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Effect of Volume and Concentration on the Diffusion of Botulinum Exotoxin A
Despite the fact that precise placement and appropriate dose of botulinum exotoxin A (hereinafter, “Botox”) is the key to optimizing aesthetic outcome, the optimal dilution and injection volume for cosmetic use has not been precisely characterized. Standard practice varies widely with respect to the amount of saline that is used to reconstitute a standard bottle of Botox. In this prospective randomized controlled study, Hsu et al demonstrate that, for the treatment of dynamic forehead rhytids, a larger volume of solution used to inject equivalent units of Botox results in greater diffusion and a larger affected area. In addition, the shape of rhytid effacement was oval rather than an even, annular pattern as might be anticipated. Thus, the level of precision of Botox use may be manipulated by altering the volume of reconstitution.
Nonablative Facial Remodeling
Nanosecond and millisecond Nd:YAG lasers are among the modalities useful for nonablative rejuvenation. Recently, intermediate-pulsed Nd:YAG lasers have been developed. In this blinded observer analysis, Schmults et al demonstrate that a new microsecond Nd:YAG laser successfully reduced facial erythema and improved skin texture. In addition, electron microscopic analysis revealed a significant decrease in collagen fiber diameter 3 months after treatment. This ultrastructural finding is consistent with neocollagenesis and may account for the improvement in skin quality seen after such nonablative treatments.
Single-Pass Carbon Dioxide Laser Skin Resurfacing Combined With Cold-Air Cooling
Ablative laser skin resurfacing using carbon dioxide or erbium:YAG lasers remains the gold standard for treating cutaneous photodamage, perioral and periorbital rhytids, and acne scars. Intraoperative pain and postoperative adverse effects secondary to the large surface erosions remain the major disadvantages of these modalities. Air cooling during laser treatment offers substantial intraoperative and postoperative relief, yet the effect of this cooling remains unclear. In this side-by-side prospective comparison of single-pass carbon dioxide laser resurfacing with and without cold-air cooling, Raulin and Grema demonstrate that air cooling produced more rapid reepithelialization with fewer complications, less need for operative and postoperative analgesics, and greater patient acceptance, with no significant difference in efficacy.
Treatment of Atrophic Facial Acne Scars With the 1064-nm Q-Switched Nd:YAG Laser
Powerful ablative resurfacing procedures are quite effective in reducing the atrophic scarring of inflammatory acne vulgaris. Nonablative resurfacing procedures hold out the possibility of selectively inducing the wound-healing response in the upper dermis without the accompanying epidermal damage that is responsible for the prolonged recovery time and potential for postoperative erythema and pigmentation seen with ablative techniques. In this trial, Friedman et al demonstrate that the 1064-nm Nd:YAG laser produces a quantifiable improvement in acne scarring after 5 treatments. Persistent benefits well beyond the last treatment session suggest that long-term dermal remodeling continues even after the treatment course has ended.
Connective Tissue Remodeling Induced by Carbon Dioxide Laser Resurfacing of Photodamaged Human Skin
One of the most important molecular mechanisms by which carbon dioxide laser resurfacing produces facial rejuvenation is up-regulation of collagen production. The quantitative changes in neocollagenesis and the time course over which these ultrastructural events occur remain unknown. In this series of in vivo biochemical analyses after carbon dioxide laser treatment, Orringer et al demonstrate a well-organized and highly reproducible wound-healing response, beginning with elevation of proinflammatory cytokine levels, followed by increased production of collagenase 1, stromelysin, gelatinase B, and other enzymes believed necessary for the degradation of photodamaged collagen. These data offer a “measuring stick” against which the treatment effects of other modalities, including nonablative techniques, may be compared.
This Month in Archives of Dermatology. Arch Dermatol. 2004;140(11):1319. doi:10.1001/archderm.140.11.1319
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