Intraradicular diameter, remnant dentin thickness, and endodontic post to dentin distance: CBCT and microscopic analyses

The objective of this work was to measure the tooth root canals’ diameter, remnant dentin thickness, endodontic post to dentin distance, and resin-matrix cement layer after three types of root canal shaping. Thirty extracted human premolars were endodontically treated and groups of specimens were divided according to the cementation with two different endodontic posts as follow: A) Fibio Fiberglass Post™, Anthogyr, France; B) multi-filament GFRC (Rebilda GT™, VOCO, Germany). Cone beam computed tomography (CBCT) and conventional X-ray analyses were performed before and after the endodontic post cementation. After cementation, specimens were cross-sectioned and inspected by optical microscopy and scanning electron microscopy at magnification ranging from × 30 up to × 2000. Changes in shaping of the root canals caused a decrease in the thickness of the remnant tooth tissues. CBCT and microscopic analyses also revealed a clear variation of resin-matrix cement around the glass fiber-reinforced composite (GFRC) posts. A multi-filament GFRC post provided an adequate distribution of filaments although the resin-matrix cement revealed a high volume among the filaments. An increase in thickness and volume of resin-matrix cement was noticed at the coronal third since the fitting was compromised due to tooth anatomic variations and root canal preparation. Defects such macro-scale pores, cracks, and voids were also detected by microscopic analyses. The root canal shaping can promote a decrease in the thickness of the remnant tooth tissues that can increase the risks of clinical failures by fracture. The thickness and volume of resin-matrix cement varied around both GFRC posts and increased from the apex up to the coronal third due to the lack of fitting. Graphical Abstract: (Figure presented.)