lip retraction

lip re·trac·tion

(lip rĕ-trak'shŭn)
An atypical oral pattern that occurs when the lips are drawn back to form a tight horizontal line over the mouth, making it difficult to assist with sucking liquids, removing food from a spoon or cup, and retaining food in the mouth.
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References in periodicals archive ?
Our results are in concordance with the findings of Chung KR et al21 and Caplan MJ22 who also showed lip retraction with 1st premolar extractions.
However, other soft tissue measurements such as z-angle and s-line41 can be used to confirm lip retraction and lower facial profile changes following 1st premolar extraction.