In vivo comparison of near infrared lasers for skin welding

Experimental study on the effect of scanning path on skin tissue properties of femtosecond laser welding

To study the influence pattern of femtosecond laser scanning path on the welding effect of skin tissue, this experiment analyzed the influence of scanning path on the surface morphology, degree of thermal damage, tensile strength, and microstructure of skin samples after skin attachment by designing nine scanning paths to weld skin tissue. The results showed that the skin samples connected by interrupted parallel mattress eversion sewing method with d = 0.2 mm showed no obvious color changes in morphology, the skin samples were connected on both front and back sides, the tensile strength was the highest, reaching 12.80 N/cm2 , the thermal damage parameter was low at 1.08 × 10-2 , the microstructure had obvious directionality, and the texture was clear and uniformly distributed.

In Vitro Feasibility Analysis of a New Sutureless Wound-Closure System Based on a Temperature-Regulated Laser and a Transparent Collagen Membrane for Laser Tissue Soldering (LTS)

For the post-surgical treatment of oral wounds and mucosal defects beyond a certain size, the gold standard is still an autologous skin or mucosal graft in combination with complex suturing techniques. A variety of techniques and biomaterials has been developed for sutureless wound closure including different tissue glues or collagen patches. However, no wound covering that enables for sutureless fixation has yet been introduced. Thus, a new system was developed that allows for sutureless wound covering including a transparent collagen membrane, which can be attached to the mucosa using a specially modified 2λ laser beam with integrated temperature sensors and serum albumin as bio-adhesive. The sutureless wound closure system was tested for its applicability and its cytocompatibility by an established in vitro model in the present study. The feasibility of the laser system was tested ex vivo on a porcine palate. The in vitro cytocompatibility tests excluded the potential release of toxic substances from the laser-irradiated collagen membrane and the bio-adhesive. The results of the ex vivo feasibility study using a porcine palate revealed satisfactory mean tensile strength of 1.2–1.5 N for the bonding of the membrane to the tissue fixed with laser of 980 nm. The results suggest that our newly developed laser-assisted wound closure system is a feasible approach and could be a first step on the way towards a laser based sutureless clinical application in tissue repair and oral surgery.

Hard dental tissues laser welding: a new help for fractured teeth? A preliminary ex vivo study

Background and Aim

An important surgical goal is to provide a first intention wound healing without trauma produced by sutures and for this aim in the past several methods have been tested. The aim of this ex vivo preliminary study was to demonstrate the capacity of a 1070 nm pulsed fiber laser to treat the dental fractures by enamel and dentine melting with the apposition of hydroxyapatite nanoparticles as filler.

Methods

Out of thirty freshly-extracted human third molars, decay-free, twenty-four cylinders of 5 mm thickness were obtained to perform the test.The device used was a 1070 nm Yb-doped pulsed fiber laser: this source has a maximum average output power of 20 W and a fixed pulse duration of 100 ns, while the repetition rate ranges from 20 kHz to 100 kHz. The samples were divided in three groups (a, b, c) of eight teeth and each specimen, with the two portions strictly placed side by side, was put inside the box and irradiated three times, the first and the second at 30 kW and the last at 10 kW peak power (average powers of 60 and 20 W).The repetition rate was maintained at 20 kHz for all the tests as well as the speed of the beam at 10 mm/sec.The samples of the group a were irradiated without apposition, in the group b nanoparticles (< 200 nm) of hydroxyapatite were put in the gap between the two portions while in the group c, a powder of hydroxyapatite was employed.

Results

Only the specimens of the group b showed a real process of welding of the two parts, while specimens of groups a and c did not reach a complete welding process.

Conclusion

This ex vivo preliminary study, based on the enamel and dentine welding obtained by a 1070 nm pulsed fiber laser associated to the hydroxyapatite nanoparticles, may represent a new and original approach for the treatment of the fractured teeth, even if further studies will be necessary to confirm these results.

Closure of skin incision by dual wavelength (980 and 1064 nm) laser application

Thermal effect of dual wavelength (980 and 1064 nm) laser application in skin incision closure was assessed on 18 male and female Wister rats. 1-cm-long incisions were made on the shaved dorsal region of 220-250 g animals. The incisions were closed by laser irradiation at 1 W and exposure time, 5 seconds in continuous-wave mode (CW) and 1 W and exposure time, 10 seconds in pulsed mode to deliver total energies of 5 J and 10 J per spot onto the incisions, respectively. Animals from each group were sacrificed at 0th, 4th, and 7th days and the skin samples of the weld area were excised for histological analysis using Hematoxylin and Eosin (H & E) stain. Mean thermally altered area (TAA) of CW-mode laser-treated groups was found to increase significantly (p < 0.05) compared with pulsed mode laser treated group at 0th and 4th days post-irradiation while no significant difference (p > 0.05) was statistically found at 7th day post-irradiation. Moreover, tighter closure was observed with CW group at 7th day post-irradiation. We thus conclude that 1 W, 5 J for 5 seconds CW mode laser application of 980 and 1064 nm combined beam form in skin incision closure was found to have absolute wound healing capability with minimal thermal alteration.

Refining analgesia strategies using lasers

Sound programs for the humane care and use of animals within research facilities incorporate experimental refinements such as multimodal approaches for pain management. These approaches can include non-traditional strategies along with more established ones. The use of lasers for pain relief is growing in popularity among companion animal veterinary practitioners and technologists. Therefore, its application in the research sector warrants closer consideration.

A review of indocyanine green fluorescent imaging in surgery

The purpose of this paper is to give an overview of the recent surgical intraoperational applications of indocyanine green fluorescence imaging methods, the basics of the technology, and instrumentation used. Well over 200 papers describing this technique in clinical setting are reviewed. In addition to the surgical applications, other recent medical applications of ICG are briefly examined.

Preparation of dissolvable albumin stents for vascular anastomosis with a 1.9 µm laser and in vitro mechanical strength assessments

INTRODUCTION

We present a clinically relevant method for producing and sterilizing dissolvable albumin stents to provide intraluminal support during vascular anastomosis, and a method for photothermally soldering vessels using a 1.9 µm diode laser with a 200-µm spot size, albumin solder, and water as the chromophore. Our aim in this study was to assess the mechanical integrity of soldered vessels, and to determine if gamma-irradiation affected the solubility of the stents.

MATERIALS AND METHODS

The axial tensile strength and burst pressure of 3.75 ± 0.3 mm inner-diameter vessels soldered with varied swath width (1-7 mm), laser power (430-610 mW), solder concentration (22-46%w/w), and solder layering (1-3 layers) was tested in vitro. Stent dissolution was monitored by weight in blood, and with UV absorbance measurements in phosphate buffered saline (PBS). Solubility was measured for stents sterilized by 25 kGy gamma-irradiation, and stents with varied diameter and wall thickness.

RESULTS

Optimized soldering parameters yielded tensile strengths of 4.4 ± 1.2 N and burst pressures of 400 ± 90 mm Hg with stay sutures. Differences in stent solubility in blood and PBS were not statistically significant (p = 0.99). Sterilization by 25 kGy gamma-irradiation did not cause significant changes (p > 0.6) in stent solubility, which was primarily volume-dependent. Under simulated intravascular flow conditions, 3 mm stents dissolved completely with 2.7 ± 0.7 ml/mg.

CONCLUSIONS

The results show that fast-dissolving stents can be produced reliably using the extrusion technique, and sterilized by gamma-irradiation. Without stay sutures, soldered vessels exhibited low tensile strength, but burst pressures comparable to sutured vessels. It was concluded that stay sutures would be necessary in vivo due to degradation of the tensile strength of soldered vessels with exposure to moisture.

Closure of skin incisions by laser-welding with a combination of two near-infrared diode lasers: preliminary study for determination of optimal parameters

Laser welding has the potential to become an effective method for wound closure and healing without sutures. Closure of skin incisions by laser welding with a combination of two near-infrared lasers (980 and 1064 nm), was performed for the first time in this study. One centimeter long, full-thickness incisions were made on the Wistar rat's dorsal skin. The efficiencies of laser-welding with different parameters were investigated. Incision-healing, histology examination, and a tensile strength test of incisions were recorded. Laser welding with the irradiance level of 15.9 W∕cm(2) for both 980 and 1064-nm lasers and exposure time of 5 s per spot in continuous wave mode yielded a more effective closure and healing with minimal thermal damage, faster recovery, and stronger apposition in comparison with a suturing technique. The conclusion is that skin welding with a combination of two near-infrared diode lasers can be a good candidate for incision closure, and further investigations are in progress for clinical use.

Modulated and continuous-wave operations of low-power thulium (Tm:YAP) laser in tissue welding

Our aim is to explore the welding capabilities of a thulium (Tm:YAP) laser in modulated and continuous-wave (CW) modes of operation. The Tm:YAP laser system developed for this study includes a Tm:YAP laser resonator, diode laser driver, water chiller, modulation controller unit, and acquisition/control software. Full-thickness incisions on Wistar rat skin were welded by the Tm:YAP laser system at 100 mW and 5 s in both modulated and CW modes of operation (34.66 Wcm(2)). The skin samples were examined during a 21-day healing period by histology and tensile tests. The results were compared with the samples closed by conventional suture technique. For the laser groups, immediate closure at the surface layers of the incisions was observed. Full closures were observed for both modulated and CW modes of operation at day 4. The tensile forces for both modulated and CW modes of operation were found to be significantly higher than the values found by conventional suture technique. The 1980-nm Tm:YAP laser system operating in both modulated and CW modes maximizes the therapeutic effect while minimizing undesired side effects of laser tissue welding. Hence, it is a potentially important alternative tool to the conventional suturing technique.