Inclusion Criteria:  ≥ 3.0-mm anterior gingival exposure upon unrestricted, "full-blown" smiling healthy adults  Exclusion Criteria:  contraindication of BTX-A previous diseases or treatments affecting the position of the gingiva or upper lips history of BTX-A injections to the head or neck region facial paralysis having received and/or receiving active orthodontic treatment that includes vertical dimension treatment, such as extrusion and intrusion, and presence of periodontal disease subject's refusal to participate