Comparison of isthmus detection methods in the apical third of mesial roots of maxillary and mandibular first molars: macroscopic observation versus operating microscope

Abstract

The aims of this study were to assess the presence and the frequency of isthmuses in the mesial roots of the maxillary and mandibular first molars (at two resection levels from the apex), and to compare the findings obtained by macroscopic observation (MO) and operating microscope (OM). Forty maxillary and 40 mandibular mesial roots were observed at 3 and 5 mm from the apex initially macroscopically and then with the use of an OM. The presence of an isthmus and the number of root canals detected were recorded. Data were analyzed statistically by Fisher's exact test for isthmus evaluation and Wilcoxon signed rank-test for number of root canals at a confidence interval of 95%. Comparison between MO and OM regarding the number of roots with isthmuses provided the following results: Mandibular group: At 3 mm level: MO 19 vs. OM 27; at 5 mm level: MO 31 vs. OM 32. Maxillary group: At 3 mm level: MO 9 vs. OM 14; at 5 mm level: MO 19 vs. OM 21. Significant differences (p<0.05) were found concerning the accuracy of the isthmus detection methods at both resection levels (3 and 5 mm) and both types of roots, as well as for the number of the canals inspected under the OM between the two resection levels of the mesial roots of the maxillary first molars. Under the tested conditions, OM increased the diagnostic accuracy of isthmus detection at both resection levels and root types.

An in vitro assessment of type, position and incidence of isthmus in human permanent molars

“…The presence of isthmus in roots of human molars has been investigated by both sectioning methods 1,5,6,8,11,12,17,18,21,25,26 micro-computed tomography 7,8,10,13,19,20,23,24 and cone beam computed tomography 14 .…”

Incidencia y Tipo de Istmos en Primeros Molares Permanentes Humanos, Evaluación in vitro

“…Una gran cantidad de estudios se han llevado a cabo para determinar la prevalencia de istmos en molares humanos bajo distintas metodologías; algunas de ellas seccionando longitudinal o transversalmente las raíces para observarlas al microscopio, ya sea estereoscópico, de disecciones, electrónico de barrido o incluso microscopio quirúrgico (Kontakiotis et al, 2010;Bao et al, 2012); tiñéndolas y embebiéndolas en resinas para posteriormente seccionarlas o diafanizando las raíces para evidenciar el istmo sin seccionar la raíz, y más recientemente se ha hecho uso de tecnologías como la endoscopía o la tomografía tanto de haz cónico como micro computarizada para tal fin (von Arx, 2005;Pécora et al, 2013;Estrela et al, 2015;Versiani et al, 2016). Otro punto de variación en los distintos estudios es la cantidad de segmentos analizados de cada raíz, muchos trabajos han estudiado la presencia de istmo en los tercios apical, medio y cervical mientras que otros la analizan en hasta 5 o 6 secciones de 1 mm de espesor para cada raíz.…”