A potentially damaging temperature rise within the root canal and thus on the external root surface may be induced because of frictional contact of ultrasonic tips during the removal of separated instruments. The efficiency of a new ultrasonic unit, with air-spray function and ET40D (Satelec/Acteon, Merignac, France) and CPR5 (Obtura-Spartan, Fenton, MO) ultrasonic tips, in reducing temperature rise on the external root surface during the removal of fractured files was investigated.Methods
Four millimeters of F2 ProTaper files (Dentsply, Surrey, UK) were fractured 2.5 mm from the canal access of 60 lower incisor roots. Roots were randomly divided into six groups: groups CPR5/no air and ET40D/no air in which tips were used without air flow, groups CPR5/15 psi and ET40D/15 psi (tips used with 15-psi air pressure), and groups CPR5/10 psi and ET40D/10 psi (10-psi air pressure). The temperature rise was measured on the external proximal root surface, adjacent to the most coronal aspect of the fractured fragment, at 15 seconds and then at 30-second intervals up to 120 seconds.Results
After 120 seconds, the mean temperature rise (4.2°C) with the air flow active was significantly lower than that with nonactive air flow (11°C). At 10- and 15-psi pressures, the temperature rise after 120 seconds induced by ET40D tips was 4° and 2.4°C, respectively. These were significantly lower than with CPR5 tips (6.3° and 4.2°C, respectively).Conclusions
A new ultrasonic unit incorporating an air-flow function proved to be effective in reducing the temperature rise during removal of fractured files. ET40D ultrasonic tips were more effective than the CPR5 tip. However, both tips could be safely activated with air spray up to 120 seconds.