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The devices used create transient epidermal and dermal openings ranging in size from 25 to 3000 um in depth as a microinjury, with the goal of stimulating the inherent skin repair mechanisms. These microwounds or microinjuries initiate the release of growth factors, which trigger and stimulate collagen and elastin formation in the dermis. That leads to healthier skin with improved texture. The microwounds are microchannels and heal following the classic wound‐healing cascade: inflammation, proliferation, and remodeling. This cascade is brought on by the needles’ disruption of the stratum corneum; the endothelial lining and the subendothelial matrix recruits platelets and neutrophils to the site of injury. Needling exposes thrombin and collagen fragments, which attract and activate platelets. The platelets form a plug and initiate the clotting cascade, which involves local platelet aggregation, inflammation, and blood coagulation through increased levels of thrombin and fibrin.
The needles carry an electric potential that stimulates fibroblast proliferation [10]. The mechanical injury triggers the release of potassium and proteins that alter intercellular resting potential, drawing in fibroblasts and stimulating neocollagenesis and revascularization [6].
Research has shown up‐regulation of TGFβ3, a cytokine that prevents aberrant scarring; increased gene expression for collagen type I; and elevated levels of vascular endothelial growth factor, fibroblast growth factor, and epidermal growth factor [11–13]. Histological studies have shown huge variation in epidermal thickness. Randomized murine studies have reported statistically significant epidermal thickening from 140% up to 685% after microneedling plus topical vitamins A and C when compared to control [13, 14]. This is thought to be one of the reasons microneedling is effective for scar therapy and notable skin rejuvenation.
A human study of 480 patients treated with microneedling plus topical vitamins A and C reported thickening of the stratum spinosum lasting up to one year [8, 15].
Increased collagen types I, III, and VII and tropoelastin in human biopsies were found after six sessions of microneedling, ten with elevated levels of collagen type I and elastin persisting at six months. The number of melanocytes was unchanged postprocedurally.
These results support the safe use of this modality in patients with darker skin types [8, 15]. Having a safe and effective treatment modality for all skin types is advantageous in an aesthetic practice.
The devices
Modern microneedling devices consist of rollers, stamps, and pens. Needling devices have evolved over the past decade through a variety of advancements. Currently, there are multiple devices based on needle length, drum size, and automation. To date, there are five FDA‐approved pen devices. Physicians and providers need to consider important factors like needle length, needle material, and clinical indications in selecting which device to utilize [9].
Pens
Most pens utilize sterile single‐use cartridges and variable needle length to be able to customize the treatment depending on the unique characteristics of the patient’s skin and the area being treated. They are automated and the physician has the ability to adjust the needle length for customized treatment options and the pressure and depth during treatment can be more uniform (see Figure 1.3) [16].
The pen itself is reusable, and most pens have a protective disposable sleeve. The needle tips are the disposable/consumable in these devices. Because of their size the tips are able to treat curved and small areas such as the nasal ala and the periocular and perioral areas. Most devices have a rechargeable battery that operates in two modes: high speed mode (700 cycles/minute) and low speed mode (412 cycles/minute) in a vibrating stamplike manner [17].
Figure 1.3 Pen: Single‐use cartridge with adjustable frequency and needle length.
Source: Sakurra/Shutterstock.
The devices contain multiple fine needles, ranging from 0.5 to 1.5 mm in length, that are rolled onto the skin. Needles between 1.5 and 3.0 mm are available but are preferred for the use of scars and damaged skin. The roller device is a drum‐shaped tool with a cylindrical head that is rolled back and forth to induce thousands of tiny pores in the stratum corneum and papillary dermis.
The length of needle selected for an individual patient depends upon the indication for microneedling and on the thickness of epidermis and dermis of the skin being treated. For treating acne and other scars, on average a needle length of 1.5–2 mm is utilized. When microneedling is used as a procedure to treat skin aging and wrinkles, a needle length of 0.5 mm or 1.0 mm is recommended [18]. The frequency interval for microneedling depends upon the indication for which the procedure is being done as well as the needle length of the dermaroller device used. Microneedling generally requires more than one session and a series of treatments is usually recommended.
Five basic types of medical dermarollers, which are registered with the FDA, have been described in the dermaroller series by Anastassakis and most dermarolling devices are adopted from these elementary types [19].
Stamps
Stamps were popular in the late 1990s and have made a resurgence recently. The stamps currently offered have attached microchambers which have the ability to directly administer a form of mesotherapy using the stamping device. Stamps have different needle lengths (0.2–3 mm) and a diameter of 0.12 mm These are useful in the administration of treatment to scars and anatomically small surface areas such as the perioral, periocular, and nasal regions where greater control is beneficial, and may be used on isolated scars and wrinkles (see Figure 1.4) [3, 20–22].
Figure 1.4 Microneedling stamp: fixed needle length with customizable vial for needling infusion.
Source: Aquavit Pharmaceuticals, Inc.
Rollers
Rollers have many fine‐gauged needles that are on a cylindrical surface that pierces the skin on an angle. The rollers are fixed; the parameters are uniform for each device that you use. Unlike pens, you can not mechanically adjust rollers. The quality of rollers is also critical. Patients are seeking at‐home rollers but the quality of the needles is paramount. Needles that are dull or loose may cause tears in the skin and foreign body reactions, including but not limited to granulomas.
The most important factor is needle length. A high ratio of tip length to diameter (13:1) is an important property of good needles [9]. The length of needle selected for an individual patient depends upon the indication for microneedling. For treating acne and other scars as a routine, a needle length of 1.5–2 mm is usually used. When microneedling is used as a procedure to treat aging skin and wrinkles, a needle length of 0.5 mm or 1.0 mm is usually recommended [19]. The needle length to use will also depend on the thickness of the epidermis and dermis of the skin for optimal