Er:YAG laser ablation of tissue: effect of pulse duration and tissue type on thermal damage

Full-face and neck resurfacing with a novel ablative fractional 2910 nm erbium-doped fluoride glass fiber laser for advanced photoaging

OBJECTIVES

Ablative fractional lasers have long been considered the gold standard for facial resurfacing for advanced photoaging. These lasers offer an improved safety profile compared to traditional ablative lasers but typically require more treatment sessions given their fractional approach. In this study, we evaluate a new novel 2910 nm erbium-doped fluoride glass fiber laser (2910 nm fiber laser) (UltraClear; Acclaro Medical) for full-face and neck resurfacing for the treatment of advanced photoaging.

METHODS

Twenty-two healthy subjects aged 44-80 years presenting for advanced facial photoaging and rhytides were enrolled in the study. All subjects received three full-face and neck, multipass treatments utilizing the 2910 nm fiber laser spaced 6-8 weeks apart. Subjects were asked to rate the average level of pain during the treatment. At 90 days following subjects' third treatment subjects evaluated their improvement using a Global Aesthetic Improvement Scale (GAIS) and rated their satisfaction with the treatment. Evaluation of pretreatment and posttreatment photos was completed by two blinded physician reviewers. Reviewers were asked to identify the pretreatment and posttreatment photographs and to rate the degree of improvement utilizing a GAIS.

RESULTS

Fifteen participants completed the study; six were exited from the study (withdrew or lost to follow-up). The average subject GAIS score for overall appearance was 3.8. The average subject satisfaction level at follow-up was 4.8. The average subject pain score was 4.9. One blinded physician reviewer correctly identified 100% of subjects' posttreatment photographs, while the second blinded reviewer correctly identified 93%. Blinded evaluation of digital photographs revealed an average GAIS score of 3.2. Posttreatment skin responses included pin-point hemorrhage, erythema, edema, and soft tissue crusting lasting 5-7 days. There were no instances of infection, scarring or hypopigmentation. There were two instances of temporary hyperpigmentation.

CONCLUSIONS

Treatment with the novel 2910 nm fiber laser is safe and effective in treating advanced photoaging and rhytides. Three treatments produced moderate to marked improvement with high patient satisfaction and treatment was associated with less discomfort and downtime compared to conventional fractional ablative lasers.

Relevant parameters for laser surgery of soft tissue

In recent years, the laser has become an important tool in hospitals. Laser surgery in particular has many advantages. However, there is still a lack of the understanding of the influence of the relevant parameters for laser surgery. In order to fill this gap, the parameters pulse frequency, use of an exhaustion system, air cooling, laser power, laser scan speed, laser line energy and waiting time between cuts were analysed by ANOVA using inter-animal variation as a benchmark. The quality of the cuts was quantized by a previously published scoring system. A total of 1710 cuts were performed with a [Formula: see text] laser. Of the parameters investigated, laser power and scan speed have the strongest influence. Only the right combination of these two parameters allows good results. Other effects, such as the use of pulsed or continuous wave (CW) laser operation, or air cooling, show a small or negligible influence. By modulating only the laser power and scan speed, an almost perfect cut can be achieved with a [Formula: see text] laser, regardless of the external cooling used or the laser pulse duration or repetition rate from CW to nanosecond pulses.

Influence of tissue desiccation on critical temperature for thermal damage during Er:YAG laser skin treatments

OBJECTIVES

Erbium lasers have become an accepted tool for performing both ablative and non-ablative medical procedures, especially when minimal invasiveness is desired. Hard-tissue desiccation during Er:YAG laser procedures is a well-known phenomenon in dentistry, the effect of which is to a certain degree being addressed by the accompanying cooling water spray. The desiccation of soft tissue has attracted much less attention due to the soft tissue's high-water content, resulting in a smaller effect on the ablation process.

MATERIALS AND METHODS

In this study, the characteristics of skin temperature decay following irradiations with Er:YAG laser pulses were measured using a fast thermal camera.

RESULTS

The measurements revealed a substantial increase in temperature decay times and resulting thermal exposure times following irradiations with Er:YAG pulses with fluences below the laser ablation threshold. Based on an analytical model where the skin surface cooling time is calculated from the estimated thickness of the heated superficial layer of the stratum corneum (SC), the observed phenomena is attributed to the accelerated evaporation of water from the SC's surface. By using an Arrhenius damage integral-based variable heat shock model to describe the dependence of the critical temperature on the duration of thermal exposure, it is shown that contrary to what an inexperienced practitioner might expect, the low-to-medium level fluences may result in a larger thermal damage in comparison to treatments where higher fluences are used. This effect may be alleviated by hydrating the skin before Er:YAG treatments.

CONCLUSION

Our study indicates that tissue desiccation may play a more important role than expected for soft-tissue procedures. It is proposed that its effect may be alleviated by hydrating the skin before Er:YAG treatments.

High-Power Laser Application for Immediate Implant Placement in Infected Sites: A Systematic Review

Objective: The purpose of this study was to review the literatures regarding the treatment outcomes of applying laser to the infected sites in immediate implant placement. The review tended to primarily target a question: does applying high-power laser have any positive effect on infected sites in immediate implant placement? Background: Although immediate placement of dental implants has been referred to as a predictable and successful procedure, it is prone to the presence of infection that interferes with the healing process, and triggers the failure of implants. Materials and methods: A thorough electronic database search was conducted on PubMed/Medline, Embase, Web of Science, Google Scholar, and the Cochrane library in compliance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Two writers worked separately on screening the eligible studies, assessing whether there was a risk of bias, and extracting the required data. Results: Five out of the 60 studies nominated by the database search matched the inclusion criteria. The studies were carried out on a total of 192 patients with 296 implants in all. Ultimately, the study focused on 245 implants whose infected bed had been already decontaminated and prepared with the help of the high-intensity laser, used either alone or in combination with other approaches before implantation. With only nine failures, the implants inserted in infected and irradiated areas had a 96.3% overall survival rate. Conclusions: Taking the limitations of the review into account, the authors arrived at the conclusion that high-power laser irradiation can be beneficial for immediate implant placement in infected sites.

Photoinactivation and Photoablation of Porphyromonas gingivalis

Several types of phototherapy target human pathogens and Porphyromonas gingivitis (Pg) in particular. The various approaches can be organized into five different treatment modes sorted by different power densities, interaction times, effective wavelengths and mechanisms of action. Mode 1: antimicrobial ultraviolet (aUV); mode 2: antimicrobial blue light (aBL); mode 3: antimicrobial selective photothermolysis (aSP); mode 4: antimicrobial vaporization; mode 5: antimicrobial photodynamic therapy (aPDT). This report reviews the literature to identify for each mode (a) the putative molecular mechanism of action; (b) the effective wavelength range and penetration depth; (c) selectivity; (d) in vitro outcomes; and (e) clinical trial/study outcomes as these elements apply to Porphyromonas gingivalis (Pg). The characteristics of each mode influence how each is translated into the clinic.

Effect of Er:YAG Laser Exposure on the Amorphous Smear Layer in the Marginal Zone of the Osteotomy Site for Placement of Dental Screw Implants: A Histomorphological Study

The placement of dental screw implants typically involves the use of rotary techniques and drills to create a bone bed. This study explores the potential benefits of combining this method with an Er:YAG laser. Split osteotomies were performed on 10 jaws of euthanized domestic pigs (Sus scrofa domestica), with 12 mandibular implant osteotomies in each jaw, divided into 4 groups. In order to make a comprehensive assessment of the effect of Er:YAG lasers, histomorphological techniques were used to measure the reduction in amorphous layer thickness after Er:YAG laser treatment, both with and without the placement of dental screw implants from different manufacturers. Following bone decalcification and staining, the thickness of the amorphous layer was measured in four groups: Group A-osteotomy performed without Er:YAG laser treatment-had amorphous layer thicknesses ranging from 21.813 to 222.13 µm; Group B-osteotomy performed with Er:YAG laser treatment-had amorphous layer thicknesses ranging from 6.08 to 64.64 µm; Group C-an implant placed in the bone without laser treatment-had amorphous layer thicknesses of 5.90 to 54.52 µm; and Group D-an implant placed after bone treatment with Er:YAG laser-had amorphous layer thicknesses of 1.29 to 7.98 µm. The examination and photomicrodocumentation was performed using a LEICA DM1000 LED microscope (Germany) and LAS V 4.8 software (Leica Application Suite V4, Leica Microsystems, Germany). When comparing group A to group B and group C to D, statistically significant differences were indicated (p-value = 0.000, p < 0.05). The study demonstrates the synergistic effects and the possibility of integrating lasers into the conventional implantation protocol. By applying our own method of biomodification, the smear layer formed during rotary osteotomy can be reduced using Er:YAG lasers. This reduction leads to a narrower peri-implant space and improved bone-to-implant contact, facilitating accelerated osseointegration.

Performance of the mid-infrared Q-switched LD side-pumped Er:YSGG MOPA laser

We report on a laser-diode (LD)-pumped master-oscillator power amplifier (MOPA) mid-infrared laser system based on an LD side-pumped Er:YSGG seed laser that can operate in both free-running and Q-switched regimes. In the free-running mode of the seed laser, the maximum amplified single-pulse energy was 83.4 mJ. In Q-switched mode of the seed laser, a maximum single-pulse energy of 7.8 mJ was achieved at 100 Hz repetition rate with the pulse width of 90 ns, corresponding to the peak power of 86.7 kW and the single-pass amplification factor of 1.66. The results indicate that the LD side-pumped MOPA structure is an effective way to realize a nanosecond ∼3µm mid-infrared laser with high repetition rate and high pulse energy.

Comparison of Osseointegration of Dental Implants Placed in Rabbit Tibia Using Two Dental Laser and Implant Handpiece Systems

The present study aimed to confirm the usefulness of a multi-laser handpiece system currently under development. Implants were placed in the tibia of rabbits using a conventional separate laser-implant handpiece system (control group; SurgicPro+; NSK, Kanuma, Japan and Epic 10; Biolase, Irvine, CA, USA) and a multi-laser handpiece system (experimental group; BLP 10; Saeshin, Daegu, Korea). Implants were placed in left and right tibias of five rabbits using a conventional laser-implant handpiece system and a multi-laser handpiece system (N = 5 per group). Subsequently, micro-computed tomography (micro-CT; bone-to-implant contact evaluation), implant stability quotient (ISQ) measurement, and histological evaluations were performed to confirm the implant placement results. The independent t-test and the paired t-test were used to compare the ISQ values and the results of the two implant-laser handpiece groups (α = 0.05), respectively. No statistically significant difference in micro-CT, ISQ, and histological evaluations was observed between implant placement by the two systems (p > 0.05) except implant initial stability. The use of the multi-laser handpiece system is expected to produce the same results as a conventional separate laser-implant handpiece system with the higher implant initial stability. Additionally, it will potentially make the clinical environment more pleasant and will provide convenience for the clinicians.

A Novel Concept of Combined High-Level-Laser Treatment and Transcutaneous Photobiomodulation Therapy Utilisation in Orthodontic Periodontal Interface Management

This case report is aimed to demonstrate the synergetic effects of λ940 nm laser photobiomodulation (PBM) therapy in augmenting the advantages of high-level-laser treatment (HLLT)-mediated reaction orthodontic periodontal interface management. Materials and Methods: A 32-year-old female who presented with a persistent gummy smile of upper incisors and low upper midline frenum attachment post-orthodontic treatment, was seeking a better smile appearance. She had a history of delayed wound healing without underlying medical conditions; otherwise, she was fit and healthy. She underwent laser ablation of the upper midline frenum and gingivoplasty of the upper incisors region with λ940 nm and λ2780, respectively, as well as transcutaneous PBM therapy (λ940 nm) to accelerate wound healing. The laser protocols were as follows: λ2780 nm: power output—2 W, pulse width—60 μs, free running pulse (FRP), spot area—0.0016 cm², pulse repetition rate—25 pulses per second (s), 80 mJ/pulse, 90 s, λ940 nm: 1.2 W, continuous wave (CW) emission mode, 300 μm, 60 s; whereas the adjunctive λ940 nm induced-PBM parameters were as follows: power output—1.4 W, CW—120 s, single application, spot area—2.8 cm². An acceleration of the wound healing was observed on the 4th day of treatment with no immediate or post-operative complications. The results showed no functional or aesthetic relapses at a long-term follow-up of 6 months. The authors concluded that λ940 nm laser-PBM can provide a synergetic effect to HLLT in accelerating wound healing and offering a precision smile with minimal to none post-operative complications. It is safe and justifiable to utilise dual therapy over the conventional methods, which serves our patients’ needs in our daily practice and in various clinical indications. The concept and laser protocols of this clinical case report can pave the roadmap for future extensive studies.

Jet injectors: Perspectives for small volume delivery with lasers

Needle-free jet injectors have been proposed as an alternative to injections with hypodermic needles. Currently, a handful of commercial needle-free jet injectors already exist. However, these injectors are designed for specific injections, typically limited to large injection volumes into the deeper layers beneath the skin. There is growing evidence of advantages when delivering small volumes into the superficial skin layers, namely the epidermis and dermis. Injections such as vaccines and insulin would benefit from delivery into these superficial layers. Furthermore, the same technology for small volume needle-free injections can serve (medical) tattooing as well as other personalized medicine treatments. The research dedicated to needle-free jet injectors actuated by laser energy has increased in the last decade. In this case, the absorption of the optical energy by the liquid results in an explosively growing bubble. This bubble displaces the rest of the liquid, resulting in a fast microfluidic jet which can penetrate the skin. This technique allows for precise control over volumes (pL to µL) and penetration depths (µm to mm). Furthermore, these injections can be tuned without changing the device, by varying parameters such as laser power, beam diameter and filling level of the liquid container. Despite the published research on the working principles and capabilities of individual laser-actuated jet injectors, a thorough overview encompassing all of them is lacking. In this perspective, we will discuss the current status of laser-based jet injectors and contrast their advantages and limitations, as well as their potential and challenges.

Finite element modeling of shape memory polyurethane foams for treatment of cerebral aneurysms

In this paper, a thermo-mechanical analysis of shape memory polyurethane foams (SMPUFs) with aiding of a finite element model (FEM) for treating cerebral aneurysms (CAs) is introduced. Since the deformation of foam cells is extremely difficult to observe experimentally due to their small size, a structural cell-assembly model is established in this work via finite element modeling to examine all-level deformation details. Representative volume elements of random equilateral Kelvin open-cell microstructures are adopted for the cell foam. Also, a user-defined material subroutine (UMAT) is developed based on a thermo-visco-elastic constitutive model for SMPUFs, and implemented in the ABAQUS software package. The model is able to capture thermo-mechanical responses of SMPUFs for a full shape memory thermodynamic cycle. One of the latest treatments of CAs is filling the inside of aneurysms with SMPUFs. The developed FEM is conducted on patient-specific basilar aneurysms treated by SMPUFs. Three sizes of foams are selected for the filling inside of the aneurysm and then governing boundary conditions and loadings are applied to the foams. The results of the distribution of stress and displacement in the absence and presence of the foam are compared. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem and provide pertinent results that are instrumental in the design of SMPUFs for treating CAs.

Laser Resurfacing Monotherapy for the Treatment of Actinic Keratosis

Treating actinic keratosis (AK) and photodamaged skin is critical to reduce the risk of progression to skin cancer. Laser resurfacing for AK treatment is available as either lesion-directed or field therapy. Laser resurfacing removes the superficial epidermis and dermis containing actinic damage, promoting re-epithelialization of healthy skin. Although laser resurfacing has been explored as a modality for AK treatment in the literature, studies summarizing its efficacy in the treatment of AK are lacking. This review summarizes existing research on laser resurfacing as a monotherapy for AK treatment, highlighting the various laser resurfacing modalities available for AK treatment as well as their complications and efficacy in comparison to other therapies. Despite longer healing time, fully ablative laser resurfacing, including carbon dioxide and erbium-doped yttrium aluminum garnet were found to be more effective for AK treatment than fractional ablative techniques. Although some studies suggest laser resurfacing monotherapy as less efficacious than photodynamic therapy, and equally effective to 5-fluorouracil and 30% trichloroacetic acid, clinical trials of larger sample size are required to establish stronger evidence-based conclusions. Moreover, laser resurfacing used as lesion-directed therapy, as opposed to the usual field-therapy, requires further investigation.

High energy (0.8 J) mechanically Q-switched 2.94 μm Er:YAG laser

We report a flashlamp pumped mechanically Q-switched (MQS) 2.94 μm Er:YAG laser based on a spinning mirror with a highest output energy of 805 mJ at a pulse duration of 61 ns and 13 MW of peak power at 1 Hz repetition rate. This record output energy was achieved with the use of 300 mm long MQS Er:YAG laser cavity consisting of a 70% output coupler, 7 × 120 mm AR coated Er(50%):YAG crystal, and 4200 rad/s angular speed of the spinning mirror. The pulse jitter was also measured by using optical triggering and was smaller than 10 ns for 150 ns Q-switched pulses, which could be applicable to many laser applications where precise synchronization of pulses is required.

Effects of Dentin Ablation by a Q-Switching Er:YSGG Laser with a High Pulse Repetition Rate

Objective: The aim of the study was to evaluate the characteristics of dentin ablation with a high pulse repetition rate Q-switching 2.79 μm laser. Materials and methods: Dentin was ablated using a homemade Q-switching Er:YSGG laser with a high pulse repetition rate. Er:YSGG radiation was applied with a pulse energy of 1 or 10 mJ for 100 or 3 Hz pulse repetition rate, respectively. A scanning electron microscope (SEM) was used to observe the microstructures of dentin samples after ablation. Teeth were irradiated in vitro with a 100 Hz pulse repetition rate under two different modes: free running and Q-switching. A thermocouple was applied to measure the temperature in the pulp cavity during ablation. Results: A 100 or 3 Hz Q-switching laser was used to irradiate dentin for 30 and 100 sec, respectively. There was no significant difference in ablation mass loss between the two conditions. The SEM photographs showed more dentinal tubules and no damage in the ablation area when using the 100 Hz Q-switching laser. The temperature of the pulp cavity was maintained below 41°C when using a Q-switching laser. Conclusions: The Q-switching Er:YSGG laser with a high pulse repetition rate exhibited greater ablation efficiency and better morphology than the low pulse repetition rate Q-switching laser. The experimental results also demonstrate the significant advantage of the Q-switching laser over free-running lasers for protecting dental pulp tissue. The Q-switching Er:YSGG laser with a high pulse repetition rate is expected to become an efficient new dental tool.

Optimizing deep bone ablation by means of a microsecond Er:YAG laser and a novel water microjet irrigation system

The microsecond Er:YAG pulsed laser with a wavelength of λ = 2.94 μm has been widely used in the medical field, particularly for ablating dental tissues. Since bone and dental tissues have similar compositions, consisting of mineralized and rigid structures, the Er:YAG laser represents a promising tool for laserosteotomy applications. In this study, we explored the use of the Er:YAG laser for deep bone ablation, in an attempt to optimize its performance and identify its limitations. Tissue irrigation and the laser settings were optimized independently. We propose an automated irrigation feedback system capable of recognizing the temperature of the tissue and delivering water accordingly. The irrigation system used consists of a thin 50 μm diameter water jet. The water jet was able to penetrate deep into the crater during ablation, with a laminar flow length of 15 cm, ensuring the irrigation of deeper layers unreachable by conventional spray systems. Once the irrigation was optimized, ablation was considered independently of the irrigation water. In this way, we could better understand and adjust the laser parameters to suit our needs. We obtained line cuts as deep as 21 mm without causing any visible thermal damage to the surrounding tissue. The automated experimental setup proposed here has the potential to support deeper and faster ablation in laserosteotomy applications.

Disinfection of contaminated metal implants with an Er:YAG laser

Infections related to orthopedic procedures are considered particularly severe when implantation materials are used, because effective treatments for biofilm removal are lacking. In this study, the relatively new approach for infection control by using an erbium:yttrium-aluminum-garnet (Er:YAG) laser was tested. This laser vaporizes all water containing cells in a very effective, precise, and predictable manner and results in only minimal thermal damage. For preliminary testing, 42 steel plates and 42 pins were seeded with mixed cultures. First, the minimally necessary laser energy for biofilm removal was determined. Subsequently, the effectiveness of biofilm removal with the Er:YAG laser and the cleansing of the metal implants with octenidine-soaked gauze was compared. Then, we compared the effectiveness of biofilm removal on 207 steel pins from 41 patients directly after explantation. Sonication and scanning electron microscopy were used for analysis. Laser fluences exceeding 2.8  J/cm² caused a complete extinction of all living cells by a single-laser impulse. Cleansing with octenidine-soaked gauze and irradiation with the Er:YAG laser are both thoroughly effective when applied to seeded pins. In contrast, when explanted pins with fully developed biofilms were analyzed, we found a significant advantage of the laser procedure. The Er:YAG laser offers a secure, complete, and nontoxic eradication of all kinds of pathogens from metal implants without damaging the implant and without the possible development of resistance. The precise noncontact removal of adjacent tissue is a decisive advantage over conventional disinfectants. Therefore, laser irradiation could become a valuable method in every debridement, antibiotics, and implant retention procedure.

Dermatologic Laser Side Effects and Complications: Prevention and Management

The evolution of modern laser and light-based systems has mirrored the demand for clinically effective treatments and the need for safer technologies with reduced postoperative recovery, side effects, and complications. With each new generation of lasers, more selective tissue destruction can be achieved with reduced unwanted sequelae. Patient selection and preparation, operator technique, and expeditious recognition and management of post-treatment side effects are paramount in avoiding complications and patient dissatisfaction. An overview of important variables to consider for dermatologic laser treatments are presented in order to provide a framework to reduce the severity and duration of possible post-treatment side effects and complications.

Evaluation of laser-induced plasma ablation focusing on the difference in pulse duration

A pulsed laser cause vaporization of tissue by plasma if a laser can provide high-density energy within a very short pulse duration. Such phenomena are called laser-induced plasma ablation. The influence of the laser-induced plasma ablation for tissue is unclear because the ablation mechanism is differing regardless of two lasers provide almost the same power density. The two kinds of lasers' vaporization mechanism (Nanosecond laser output could cause an optical breakdown in the air depending on power density and pulse duration of the laser and Femtosecond laser output could cause a breakdown only on solids surface since pulse irradiation time is shorter than energy transfer time) are evaluated by using thermal damage and destruction of tissue. The experimental results show that nanosecond laser caused vaporization without thermal damage and destruction at the tissue approximant 300 μm away from the ablation area. The pulsed laser which has high power density and longer pulse duration than energy transfer time is suitable for plasma ablation not depending on thermal process.

[Clinical application of laser in crown lengthening]

Crown lengthening is one of the most common surgeries in clinical practice. Under the premise of ensuring the biologic width, the adequate crown is exposed by resecting the periodontal soft tissue and (or) hard tissue to meet the prosthodontic and (or) aesthetic requirements. Considering the various advantages of oral laser, such as safe, precise, minimally invasive and comfort, laser has become a promising technology which can be used to improve the traditional crown lengthening. In this review, the principles and characteristics of laser application in crown lengthening, especially in the minimally invasive or flapless crown lengthening will be reviewed. Its pros and cons will also be discussed.

Correlation between light absorbance and skin color using fabricated skin phantoms with different colors

The objective of this study is to investigate the need for detailed classification of skin colors through the quantification of skin color and light absorbance differences. Skin color is one of the most important factors in dermatological laser treatments. Dermatological laser treatments are currently performed based on the experience and judgment of the doctor with the Fitzpatrick scale. However, the Fitzpatrick scale and the doctor's experience were not quantified assessment methods for skin color classification and laser parameters selection. Improper selection of laser irradiating parameters can lead to undesirable tissue effects and treatment outcomes. We analyzed the correlations between absorbance and quantified colors using skin phantoms to identify that using the Fitzpatrick scale in dermatological treatments have limitations. Absorbance differences for different skin colors are measured at 532 nm with a custom-built system for radiant power measurements using skin phantoms fabricated with nine different colors. Some correlations between the color and absorbance agree with the Fitzpatrick scale. Generally, absorbance for the bright colored phantoms is lower than that for the darker colored phantoms. However, some phantoms fabricated with bright colors exceptionally have higher absorbance than those with darker colors. This means that for conventional standards, the Fitzpatrick scale may not always be accurate at 532-nm lights. Through these experiments, we demonstrate the need for a reliable classification standard for skin colors based on quantification of the skin colors and absorbance differences for each skin color as an alternative to the Fitzpatrick scale, which has limitations at certain wavelengths.

Laser Ablation Electrospray Ionization Time-of-Flight Mass Spectrometry for Direct Analysis of Biological Tissue

Direct analysis and identification of biological tissue is significant for clinical applications. In this study, porcine liver and kidney have been analyzed using laser ablation electrospray ionization time-of-flight mass spectrometry (LAESI-TOFMS). This method showed good reproducibility for the same types of tissue and is capable of distinguishing different tissue species. The margin assessment was also performed using porcine renal tissue, and the response time was less than 6 s. Furthermore, human hepatocarcinoma tissue and normal tissue were identified using this method. Our results indicate that LAESI-TOFMS is a feasible approach for direct identification of tumor tissue and potential for assessment of the resection margin.

Photonic Therapy in Periodontal Diseases an Overview with Appraisal of the Literature and Reasoned Treatment Recommendations

Recent reviews and meta-analyses of the literature over the past quarter-century have failed to provide enough evidence to prove or disprove the actual utility of photonic therapy in periodontitis, alone or adjunctive to conventional approaches. This apparent paradox has been explained by the many physical, molecular, biological, anatomical, and technical variables of photonic treatments, which can differ in light-emitting devices (laser or LED), wavelengths, irradiation power and modes, clinical objectives, follow-up times, disease grading, and assessment methods. This multi-faceted, controversial scenario has led practitioners to underestimate the actual potential of photonic therapy in periodontal diseases. In this critical appraisal of the literature, we have briefly summarized the main photonic therapies and instruments used in Periodontology, highlighting their main characteristics and limitations. Then, we have tried to identify and discuss the key methodological issues which can have an impact on the outcome of photonic therapies. Our main goal was to identify the best parameters, settings, and methodologies to perform effective periodontal photonic treatments and to extrapolate some recommendations for clinical use. Should these recommendations find a consensus among periodontologists and be adopted in future clinical studies, they will hopefully contribute to dissipate the present confusion and uncertainty on this complex matter.

Investigation of laser pulsing parameters' importance in Er:YAG laser skin ablation: a theoretical study conducted via newly developed thermo-mechanical ablation model

Objective: Importance of laser pulsing parameters and tissue's mechanical properties in the Er:YAG laser skin-tissue ablation is not adequately understood. The goal here was to develop a computational model that incorporates skin tissue's mechanical properties to investigate the influence of Er:YAG laser pulsing parameters on tissue ablation and coagulation. Methods: Tissue's mechanical properties were incorporated by modeling ablation as a tissue water vaporization occurring under elevated pressures that depend on tissue's stress-strain relationships. Tissue deformation was assumed unidirectional; therefore, a one-dimensional model was utilized. Analytical solution and experimental results were used to verify and validate the model. Then, influence of pulse duration (10 µs-2 ms) and fluence (0-30 J cm^-2) on coagulation depth and ablation efficiency was explored. Results: Verification and validation results suggested that the model is acceptably accurate. Minimal effect of pulse duration on coagulation depth was predicted at sub-ablative conditions. At those conditions, coagulation depth increased asymptotically to ∼90 µm with increasing pulse fluence. At ablative conditions, coagulation depth decreased asymptotically to 22-28 µm with increasing pulse irradiance. Ablation efficiency plateaued at high pulse fluences and long pulse durations. Mechanical properties were important as about 50% increase in coagulation depth and 25% decrease in ablation efficiency were predicted when considering the high strain-rate loading effect in comparison with quasi-static loading. Conclusions: Proper tuning of Er:YAG laser pulsing parameters can substantially improve its therapeutic outcomes. The effect of these parameters varies and depends on whether the laser-tissue conditions are ablative or sub-ablative.

Characterization of Ablated Bone and Muscle for Long-Pulsed Laser Ablation in Dry and Wet Conditions

Smart laser technologies are desired that can accurately cut and characterize tissues, such as bone and muscle, with minimal thermal damage and fast healing. Using a long-pulsed laser with a 0.5–10 ms pulse width at a wavelength of 1.07 µm, we investigated the optimum laser parameters for producing craters with minimal thermal damage under both wet and dry conditions. In different tissues (bone and muscle), we analyzed craters of various morphologies, depths, and volumes. We used a two-way Analysis of Variance (ANOVA) test to investigate whether there are significant differences in the ablation efficiency in wet versus dry conditions at each level of the pulse energy. We found that bone and muscle tissue ablated under wet conditions produced fewer cracks and less thermal damage around the craters than under dry conditions. In contrast to muscle, the ablation efficiency of bone under wet conditions was not higher than under dry conditions. Tissue differentiation was carried out based on measured acoustic waves. A Principal Component Analysis of the measured acoustic waves and Mahalanobis distances were used to differentiate bone and muscle under wet conditions. Bone and muscle ablated in wet conditions demonstrated a classification error of less than 6.66% and 3.33%, when measured by a microphone and a fiber Bragg grating, respectively.

Observations of in vivo laser tissue ablation in animal models with different chromophores on the skin and modulating duration per laser exposure

Characteristics such as skin tone and pigmentation color vary among patients, but most researches on laser irradiation in laser ablation have revolved around minimizing damage to reduce pain. Chromophores are the most important factors in photon energy absorption, a key principle of laser ablation. We investigated the influences on ablation depth by different chromophores on the target and modulating duration per laser exposure using an Nd:YVO4 nanosecond 532-nm laser. We used a Fourier-domain optical coherence tomography (Fd-OCT) system combined with a 532-nm Nd:YVO4 laser to observe the ablation process. In addition, an external customized shutter and water-based color pens (red, green, blue, black) were used to determine the effects of modulating the duration per laser exposure and coloring chromophores on porcine skin and hairless mouse models. Experiments with modulating duration per laser exposure demonstrated that shorter duration generated shallower craters than longer one. Painted experimental group showed damaged region as craters in the experiments with coloring various chromophores. In this research, we investigated the effects of modulating duration per laser exposure and different chromophores on the target. Coloring chromophores with water-based dyes using pens increased tissue damage without dyeing cells or tissue.

A three-dimensional transient computational study of 532-nm laser thermal ablation in a geometrical model representing prostate tissue

OBJECTIVE

Laser with 532-nm wavelength (GreenLight^TM) is clinically approved to treat benign prostatic hyperplasia (BPH). However, low rate of tissue ablation and excessive thermal coagulation are shortcomings of this therapy. The goal of this study was to use a mathematical model to identify clinically viable laser settings that have the potential to improve treatment time and outcomes.

METHODS

A three-dimensional transient computational model was developed, validated against analytical and experimental results, and utilized to investigate the response of tissues subjected to continuous-wave and pulsed lasers emitting 532-nm light (GreenLight^TM laser). The impact of laser power (10-125 W), pulse duration (100 ns and 100 µs) and pulse frequency (10 and 100 Hz) on tissue ablation and coagulation rates and sizes was explored.

RESULTS

Good agreement between the computational model and analytical and experimental results was found. Continuous-wave laser results in 13% less coagulation zone thickness and 10% higher ablation rate than the low frequency pulsed laser. With increasing laser power; ablation rate is expected to increase linearly, while coagulation zone thickness is expected to increase asymptotically. Pulse frequency influence on tissue ablation and coagulation is relevant at high power, but pulse duration is found to have minimal effect at all powers.

CONCLUSIONS

Laser thermal tissue ablation employing continuous wave mode lasers outperforms that employing pulsed mode lasers. Laser power settings should be carefully selected to maximize the rate of tissue ablation and minimize tissue coagulation.

Laser micro-ablation of fibrocartilage tissue: Effects of tissue processing on porosity modification and mechanics

The temporomandibular joint disk (TMJd) is an extremely dense and avascular fibrocartilaginous extracellular matrix (ECM) resulting in a limited regenerative capacity. The use of decellularized TMJd as a biocompatible scaffold to guide tissue regeneration is restricted by innate subcellular porosity of the ECM that hinders cellular infiltration and regenerative events. Incorporation of an artificial microporosity through laser micro-ablation (LMA) can alleviate these cell and diffusion based limitations. In this study, LMA was performed either before or after decellularization to assess to effect of surfactant treatment on porosity modification as well as the resultant mechanical and physical scaffold properties. Under convective flow or agitation schemes, pristine and laser ablated disks were decellularized using either low (0.1% w/v) or high (1% w/v) concentrations of sodium dodecyl sulfate (SDS). Results show that lower concentrations of SDS minimized collagen degradation and tissue swelling while retaining its capacity to solubilize cellular content. Regardless of processing scheme, laser ablated channels incorporated after SDS treatment were relatively smaller and more uniform than those incorporated before SDS treatment, indicating an altered laser interaction with surfactant treated tissues. Smaller channels correlated with less disruption of native biomechanical properties indicating surfactant pre-treatment is an important consideration when using LMA to produce artificial porosity in ex vivo derived tissues. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1858-1868, 2018.

High-energy picosecond pulses from a 2850 nm fiber amplifier

We report the demonstration of a 2850 nm diode-pumped Ho³⁺, Pr³⁺ co-doped fluoride fiber amplifier that delivers pulses with an average power of 2.45 W, 122 μJ energy, and 500 ps duration at a repetition rate of 20 kHz. To the best of our knowledge, the average power and pulse energy are the highest to be obtained from a sub-nanosecond fiber source operating in the 3 μm spectral region. The amplifier is seeded by an optical parametric generation source and is pumped around 915 nm using widely available InGaAs laser diodes.

Assessment of skin lesions produced by focused, tunable, mid-infrared chalcogenide laser radiation

BACKGROUND

Traditionally, fractional laser treatments are performed with focused laser sources operating at a fixed wavelength. Using a tunable laser in the mid-infrared wavelength range, wavelength-dependent absorption properties on the ablation process and thermal damage formation were assessed with the goal to obtain customizable tissue ablations to provide guidance in finding optimized laser exposure parameters for clinical applications.

METHODS

Laser tissue experiments were carried out on full thickness ex vivo human abdominal skin using a mid-infrared tunable chromium-doped zinc selenide/sulfide chalcogenide laser. The laser has two independent channels: a continuous wave (CW) output channel which covers a spectrum ranging from 2.4 μm to 3.0 μm with up to 9.2 W output power, and a pulsed output channel which ranges from 2.35 μm to 2.95 μm. The maximum pulse energy of the pulsed channel goes up to 2.8 mJ at 100 Hz to 1,000 Hz repetition rate with wavelength-dependent pulse durations of 4-7 ns.

RESULTS

Total ablation depth, ablation efficiency, and coagulation zone thickness were highly correlated to wavelength, pulse width, and pulse energy. Using the same total radiant exposure at 2.85 μm wavelength resulted in 10-times smaller coagulation zones and 5-times deeper ablation craters for one hundred 6 ns pulses compared to one 100 ms pulse. For a fixed pulse duration of 6 ns and a total radiant exposure of 2.25 kJ/cm² the ablation depth increased with longer wavelengths.

CONCLUSION

The tunable laser system provides a useful research tool to investigate specific laser parameters such as wavelength on lesion shape, ablation depth and thermal tissue damage. It also allows for customization of the characteristics of laser lesions and therefore facilitates the selection of suitable laser parameters for optimized fractional laser treatments. Lasers Surg. Med. 50:961-972, 2018.© 2018 Wiley Periodicals, Inc.

Characterization of a novel miniaturized burst-mode infrared laser system for IR-MALDESI mass spectrometry imaging

Laser systems are widely used in mass spectrometry as sample probes and ionization sources. Mid-infrared lasers are particularly suitable for analysis of high water content samples such as animal and plant tissues, using water as a resonantly excited sacrificial matrix. Commercially available mid-IR lasers have historically been bulky and expensive due to cooling requirements. This work presents a novel air-cooled miniature mid-IR laser with adjustable burst-mode output and details an evaluation of its performance for mass spectrometry imaging. The miniature laser was found capable of generating sufficient energy for complete ablation of animal tissue in the context of an IR-MALDESI experiment with exogenously added ice matrix, yielding several hundred confident metabolite identifications. Graphical abstract The use of a novel miniature 2.94 μm burst-mode laser in IR-MALDESI allows for rapid and sensitive mass spectrometry imaging of a whole mouse.

Laser surface modification of decellularized extracellular cartilage matrix for cartilage tissue engineering

The implantation of autologous cartilage as the gold standard operative procedure for the reconstruction of cartilage defects in the head and neck region unfortunately implicates a variety of negative effects at the donor site. Tissue-engineered cartilage appears to be a promising alternative. However, due to the complex requirements, the optimal material is yet to be determined. As demonstrated previously, decellularized porcine cartilage (DECM) might be a good option to engineer vital cartilage. As the dense structure of DECM limits cellular infiltration, we investigated surface modifications of the scaffolds by carbon dioxide (CO₂) and Er:YAG laser application to facilitate the migration of chondrocytes inside the scaffold. After laser treatment, the scaffolds were seeded with human nasal septal chondrocytes and analyzed with respect to cell migration and formation of new extracellular matrix proteins. Histology, immunohistochemistry, SEM, and TEM examination revealed an increase of the scaffolds' surface area with proliferation of cell numbers on the scaffolds for both laser types. The lack of cytotoxic effects was demonstrated by standard cytotoxicity testing. However, a thermal denaturation area seemed to hinder the migration of the chondrocytes inside the scaffolds, even more so after CO₂ laser treatment. Therefore, the Er:YAG laser seemed to be better suitable. Further modifications of the laser adjustments or the use of alternative laser systems might be advantageous for surface enlargement and to facilitate migration of chondrocytes into the scaffold in one step.

Effect of ablative laser on in vitro transungual delivery

Topical therapy of nail psoriasis using methotrexate has not been realized due to the high molecular weight and low permeability of the compound. In this study, we used a 2940nm fractional ablative laser to disrupt the nail barrier to enhance the in vitro transungual delivery of methotrexate. Bovine hoof membrane-an in vitro model of the human nail-was treated by the laser at different energy levels and pore densities. A successful microporation was characterized by mechanical properties, scanning electron microscopy, Fourier transform infrared spectrophotometer, dye binding, histology, pore uniformity, confocal laser microscopy, nail integrity measurement, and permeation studies. No significant difference in the pore dimension was found in different treatment groups (p>0.05). Increases in pore depth corresponded with increases in the laser energy. Laser ablation was found to affect the mechanical properties of the hoof membrane. In in vitro permeation studies, laser ablation resulted in a significant increase in the drug cumulative delivery, flux, and permeability coefficient as compared to the untreated group (n=3, p<0.05). A change in the laser energy and pore density was found to alter the drug permeability. Thus, transungual methotrexate delivery was enhanced by the fractional laser ablation.

Thermal analysis and laser performance of a GYSGG/Cr,Er,Pr:GYSGG composite laser crystal operated at 2.79 μm

We demonstrate the thermal analysis and laser performance of a GYSGG/Cr,Er,Pr:GYSGG composite crystal. The lifetime ratio of lower and upper levels of Er³⁺ in Cr,Er,Pr:GYSGG crystal is further reduced due to the optimized doping concentrations. The thermal effect of composite crystal is lower than that of Cr,Er,Pr:GYSGG crystal. A maximum pulse energy 342.8 mJ operated at 5 Hz and 2.79 μm is obtained on the composite crystal, corresponding to electrical-to-optical efficiency of 0.86% and slope efficiency of 1.08%. Under the same condition, these values on the Cr,Er,Pr:GYSGG crystal are only 315.8 mJ, 0.79% and 1.04%, respectively. Moreover, the composite crystal has also a relative high laser beam quality, exhibiting obvious advantage in reducing thermal effects and improving laser performances.

Laser-Assisted Osteotomy for Implant Site Preparation: A Literature Review

PURPOSE

The aim of this study was to review the scientific evidence about the laser osteotomy in implant bed preparation.

METHODS

An electronic search was performed on relevant English articles up to April 2016 in the PubMed, Scopus, and Google Scholar databases.

RESULTS

Twenty-two articles (1 clinical, 13 animal, and 8 ex vivo studies) were included. Implant sites prepared by erbium family lasers and drill showed comparable results regarding the percentage of bone-to-implant contact, values of biomechanical tests, and healing process. Selection of proper laser wavelength and parameters was of paramount importance to minimize the risk of thermal bone damage. Lack of depth control and long time needed for implant site osteotomy with laser were the most challenging concerns for its clinical applicability. Computer-guided laser osteotomy showed promise for future use of laser osteotomy in clinical settings.

CONCLUSION

Evidence from animal studies shows promising results regarding laser osteotomy in implant site preparation. However, because of the lack of clinical studies, it is not possible to make a conclusive result whether there is superiority of laser osteotomy in clinical practice.

Finite element method simulating temperature distribution in skin induced by 980-nm pulsed laser based on pain stimulation

For predicting the temperature distribution within skin tissue in 980-nm laser-evoked potentials (LEPs) experiments, a five-layer finite element model (FEM-5) was constructed based on Pennes bio-heat conduction equation and the Lambert-Beer law. The prediction results of the FEM-5 model were verified by ex vivo pig skin and in vivo rat experiments. Thirty ex vivo pig skin samples were used to verify the temperature distribution predicted by the model. The output energy of the laser was 1.8, 3, and 4.4 J. The laser spot radius was 1 mm. The experiment time was 30 s. The laser stimulated the surface of the ex vivo pig skin beginning at 10 s and lasted for 40 ms. A thermocouple thermometer was used to measure the temperature of the surface and internal layers of the ex vivo pig skin, and the sampling frequency was set to 60 Hz. For the in vivo experiments, nine adult male Wistar rats weighing 180 ± 10 g were used to verify the prediction results of the model by tail-flick latency. The output energy of the laser was 1.4 and 2.08 J. The pulsed width was 40 ms. The laser spot radius was 1 mm. The Pearson product-moment correlation and Kruskal-Wallis test were used to analyze the correlation and the difference of data. The results of all experiments showed that the measured and predicted data had no significant difference (P > 0.05) and good correlation (r > 0.9). The safe laser output energy range (1.8-3 J) was also predicted. Using the FEM-5 model prediction, the effective pain depth could be accurately controlled, and the nociceptors could be selectively activated. The FEM-5 model can be extended to guide experimental research and clinical applications for humans.

Periodontal and peri-implant wound healing following laser therapy

Laser irradiation has numerous favorable characteristics, such as ablation or vaporization, hemostasis, biostimulation (photobiomodulation) and microbial inhibition and destruction, which induce various beneficial therapeutic effects and biological responses. Therefore, the use of lasers is considered effective and suitable for treating a variety of inflammatory and infectious oral conditions. The CO2 , neodymium-doped yttrium-aluminium-garnet (Nd:YAG) and diode lasers have mainly been used for periodontal soft-tissue management. With development of the erbium-doped yttrium-aluminium-garnet (Er:YAG) and erbium, chromium-doped yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers, which can be applied not only on soft tissues but also on dental hard tissues, the application of lasers dramatically expanded from periodontal soft-tissue management to hard-tissue treatment. Currently, various periodontal tissues (such as gingiva, tooth roots and bone tissue), as well as titanium implant surfaces, can be treated with lasers, and a variety of dental laser systems are being employed for the management of periodontal and peri-implant diseases. In periodontics, mechanical therapy has conventionally been the mainstream of treatment; however, complete bacterial eradication and/or optimal wound healing may not be necessarily achieved with conventional mechanical therapy alone. Consequently, in addition to chemotherapy consisting of antibiotics and anti-inflammatory agents, phototherapy using lasers and light-emitting diodes has been gradually integrated with mechanical therapy to enhance subsequent wound healing by achieving thorough debridement, decontamination and tissue stimulation. With increasing evidence of benefits, therapies with low- and high-level lasers play an important role in wound healing/tissue regeneration in the treatment of periodontal and peri-implant diseases. This article discusses the outcomes of laser therapy in soft-tissue management, periodontal nonsurgical and surgical treatment, osseous surgery and peri-implant treatment, focusing on postoperative wound healing of periodontal and peri-implant tissues, based on scientific evidence from currently available basic and clinical studies, as well as on case reports.

Erbium YAG laser treatment of periorbital syringomas by using the multiple ovoid-shape ablation method

INTRODUCTION

Syringomas are benign tumours that develop predominantly in the periorbital areas of women. As periorbital syringoma is adjacent to the appendages, Erbium YAG (Er:YAG) laser treatment should be an ideal tool for its precise ablation, although its use has not previously been reported. We retrospectively analysed our new ovoid-shape Er:YAG laser ablation method for the treatment of syringoma.

MATERIALS AND METHODS

We developed an extirpation method in which multiple, 2- to 4-mm, egg-shaped ablation fields were created. This method was used to treat 49 patients, 35 of whom had predominantly accumulated syringomas, and 14 had disseminated syringomas. Treatment was repeated every 2 months.

RESULTS

Our approach was successful in both disseminated- and accumulated-type syringoma as well as plaque-type syringoma, which is considered to be the most difficult to treat. After an average of 3.77 treatments, more than 75% of the syringoma in the treated area had disappeared in 43 of 49 patients.

CONCLUSION

Our ovoid-shape ablation method gives good cosmetic results even in the most difficult type of syringoma.

Holmium: Yag Laser Angioplasty

This experimental study was designed to define the potential value of a mid-infrared holmium laser in the free running mode for angioplasty. Immediately after removal, fresh normal and diseased human cadaveric arteries were irradiated under saline with a Ho:YAG laser (wavelength 2.13 μm). The laser was pulsed at 3 Hz, 250 μs pulse width and fluences of 10 to 40 J/cm2. The laser beam was coupled to ring catheters with multiple low-OH quartz fibers. The tip of the delivery device was held in direct contact with the vessel surface with the laser beam oriented perpendicularly. Ablation of atherosclerotic plaque was accomplished at an ablation threshold of 10 J/cm2. The ablation rate was 2.1 to 8.3 μm/pulse. Removal of calcified plaque was only partially effective. There were marked thermal effects with vacuolizations extending up to 1505 ± 178 μm into the adjacent tissue. Laser light at the mid-infrared wavelength of 2.13 μm is supposed to be attractive as it is readily absorbed in water and can easily be transmitted through optical fibers. However, Q-switching seems to be essential to minimize thermal side effects and to make effective ablation of calcium possible.

Treatment of atrophic facial acne scars with fractional Er:YAG laser in skin phototype III-IV: A pilot study

BACKGROUND

Fractional ablative lasers have recently been used for the treatment of skin scars. The objective of this study was to assess the efficacy and safety of the fractional erbium-doped yttrium aluminum garnet (Er:YAG) laser (2940 nm) in the treatment of skin scars.

MATERIALS AND METHODS

A total of 9 patients (8 female, 1 male) with Fitzpatrick skin types III and IV suffering from atrophic facial acne scars were treated with a fractional Er:YAG laser for 2-5 (mean 3.3) sessions 4-6 weeks apart. One independent investigator assessed the efficacy, using standardized photographs, before and 1 month after the last treatment. The patients' satisfaction rate was also evaluated.

RESULTS

The treatment was well tolerated by all patients without any anesthesia. The downtime was 2-3 days. All patients showed improvement in scars: excellent in 1, good in 1, and fair in 7 patients. Six patients were highly satisfied and 3 were satisfied with treatment. No adverse effect was noted.

CONCLUSION

A fractional Er:YAG laser can deliver an effective and minimally invasive treatment for acne scars.

Dental hard tissue ablation using mid-infrared tunable nanosecond pulsed Cr:CdSe laser

BACKGROUND AND OBJECTIVE

Mid-infrared erbium: yttrium-aluminum-garnet (Er:YAG) and erbium, chromium: yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers (2.94- and 2.78-μm, respectively) are utilized for effective dental hard tissue treatment because of their high absorption in water, hydroxide ion, or both. Recently, a mid-infrared tunable, nanosecond pulsed, all-solid-state chromium-doped: cadmium-selenide (Cr:CdSe) laser system was developed, which enables laser oscillation in the broad spectral range around 2.9 μm. The purpose of this study was to evaluate the ablation of dental hard tissue by the nanosecond pulsed Cr:CdSe laser at a wavelength range of 2.76-3.00 μm.

STUDY DESIGN/MATERIALS AND METHODS

Enamel, dentin, and cementum tissue were irradiated at a spot or line at a fluence of 0-11.20 J/cm² /pulse (energy output: 0-2.00 mJ/pulse) with a repetition rate of 10 Hz and beam diameter of ∼150 μm on the target (pulse width ∼250 ns). After irradiation, morphological changes, ablation threshold, depth, and efficiency, and thickness of the structurally and thermally affected layer of irradiated surfaces were analyzed using stereomicroscopy, scanning electron microscopy (SEM), and light microscopy of non-decalcified histological sections.

RESULTS

The nanosecond pulsed irradiation without water spray effectively ablated dental hard tissue with no visible thermal damage such as carbonization. The SEM analysis revealed characteristic micro-irregularities without major melting and cracks in the lased tissue. The ablation threshold of dentin was the lowest at 2.76 μm and the highest at 3.00 μm. The histological analysis revealed minimal thermal and structural changes ∼20 μm wide on the irradiated dentin surfaces with no significant differences between wavelengths. The efficiency of dentin ablation gradually increased from 3.00 to 2.76 μm, at which point the highest ablation efficiency was observed.

CONCLUSION

The nanosecond pulsed Cr:CdSe laser demonstrated an effective ablation ability of hard dental tissues, which was remarkably wavelength-dependent on dentin at the spectral range of 2.76-3.00 μm. These results demonstrate the potential feasibility of the use of pulsed Cr:CdSe laser as a novel laser system for dental treatment. Lasers Surg. Med. 48:965-977, 2016. © 2016 Wiley Periodicals, Inc.

Laser treatment of periocular skin conditions

Advances in laser technology in recent decades have increased the options for the treatment of dermatologic conditions of the eye and eyelid. Benign tumors can be laser-ablated with relative ease, and vascular and melanocytic lesions can be precisely targeted with modern lasers. In this contribution, we review treatment of periocular pigmented lesions, including melanocytic nevi and nevus of Ota; vascular lesions including telangiectasias, port wine stains, and infantile hemangiomas; hair removal; eyeliner tattoo removal; laser ablation of common benign periocular tumors, such as syringomas, xanthelasma, milia, and seborrheic keratoses; and laser resurfacing. The recent advent of fractionated laser technology has resulted in dramatically decreased healing times for periocular skin resurfacing and fewer adverse effects. Fractionated laser resurfacing has now nearly supplanted traditional full-field laser resurfacing, and safe treatment of rhytides on the thin skin of the eyelids is possible. Proper eye protection is, of course, essential when using lasers near the eye. Patient preparation, safety precautions, and risks--intraocular and extraocular--are discussed herein. As laser technology continues to advance, we are sure to see improvements in current treatments, as well as development of new applications of cutaneous lasers.