Apical Constriction: Location and Dimensions in Molars—A Micro–Computed Tomography Study

• Published in: Journal of endodontics Vol. 40; no. 8; pp. 1095 - 1099
• Main Authors: ElAyouti, Ashraf, Dr med dent, Hülber-J, Maren, Dr med dent, Judenhofer, Martin S., Dr Dipl-Ing (FH), PhD, Connert, Thomas, Dr med dent, Mannheim, Julia G., Dipl-Ing (FH), Löst, Claus, Prof Dr med dent, Pichler, Bernd J., Prof Dr rer nat, von Ohle, Christiane, Dr med dent
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2014
• Subjects: Adolescent; Adult; Anatomy, Cross-Sectional - methods; Apical anatomy; apical constriction; Dental Pulp Cavity - anatomy & histology; Dental Pulp Cavity - diagnostic imaging; Dentistry; Endocrinology & Metabolism; Humans; Image Processing, Computer-Assisted - methods; micro computed tomography; Middle Aged; Molar - anatomy & histology; Molar - diagnostic imaging; molars; multi threshold segmentation; Multimodal Imaging - methods; Tomography, Emission-Computed, Single-Photon - methods; Tomography, X-Ray Computed - methods; Tooth Apex - anatomy & histology; Tooth Apex - diagnostic imaging; X-Ray Microtomography - methods; Young Adult; apical constriction; multi threshold segmentation; molars; Apical anatomy; micro computed tomography
• ISSN: 0099-2399; 1878-3554
• DOI: 10.1016/j.joen.2013.12.002

Abstract Introduction The existence of the apical constriction has been repeatedly questioned. The aim of the present study was to validate the existence of the apical constriction and determine its location and dimensions in molars by using substantial micro–computed tomography analysis. Methods: Ninety human molars with 271 canals were evaluated. Teeth with resorption, defects, or incomplete root formation as well as wisdom teeth were excluded. Patients' age was categorized into 3 groups. Teeth were scanned by micro–computed tomography with a resolution of 27 μm. Multi-threshold segmentation was performed to trace the canal outline in a total of 25,093 sections. In each cross section, 88 parameters, eg, area, circumference, and maximum and minimum diameter were recorded and analyzed. The apical constriction (AC) was defined to be the narrowest area extending along a distance of 0.1 mm or more at the apex. Size and form of the constriction were recorded as well as the distance to the apical foramen (AC-AF) and apex (AC-A). Results The mean distance of AC-AF was 0.2 mm (99% confidence interval, 0.15–0.24; range, 0–0.6 mm), and of AC-A it was 0.9 mm (99% confidence interval, 0.86–1.0; range, 0.1–1.7 mm). The type of canal had no influence on AC-AF and AC-A. In 76% of all canals the apical constriction was parallel. The mean size of constriction in molars was instrument size 30. Patients aged 30 or younger had significantly wider constrictions. Conclusions The apical constriction was found to be located at or close to the foramen. The most common form was the parallel form.