Deformation characteristics of hydrogel products based on cross-linked hyaluronic acid.

[BACKGROUND] The cross-linked hyaluronic acid (HA) fillers are the viscoelastic hydrogel with a dominant elasticity rather than a viscosity as a useful medical device in the soft tissue augmentation. These HA fillers undergo deformation to begin the biodegradation by the biochemical and physical environment of the body, and result of deformations are closely related to clinical performance.

[AIMS] The specific equation of molding index is newly generated and proved with Collin's equation, which is used for strong elastomers, for selecting optimal product in facial treatment.

[METHODS] In this study, the results of amplitude sweep test from five marketed HA fillers were mathematically demonstrated for the proper clinical application.

[RESULTS] The increment of loss modulus by deformation was evaluated as a useful factor for the maintenance of optimal shape molding performance and resistance to external deformation of the cross-linked HA gel. From this study, the equation of molding index for weak viscoelastic hydrogels like HA products can be applied for choosing which products even in aesthetic plastic field. This molding index equation is compared to Collins' equation that index of deformation as elastomer like rubber and then found the positive correlation between two equations.

[CONCLUSION] This study could provide a basic theory that achieve useful clinical performance according to characteristics among many types of medical devices based on the molding index.