Thermafil retreatment using a new "System B" technique or a solvent

The solid plastic carrier in the Thermafil obturation system must be remove d to facilitate retreatment The purpose of this study was to compare the ef ficacy and time required to retreat canals obturated with Thermafil with pl astic carriers using a new technique based on the System B HeatSource or a solvent, Fifty-two extracted human mandibular premolars with single canals were instrumented and then obturated with Thermafil with plastic carriers. After 2 wk storage at 22 degrees C and 100% humidity, they were randomly di vided into 2 groups of 26 teeth each. Group 1 teeth were retreated using ch loroform and hand files, whereas teeth in group 2 Were retreated with a new technique using the System:BI HeatSource. The end point of retreatment was defined as complete removal of the plastic carrier. The time required for retreatment was recorded, Then, the apical 5 mm segment of each root was se ctioned horizontally at 1 mm intervals and each section digitally imaged. T he total area of the canal and the area of the canal occupied by gutta-perc ha and sealer were measured using NIH image software, Data were analyzed us ing an unpaired t test. The mean time for retrieval of the plastic Carrier was significantly less for the System B technique (1.8 min) than for the so lvent technique (3.6 min) (p < 0.001), The difference between the two group s)ln the amount of filling material (carrier, gutta-percha, and sealer) rem oved was not significant (p > 0.05).