[Modern polymer materials in aligner production: analysis of mechanical properties and clinical significance in the correction of dental crowding].

The clinical efficacy of aligner therapy in correcting dental crowding directly depends on the physical and mechanical properties of the polymer materials used for aligner fabrication. The aim of this review is to systematize current data on the characteristics of modern thermoplastic polymers and to substantiate principles for the clinical selection of materials with optimized properties in the treatment of dental crowding, especially in the anterior region. The article focuses on key parameters determining aligner biomechanics: elastic modulus, stress relaxation, creep, and the influence of temperature fluctuations and the oral environment. A comparative analysis of common single-layer materials (PET-G and thermoplastic polyurethanes) and innovative multilayer systems is presented. Available evidence indicates that rapid stress relaxation and pronounced creep reduce the predictability of complex orthodontic movements (derotation, bodily movement, changes in inclination) and contribute to geometric discrepancies between planned and achieved tooth positions. The clinical rationale for choosing materials with a more favorable viscoelastic profile and greater stability of mechanical properties is discussed, together with the importance of 3D technologies (model superimposition on reference areas) for quantitative assessment of treatment accuracy.