Abstract: Treatment designs of the extraction or non-extraction borderline cases were complex,and they varied as different technologies were applied.With the development of advanced medical technology,clear aligners were widely accepted and their efficacy in moving orthodontic teeth had been verified.Some experts suggested that clear aligners had certain advantages over the conventional labial fixed appliances in treating extraction or non-extraction borderline cases with non-extracted plans.In this article,the three-dimensional features of clear aligners in moving teeth were discussed and their advantages over the fixed appliances were analyzed,both of which could provide the clinical reference for treating the extraction or non-extraction borderline cases.

Key words: clear aligner, extraction or non-extraction borderline cases, orthodontics