Heat Influence on Different Hyaluronic Acid Fillers

Facial volume deficits, providing long-term facial aesthetic enhancement outcomes for the signs of aging and/or facial contouring. Numerous hyaluronic acid (HA) fillers seem to have similar characteristics, although their properties regarding rheology, viscoelasticity, heat resistance are different in many ways. The resistance heat degradation is important when hyaluronic acid fillers and energy-based devices are going to be used sequentially. Our objective was to determine the characteristics of HA gels in terms of heat resistance. Degradation of the gels was measured as a change of surface area of the sample. Five types of HA fillers, chosen from most common products on the market for temporary correction of congenital and acquired soft tissue deficits of the face via intradermal or subcutaneous injection: 20mg/ml HA-BDDE, 20mg/ml HA-BDDE, 20mg/ml HA-BDDE, 25 mg/ml HA-BDDE, 28mg/ml HA-PEG were tested in this study. Even though the three dermal fillers contained the same concentration of HA and were cross-linked with the same cross-linking agent, they were produced by different manufacturers using different technologies developed by individual companies. We tested in vitro resistance to heat degradation using Celltibator GT (Medikan Co., LTD, Seoul, Rep. of Korea) and Autoclave (Medotti 22L PRO, Poland). All of the HA fillers samples (0,3 ml) were placed on the petri dishes and put into the autoclave for 10 minutes (temp. 72,4°C). Three of the gels samples (20mg/ml HA-BDDE, 25mg/ml HA-BDDE, 28mg/ml HA-PEG) each 0,3ml were placed into Celltibator for 10 min, temp. 55,2°C degree, centrifugation: 30 RPM. Centrifugation was used to imitate the behaviour of the fillers under the conditions of forces acting on it in the tissue (stress under the influence of facial expressions, exercises, etc.). The temperatures used during this test correspond with commonly used heat-based devices, such as radio-frequency devices (about 45°C), infrared (about 55-65°C) and HiFU (about 70-75°C). Before and after each test pictures of the samples were taken. Heat degradation of the HA samples was measured by comparing (before and after) the changes of the surface area of samples on the petri dishes (on the graph paper). The 28-mg/ml HA-PEG gel filler demonstrated greater resistance to heat versus the 20- mg/ml and 25-mg/ml BDDE gel fillers. The 28-mg/ml HA-PEG, demonstrated in both test (celltibator with/without rotation and autoclave) greater resistance to heat in terms of deformation / thermal degradation and change of surface area. Selection of dermal filler with the right rheological properties is a key factor in achieving a natural-looking long-lasting desired aesthetic outcome. Hyaluronic acid fillers combined with energy-based devices are frequently used sequentially during the same session, however, in some cases it might cause thermal damage of HA. Caution is advised in using IR over recently injected filler (selection of dermal fillers is crucial in this case). Study limitations include use of in vitro model and lack of inflammatory response in an ex-vivo model.