Mechanical Characterization of Intermaxillary Orthodontic Elastics: Energy-Based Metrics and Clinical Guidance

Background: Intermaxillary elastics are widely used in orthodontics to deliver controlled forces for malocclusion correction, aiding in the correction of anteroposterior, vertical, or transverse problems. Despite their clinical relevance, comprehensive mechanical characterization remains limited. Objective: This study aimed to evaluate the mechanical properties of nine types of intermaxillary elastics available on the market to guide evidence-based clinical selection. Methods: Elastics were tested under uniaxial tensile loading following ISO 37:2011 and ISO 21606:2007, with six replicates per type. Load-displacement and stress-strain responses were analyzed, measuring peak force, elongation at rupture, work-to-rupture, and specific rupture work. Non-linear behavior was modeled using cubic polynomial regression, and normalized stress-strain curves enabled intrinsic material comparisons. One-way ANOVA with post-hoc tests assessed differences among elastics. Results: All elastics displayed characteristic non-linear elastomeric responses. Functional grouping distinguished short-displacement/high-stiffness, intermediate-displacement/moderate-stiffness, and long-displacement/high-capacity bands. Work-to-rupture, specific rupture work, and normalized stress-strain metrics varied significantly, reflecting differences in energy absorption and force delivery (p < 0.05). Conclusions: Mechanical characterization, including energy-based descriptors and normalized stress-strain analysis, supports informed elastic selection, enhancing orthodontic treatment predictability and patient safety.