Variable Square Pulse Research Articles

The Efficacy and Safety of a Variable Square Pulse (VSP) Erbium:YAG Laser for Treatment of Enlarged Pores in Asians.

Enlarged pores are one of the most common causes of skin surface irregularities. Existing studies supporting the benefit of lasers and energy-based devices (EBD) for this condition are limited, with a short duration of follow-up period. We aimed to evaluate the efficacy and adverse effects of Er:YAG laser for treatment of enlarged pores in dark-skinned patients. Nineteen subjects (aged 26-47 years) with skin phototypes III (21.1%) and IV (78.9%) and enlarged pores were treated with 4 monthly sessions of Erbium:YAG laser. Objective (ultraviolet light A video camera) and subjective (clinical evaluation by two blinded dermatologists) assessments were obtained at baseline, 1-month after each treatment and at 1, 3, and 6 months after the final treatment. The weighted mean score of quartile grading scales showed significant improvement in pore size from baseline starting at 1-month after the third treatment and continued until 3 months after the fourth (final) treatment (P < 0.001). However, the improvement dropped significantly at 6 months after the final treatment. Objective measurements of the improvements in skin surface smoothness and wrinkles corresponded with the physician raters' clinical evaluation. Erbium:YAG laser is a safe and effective treatment for enlarged pores in dark-skinned individuals. Maintenance treatments are recommended to achieve a longer-lasting outcome. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Resurfacing of Facial Acne Scars With a New Variable-Pulsed Er:YAG Laser in Fitzpatrick Skin Types IV and V.

Introduction:The Er:YAG laser, considered to be less effective than CO2 laser in its traditional form, in its new modulated version has variable pulse technology that is claimed to be superior to the earlier versions of the laser.Aim:The aim of the study was to check efficacy and safety of the new variable square pulse (VSP) Er:YAG laser in the management of acne scar in patients with Fitzpatrick skin types IV and V.Materials and Methods:This retrospective study consisted of 80 patients (Fitzpatrick skin types IV and V) with atrophic and hypertrophic facial acne scars. Records of the patients who had undergone four treatment sessions with VSP technology equipped with Er:YAG laser were extracted. Each patient had undergone a minimum of four sessions. Fractional mode at medium laser pulse (SP) and long pulse (LP) was employed for the depressed center of the scars to stimulate neocollagenogenesis. Short laser pulse (MSP) in nonfractionated mode was used for ablating the raised scar border and hypertrophic scars. Goodman and Baron global scarring grading system was used for qualitative and quantitative assessments. Patient’s satisfaction to the treatment and observer’s assessment of improvement (based on photographs) was graded as poor (<25% improvement), fair (25–50% improvement), good (51–75% improvement), and excellent (>75% improvement).Results:At the end of the four sessions, the number of patients in grade IV postacne scarring reduced from 16 to 2 and that in grade III from 47 to 29. The mean score significantly dropped from 36.94 to 27.5. Subjective assessment revealed that 78 of 80 patients had noticed more than 25% improvement, with 50 of them showing more than 50% improvement at the end of four sessions. Eight patients perceived an excellent response and 42 reported a good response. This is notably higher than the observer’s grading, which showed an excellent response in only 2 patients and a good response in 35. Adverse effects were limited to prolonged erythema (two patients), prolonged crusting (one patient), and postinflammatory hyperpigmentation (one patient).Conclusion:Ninety-seven percent of the subjects in our study perceived at least a fair improvement. We also saw a significant change in the objective score with a fall of the mean quantitative score from 36.94 to 27.15. This underscores the new variable-pulsed Er:YAG laser’s effectiveness in the treatment of acne scars. It also has the added advantage of lesser adverse events and faster healing.

Ablative Potential of Er:YAG Laser in Dentin: Quantum Versus Variable Square Pulse.

The primary objective of this study was to compare the dentin ablation volume and ablation rate of quantum square pulse (QSP), using two different pulse energy settings plus a new digitally controlled dental laser handpiece (X-Runner), with those of variable square pulse (VSP), using three different pulse durations. The secondary objective was to examine, by scanning electron microscopy (SEM), the surface effects of ablation with the different Er:YAG laser modes on the dentin surfaces. The available literature has limited data on the efficiency of different operating modes, pulse durations, and the new digitally controlled handpiece of the Er:YAG laser on human dentin. Freshly extracted human molars (n = 72) were divided into two experimental groups (n = 36 each): (1) QSP group, and (2) VSP group. Each group was randomly divided into three subgroups (n = 12 each). In the QSP group, preparations in dentin were performed using 250 and 500 mJ of pulse energy with the conventional handpiece, and with the X-Runner handpiece set at 250 mJ pulse energy. In the VSP group, cavity preparations were performed using three pulse variables: super short pulse (SSP), micro short pulse (MSP), and short pulse (SP). Cavity preparations were made in dentin at time intervals of 1, 2, and 5 sec. A laser triangulation profilometer was used to determine cavity volumes. Surface analysis of the ablated dentin specimens was performed by SEM. For time intervals of 1 and 2 sec, ablated volume and ablation rate for QSP-500 mJ were significantly higher than for all other groups (p < 0.0001). For the 5-sec time interval, X-Runner and QSP-500 mJ were the most efficient in dentin ablation (p < 0.0001). Dentin surfaces were free of smear layer in all groups. The most efficient modes of dentin ablation in the study were the QSP-500 mJ and X-Runner groups. Dentin surfaces were free of smear layer in all groups.

Influence of Sodium Hypochlorite on Er:YAG Laser-Irradiated Dentin and its Effect on the Quality of Adaptation of the Composite Restoration Margins

The aims of this in vitro study were to evaluate: (1) the influence of 5% NaOCl application on Er:YAG-irradiated dentin; and (2) its effect on the quality of adaptation of the composite restoration margins. Previous research has shown that Er:YAG dentin irradiation produces a thermally affected tissue layer that results in lower bond strength than that of nonirradiated dentin. The removal of this thermally-affected layer may enhance the quality of dentin bonding. Forty-nine caries-free extracted human molars were transversely sectioned in order to totally expose the dentin. Four standardized cavities were created on the dentinal surface of each molar. First, two cavities were irradiated with Er:YAG laser (2.94 nm): 150 mJ, 10 Hz, variable square pulse (VSP) mode (100 μsec), beam diameter=0.9 mm, speed of irradiation=1 mm/sec, 20% air and 20% water. Then, one of irradiated cavities and one of nonirradiated cavities were treated for 30 sec with 5% NaOCl solution. Finally, they went through a standard bonding treatment for composite restoration, etching, bonding, and composite filling. We obtained four groups of cavities: (1) one control group of nonirradiated cavities not pretreated with NaOCl; (2) one group of nonirradiated cavities, pretreated with NaOCl; (3) one group of irradiated cavities, not pretreated with NaOCl; and (4) one group of irradiated cavities, pretreated with NaOCl. All samples were subjected to thermocycling. Every cavity was immersed into a 0.5% solution of methylene blue. The percentage of dye penetration (microleakage) in the composite-dentin interface was evaluated. Six molars were analyzed by scanning electron microscope. Dye infiltration depth was significantly reduced in irradiated cavities treated with 5% NaOCl solution. The application of a 5% NaOCl solution on Er:YAG irradiated cavities can significantly improve the marginal quality of composite bonding.

Periorbital Rejuvenation with Fractional 1,550-nm Ytterbium/Erbium Fiber Laser and Variable Square Pulse 2,940-nm Erbium:YAG laser in Asians: A Comparison Study

Ablative and fractional lasers are used for periorbital rejuvenation, with different downtime, side effects, and efficacy. To compare effects of fractional 1,550-nm ytterbium- and erbium-doped (Yb/Er) fiber laser and variable square pulse (VSP) 2,940-nm erbium-doped yttrium aluminum garnet (Er:YAG) laser treatment for periorbital wrinkles. This side-by-side comparison study randomized 22 women with mild to moderate periorbital rhytides to receive three treatments with fractional 1,550-nm Yb/Er fiber laser or 2,940-nm Er:YAG laser treatment on either side at 4-week intervals. A video camera was used for objective assessment of wrinkles. Standardized photographs, patient satisfaction, side effects, and pain score were recorded. Twenty subjects completed the study. The median change in wrinkle measurement 3 months after laser treatments from baseline of the fractional Yb/Er fiber laser side was -3.03 versus -3.09 on the VSP Er:YAG side (p = .63, Wilcoxon signed-rank test). There was no significant difference in degree of wrinkle improvement analyzed according to global assessment between the sides (p = .25, Wilcoxon signed-rank test). Less downtime correlated with greater patient satisfaction of the fractional laser treatment . Two subjects experienced hyperpigmentation. Fractional Yb/Er fiber and VSP Er:YAG lasers are effective in improving periorbital wrinkles in Asians, with minimal side effects.

Variable square pulse vs conventional PFN pumping of Er:YAG laser

The influence of the flashlamp pump current pulse shape on Er:YAG laser efficiency and laser rod thermal focusing was studied theoretically and experimentally. Two pulse shapes, PFN (Pulse Forming Network) and VSP (Variable Square Pulse), were considered. Theoretical modeling and experimental measurements show that the pump pulse shape itself does not have a significant influence on the Er:YAG laser efficiency or thermal focusing. Instead, the major parameter influencing Er:YAG laser efficiency and thermal focusing was found to be the overall pulse duration. For PFN pulses, rise and fall times directly define the overall pulse duration, and therefore do have influence on thermal focusing. By contrast, VSP pulse duration is defined by the externally controlled on-time of the switching transistor. For square shaped pulses, short rise and fall times do not have a direct beneficial influence on thermal lensing.

Erbium-Doped Yttrium Aluminium Garnet Laser–Assisted Access Osteotomy for Maxillary Sinus Elevation: A Human and Animal Cadaver Study

To evaluate the usability of a variable square pulse (VSP) erbium-doped yttrium aluminium garnet (Er:YAG) laser for a lateral access osteotomy to the maxillary sinus in the course of a sinus elevation procedure. In six formalin-fixed human heads and six fresh sheep heads, a VSP Er:YAG laser was used to perform a bilateral maxillary access osteotomy. For the osteotomies, the Er:YAG laser was applied with a pulse energy of 1000 mJ, a pulse duration of 300 mus, and a frequency of 12 Hz. The spot size was 0.9 mm, and the handpiece was kept approximately 10 mm from the bone surface. In all 24 sites investigated, the Er:YAG laser osteotomy was possible without any visible carbonization or thermal damage. The average time required for laser osteotomy for 12 standardized rectangular lateral windows in human cadavers was 39 s. No anatomical structures limited laser osteotomy, yet a critical evaluation of any membrane perforations was not possible because the postmortem fixation method caused partial detachment and fractional destruction. Laser-access osteotomy in six fresh sheep heads (12 sites) revealed major disruptions and perforations (<8 mm) of the sinus membrane (100%). Even though VSP Er:YAG laser osteotomy showed convincing results for efficient bone cutting without thermal damage, applied laser parameters do not seem to be practicable for any clinical sinus elevation procedure. Missing depth control resulted in uncontrollable severe damage of the underlying membrane.

Effect of pulse width of a variable square pulse (VSP) erbium:YAG laser on the treatment outcome of periorbital wrinkles in Asians

Uses of appropriate laser parameters are essential for an optimum outcome with minimal risks of complications. To evaluate the effect of pulse width of a variable square pulse (VSP) Er:YAG laser on the treatment outcome. Twenty-four Thais with periorbital wrinkles received two treatments with a low-fluence, VSP Er:YAG laser resurfacing 1 month apart. Subjects were randomly divided into two groups and treated with two different parameters including a pulse width of 0.3 ms (short pulse, SP) for one group and a pulse width of 250 ms (super-long pulse, SL) for the other group. Assessments were evaluated at baseline, 1-month and 3-month follow-up visits. After one treatment, 63.7% and 33.4% of the subjects in the SP and SL groups, respectively, were assessed to have obvious to marked improvement of their wrinkles. After two treatments, a higher percentage of the subjects were rated to have obvious to marked improvement including 91% and 66.7% in the SP and SL groups, respectively. There was no significant difference in therapeutic outcome between the SP and SL groups. There was no significant difference in efficacy and side effects, between the SP and SL groups. However, a trend toward better response with the shorter pulse width was observed.

Treatment of Punched-Out Atrophic and Rolling Acne Scars in Skin Phototypes III, IV, and V with Variable Square Pulse Erbium

Treatment of acne scars remains a challenge, especially in dark-skinned individuals. Treatment parameters may be optimized by selecting appropriate pulse width and laser energy that enhance tissue thermal response with limited morbidity. To determine the efficacy and side effects of variable square pulse (VSP) erbium:yttrium-aluminum-garnet (Er:YAG) laser resurfacing for treatment of punched-out atrophic and rolling acne scars. METHODS Twenty-four subjects with acne scars were treated monthly for 2 months with four passes of VSP Er:YAG laser resurfacing using a 7-mm spot size and a fluence of 0.4 J/cm(2). Subjects were divided into two groups and treated with two different pulse widths: 300 micros (short pulse, SP) and 1,500 micros (extra-long pulse, XLP). Objective and subjective assessments were obtained at baseline and 1, 2, and 4 months after treatment. In the SP group, skin smoothness improved significantly (p<.01); in the XLP group, skin smoothness (p<.05) and scar volume (p<.05) improved significantly from baseline. Adverse effects consisted of transient postinflammatory hyperpigmentation (18%) and acneiform eruption (9%). Low-fluence VSP Er:YAG laser resurfacing is a promising treatment option for acne scars, with minimal risk of side effects. Laser pulse width and energy determine the efficacy and the risk of side effects. The authors have indicated no significant interests with commercial supporters.

Harvesting of intraoral autogenous block grafts from the chin and ramus region: Preliminary results with a variable square pulse Er:YAG laser

It was the aim of this pilot study to evaluate the feasibility, benefits and limitations of a variable square pulse (VSP) Er:YAG laser for harvesting intraoral bone grafts from either the chin or ramus region. In 12 patients (5 female, 7 male) a VSP Er:YAG laser was used to harvest bone grafts either from the ramus (3) or the symphyseal area (9). For the osteotomies, the Er:YAG laser was applied with a pulse energy of 1,000 mJ, a pulse duration of 300 microseconds, and a frequency of 12 Hz (energy density 157 J/cm(2)). The spot size was 0.9 mm and the handpiece was kept at a distance of about 10 mm from the bone surface. There was no visible carbonization or osseous debris on the surface of the osteotomy gap. Damage of adjacent soft tissue structures by mechanical or thermal trauma was minimal. Cutting efficiency was excellent and the overall time required for the procedure was not increased. However, due to a free manual positioning of the laser beam in the non-contact mode, it was difficult to get a well defined osteotomy line without irregularities on the surface. Slight deviations of the original angulation of the laser beam led to considerable bone loss which restricted osteotomy of ramus grafts to three cases. Depth control was limited to visual inspection. The bone ablation technique using a (VSP) Er:YAG laser yielded superior clinical results without impairment of wound healing and in comparison to other laser systems, no significant time loss occurred. Yet, the missing depth control and the necessity of carefully handling the laser beam position and its angulation limit the use of a (VSP) Er:YAG laser to regions where a safe and fixed guidance of the laser beam is feasible.

Laser dental hard tissue ablation: Comparison Er-lasers and scanned ultra-short pulse laser

Laser treatment of dentine was performed with two free-running Erbium laser systems operated at 3 W average power, and a mode-locked 12-ps Nd:vanadate laser at an average power of 3.5 W. Mean ablated volumes per laser pulse were determined by means of a three-dimensional digital evaluation method. The temporal pulse profiles of the Erbium systems was analysed to explain the ablation rate results. Additionally, the morphology of the laser treated surfaces was examined. Two Erbium laser systems were involved in this study. The Er:YAG laser, emitting at a wavelength of 2940 nm, has a maximum pulse energy of 1.5 J and adjustable pulse repetition rate up to 50 Hz. It was operated in the VSP (variable square pulse) mode. The laser beam is delivered via a mirror articulated arm and outcoupled through a conically shaped sapphire tip. The second system, was an Er,Cr:YSGG laser with a wavelength of 2780 nm, has a maximum pulse energy of 300 mJ and fixed pulse repetition rate of 20 Hz. A fibre delivery system is implemented in this laser. Again, a conically shaped sapphire tip was used. Laser treatment was performed at 3 W and 20 Hz with an air-water spray.

In vitro study of the variable square pulse Er:YAG laser cutting efficacy for apicectomy

Variable square pulse (VSP) Er:YAG laser should be quicker than older Er:YAG lasers. The objectives were: (1) comparison of VSP laser and mechanical handpiece efficacy for apicectomy and (2) determination of optimal pulse width/energy/frequency combination. Sixty extracted, single-rooted mature human teeth with round apical parts were instrumented, root filled, cleaned, and divided into four groups. Apical 2 mm of each root were apicectomized with mechanical handpiece and Er:YAG laser with three different settings (LaserA = 200 mJ/300 microseconds/ 8 Hz; LaserB = 200 mJ/100 microseconds/8 Hz; LaserC = 380 mJ/100 microseconds/20 Hz). Timing results were statistically compared. LaserC was the most efficient setting. Differences between groups were significant except between LaserC-Mechanical and LaserA-LaserC (P < 0.05). VSP Er:YAG laser used for apicectomy is slower by a factor of 7-31 than mechanical handpiece, but treatment outcome is acceptable. Optimal settings for apicectomy with VSP laser are 380 mJ/100 microseconds/20 Hz.