Effects of ultrasonic root-end preparation on microcrack formation and leakage.

Root-end preparations made with conventional ultrasonic (CUS) tips, diamond-coated ultrasonic (DUS) tips, and high-speed stainless-steel burs (HSB) were compared for the incidence of microcracks and dye leakage. One hundred twenty incisors were instrumented, obturated, and had 3 mm resected from their apices. Sixty teeth were used for microcrack evaluation before and after root-end preparation with CUS, DUS, or HSB. Three types of microcracks were observed: intracanal, extracanal, and communicating. Four of the five cracks observed after root resection (before root-end preparation) were of the extracanal or intracanal type. After root-end preparation, 19 of the 41 new microcracks that developed were the communicating type. There was no significant difference among CUS, DUS, or HSB for the number or type of cracks. Of the remaining 60 resected teeth, 25 were prepared with DUS, 25 with CUS, and 10 served as controls. All of the DUS and CUS teeth were filled with Super-EBA. Dye penetration was measured after immersion in Pelikan ink for 5 days. The dye penetration difference between DUS and CUS was not significant.