Microanatomy and Histological Features of Central Myelin in the Root Exit Zone of Facial Nerve

OBJECTIVE: The aim of this study was to evaluate the microanatomy and histological features of the central myelin in the root exit zone of facial nerve. METHODS: Forty facial nerves with brain stem were obtained from 20 formalin fixed cadavers. Among them 17 facial nerves were ruined during preparation and 23 root entry zone (REZ) of facial nerves could be examined. The length of medial REZ, from detach point of facial nerve at the brain stem to transitional area, and the thickness of glial membrane of central myelin was measured. We cut brain stem along the facial nerve and made a tissue block of facial nerve REZ. Each tissue block was embedded with paraffin and serially sectioned. Slices were stained with hematoxylin and eosin (H&E), periodic acid-Schiff, and glial fibrillary acid protein. Microscopy was used to measure the extent of central myelin and thickness of outer glial membrane of central myelin. Thickness of glial membrane was examined at two different points, the thickest area of proximal and distal REZ. RESULTS: Special stain with PAS and GFAP could be differentiated the central and peripheral myelin of facial nerve. The length of medial REZ was mean 2.6 mm (1.6-3.5 mm). The glial limiting membrane of brain stem is continued to the end of central myelin. We called it glial sheath of REZ. The thickness of glial sheath was mean 66.5 microm (40-110 microm) at proximal REZ and 7.4 microm (5-10 microm) at distal REZ. CONCLUSION: Medial REZ of facial nerve is mean 2.6 mm in length and covered by glial sheath continued from glial limiting membrane of brain stem. Glial sheath of central myelin tends to become thin toward transitional zone.

Evaluación del sellado apical de sistemas resinosos en la obturación de conductos radiculares: “Estudio in Vitro”

El propósito de este estudio fue evaluar el sellado apical entre los cementos AH plus y los sistemas resinosos de obturación Endo-Rez y Epiphany. Se incluyeron 68 premolares humanos monorradiculares de reciente extracción, los cuales fueron decoronados e instrumentados con la técnica corono-apical hasta la lima # 50. Posteriormente, se dividieron en tres grupos de 20 raíces cada uno para ser obturados por condensación lateral: Grupo 1.- AH Plus, Grupo 2.- Endo-Rez, Grupo 3.- Epiphany y dos grupos de cuatro especímenes como controles (positivo y negativo). Los especímenes fueron teñidos con azul de metileno al 2% durante 48 hs en un ambiente de vacío. Los resultados revelaron una filtración promedio de 0.27 mm con AH Plus, de 0.40 mm para el Endo-Rez y de 0.41 mm para el Epiphany. La prueba de ANOVA complementada con la prueba DSH Post-Hoc de Tukey’s Test reveló los mejores resultados con AH plus (p<0.05), y entre los otros grupos no hubo diferencias estadísticas significativas. Bajo las condiciones de éste estudio concluimos, que el cemento AH Plus mostró las mejores condiciones de sellado apical.

The purpose of this study is to compare the capacity of apical sealed between the cements AH Plus, Endo-Rez and Epiphany. Sixty eight human single-rooted inferior premolars of recent extraction were included. The specimens were decrowned and instrumented with the crown-down technique until the #50 file. The teeth were randomly divided into three groups of 20 each one and obturated with the technique of lateral condensation. Group 1: AH Plus, Group 2: Endo-Rez, Group 3: Epiphany and two groups of fourth specimens for control (positive and negative). The specimens were prepared to be submerged in 2% blue of methylene solution by 48 hours in to vacuum atmosphere. The results showed an apical sealed average of 0.27 mm for AH Plus, 0.40 mm for the Endo-Rez and 0.41 mm for the Epiphany. The ANOVA test supplemented with the Post-Hoc Tukey’s HSD Test revealed best apical sealed for the group with AH plus (p <0.05) and no statically significant differences were found between other groups. Under the conditions of this study, the AH Plus cement showed the best conditions of apical sealed.