Dual wavelength (1540nm nm) mixed technology for fractional resurfacing in skin rejuvenation Background

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1 Dual wavelength (1540nm nm) mixed technology for fractional resurfacing in skin rejuvenation Dr. Paolo Sbano, M.D. Specialist in Dermatology and Venereology Department of Dermatology of Belcolle Hospital A.S.L. Viterbo, Italy Background Despite the fact that laser resurfacing represents the most effective option in the treatment of aged skin to date, the risks and side effects connected with that have encouraged industry and clinical research to purpose alternative skin resurfacing techniques. Fractionated photothermolysis (FP) represents one of the most exciting technological discoveries in laser resurfacing of the last two decades. In 2004 Manstein and colleagues introduced FP with their original prototype device. The device emitted light in a pixilated fashion to the skin, producing an array of micro-thermal zone and creating small columns of thermal injury to the skin without ablation (non ablative FP). This concept of fractional emission of light into microscopic zones of injury contrasts with full ablative skin resurfacing, in which a confluent, uniform patch of epidermal or dermal injury is induced. The scientific concept underlying FP involves the application of microscopic beams of pixilated light, which induce small, focal zones of tissue injury. Because the pixilated zones of treatment spare surrounding normal tissue, re-epithelialization occurs at a significantly faster pace. The tissue injury created with FP stimulates the process of collagen remodeling and deposition and promotes elastic tissue formation. These molecular changes are postulated to be responsible for the clinical improvements seen with FP. With FP, laser parameters can be customized to produce differing three-dimensional columns of in- jury with varying shapes and depths. Hantash and colleagues demonstrated the first report of a prototype device of a novel ablative FP (fractionated CO2 laser) device in human skin in vivo in The results indicated a similar column of thermal coagulation as with the non-ablative FP device of Manstein and colleagues, with the critical distinction of a confluent column of ablation and thermal injury that extended from the dermis and epidermis through the stratum corneum. With ablative FP, immune-histochemical studies indicated a prolonged wound remodeling response for at least 3 months after treatment. With this prolonged stimulation of wound repair induced by ablative FP, Hantash and colleagues theorized that greater clinical improvements in skin texture and wrinkling could be achieved with ablative FP than with FP.

2 The uses of computer-aided scanners permits to vary the ablation/coagulation depth without varying the fluence (trough the repeated heat on the same point: staking), the space between points, the ord of emission in the square. Ablative FP have demonstrated a very low risk of side effects (post inflammatory hyperpigmentation, prolonged erythema and edema, scarring), even in dark skin phototypes, and a very shorter down time period if compared with full ablative resurfacing. Ablative FP has demonstrated useful in moderate to severe acne scarring in terms of clinical improvement and topographic mapping of decreases in individual scar volume, even non-ablative FP have been demonstrated greater results in scar remodeling if compared with ablative FP. In addition, ablative FP has shown great result in reducing skin surface and texture abnormalities, including moderate to severe rhytides and skin laxity on the face, neck, and chest. The relative limit of ablative FP is that, to obtain greater results, is necessary to use energy densities similar to the full ablative technique. The excitement of the initial reports of the efficacy of ablative FP in skin tightening, with similar results to those of traditional full ablative CO2 resurfacing, with advantages of only 7 to 14 days of downtime and less risk of permanent scarring and depigmentation have actually been resized. On the other hand, the results of non-ablative FP in aged skin cannot be compared with ablative techniques ones. Moreover, even if post-treatment associated down-time is shorter (with slight erythema and edema), more treatment sessions are needed with extended time loss for the patient and the physician too. In order to resolve these limitations of ablative/non-ablative FP a new device, combining a nonablative source (1540 nm wavelength) with an ablative one (10600 nm wavelength), both fractionated, have been proposed. The present study has the aim to investigate the efficacy, down-time period and possible side effects of a new treatment with a double wavelength (1540 nm nm) device in photo-aged skin. Patients and methods Patients 10 Subjects, all female, mean age of 46 years (34 to 72 years) with skin phototype II-III were enrolled for the study. All subjects underwent a pre-treatment medical examination, clinical history was taken, presence of hypertrophic scars and dermatological pathologies associated with photosensitivity were investigated, risk of infection (personal history of labial herpes simplex) and any medication in place was asked. The subjects were divided into two groups on the basis of the degree of skin aging (Glogau scale): in group A were included subjects with mild-average aging (type I-II Glogau scale) and in group B with more marked aging (type III-IV Glogau scale).

3 Fractional Resurfacing Technique All subjects were treated with both sources (1540 nm and nm) in sequential mode in which the first impulse was of 1540 and the second pulse that of This output mode has been selected on the basis of our histologic studies in an in vivo animal model that showed this as the way that offers the maximum capacity of laser penetration into the dermis and deep and lateral coagulation with reduced ablation area. The specific characteristics of the treatment for the two groups are shown in Table 1. All subjects received a full-face fractional resurfacing, however in each patient was drawn a pretreatment map with an area of more intense treatment and areas of shade and of conjunction. The parameters that have been changed between the treatment area and the shade area were the staking and density, while the fluence were unchanged. Laser treatment parameters Group A Group B Power 1540 (W) 8 8 Pulse duration 1540 (msec) 4 6 Pause between 1540 and pulse (msec) Power (W) Pulse duration (msec) Stack 1 2 Stacking pause (msec) 2 2 Density medium medium None of the treated subjects had need of pre-treatment with anesthesia (sedation). None of the subjects in group A was treated with the aid of local or topic anesthesia. 3/5 of the subjects in group B were treated with local (regional) anesthesia in the peri-oral area. All subjects were treated with aid of cooling air system (Zimmer). Post-treatment therapy included in all subjects: doxiciclyn 100 mg/day orally for 15 days. Antiviral drugs (acyclovir 1200 mg/day orally for 7 days) were prescribed in case of herpes simplex personal history.

4 Results Mean down-time after treatment was 4 days in group A and 7 days in group B. Group A subjects experienced only mild to severe erythema and oedema (especially in first two days after treatment) and slight crusting. All the group A subjects obtained complete healing after 7 days. Group B subjects presented severe erythema and oedema (especially in peri-orbital area) in the first 3 days, with pinpoint crusting. All group B subjects assumed anti-inflammatory drugs in the first 3 days after treatment. At day 10 all the group B subjects had complete healing with no evidence of erythema. No side effects or complications were observed in any treated subject. All treated subjects obtained an objective improvement of their skin texture 3 months after treatment. All subjects showed satisfaction from the treatment received. We have submitted a questionnaire to the subjects dealt with a scale of evaluation of the results obtained with a value from 1 (poor performance) to 10 (excellent result). The average rating by the subjects in group A was 7 and for individuals in group B was 8.5. The different measurement is in our opinion related to the specific treatment, more incisive in subjects of group B compared to group A. The objective evaluation on the average reduction of wrinkle depth was 15% in patients of group A and 35% in patients of group B. The improvement in skin texture was 35% in group A and 55% in group B. Comment The growing demand by patients of methodologies useful to treat photo-aging that demonstrate effectiveness and at the same time not forcing long periods of abstention from social activities has led the industry of laser technologies to develop new tools and application protocols. In recent years the development of fractional technology has allowed a clear step forward in this direction, allowing savings in down-time and post-treatment risk reduction compared to the previous technique of full-ablative resurfacing. However it was noted that to obtain good results it is

5 necessary to push the fractional technology level in the direction of more aggressive treatments, with a surface ablation of 50-75%. This resulted in a return to long recovery time for the patient and with an increased risk of side effects. The possibility of combining an ablative fractional technology with a non-ablative one seems to offer a solution to the problem, since it allows to obtain a large coagulation effect into the medium and deep dermis with a net savings on the surface ablation. This leads to achieve the same effects in the depth of dermal remodelling with a net savings on collection times post-treatment for the patient, which are essentially related to epidermal damage. The present study shows how new technology Dual Wavelength (1540 nm nm) allows to obtain good results on remodelling and skin texture with a marked reduction in recovery time compared to normal techniques of ablative fractional resurfacing.