The canal orifice is the gateway to the apical third. If the orifice and coronal third is not enlarged correctly, compromises will occur in subsequent apical treatment. Alternatively, if the orifice is managed well, optimal apical cleaning and shaping can occur.
Management in this context means the orifice is enlarged to the appropriate circumferential dimension (width) and the canal is left negotiable after orifice shaping. Such a dimension allows unrestricted access to the more apical portions of the canal, allows a tapering funnel to be prepared without risk of perforation or other iatrogenic events, allows optimal activated irrigation, and facilitates a heat softened three dimensional obturation in addition to other attributes.
Optimal orifice and coronal third shaping is only possible when straight-line access (SLA) is prepared first. SLA provides the clinician with the ability to place a hand file into the canal without deflection to the point of first canal curvature.