Biomechanical impact of instrumentation and adhesive restoration on pericervical dentin stress in primary second mandibular molars: a finite element analysis

To evaluate the biomechanical impact of canal instrumentation techniques and adhesive coronal restoration on pericervical dentin (PCD) stress distribution in primary second mandibular molars using finite element analysis (FEA). Finite element models (FEMs) of primary second mandibular molars were constructed from high-resolution Cone Beam Computed Tomography (CBCT) scans. Five groups were analysed: Group I (Intact Teeth - Control), Group II (Access Cavity Preparation), Group III (XP-endo Shaper - Minimal taper), Group IV (Neoendo Pedoflex Files; 4% taper), and Group V (Kedo SG Files - Variable taper 4%–8%). Stress distribution patterns were analysed under occlusal loading at angles of 0°, 45°, and 90° in two critical regions: the coronal and radicular areas adjacent to the cemento-enamel junction (CEJ). The unrestored access cavity group (Group II) exhibited the highest stress concentrations under nearly all loading conditions examined. Among the three instrumented and adhesively restored groups (Groups III–V), only minimal Von Mises stress differences were observed, irrespective of the taper design, with all three groups closely approximating the intact tooth. The pericervical dentin zone represented the region of interest for stress concentration analysis in this study, and stress within this zone was elevated when the coronal restoration was absent. The unrestored access-cavity model (ACP) showed the highest pericervical dentin stress values among the groups studied. Adhesive composite resin restoration appeared to exert a substantial biomechanical equalising effect, reducing taper-related differences to a small magnitude within this model, although the independent contribution of restoration could not be isolated from instrumentation. Prompt, well-bonded adhesive coronal restoration following pulpectomy is an important step in preserving pericervical dentin integrity. Prompt placement of adhesive coronal restoration following pulpectomy in primary molars appears to be an important component of preserving structural integrity, alongside the choice of instrumentation. Regardless of the file system selected, coronal sealing with adhesive composite resin should be prioritised as an integral step in conservative paediatric endodontic management.