RESUMEN
For the pre-treatment prior to laser resurfacing, materials such as glycolic acid, tretinoin, and/or hydroquinone have been widely used. However, the optimal duration of pretreatment is still controversial. The authors chose guinea pig skin which is similar to human skin, pre-treated it with tretinoin and hydroquinone with different duration, and examined gross and histologic changes after performing laser resurfacing in an attempt to study the effect of pre-treatment period on CO2 laser resurfacing. Sixteen guinea pigs were divided into four groups, and the dorsal skin was pre-treated with 0.05% tretinoin cream and 4% hydroquinone for 4, 8, and 12 weeks respectively while groupI underwent no pre-treatment as control. During the pre-treatment period, the authors observed gross skin reactions, and also examined the number of epithelial layers, thickness changes, the extent of epithelial regeneration, and collagen tissue change within dermis layer with skin tissue samples before and after laser resurfacing. Compared to group I(control) which received no pre- treatment, pre-treatment groups showed rapid epithelial hyperplasia and increase in the number and thickness of squamous epithelial cells and granular cell layer. However, there was no statistically significant difference in epithelial regeneration and number and thickness of epithelial cell layer between the 4-weeks, 8-weeks, 12- weeks pretreated groups. Pre-treatment with tretinoin and hydroquinone prior to laser resurfacing helped epithelial regeneration after resurfacing, but as to the benefit of long-term pre-treatment more than 4 weeks was not necessary.