Temperature-Dependent Dissolution Kinetics of Pulp Tissue: A Comparative Analysis of Sodium and Calcium Hypochlorite Irrigants

Objective: To investigate the temperature-dependent dissolution kinetics of 5.25% sodium hypochlorite (SH) and 5.25% calcium hypochlorite (CH) by using time-to-complete dissolution as the primary endpoint under static conditions.Methods: Standardized bovine pulp fragments (12 ± 2 mg) were randomly allocated to distilled water (control), 5.25% SH, or 5.25% CH at 24-, 36-, or 60 °C (9 groups; n = 10; total n = 90). Each specimen was immersed in 1.5 mL of the assigned irrigant without agitation/activation for up to 30 min with fresh-solution renewal every 5 min to reduce solution exhaustion and temperature drift. Time to complete dissolution (no visible tissue remnant) was recorded; specimens not fully dissolved within 30 min were reweighed to calculate percentage dissolution and treated as censored observations.Results: Distilled water showed minimal weight loss (3.2-6.0%). Both hypochlorite solutions exhibited progressively faster dissolution with increasing temperature. At 36 °C, both SH and CH dissolved pulp tissue significantly faster than distilled water (both p < .05). At 60 °C, most specimens in both SH and CH groups completely dissolved within the experimental period. SH and CH demonstrated comparable dissolution behavior at matched temperatures.Conclusion: Under the present static laboratory conditions, higher target temperatures were associated with faster and more complete pulp tissue dissolution by hypochlorite irrigants.