Efeito da rigidez da contenção no deslocamento dentário e na distribuição de tensões em fraturas radiculares: estudo experimental e por elementos finitos

Abstract

The ideal splint rigidity for horizontal root fractures remains controversial. While insufficient stabilization may impair healing, excessive rigidity may restrict physiological tooth displacement and can also compromise the periodontal ligament healing. This study evaluated the influence of splint rigidity and fracture location on tooth displacement and stress distribution in horizontal root fractures. A three-dimensional-printed polymer maxillary model was generated from cone-beam computed tomography data. Horizontal cervical, middle, and apical central incisor root fractures, along with adjacent intact central incisors serving as controls, were three-dimensional-printed in resin composite. Three wire–resin composite splinting systems with different rigidity levels were evaluated: flexible (1.0-mm nylon), semi-rigid (0.6-mm steel wire), and rigid (0.9-mm steel wire). Non-splinted fractured teeth were used as negative controls. Coronal tooth displacement (m) was measured using a deflectometer (Instron) at baseline and after 50 cycles of cyclic loading at 1 Hz with a force range of 25–50 N. Three-dimensional finite element models were developed from the same cone-beam computed tomography data set. A nonlinear biting force analysis was performed to evaluate tooth displacement and stress distribution. Experimentally measured tooth displacements were analyzed using two-way analysis of variance, followed by Tukey’s post hoc test (α = 0.05). Stress distribution was assessed qualitatively using modified von Mises stress (MPa). Coronal tooth displacement in non-splinted teeth increased significantly from apical to cervical root fractures (P < 0.01) and from the initial to final cyclic loading (P < 0.01). All splint types significantly reduced coronal tooth displacement (P < 0.01) and stress concentration at the fracture line. Stress concentration at the fracture line was higher in cervical fractures and non-splinted teeth. The 0.9-mm steel wire splint resulted in significantly lower displacement than that observed in intact teeth. Cyclic loading had no significant effect on tooth displacement in splinted fractured teeth (P > 0.01). Splinting stabilized adequately the root fractures regardless of fracture level. Flexible and semi-rigid splints provided required stabilization allowing functional tooth displacement similar to intact teeth.