The following white paper and results of a preliminary clinical study was presented by Dr Daniel A Cassuto at the introduction of Lasering MiXto SX Fractional CO-2 Laser in 2007.

Background

CO2 laser resurfacing is a powerful tool for the treatment of several skin conditions such as fine and coarse wrinkles, scars of various origin, uneven pigmentation, dilated pores et al. Some major drawbacks have progressively limited its use: the need for effective anaesthesia, the downtime, the risk of dyspigmentation and scarring, the need for intensive postoperative care, the long-lasting erythema and the long avoidance of sun exposure

Fractional photothermolysis was introduced by Huzaira and colleagues in 2003. It was developed to overcome the above-mentioned drawbacks in the treatment of photo damaged skin. Fractional Laser Resurfacing with the midinfrared lasers uses an invisible laser beam which is strongly absorbed by water, in order to reverse the effects of skin aging and scarring. Near infrared wavelengths (Fraxel, Reliant, 1550nm; Lux 1540, Palomar) cause significant pain and require some form of anesthesia. This is a time consuming and costly aspect. Another disadvantage for the operator is that most of these devices are only capable of performing this kind of treatment. The use of ablative lasers in a fractional mode was introduced in 2006. The lesser depth of immediate tissue necrosis, in comparison to the mid infrared wavelengths, together with the possibility of further heat deposition in the dermis, significantly reduces the pain caused by the procedure, without decreasing its efficacy. A new CO2 laser (Active FX, Lumenis, 10600nm) with less penetration was shown to be more tolerable, but the 1.3 mm spot still makes some local anaesthesia and\or cooling necessary. The spot distribution is not distributed as uniformly as with the midinfrared devices. A more recent CO2 laser system (Slim Evolution, Lasering,) with a microspot system (300μ) fractional modality (Mixto SX) has been developed with a new scanning algorithm that keeps the longest possible interval between two adjacent spots, in order to minimize the heat accumulation around the treated areas. This is supposed to significantly reduce the pain during the procedure.
Objective

A new CO2 laser system (Slim Evolution, Lasering, Modena, Italy) with a unique fractional modality (Mixto SX), added to a high-speed scanner is tested as a tool for skin rejuvenation. It will be tested to evaluate its efficacy and tolerability as a tool for skin rejuvenation without any form of anaesthesia or cooling.
Materials and Methods

The Mixto SX™ system (Lasering S.r.l, Modena, Italy) is a fractional CO2 laser equipped with a new generation Computerized Pattern Generator (CPG). Its recently developed algorithm allows the 300μ beam to be delivered at such intervals that greatly increase its tolerability. Its pattern results in a precise beam delivery over the treated area. The operator can chose particular scarred and sun damaged areas for treatment as needed. It can perform traditional and fractional resurfacing at depths ranging from 20 to 500 microns, treating 20% or 100% of the scanned area. The traditional single beam is also available for vaporizing solid lesions or cutting purposes. A series of 24 consecutive patients (skin types II-IV) has been treated with one pass of the above-mentioned fractional CO2 laser (11 faces, 5 necks, 8 hands). No anaesthesia or skin cooling was used. The power used was between 8 and 10 watts, with SX index values of 6-8, according to the indication and to patient tolerance. A single pass was done over the whole area. The postoperative management included a thermal water based cream (Cicalfate, Avène, France) and free use of makeup. Pain tolerance was measured with a 0-5 score (see table 2). Digital clinical microphotography was used before and 3 months after treatment, in order to assess the results, by an independent evaluator according to the scale shown in table 3. All patients according to how strongly they would recommend the treatment to their friends completed satisfaction questionnaires. In order to eliminate the bias in satisfaction questionnaires (see table 4) all patients were charged for the treatments.
Results

All patients showed significant improvement in skin texture and colour after one single treatment. The average improvement score given by the independent observer was 3.83. Postoperative undesired effects were immediate erythema and swelling that subsided within 24 hours. Fine pinpoint microcrusting (as shown in picture number 1) occurred in all cases and resolved within one week.

Picture 1. Highly magnified appearance of the microcrusting 48 hours after treatment. Each microcrust has a
300μ diameter.

With camouflage it looked like an exaggerated tan and was well tolerated. All patients tolerated the treatment sessions. The mean pain score was 1.8 (score 2=easily tolerated). All patients expressed almost unanimously full satisfaction from the laser treatment (mean satisfaction score was 3.958). No dropouts were observed. Postoperative undesired effects were immediate erythema and mild swelling that subsided within 48 hours. With camouflage these effects looked like a suntan and were well tolerated with no downtime. No long-term side effects were observed after 6 months of follow up.

Picture 2: A 41 yr old patient with a Mediterranean skin and moderate sun damage. Left picture before treatment.
Right picture – 3 months after treatment. Notice the improvement in skin texture and colour. The fine wrinkles are almost erased from the cheek.

Picture 3: a 19 yr old Hispanic patient with hyperpigmented severe acne scarring. Left picture before treatment.
Right picture – 3 months after treatment (2 sessions with a 1-month interval). The improvements in skin colour and scar remodelling are visible.
Discussion

Like other ablative fractional lasers, the Mixto SX™ showed to be more tolerable than the midinfrared devices, due to the deeper penetration of the latter. However, this did not result in a lesser efficacy, due to the fact that deep tissue irreversible damage is not necessary in order to stimulate rejuvenation by shrinkage (immediate) and new collagen formation (after 6-12 weeks). This effect is readily achieved by the lower SX indexes that cause a further heat delivery after the initial ablation. Varying the power (watts) can regulate the depth of this ablation. This versatility is quite promising, as it allows the operator to adjust the settings according to the different areas of the body, as skin thickness may vary from 150μ, as in an aged lid, to a few millimeters on the forehead. Alternatively, the operator can make an overlapping scanned spot with a 45° angle of rotation, in order to achieve a microspot density of about 40%. This technique is particularly useful when treating areas with more intense photoaging (senile stains, deeper wrinkles) without recurring to more aggressive settings that would increase the pain. A 1-2 weeks lasting localized slight erythema should be expected in these areas. Solid benign lesions such as skin tags, seborrheic keratoses etc, can be ablated during the same treatment. Switching to a single beam emission for bloodless ablation or incision is done through the touch screen in 3 seconds, without changing the handpiece.
Conclusions

The Mixto SX™ is an effective and safe tool for skin rejuvenation by fractional laser resurfacing. Its versatility allows the operator to perform minimally invasive treatments, together with more aggressive resurfacing and or tissue ablation if needed. The remarkable tolerability makes its acceptance by patients easier and eliminates the need for cumbersome and time consuming cooling or anaesthetic procedures. The results are reproducible without need for any gel or other substance to be applied. Some tips are available in order to optimize the results.
Reference

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