Cryotherapy, PGE2, NGF Levels and Pain After Endodontic Retreatment

Postoperative pain following endodontic retreatment is associated with periapicalinflammation mediated by prostaglandin E2 (PGE2) and nerve growth factor (NGF).Intracanal cryotherapy has been proposed to reduce postoperative pain through localhypothermia‐induced vasoconstriction, neuropraxia, and reduced metabolic and inflammatorymediator activity. While prior studies have examined cryotherapy's effect onpostoperative pain, no randomized controlled trial has jointly measured PGE2 and NGFusing minimally invasive sampling methods (GCF and saliva) in the context of single‐visitretreatment.Eligible patients will be systemically healthy adults (18‐65 years, ASA I‐II) with asingle‐rooted mandibular premolar tooth requiring non‐surgical retreatment due to apreviously inadequate root canal treatment, presenting with asymptomatic apicalperiodontitis and periapical radiolucency (PAI ≥ 3). Key exclusion criteria includepregnancy or lactation, uncontrolled diabetes mellitus (HbA1c > 7%), autoimmune disease,immunosuppressive therapy, systemic corticosteroid use within the past 3 months, BMI > 35kg/m², acute infection (abscess/cellulitis), advanced periodontal breakdown, heavysmoking (>10 cigarettes/day), recent analgesic/NSAID or antibiotic use, and chronic painsyndromes.Patients will be randomly allocated (computer‐generated randomization, sealed envelopes)to one of two parallel groups:Group A (Cryotherapy): Following standard non‐surgical retreatment instrumentation, finalintracanal irrigation with sterile saline cooled to 2.5°C, 20 mL, over 5 minutes.Group B (Control): Identical protocol using sterile saline at room temperature (20‐22°C),20 mL, over 5 minutes.All treatments will be performed in a single visit by one calibrated operator following astandardized protocol; the two groups differ only in irrigation temperature. Given thenature of the intervention, the operator cannot be blinded; however, laboratory personnelanalyzing saliva/GCF samples and statisticians will remain blinded to group allocation(single‐blind design).Outcome measures:Primary: Postoperative pain intensity measured by VAS (0‐100 mm) at 6, 12, 24, 48, and 72hours and on day 7, with the 24‐hour time point as the primary comparison.Secondary: Salivary NGF levels (ELISA) and GCF PGE2 levels (ELISA) at baseline (T0), 24hours (T1), and 72 hours (T2); rescue analgesic (paracetamol 500 mg, oral, as needed)consumption over 7 days; and correlation between biomarker levels and VAS pain scores.Each patient will be followed for a total of 7 days. Saliva and GCF samples will becollected between 08:00‐10:00 to minimize circadian variation. Sample size was calculatedusing G*Power 3.1.9.7 (repeated‐measures ANOVA, 80% power, α=0.05, f=0.25), yielding aminimum of 34 participants per group; accounting for an estimated 20% dropout rate, 50patients per group (100 total) will be enrolled. Statistical significance will be set atp<0.05. The study is sponsored and funded internally by Alanya Alaaddin KeykubatUniversity, with no external funding or industry sponsorship.