In this randomized clinical trial , two groups will be included to compare the effectiveness of a treatment modality of botulinum toxin-A injection , in the first group , on gingival display during smiling ,patient satisfaction , lower face esthetics ( upper lip length , upper lip vermillion length , interlabial gap , nasolabial angle) and the postoperative side effects . the comparator group will receive treatment by modified lip repositioning surgery ,to compare the results of the intervention group that can possibly obtained without undergoing surgery.