RESUMEN
BACKGROUND: There are several published articles on characterization of fillers, describing methods for both chemical and physicochemical characterization. Recently a lot of focus has been on the development of methods for measuring cohesion of hyaluronic acid (HA) fillers. OBJECTIVE: The aim of this study is to investigate and compare the drop-weight method and the correlation between cohesion and other physicochemical properties using a variety of HA fillers. MATERIALS AND METHODS: HA fillers covering several product families and manufacturing techniques were used. The HA fillers also covered a range of HA concentrations from 12 to 24 mg/mL. Cohesion was determined using sensory evaluation and the drop-weight method. Other physicochemical properties evaluated were rheology and the swelling factor. RESULTS: In this study, it was verified that values obtained by the drop-weight method reflect the perceived cohesion very well. The correlation with rheology is affected by the HA concentration in the products. A remarkably good correlation between swelling factor and cohesion was found. CONCLUSION: Cohesion correlates with other physicochemical methods. It could be discussed whether there is a need for a separate cohesion method because other already established physicochemical methods such as rheology and swelling factor can describe the underlying properties that affect cohesion.
Asunto(s)
Rellenos Dérmicos/química , Ácido Hialurónico/química , ReologíaRESUMEN
BACKGROUND: The terms "biphasic" and "monophasic" have been used frequently as a means of differentiating hyaluronic acid (HA) fillers. This type of categorization is based on misinterpretations of the term "phase" and provides no help to the practitioner when selecting the most appropriate product for each indication, patient, and injection technique. OBJECTIVE: The purpose of this study was to analyze the properties of 2 HA filler families; Juvederm (JUV) (Allergan), often stated to be monophasic and Restylane (RES) (Galderma), often stated to be biphasic, and discuss what properties may have led to the use of the terms monophasic and biphasic. MATERIALS AND METHODS: Three different methods were used for JUV and RES: determination of extractable HA; determination of water uptake; and microscopy. RESULTS: The analyzed products were shown to contain both observable gel particles and extractable HA and have the ability to absorb added water. CONCLUSION: The categorization of HA fillers as biphasic or monophasic was shown to be scientifically incorrect and should therefore be avoided. Further analytical measurement of the properties leading to this misinterpretation can provide information to discriminate and categorize HA fillers on a sounder scientific basis.
Asunto(s)
Técnicas Cosméticas , Ácido Hialurónico/análogos & derivados , Ensayo de Materiales/métodos , Envejecimiento de la Piel/efectos de los fármacos , Humanos , Ácido Hialurónico/químicaRESUMEN
BACKGROUND: Cohesion is described as the force between particles of the same substance that acts to unite them. Contrary to rheology, there are currently no ready-made instruments designed to measure cohesion, or methods which could be easily adapted to gels. To study and compare the possible clinical effects from the cohesive properties of a gel, it is necessary to standardize the definition and measurement of cohesion. OBJECTIVE: The purpose of this study was to develop and evaluate methods for measuring cohesion. METHODS AND MATERIALS: Three different methods were evaluated and compared with measures of perceived cohesion; compression force, dispersion in water and drop weight. Two different families of fillers (Emervel and Restylane) were used for evaluating the different methods. RESULTS: The compression force did not reflect the measures of perceived cohesion. The dispersion method showed variable results over time, had some practical issues, and is evaluated by subjective assessment. The best correlation to the perceived cohesion was found with the drop weight method. CONCLUSION: The drop weight method which closely resembles the definition of cohesion (IUPAC) was considered to be the best method for measuring cohesion.