Effect of pulp-chamber lateral wall thickness and number on fracture resistance in endocrown-restored molars: An in vitro study

It remains unclear how the thickness and number of pulp-chamber lateral walls (PCLWs) affects fracture resistance in endocrown-restored teeth. 64 mandibular molars were collected and randomly divided into eight groups (n = 8). In group C (control group), the teeth were untreated. In groups T1, T2, and T3, the teeth were subjected to endodontic treatment and restored with nanoceramic endocrowns exhibiting different PCLW thicknesses (T1: 0.5 mm, T2: 1.0 mm, and T3: 1.5 mm). In groups N1, N2, N3, and N4, the numbers of missing PCLWs in prepared teeth were one (N1), two (N2), three (N3), and four (N4). All restored teeth were subjected to axial loading until fracture using a universal testing machine. The mean fracture loads were recorded and compared by one-way analysis of variance; the fractured samples were observed under a stereo microscope. The results showed no statistically significant differences in fracture load among groups T1, T2, and T3 (P > 0.05). Although the fracture loads gradually decreased as the number of missing PCLWs increased, there were no statistically significant differences in fracture load among groups C, N1, N2, and N3, and N4 (P > 0.05). Both thickness and remaining number of PCLW does not affect fracture resistance in endodontically treated molars restored with nanoceramic endocrowns.