Validation of laboratory models used to simulate heat exchange between the root canal and periodontium by comparison to clinical data

to record the temperature in the root canal of human teeth ex vivo during and after syringe delivery of an irrigant at 60 °C or at room temperature while simulating heat exchange with the periodontium by five different models and to compare it to previously published clinical data.

The root canals of four extracted human teeth were prepared to size 40/0.04 taper. Thermocouples were inserted into the roots to monitor the intracanal temperature. The roots were surrounded by air at room temperature (model A), water at 35 °C (model W), gelatinized Hank's Balanced Salt Solution at 37 °C (model G), pre-soaked liquid-absorbing floral foam at room temperature (model F), or alginate at 37 °C (model AL). The root canals were irrigated with distilled water at 60 °C or at room temperature. Agreement of the intracanal temperature with previously published clinical data was assessed using non-parametric Bland-Altman plots and the Concordance Correlation Coefficient (CCC).

The intracanal temperature agreed closely with the clinical data during the delivery of the irrigant. Afterwards, models W, AL, and G showed moderate to substantial agreement with the in vivo data (CCC = 0.90-0.99) in most cases. Conversely, models A and F showed no to poor agreement (CCC=-0.01-0.64).

The use of models A and F is not warranted. The optimum choice among the other three models depends on the requirements of each experiment.

Laboratory studies should employ models that mimic the in vivo conditions as closely as possible.