title: Rheological Properties and In Vivo Performance Characteristics of Soft Tissue Fillers.
abstract: BACKGROUND
  Physicochemical properties and performance in nonclinical animal models can provide insights into soft tissue filler performance.
  
  
  OBJECTIVE
  To evaluate the in vivo performance of fillers with different compositions and physicochemical properties.
  
  
  METHODS
  Physicochemical properties were measured in vitro. Rat models were developed and used to compare lift capacity, resistance to deformation, and tissue integration. Four homogeneous hyaluronic acid (HA) fillers, 2 nonanimal stabilized HA (NASHA) fillers, and 1 calcium hydroxylapatite/carboxymethyl cellulose (CaHA/CMC) filler were evaluated.
  
  
  RESULTS
  Filler lift capacity correlated better with filler composition/type (homogeneous > NASHA > CaHA/CMC) than with specific rheological properties. The CaHA/CMC filler had high initial resistance to deformation relative to other groups; all HA fillers exhibited lower initial resistance to deformation, which increased over time. Homogeneous HA fillers were integrated with surrounding tissue, whereas integration within particle-based fillers (NASHA and CaHA/CMC) was variable, with some areas void of tissue.
  
  
  CONCLUSIONS
  The animal models provide a platform to make comparative evaluations among fillers. The results indicated that biological interaction plays an important role in how the filler performs. Rheology alone was not sufficient to understand filler performance but was most useful when comparing within fillers of similar composition.
authors.affiliation: *Allergan, Inc., Irvine, California; †Bay Area Laser Institute, San Francisco, California.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Hee
authors.forename: Garrett T
authors.initials: GT
authors.lastname: Shumate
authors.forename: Vic
authors.initials: V
authors.lastname: Narurkar
authors.forename: Aude
authors.initials: A
authors.lastname: Bernardin
authors.forename: Darin J
authors.initials: DJ
authors.lastname: Messina
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D003357:Cosmetic Techniques; D017886:Durapatite / Q000737:chemistry*; D006820:Hyaluronic Acid / Q000737:chemistry*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012212:Rheology / Q000379:methods*; D015595:Skin Aging / Q000187:drug effects*; D055675:Viscosupplements / Q000737:chemistry
chemical_list: D001672:Biocompatible Materials; D055675:Viscosupplements; D006820:Hyaluronic Acid; D017886:Durapatite