Stress Distribution in Teeth and the Periodontal Ligament During Leveling of the Curve of Spee: A Finite Element Study

Background: An exaggerated curve of Spee is a common finding in malocclusions with a deep overbite and requires correction to achieve functional occlusion and long-term stability. Leveling of the curve of Spee using continuous archwire mechanics generates complex force systems, the biomechanical effects of which depend on archwire material properties, cross-sectional dimensions, and the depth of the curvature being corrected. Quantitative data describing stress distribution within the teeth and periodontal ligament during this process remain limited. Objective: To evaluate and compare the stresses generated in the mandibular teeth and periodontal ligament during leveling of the curve of Spee using orthodontic archwires of different materials and dimensions through three-dimensional finite element analysis. Materials and Methods: A three-dimensional finite element model of the mandibular dentition, periodontal ligament, and supporting alveolar bone was constructed from computed tomography data. Orthodontic brackets and archwires of stainless steel, nickel–titanium, and titanium–molybdenum alloy were modeled in four dimensions: 0.014-inch, 0.016-inch, 0.016 × 0.022-inch, and 0.019 × 0.025-inch. Leveling of the curve of Spee was simulated at incremental depths ranging from 2 mm to 6 mm using displacement-controlled activation. Von Mises stresses generated within the teeth and periodontal ligament were recorded and compared across all simulations. Results: Stress magnitudes increased with increasing depth of the curve of Spee, larger archwire dimensions, and greater wire stiffness. Stainless steel archwires produced the highest stresses, followed by titanium–molybdenum alloy, while nickel–titanium archwires consistently generated the lowest stresses in both teeth and periodontal ligament. Conclusions: Archwire material and dimension significantly influence stress generation during leveling of the curve of Spee. Flexible archwires produce lower stress levels and may be advantageous during early correction of deeper curves.