Influence of Soffit Preservation on Root Stress Distribution in Mandibular Molars: A Finite Element Study

This study evaluated the influence of soffit preservation on stress distribution in roots of mandibular molars using finite element analysis.

An extracted two-rooted mandibular molar was scanned by micro-computed tomography to create 3 models: an intact tooth, a contracted access cavity with partial soffit preservation, and a contracted access cavity without soffit. The models were integrated into a three-dimensional mandibular bone block including cortical and trabecular bone, periodontal ligament, and lamina dura. All regions were initially assumed to be fully tied together. Static loads were applied simulating normal vertical loading (250 N), maximum vertical loading (600 N and 800 N), and lateral loading (225 N). In the prepared models, root canals were digitally filled with gutta-percha and access cavities restored with composite resin. Stress distribution and von Mises stress were evaluated at the pericervical area, furcation region, middle third, and apical third of the roots.

Access cavity preparation altered stress distribution compared to the intact model, with peak von Mises stresses consistently located at the pericervical and furcation regions. Lateral loading produced lower stress values than vertical loading. No significant differences in stress magnitude or distribution were observed between models with and without soffit preservation. Under higher vertical loads, peak stresses occurred on the distal aspect of the distal root (pericervical level) and the distal aspect of the mesial root (middle third).

Soffit preservation did not significantly influence stress distribution in mandibular molar roots under the conditions tested, suggesting that it may offer limited biomechanical benefit in reducing fracture risk following access cavity preparation.