Laser Tissue Interactions in Scar Treatment and Skin Rejuvenation: Histology, Imaging, and Device Selection

Conclusions

• Device and parameter selection for scars and rejuvenation should be individualized to the patient’s skin type, scar depth, scar size, and the mechanism of the energy-based device.
• Microneedling is a purely mechanical, non-thermal treatment that is broadly safe across skin types, and it can also be useful for drug delivery when timing and drug properties are optimized.
• Laser-assisted or device-assisted drug delivery works best when the treatment creates channels large enough for the drug or filler being used, and application timing can materially affect penetration depth.
• Fractional radiofrequency microneedling appears to provide stronger rejuvenation and wrinkle improvement than microneedling alone, with deeper collagen remodeling and less evidence of cellular senescence.
• Fractional picosecond lasers create laser-induced optical breakdown without thermal injury and are particularly useful for scar remodeling and erythematous scars, with superficial cavitation generally making them safer for darker skin.
• Monopolar radiofrequency and focused ultrasound both achieve dermal tightening by controlled thermal coagulation while largely sparing the epidermis, making them useful options for rejuvenation in skin of color.
• Ablative fractional lasers create larger channels and more substantial tissue vaporization, which makes them especially effective for drug delivery and for treating more pronounced scar pathology.
• Non-ablative fractional lasers cause limited coagulation with little or no ablative channel formation, so they are safer and better suited for more superficial indications, but they are less effective for delivering large particles or deep dermal payloads.
• Higher water absorption generally produces shallower penetration, explaining why 1,927-nm lasers are better for superficial pigment problems while 1,540/1,550-nm lasers reach deeper dermis.
• Lower density and higher-energy fractional settings reduce the risk of post-inflammatory hyperpigmentation compared with denser treatment patterns, especially in skin of color.
• Fully ablative lasers remain effective for selected small facial areas and deeper resurfacing indications, but they cause prolonged wound healing and are generally not recommended for darker skin types.
• Overall, the safest and most effective approach is to match the device and settings to the target tissue depth and desired injury pattern while minimizing epidermal damage and pigmentary risk.