Apical Constriction
The narrowest anatomical diameter of the root canal, located 0.5–1.5 mm short of the apical foramen, representing the ideal terminus for instrumentation.
Full Definition
The apical constriction (also referred to as the minor apical foramen or the cementodentinal junction in older literature) is the naturally occurring narrowest point of the root canal, physiologically positioned coronal to the apical foramen. It is the anatomical landmark used to establish working length in endodontic treatment, since instrumentation and obturation ideally terminate at or just coronal to this point to prevent periapical tissue damage. Its location is highly variable and influenced by root maturity and patient age. Editors should be aware that 'apical constriction' and 'cementodentinal junction' are sometimes used synonymously in older texts, though they refer to slightly different concepts.
Usage
Usage note: Two words; do not hyphenate. Distinguish clearly from 'apical foramen' (the external opening) in all editorial contexts.
In Context
- "Working length was established 0.5 mm short of the apical constriction as determined by the EAL reading." — Endodontic procedure note
- "The term 'apical constriction' should not be used interchangeably with 'apical foramen'; the foramen is the exit point of the canal, whereas the constriction is its narrowest internal diameter." — Anatomy textbook editorial note