Soft tissue changes of upper lip in patients with Class Ⅰ malocclusion with different premolar extraction patterns

ZHANG Shuo-fei1，LIN Xin-ping2，ZHENG Min-ling1

West China Journal of Stomatology . 2010, (03): 268 -272 . DOI: 10.3969/j.issn.1000-1182.2010.03.011