Effect of Cryotherapy Methods and Cavity Preparation Depth on Intrapulpal Thermal Response: An In Vitro Study

Local cooling may supplement endodontic anesthesia, but its intrapulpal thermal effects remain incompletely characterized. This in vitro study compared peak intrapulpal temperature reduction (ΔT), recovery from the temperature minimum, and maximum cooling rate for gauze-wrapped ice, an Endo-Frost-cooled cotton pellet, and a direct ice stick across unprepared, 2 mm, and 4 mm cavity-preparation conditions. Ten extracted mandibular first molars received 10 applications per protocol and condition. Intrapulpal temperature was recorded every second with the roots in a 37.0 ± 0.1 °C water bath. Outcomes were analyzed using linear mixed-effects models. Protocol, preparation condition, and their interaction affected ΔT (all p < 0.001); estimated reductions increased with preparation depth and ranged from 3.67 to 5.06 °C for direct ice, 4.59 to 6.43 °C for gauze-wrapped ice, and 10.24 to 13.32 °C for the cooled pellet. Recovery to 50, 75, and 100% of the maximal drop showed significant protocol-by-condition interactions (all p ≤ 0.022). Gauze-wrapped ice had the shortest minimum-to-baseline recovery interval at every condition (all p < 0.001 versus the other protocols), whereas the cooled pellet had the highest pooled estimated maximum cooling rate. These findings do not establish clinical anesthetic efficacy or an isolated effect of remaining dentin thickness.