Effect of Varying Thickness of Clear Aligners in Orthodontic Therapy - A Review

Clear aligner therapy (CAT) is one of the most rapidly expanding fields of orthodontics, propelled by patient interest in appliances that are aesthetic and removable. From the launch of Invisalign, ongoing improvements have broadened the applications of aligners from basic anterior alignment to advanced treatments. This review assesses the impact of aligner thickness on biomechanics, material properties, clinical results, and patient-centric factors and synthesizes evidence from laboratory research, computational simulations, and clinical research. An extensive search of PubMed, Scopus, and Google Scholar was conducted without year restrictions. The 25 included studies examined aligner thickness in terms of orthodontic performance, material response, or patient outcomes. Laboratory and computational analysis all show that aligner thickness increases with better stiffness and force delivery, but at the cost of patient comfort. Slimmer aligners are more tolerable but compromise biomechanical control. Thermoformed aligners are non-uniform in thickness, whereas 3D-printed aligners are more uniform and stable. Over time wear thins out aligners, so staged replacement regimens are required. Patients experience a compromise among comfort, aesthetics, and mechanical function. The evidence indicates that thickness is a variable with immediate clinical significance. In conclusion thicker aligners enhance force control, whereas thinner ones are more comfortable and invite wear. Choice of material and fabrication technique influence thickness stability. Despite robust in vitro and computational evidence, evidence from the clinic is limited. Randomized trials, standardized measures, patient reports, and novel polymers should be the focus of future research to design customized thickness strategies enhancing biological efficacy and patient satisfaction Keywords: Orthodontic Appliances, Removable; Clear Aligner Therapy; Thermoplastic Materials; Finite Element Analysis; Biomechanics.