Introduction: A trend is currently observed towards the indication of less invasive procedures, isolated or combined, in the treatment of stretch marks, scars, and the effects of aging. Microneedling is an option that stimulates collagen production without causing the total de-epithelization observed in ablative techniques. Objective: To carry out an experimental study aimed at establishing the correlation between the lengths of the cylinder's needles used for microneedling with the depth of the damage inflicted to the skin. Methods: Biopsies were performed in skin areas of alive pigs that underwent microneedling with cylinders containing 192 needles of 0. 5 - 1, 1. 5 -2 and 2. 5 mm. Results: Microscopic examination carried out immediately after the procedure revealed vascular ectasia with extravasation of red blood cells, affecting the papillary dermis with 0. 5 mm needles and reaching the reticular dermis with longer needles. The authors propose classifying the inflicted injury as mild (0. 5 mm needles), moderate (1. 0 and 1. 5 mm needles), and deep (2. 0 to 2. 5mm needles). Conclusion: The microneedling procedure can be indicated for a broad spectrum of skin alterations when the goal is to stimulate the production of collagen. Establishing the relationship between the length of the needle used and the resulting damage to the skin assists in choosing the microneedling tool used in different directions.

Keywords: DESEARCH DESIGN, COLLAGEN, WOUND HEALING, AMBULATORY SURGICAL PROCEDURES, REJUVENATION

Introduction: Retinoic acid in peeling solution is widely used in the treatment of photoaging. To date, the degree of sterility of these solutions or the safety of their use in skins whose integrity has been lost through microneedling interventions is unknown.
Objectives: To evaluate the bactericidal potential of 3% and 5% retinoic acid in peeling solution, with and without a colored vehicle, as well as the safety and tolerance to its administration immediately after application with microneedles.
Methods: Samples of 3% and 5% retinoic acid solution, with and without a colored vehicle, prepared by two dispensing pharmacies (A and B) were exposed to Pseudomonas aeruginosa and Staphylococcus aureus colonies. These solutions were used as drug delivery agents after percutaneous induction of collagen with needles.
Results: The samples evaluated in D0, D30, D60 and D90 indicated the presence of bactericidal capacity of the tested agents. The use of the solutions following intervention with microneedles was well tolerated and yielded satisfactory results.
Conclusion: The retinoic acid peeling solution can be safely used following procedures that lead to a loss of integrity of the skin barrier. The absence of adverse effects and good results yielded by the procedure suggest that the association of microneedling and retinoic acid peeling is an innovative, reproducible and safe proposal.

Keywords: Chemexfoliation; Therapeutics; Tretinoin