Remodelage et photoréjuvénation

Resurfacing by CO₂ or Er:YAG laser techniques in the treatment of facial rhytids has traditionally involved ablative methods with, however, associated complications and limitations due to the epidermis “sacrifice”. Recently, rhytid improvement and dermal remodelling have been observed, with the utilization of non-ablative approaches. The underlying principle of non-ablative laser remodelling is to induce a controlled injury to the collagen in the dermis, while completely sparing the epidermis from damage. As dermal collagen heals and remodels under an undamaged outer layer, the skin tightens and smoothes, thus improving it’s appearance. Two classes of lasers are used for non-ablative laser remodelling : i) visible light lasers, including green and yellow light lasers adapted or modified from their original use as treatments for vascular lesions. 532nm (green) and 585nm (yellow) light are strongly absorbed by oxyhemoglobin and melanin in the epidermis and upper dermis. The heating effect in these skin layers triggers the release of various growth factors that stimulate collagen remodelling and tightening. ii) infrared lasers, emitting at 980nm, 1320nm, 1450nm and 1540nm produce invisible light that is absorbed by primarily by water, which heats the superficial layers of the skin. These lasers use contact or non-contact skin cooling to limit the heating effect to the dermis, creating a controlled injury to the dermal collagen, with subsequent remodelling and tightening. More recently, non-ablative photorejuvenation with intense pulsed light (IPL) has been introduced. Several clinical studies on non-ablative lasers, using objective evaluations (silicone imprints, cutometer, ultrasound imaging) have clearly demonstrated a progressive improvement over months. Histological examinations of the treated areas have clearly showed a superficial dermal band of well organized elastin and collagen fibres replacing pre-treatment elastic tissue. This improvement of the skin was not associated with any adverse effects. Concerning intense pulsed light, only a few clinical studies have reported varied clinical results with non-ablative photorejuvenation.