Abstract: Clear aligners and lingual appliances share common traits of physical invisibility, and therefore, clinical popularity. The marked differentiations between these two modalities, however, lie in treatment mechanisms and indications. This article summarized the accomplishments made and the challenges aroused in these two orthodontic mechanisms, advocating optimal selection of indications and proper use of these two appliances. Cautions are raised against excessive use of clear aligners by ignoring indication inspections.

Key words: Clear aligners, Lingual appliances, Digital technologies