Histology of laser- and high-frequency-electrosurgical incisions in the palate of pigs

A continuum thermomechanical model for the electrosurgery of soft hydrated tissues using a moving electrode

Electrosurgical radio-frequency heating of tissue is widely applied in minimally invasive surgical procedures to dissect tissue with simultaneous coagulation to obtain hemostasis. The tissue effect depends on the cumulative heating that occurs in the vicinity of the moving blade electrode. In this work, a continuum thermomechanical model based on mixture theory, which accounts for the multiphase nature of soft hydrated tissues and includes transport and evaporation losses, is used to capture the transient heating effect of a moving electrode. The model takes into account the dependence of electrical conductivity and the evaporation rate on the water content in the tissue, as it changes in response to heating. Temperature prediction is validated with mean experimental temperature measured during in situ experiments performed on porcine liver tissue at different power settings of the electrosurgical unit. The model is shown to closely capture the temperature variation in the tissue for three distinct scenarios; with no visible cutting or coagulation damage at a low 10 W power setting, with coagulation damage but no tissue cutting at an intermediate power setting of 25 W, and with both coagulation and tissue cutting at a higher power setting of 50 W. Furthermore, an Arrhenius model is shown to capture tissue damage observed in the experiments. Increase in applied power was found to correlate with tissue cutting and concentrated damage near the electrode, but had little effect on the observed coagulation damage width. The proposed model provides, for the first time, an accurate tool for predicting temperature rise and evolving damage resulting from a moving electrode in pure-cut electrosurgery.

Electrosurgery: part II. Technology, applications, and safety of electrosurgical devices

Electrosurgical currents can be delivered to tissue in monopolar or bipolar and monoterminal or biterminal modes, with the primary difference between these modes being their safety profiles. A monopolar electrosurgical circuit includes an active electrode and a dispersive (return) electrode, while there are 2 active electrodes in bipolar mode. In monoterminal mode, there is an active electrode, but there is no dispersive electrode connected to the patient's body and instead the earth acts as the return electrode. Biterminal mode uses a dispersive electrode connected to the patient's body, has a higher maximum power, and can be safer than monoterminal mode in certain situations. Electrosurgical units have different technologies for controlling the output power and for providing safety. A thorough understanding of these technologies helps with a better selection of the appropriate surgical generator and modes.

Tissue fusion, a new opportunity for sutureless bypass surgery

Microsurgical suturing is the standard for cerebral bypass surgery, a technique where temporary occlusion is usually necessary. Non-occlusive techniques such as excimer laser-assisted non-occlusive anastomosis (ELANA) have certainly widened the spectrum of treatment of complex cerebrovascular situations, such as giant cerebral aneurysms, that were otherwise non-treatable. Nevertheless, the reduction of surgical risks while widening the spectrum of indications, such as a prophylactic cerebral bypass, is still a main aim, that we would like to pursue with our sutureless tissue fusion research. The primary concern in sutureless tissue fusion- and especially in tissue fusion of cerebral vessels- is the lack of reproducibility, often caused by variations in the thermal damage of the vessel. This has prevented this novel fusion technique from being applicable in daily surgical use. In this overview, we present three ways to further improve the laser tissue soldering technique.In the first section entitled "Laser Tissue Soldering Using a Biodegradable Polymer," a porous polymer scaffold doped with albumin (BSA) and indocyanine green (ICG) is presented, leading to strong and reproducible tensile strengths in tissue soldering. Histologies and future developments are discussed.In the section "Numerical Simulation for Improvement of Laser Tissue Soldering," a powerful theoretical simulation model is used to calculate temperature distribution during soldering. The goal of this research is to have a tool in hand that allows us to determine laser irradiation parameters that guarantee strong vessel fusion without thermally damaging the inner structures such as the intima and endothelium.In a third section, "Nanoparticles in Laser Tissue Soldering," we demonstrate that nanoparticles can be used to produce a stable and well-defined spatial absorption profile in the scaffold, which is an important step towards increasing the reproducibility. The risks of implanting nanoparticles into a biodegradable scaffold are discussed.Step by step, these developments in sutureless tissue fusion have improved the tensile strength and the reproducibility, and are constantly evolving towards a clinically applicable anastomosis technique.

Thermal model for optimization of vascular laser tissue soldering

Laser tissue soldering (LTS) is a promising technique for tissue fusion based on a heat-denaturation process of proteins. Thermal damage of the fused tissue during the laser procedure has always been an important and challenging problem. Particularly in LTS of arterial blood vessels strong heating of the endothelium should be avoided to minimize the risk of thrombosis. A precise knowledge of the temperature distribution within the vessel wall during laser irradiation is inevitable. The authors developed a finite element model (FEM) to simulate the temperature distribution within blood vessels during LTS. Temperature measurements were used to verify and calibrate the model. Different parameters such as laser power, solder absorption coefficient, thickness of the solder layer, cooling of the vessel and continuous vs. pulsed energy deposition were tested to elucidate their impact on the temperature distribution within the soldering joint in order to reduce the amount of further animal experiments. A pulsed irradiation with high laser power and high absorbing solder yields the best results.

Histological evaluation of artifacts in tongue tissue produced by the CO2 laser and the electrotome

OBJECTIVE

The purpose of this study was to investigate the clinical usefulness of laser surgery in pathologic diagnosis following excisional biopsy of human oral mucosa by CO(2) laser and electrotome.

BACKGROUND DATA

When performing pathologic diagnosis and microscopic analysis of specimens excised by the CO(2) laser, there have been concerns about thermal denaturation of the excisional margin that may prevent diagnosis.

MATERIALS AND METHODS

Thirty tongue tissue samples from humans that were surgically resected using a CO(2) laser (continuous wave mode for 10 cases and pulse wave mode for 10 cases) and an electrotome (10 cases) were formalin-fixed and paraffin-embedded. These preserved specimens were then cut into thick sections and subjected to hematoxylin and eosin staining followed by microscopic assessment.

RESULTS

Despite the differences between the CO(2) laser and electrotome methods, similar thermal denaturation, such as carbonization, vacuolar degeneration, and elongation of nuclei, were observed at the excisional margins for both methods. Use of the CO(2) laser, particularly in pulse wave mode, reduced the amount of thermal denaturation significantly (p < 0.01) compared to the electrotome.

CONCLUSION

These results indicate that the CO(2) laser is better than the electrotome as a means of making excisions for performing pathologic diagnosis.

Flap and incision design in implant surgery: clinical and anatomical study

OBJECTIVES

The protection of microcircular support which is essential for healing gains importance if implant surgery is considered to affect the blood flow. The aim of the study is to establish the artery territories supplying the blood into the oral mucosa in the cadavers and to demonstrate the mucosal delivery pattern and to evaluate the effects of different incision types on the healing in the patients having the implant application.

MATERIALS AND METHODS

The study was planned in two stages as cadaver and clinical investigations. In cadaver investigation, all intra oral vascular territories were shown in ten specimens. The arterial structure and mucosal vascularity of the area were assessed microscopically and macroscopically. With the obtained data, the clinic results were established by making the crestal incision only for Group 1 (n = 30); both crestal and vertical releasing incisions for Group 2 (n = 30) were planned.

RESULTS

The results were established anatomically and clinically. In all cases, vascular territories of the mucosa in the maxilla and mandible were evaluated. In stereo microscopic assessment, although vestibule and oral mucosa had rich anastomoses, the crestal line had avascular features. There was no complication in the soft tissues of the cases, performed the vertical releasing incision during the healing period after 8-week follow-up.

CONCLUSION

The vascular richness of the oral mucosal area enables the sufficient healing in the areas of applied flap. According to the alveolar anatomical pattern and the amount of the soft tissue over it, the incisions may be applied horizontally and/or vertically.

Incision design in implant dentistry based on vascularization of the mucosa

OBJECTIVES

The delivery of an adequate amount of blood to the tissue capillaries for normal functioning of the organ is the primary purpose of the vascular system. Preserving the viability of the soft tissue segment depends on the soft tissue incision being properly designed in order to prevent impairment of the circulation. A knowledge of the course of the vessels as well as of their supply area are crucial to the decision of the incision. The aim of this study was to visualize the course of the arteries using different techniques, to perform macroscopic- and microscopic analyses, and to develop recommendations for incisions in implant dentistry.

MATERIAL AND METHODS

The vascular systems of seven edentulous human cadavers were flushed out and filled with either red-colored rubber bond or Indian ink and formalin mixture. After fixation a macroscopic preparation was performed to reveal the course, distribution and supply area of the major vessels. In the area of the edentulous alveolar ridge specimens of the mucosa were taken and analyzed microscopically.

RESULTS

The analyses revealed the major features of mucosal vascularization. The main course of the supplying arteries is from posterior to anterior, main vessels run parallel to the alveolar ridge in the vestibulum and the crestal area of the edentulous alveolar ridge is covered by a avascular zone with no anastomoses crossing the alveolar ridge.

CONCLUSION

The results suggest midline incisions on the alveolar ridge, marginal incisions in dentated areas, releasing incisions only at the anterior border of the entire incision line, and avoidance of incisions crossing the alveolar ridge.

Morphological, Histochemical, and Immunocytochemical Study of CO2and Er:YAG Laser Effect on Oral Soft Tissues

OBJECTIVE

The purpose of this study was to investigate the morphological, histochemical, and immunocytochemical changes of the oral mucosa after CO(2) or Er:YAG laser irradiation.

BACKGROUND DATA

There have been no comparative reports on CO(2) and Er:YAG laser effects on human oral soft tissues.

MATERIALS AND METHODS

Tissue preservation was studied in 40 oral biopsies of young patients obtained by CO(2) and Er:YAG laser surgery. Hematoxylin-eosin and Giemsa stains, PAS/diastase treatment, AE1 and AE2 cytokeratins, MiB1/Ki67, and bcl-2 immunoreactions were performed on the laser cut edges on formalin fixed, paraffin embedded biopsies.

RESULTS

CO(2) laser biopsies show blisters, clefts and erosions of the epithelium. Intracellular edema and lengthened nuclei were also seen. The glycogen content results decreased in CO(2) laser biopsies. Good expression for cytokeratins and cell-cycle proliferation markers were found in Er:YAG biopsies, on the contrary the apoptosis marker was better expressed in CO(2) laser biopsies.

CONCLUSION

The results suggest that Er:YAG laser may be routinely used in surgery, because of its minimal damage of the epithelial tissue, its low inflammatory reaction, its quicker healing process and its lower risk of scarring.

Electrosurgery in the head and neck

Electrosurgery is widely used in the practice of otolaryngology-head and neck surgery. Despite its popularity, few training programs give formal education in the optimal use of electrosurgical instruments. This article reviews the history, physics, and tissue effects of these commonly used devices. Armed with this knowledge, the head and neck surgeon can take full advantage of electrosurgery's ability to dissect tissues with precision and minimal blood loss.