Biomechanical Evaluation of Clear Aligners

Objectives: Clear aligners are an attractive option for orthodontic treatment of adult patients. However, the mechanical efficiency of this type of treatment is still questionable. To increase the efficiency of these appliances 2 main approaches have been taken: 1) improving the aligner material, 2) improving the mechanical force delivery system. The aim of this study was to evaluate the effects of current methodology on improving the biomechanical efficiency of aligners
Methods: We conducted a literature review of all studies published on clear aligners using search words related to mechanics, biology and aligner material. Articles were reviewed and evaluated for proper research design and methodology.
Results: 230 articles were selected. The majority of studies were focused on the material properties of aligners and very few articles investigated the biomechanical characteristics of aligners. Material studies demonstrate a trend in improving the magnitude and continuity of the force by aligners, but with no improvement in biomechanical properties of aligners. Biomechanical studies of aligners were very limited and did not use proper design or methodology. However, even these studies still showed the deficiency of aligners in producing specific types of tooth movement.
Conclusions: There is no evidence to demonstrate that biomechanically aligners can provide proper force and couples to produce different types of tooth movement. Improvement in the material properties cannot address this problem and therefore understanding of the biomechanical limitations of aligners by the clinicians is very important.