Rheologic and Physicochemical Characteristics of Hyaluronic Acid Fillers: Overview and Relationship to Product Performance

Abstract

Injections with hyaluronic acid (HA) fillers for facial rejuvenation and soft-tissue augmentation are among the most popular aesthetic procedures worldwide. Many HA fillers are available with unique manufacturing processes and distinct in vitro physicochemical and rheologic properties, which result in important differences in the fillers' clinical performance. The aim of this paper is to provide an overview of the properties most widely used to characterize HA fillers and to report their rheologic and physicochemical values obtained using standardized methodology to allow scientifically based comparisons. Understanding rheologic and physicochemical properties will guide clinicians in aligning HA characteristics to the facial area being treated for optimal clinical performance.

Bridging a Century-Old Problem: The Pathophysiology and Molecular Mechanisms of HA Filler-Induced Vascular Occlusion (FIVO)—Implications for Therapeutic Interventions

“…Specifically, the ability of a gel to take up water, known as the swelling factor, can directly impact the gel particle volume as it hydrates intraluminally. Currently available fillers exhibit swelling factors that range between 100 and 700% by volume, increasing their occlusive potential [ 101 , 102 ]. In addition, cohesivity, or the capacity of a gel to resist fragmentation and dispersal, may bear significance in the intravascular behavior of dermal fillers and their response to reversal agents [ 103 ].…”

Assimetria labial: uma correção local apenas?

“…As propriedades reológicas dos diferentes géis de AH são determinadas pelos fatores de armazenamento/módulo elástico (G'/G prime), o qual mede a rigidez e capacidade de armazenamento de energia pelo gel para recuperação de sua forma original durante a deformação. O que justificou o uso do Restylane Lyft (AHL), produto com maior G prime (977') com alta capacidade de recuperação de volume e reposicionamento tecidual, sendo assimetricamente aplicado em pontos justaósseos para a correção da assimetria facial presente no lado esquerdo da paciente (Guardia et al, 2022).…”

“…Embora exista no mercado uma gama de preenchedores de ácido hialurônico utilizados no preenchimento labial, a escolha da aplicação do Restylane Kysse (AHK) para dar volume nos lábios da paciente se deu por conta da presença de baixa elasticidade do matérial (236') e combinação adequada de coesividade, maciez e absorção de água, sendo facilmente moldável para que o tecido não se torne enrijecido (Guardia et al, 2022).…”

Filler‐based correction of tear trough depressions and eye bags in Japanese patients: A classification system and treatment algorithm

“…We typically do this using human collagen (Humallagen, Cosmetic Medicine Enterprises Inc., Palm Harbor, FL, USA; available only in Japan). Alternatively, an HA filler can be used, as long as the product injected has the required physical properties; in particular, it should have low‐to‐medium elastic modulus (G') and low cohesivity (so that it is sufficiently spreadable to avoid overcorrection or the formation of lumps and bumps), as well as low water absorption (to avoid the Tyndall effect) 12 . We use Teosyal® Redensity 2 (Teoxane Laboratories, Geneva, Switzerland) or Juvéderm® Volbella™ (Vycross 15 mg/ml HA [VYC‐15 L]; Allergan, Dublin, Ireland), owing to their longevity.…”

“…Alternatively, an HA filler can be used, as long as the product injected has the required physical properties; in particular, it should have low‐to‐medium elastic modulus (G') and low cohesivity (so that it is sufficiently spreadable to avoid overcorrection or the formation of lumps and bumps), as well as low water absorption (to avoid the Tyndall effect). 12 We use Teosyal® Redensity 2 (Teoxane Laboratories, Geneva, Switzerland) or Juvéderm® Volbella™ (Vycross 15 mg/ml HA [VYC‐15 L]; Allergan, Dublin, Ireland), owing to their longevity. If the patient wishes to have an injectable that is officially approved in Japan (as of September 2022), we use the latter.…”