Key components to non-ablative skin remodeling are epidermal protection and proper selection of laser/light irradiation wavelength and energy to evoke the desired thermal response in the papillary and upper reticular dermis. These non-ablative modalities obviate the need for epidermal injury and promote the reorganization and prolifiration of important dermal structures to reverse photodamaged and lax skin via thermal or photochemical process. Heat is generated within the zone of optical penetration immediately by direct absorption of optical energy. Heating decreases with tissue depth as absorption and scattering attenuate the incident beam. In the 800-1000nm range, penetration is deep (~2.5mm) and tissue heating is done by conduction. In contrast, in the 1.2-2.0µm, penetration is modest (~1.0mm) (see chart below) and water absorption is dominant.

The ST handpiece emits light between 780-1000nm (near infrared) where the optical window is ideal for direct subdermal heating (connective tissue, proteins) with low water absorption in the epidermis. These conditions negate the need for aggressive epidermal cooling. The ST handpiece energy output can be set between 5 - 105 J/cm2 based on 3 different selectable time intervals: 5, 10 or 15 seconds. During each time interval, the repetition rate is kept at 3Hz. The large spot size (6.4cm2) allows large coverage and true investment of energy density for better penetration and predictable thermal effect. The handpiece is applied on the skin where it is kept stationary for the entire exposure time (5, 10, or 15 sec) and fluence selected.

Skin remodeling is a biophysical phenomenon that occurs at cellular and molecular levels via the intervention of optical or thermal energy. The ST handpiece exerts its biological effect on the skin through two major mechanisms: 1) heat-induced collagen shrinkage and micro-thermal injury and; 2) dermis regeneration, repair (wound healing) and remodeling. Collagen cleavage in tissue is a probability event dependant on temperature. The in-vitro thermal cleavage of the hydrogen bond cross links of tropocollagen can result in the molecular contraction of the triple helix up to one third of its original length. Cellular contraction involves the initiation of an inflammatory/wound healing sequence that is perpetuated over several weeks. Contraction of skin is achieved through fibroblastic multiplication and contraction with the deposition of a static supporting matrix of nascent scar collagen. This cellular contraction process is a biological threshold event initiated by the degranulation of the mast cell that releases histamine. This histamine release initiates the inflammatory wound healing sequence. Following cellular contraction, collagen is laid down as a static supporting matrix in the tightened soft tissue structure. The deposition and subsequent remodeling of this nascent scar matrix provides the means to alter the consistency and geometry of soft tissue for aesthetic purposes.

Skin tightening patient candidates are typically younger patients who are not ready for surgery or are not surgical candidates. In addition they may be older patients with mild to moderate laxity who do not want or are not candidates for surgery. The typical skin tightening, toning and texture smoothing patient does not want to spend the additional money for surgical intervention or can not afford the downtime associated with surgery.