative risk (RR), relative-risk reduction (RRR), and 95% confidence intervals (CI) were calculated. Results: There was no statistically significant difference in post-operative pain incidence and intensity between the two groups at different time intervals. However, within the same group, pain intensity varied significantly over time (P<0.05). The relative risk (RR) of pain incidence and its 95% CI at 6, 12, 24, and 48 hours were: 6 hours: RR = 0.86 (95% CI: 0.63, 1.19), 12 hours: RR = 0.87 (95% CI: 0.54, 1.41), 24 hours: RR = 0.54 (95% CI: 0.23, 1.26), 48 hours: RR = 0.33 (95% CI: 0.07, 1.59). No adverse effects related to the tested materials were reported. Conclusions: Although the relative risk of pain incidence was lower in the treatment group than in the control group, the confidence intervals crossed 1, indicating no statistically significant difference. Further studies with larger sample sizes are needed to confirm these findings. Keywords: Calcium hydroxide, Distilled water, Post-operative pain, Root-canal retreatment, Silver nano-particles.