Background and Objectives Recently, several minimally invasive gynecological, ENT and esthetic procedures have been introduced that are based on delivering “smooth” sequences of Er:YAG laser pulses to cutaneous or mucosal tissue at moderate cumulative fluences that are not only below the ablation threshold but typically also do not require local anesthesia.  To explain the observed clinical results using “smooth‐resurfacing,” it has been suggested that in addition to the direct heat injury to deeper‐lying connective tissues, there is an additional mechanism based on indirect triggering of tissue regeneration through short‐exposure, intense heat shocking of epithelia. The goal of this study is to improve understanding of the complex dynamics of the exposure of tissues to a series of short Er:YAG laser pulses, during which the thermal exposure times transition from extremely short to long durations. Study Design/Materials and Methods A physical model of laser‐tissue interaction was used to calculate the temperature evolution at the irradiated surface and deeper within the tissue, in combination with a chemical model of tissue response based on the recently introduced variable heat shock (VHS) model, which assumes that the tissue damage represents a combined effect of two limiting Arrhenius′ processes, defining cell viability at extremely long and short exposure times. Superficial tissue temperature evolution was measured during smooth‐resurfacing of cutaneous and mucosal tissue, and compared with the model. Two modalities of non‐ablative resurfacing were explored: a standard “sub‐resurfacing” modality with cumulative fluences near the ablation threshold, and the “smooth‐resurfacing” modality with fluences below the patient′s pain threshold. An exemplary skin tightening clinical situation was explored by measuring pain tolerance threshold fluences for treatments on abdominal skin with and without topical anesthesia. The obtained temperature data and pain thresholds were then used to study the influence of Er:YAG laser sequence parameters on the superficial (triggering) and deep (coagulative) tissue response. Results The simulations show that for the sub‐resurfacing modality, the parameter range where no excessive damage to the tissue will occur is very narrow. On the other hand, using pain tolerance as an indicator, the smooth‐resurfacing treatments can be performed more safely and without sacrificing the treatment efficacy. Two preferred smooth‐resurfacing treatment modalities were identified. One involves using optimally long pulse sequence durations (≈1–3 seconds) with an optimal number of pulses ( N ≈ 10–30), resulting in a maximal short‐exposure superficial tissue response and moderate coagulation depths. And for deeper coagulation, without significant superficial heat shocking, very long pulse sequences (>5 seconds) with a large number of delivered pulses are to be used in combination with topical anesthesia...

Background Warts are benign epithelial proliferations that result from human papillomavirus (HPV) infection occurring on the skin and mucosa. Patients express a significant reduction in quality of life due to this cosmetic nuisance, as well as functional problems and physical discomfort. Newer methods of wart removal include different energy‐based devices, mostly lasers. Nonablative lasers such as Nd:YAG have a higher success rate and are usually used with topical or infiltrative anesthesia. The procedure may be safer without anesthesia but still tolerable with an appropriate cooling and technique. Aims The purpose of this study is to report on our experience over 3 years since the approach without anesthesia has been utilized. Patients/Methods A retrospective chart review analysis of all 85 patients who underwent 1064 nm Nd:YAG wart removal without anesthesia between November 2016 and August 2019 was conducted. One of the main outcome measures was determining the number of sessions required in order to get full clearance. Results The mean number of sessions was 2.2 (range 1‐7). The mean VAS pain score during the procedure was 6 (range: 2‐10), and side effects were negligible. Conclusion Long‐pulse 1064‐nm Nd:YAG laser without any chemical anesthesia is safe and effective for the treatment of warts.

The appearance of one's skin reflects a person's general health and is one of the main indicators of human age. 1 As skin ages, it tends to become uneven in color, roughened, lax, and wrinkled due to intrinsic and extrinsic factors (eg, photodamage). A major feature of aged skin is fragmentation of the dermal collagen matrix. Fragmentation results from the actions of specific enzymes (matrix metalloproteinases) and impairs the structural integrity of the dermis. Fibroblasts that produce and organize the collagen matrix cannot attach to fragmented collagen. Loss of attachment prevents fibroblasts from receiving mechanical information from their support, and they collapse. 2 Stretch is critical for normal balanced production of collagen and collagen-degrading enzymes. In aged skin, collapsed fibroblasts produce low levels of collagen and high levels of collagen-degrading enzymes. This imbalance advances the aging process in a selfperpetuating, never-ending deleterious cycle. 2 Many different materials, energy-based devices, and techniques have been shown to offer good results in facial rejuvenation. 3 Ablative techniques are still considered the most effective methods for improving photodamaged skin, but are associated with a prolonged recovery time and high risk of side effects. 4 The CO 2 and Er:YAG (2940 nm) wavelengths are ablative wavelengths used for many different applications including facial skin resurfacing.Ablative lasers vaporize the epidermis and part of the dermis, leaving a zone of thermal injury responsible for collagen shrinkage and remodeling. [5][6][7] Post-procedure, the epidermis has to heal, requiring at least some recovery time. Non-invasive and minimally/non-ablative methods without downtime are therefore gaining popularity in modern dermatological laser therapy. Recently, a non-ablative mode of

Acne vulgaris is one of the most common skin diseases; it will affect one out of two people in their lifetimes and about 80% of people aged between 11 and 30 years. [1][2][3] Acne scarring, a common complication, develops to some degree in the majority of acne sufferers. 4 Scars are divided into three general categories: ice-pick scars, rolling scars, and boxcar scars 5 and are a result of excessive inflammation, acne severity, physical manipulation of the skin, and a delay in seeking adequate treatment. 3 It affects people both physically and emotionally worldwide, regardless of sex, age, and ethnicity. 2,6 There is also a negative societal perception of acne scars. 7 Unfortunately, many cases of acne remain untreated or are treated sub-optimally, and patients that later develop acne scarring often need acne scarring treatment. None of the currently available treatments achieve a complete resolution of scars, and thus, prevention of scarring by early and aggressive acne treatment is the best option. 8 There are many different treatment modalities for acne scarring, such as chemical peeling, retinoids, dermabrasion, microneedling, subcision, surgical excision, dermal fillers, platelet-rich plasma (PRP), and different energy-based devices. Evidently, a combination of various treatment modalities gives better results than monotherapy. 8,9 Energy-based devices, such as intense pulsed light (IPL), radiofrequency, and lasers, have gained popularity as part of the scar treatment arsenal in recent years. The ablative 2940 nm Er:YAG and 10 600 nm CO 2 lasers have been used in treating various types of scars. However, due to adverse effects such as edema, erythema, dyspigmentation,

Background Laser hair reduction gained popularity in the last decade and is presently the most frequently used long‐term hair removal method. It works on the principle of selective photothermolysis—the laser damages the hair follicle without damaging the skin. Shorter Nd:YAG pulses are also effective in hair reduction, while maintaining better comfort for the patient. Aims The aim of this study was to compare the short and long pulsed methods of Nd:YAG for facial hair removal on darker Fitzpatrick skin types (IV–V). Patients/Methods This prospective split face, evaluator‐blinded comparison of short‐pulse Nd:YAG laser versus long‐pulse Nd:YAG laser study included 10 untanned healthy women. There were two outcome measers, two blinded dermatologists compared baseline photographs with those taken 3 months after last session and FotoFinder was used to compare the terminal hair count reduction at the baseline and 3 months after 6th session. Results Both blinded assesors observed significant hair reduction with both lasers; excellent results were achieved in 20% with long pulse and in 55% with short pulse. Both treatment options showed reduction in number of terminal hair with statistical significance using FotoFinder. Comparison of the efficacy of the two pulse durations measured by percent reduction in the number of terminal hair 3 months after the last session showed no significant difference between the groups. Conclusion Hair reduction using 1064 nm Nd:YAG is a safe and effective method of hair reduction especially in darker skin types. We have shown that short pulses are better or at least equally safe and effective as the “gold standard” long pulses.