Midfacial volume restoration is not basically correcting the
deficiency in tissue levels of HA but a true augmentation
of the HA.[14] The HA ratios in the foetal as well as the
aged skin is nearly unaltered, so HA as the filler will
only act as a mere augmentation.[14,15] It has the intricate
physical properties of increased longevity, filling capacity
and the ease of injection making it accurate for facial
rejuvenation. The longevity of the filler depends on the
degree of crosslinking in HA which increases the viscosity
and reduces free radical and enzymatic degradation. The
more the crosslinks, more is the viscosity and cohesivity
giving a sustained dermal lift but more difficult to inject
through a thin needle.[16,17] The lower molecular weight,
higher viscous HA is slowly biodegraded as it is in excess
to the naturally existing HA in the dermis. It retains
water and volume, until it reaches a critical level where it
rapidly disappears.[18]