title: Effect of a second injection of botulinum toxin on lower facial contouring, as evaluated using 3-dimensional laser scanning.
abstract: BACKGROUND
  Botulinum toxin type A (BoNT-A) is widely used to improve the lower facial contour.
  
  
  OBJECTIVE
  To determine the difference in the changes in the lower facial contour achieved with 1 and 2 sessions of BoNT-A injections using 3-dimensional (3D) laser scanning.
  
  
  METHODS
  Twenty volunteers were randomly divided into 2 groups. Group I (n = 10) received a single injection, whereas Group II (n = 10) received 2 sessions of injections, the second being administered 4 months after the first. Each injection comprised of 25 U of BoNT-A and was administered to the masseter muscle bilaterally. Evaluation of the effect of BoNT-A injection was performed using 3D laser scan images obtained before the injection and 6 months thereafter in Group I, and before the first injection and 6 months thereafter in the Group II.
  
  
  RESULTS
  The mean changes in the volume and thickness in Group I were -1,186 mm and -1.52 mm, respectively; the corresponding changes were -4,072 mm and -3.84 mm in Group II. The reductions were significantly greater in Group II than in Group I.
  
  
  CONCLUSIONS
  The administration of a second BoNT-A injection is effective for better aesthetic results for the lower facial contour.
authors.affiliation: Departments of *Orthodontics, and †Orofacial Pain and Oral Medicine, School of Dentistry, Yonsei University, Seoul, Korea; ‡Department of Orthodontics, Institute of Craniofacial Deformity, School of Dentistry, Yonsei University, Seoul, Korea.
authors.forename: Hong-Hee
authors.initials: HH
authors.lastname: Lee
authors.forename: Seong Taek
authors.initials: ST
authors.lastname: Kim
authors.forename: Kee-Joon
authors.initials: KJ
authors.lastname: Lee
authors.forename: Hyoung-Seon
authors.initials: HS
authors.lastname: Baik
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D005146:Facial Asymmetry / Q000175:diagnosis* / Q000188:drug therapy*; D005260:Female; D005500:Follow-Up Studies; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007273:Injections, Intramuscular; D007834:Lasers; D008297:Male; D008406:Masseter Muscle; D008875:Middle Aged; D009465:Neuromuscular Agents / Q000008:administration & dosage; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A