Early flaring and crown-down shaping influences the first file bind to the canal apical third

Abstract

The determination of the apical constriction, its diameter and correct cleaning are significant for the biological response in the critical apical zone. Kerekes and Tronstad evaluated morphometrically molars and reported a wide variation of constriction sizes. Additionally, the continuous cement deposition on the constriction throughout life alters its shape and size. There is a wide variation in the canal apical diameter in all tooth groups what hinders the decision making of how much to enlarge the canals. Frequently, the first file to bind does not reflect the apical canal diameter. Clinically, the estimative of the apical diameter is not precise even with the adjunct use of radiographs or electronic apex locators. Stabholz et al. demonstrated that early flaring is critical to tactile determination of the apical diameter. Without early flaring the apical diameter was determined in only 32.3% of the cases, while after this procedure the determination increased to 75%. Therefore, the tactile sensitivity determines more accurately the number of instruments required for the enlargement of the apical region. In spite of this, the tactile sensitivity does not determine whether the instrument is bound just at the constriction zone or if interferences along the root canal are negatively influencing the apical binding. Leeb and Philippas reported that the normal dentin deposition promotes the root canal constriction and narrows the cervical region in molars. Irregularities of the walls and/or curvatures of the root canal can exert a pressure against the file and interfere with the practitioner’s ability to determine whether the binding occurred at the apical region. The