Crack formation following root-end preparation in roots with the butterfly effect

Abstract

HIGHLIGHTSObjective: To investigate apical cracks in roots that exhibit the butterfly effect and that have undergone apical resection and ultrasonic root-end cavity preparation. The effect of the obturation material was also studied. Methods: Forty extracted single-rooted teeth were decoronated at the cemento-enamel junction. Roots were viewed under a light microscope and coded according to the presence or absence of the butterfly effect. Canals were prepared using ProTaper Next instruments to size X3 and assigned to two obturation groups (gutta-percha and AH Plus, and ProRoot MTA alone). Each contained twenty roots (10 with the butterfly effect and 10 without the butterfly effect). Roots were resected perpendicular to their long axis, 3 mm from the apex, and cavities were cut using ultrasonic retrotips. Resin replicas were used for crack imaging from scanning electron micrographs. Statistical analyses were performed using Stata 13.1 (StataCorp, College Station, TX, USA). Results: Cracks occurred more frequently in teeth with the butterfly effect (80%), with this difference being significant (P=0.001). Most cracks (73%) ran buccolingually. Teeth obturated with MTA developed fewer cracks compared to those obturated with GP and sealer. Conclusion: Root-ends with the butterfly effect had a significantly higher number of buccolingual cracks following resection and ultrasonic root-end preparation. This might explain the development of some vertical root fractures, which usually run buccolingually. Canal obturation with MTA may be protective.

Effect of Heat Softening versus Ultrasonic Removal of Root-End Gutta-Percha on the Quality of Root-End Preparation for Endodontic Microsurgery

“…In this experimental work, teeth that experienced cracks or fractures after root-end resection were excluded to avoid the illusion of preoperative cracking [22]. SEM analysis confirmed that the ultrasonic technique is always associated with the formation of microcracks, which is in agreement with the results of Peters et al [9][10][11][12][13]. However, our results differ from those of Calzonetti et al [23], in which ultrasonic root-end cavity preparation did not cause root microfractures by using an in situ impression technique, and other studies have also found no microcracks or fractures after root-end cavity preparation with ultrasonic tips [7,27].…”

“…They allow safe access to the long axis of the root canal, decreasing the risk of lateral perforation and preserving an adequate environment for retrograde obturation. However, some studies have reported that apical microcracks appear during root-end preparation with ultrasonic tips [9][10][11][12][13], which increase the risk of apical leakage, reduce the mechanical properties of the root-end, and negatively affect the longterm outcomes of endodontic microsurgery [14].…”

A retrospective evaluation of the prevalence of cracked teeth among an adult population.

“…Sim et al concluded that after RCT, teeth with coronal cracks had a higher survival rate than teeth with radicular cracks ( 18 ). The presence of the butterfly effect was considered as a risk factor for the formation of cracks, following ultrasonic root preparation or root resection, where cracks usually observed in the buccolingual direction ( 19 ).…”