Impact of post and core materials on the apical extension of root fracture in root canal treated teeth

Compared with vital teeth, changes in chemical and physical properties along with alterations in tooth structure after root canal treatment increase the possibility of root fracture. These aspects need to be considered in selecting materials used in the restoration of endodontically treated teeth, specifically the fabrication of posts and cores for this purpose. This study aimed to measure the apical extension of fracture in teeth subjected to root canal treatment and restoration by post- and core-fabricated materials. Forty extracted maxillary central incisors were included in the experiment and subdivided into experimental and control groups. Root canal treatment was performed for teeth in the control group, and the accessed cavity was restored with direct composite restoration. The experimental groups were restored using computer-aided design/computer-aided manufacturing (CAD/CAM) milled posts and cores of polymer-infiltrated ceramic network (PICN), zirconia and metal. Then, the cores were restored with metal crowns, subjected to a compression test to record the fracture resistance, and examined to evaluate the extension of root fracture apically. The results of the compression test were expressed in Newtons. The extension of root fracture was measured in millimeters using metric pictures of the samples taken by stereomicroscopy. The data were analyzed using ANOVA with Tukey's HSD, and a P-value of <0.05 was considered significant. Compared to PICN, zirconia and metal groups showed a non-significant increase in fracture resistance. However, the difference in resistance to fracture between the control group and PICN group was significant, with a P value of 0.02. The apical extension of root fracture in metal (3.72 ± 0.41) and zirconia (3.77 ± 0.96) was significantly higher than that in PINC (2.02 ± 1.44) (p = 0.003 and 0.002, respectively). In comparison to zirconia and metal samples, the samples in the PICN group showed less extension of root fracture apically. PICN would be an acceptable material of choice for restoring anterior teeth when post and core are required.