Skin tightening effects of the ultrapulse CO2 laser.

This study analyzed the skin tightening or contracture effect of the Ultrapulse carbon dioxide (CO2) laser on the skin of hairless guinea pigs by light and electron microscopic, histologic, and tensiometric evaluations. Two 2 X 2 cm squares of back skin were precision tattooed on each of the animals in the study (n = 12). One square served as the control, and the other square was used as experimental skin. The experimental skin was treated with three passes of the CO2 laser at 500 mJ and 5 W using a 3-mm collimated hand-piece. Skin specimens from three animals were analyzed at 1, 4, 8, and 12 weeks. After three passes, the length of the square was reduced by 27 percent, and the width was reduced by 40 percent. Over the next 12 weeks, as the animals grew, the dimensions of the control areas also increased. The laser-treated areas continued to maintain their contracted dimensions, however. By the 12th week, the laser-treated areas were 28.35 percent shorter in length and 15.5 percent shorter in width than the control areas. Histologic examination demonstrated a significantly higher content of collagen in the reticular layer, which was more compact than that of the normal skin. Electron microscopy revealed that the laser had induced shortening of the collagen fibers (7.45 percent; p = 0.026), which persisted beyond the 12th week. Laser treatment did not significantly alter the tensile strength of the skin, although, at the 8th week, the treated areas had a slightly higher tensile strength.