Abstract
Introduction: The conventional scalpel has in many applications of Oral and Maxillofacial Surgery been substituted by alternative tissue-ablative instruments such as monopolar electrosurgery (MES) and carbon dioxide laser (CDL). Upon use of these instruments various forms of tissue-delivered energy (i.e. high-frequency alternating electrical current and infrared light respectively) are converted to heat, diffused through the surgical site and inducing both beneficial and undesired tissue effects. The use of MES or CDL combines tissue ablation with adequate hemostasis. The consequent heat diffusion reduces considerably the bacterial population at the surgical site, thus minimizing the risk of intraoperative contamination. It also prevents the occurrence of micrometastasis due to intraoperative dissemination of cancer cells in the blood microcirculation upon use of these instruments for the surgical treatment of malignant lesions. The heat diffusion at the surgical site also causes denat ...
Introduction: The conventional scalpel has in many applications of Oral and Maxillofacial Surgery been substituted by alternative tissue-ablative instruments such as monopolar electrosurgery (MES) and carbon dioxide laser (CDL). Upon use of these instruments various forms of tissue-delivered energy (i.e. high-frequency alternating electrical current and infrared light respectively) are converted to heat, diffused through the surgical site and inducing both beneficial and undesired tissue effects. The use of MES or CDL combines tissue ablation with adequate hemostasis. The consequent heat diffusion reduces considerably the bacterial population at the surgical site, thus minimizing the risk of intraoperative contamination. It also prevents the occurrence of micrometastasis due to intraoperative dissemination of cancer cells in the blood microcirculation upon use of these instruments for the surgical treatment of malignant lesions. The heat diffusion at the surgical site also causes denaturation of intracellular proteins and coagulative necrosis in a varied distance from the incision, described as “lateral thermal damage” (LTD). This damage has been associated with intraoperative (discomfort or pain) and/or postoperative (disturbed function of adjoining vital structures such as the maxillary/mandibular bone or the dental pulp, delayed and/or disrupted wound healing and conspicuous scarring) morbidity and has substantially limited the use of MES and CDL for biopsy harvesting, in order to histopathologically diagnose skin or oral mucosa lesions. Purpose: The objective of this study was to investigate the effects induced upon skin and oral mucosa as a result of their incision by MES (producing electrosurgical currents of 1 and 3.8MHz) and CDL and to compare them with the effects induced after the use of conventional scalpel. Furthermore, the study aims to evaluate histologically and immunohistochemically potential differences concerning both the pattern of LTD and the healing mechanisms activated in skin and oral mucosa, in order to rehabilitate the tissue after incisions, made by the above-mentioned instruments. Material: Our material consisted of 5 adult healthy swine (3 male and 2 female) of similar body weight (22.8-25kg). Methods: The following devices were used during the experiment: a) a MES unit of the MD 62 type provided by Martin, described as “conventional monopolar electrosurgery” (CMES), b) a continuous wave CDL unit of the SMART US-20D type provided by Deka and c) a MES unit of the Surgitron FFPF EMC-Vet Surg provided by Elleman International, described as “high-frequency monopolar electrosurgery” (HFMES). All electrosurgical 184 incisions were made by active electrodes of commensurate dimensions and geometry (needlelike electrodes), using the “cut(ting)” mode of the devices. The experimental procedure consisted of the following stages: • Sedation, administration of general anaesthesia, chemoprophylaxis and corticosteroids, cleansing and draping of the surgical sites in a sterile fashion • Standardized longitudinal incisions were made by scalpel (#15 blade), CMES, CDL and HFMES at 3 predetermined surgical sites (abdominal skin, dorsal surface of the tongue, free and attached maxillary gingivae) in a randomly assigned sequence on day 1 of the experiment • Specimen harvesting by making full-thickness scalpel incisions, symmetrically extended on either side of the ½ of the original incision that had been previously made at the abovementioned sites by CMES, CDL and HFMES • Specimen harvesting by making scalpel incisions, symmetrically extended on either side of the other ½ of the original incision, 48 hours after the initial procedure (day 3 of the experiment) • Sacrifice of the animals by intravenous administration of propophol and pentobarbital combined with KCl to inflict lethal ventricular fibrillation. All specimens (60 harvested on day 1 and 60 harvested on day 3) were formalin fixed, paraffin embedded, cut into 3-5μm thick sections and stained with hematoxylin-eosin (H-E). 40 sections derived from specimens harvested from the abdominal skin and the tongue on day 3 were stained immunohistochemically (by using the MIB-1 monoclonal antibody provided by Dako) to detect the nuclear antigen Ki-67. All sections were examined by light microscopy with a calibrated eyepiece grid. Upon evaluation of the H-E stained sections harvested on day 1 the extent of LTD was investigated by measuring the distance from the original incision where lesions compatible with coagulative necrosis were detected. Upon evaluation of the immunohistochemically stained sections the expression of the nuclear antigen Ki-67 was assessed by measuring the number of moderately or intensely stained nuclei in the basal and parabasal layers of the epithelium or the dermis in specimens harvested from the oral mucosa or the skin respectively. Upon evaluation of the H-E stained sections harvested from the abdominal skin on day 3 the extent (= maximum distance from the incision where inflammatory cells were detected) and intensity (classified as mild, moderate and intense) of inflammatory infiltration around the original incision were assessed and compared between incisions made by scalpel and each of the investigated ablative instruments (CDL, CMES and HFMES). Results: Upon macroscopic evaluation (inspection) of all 60 specimens harvested on day 1, findings compatible with thermal injury (irregularity of the incisional margins, great width 185 of char, disrupted morphology and color of the surrounding tissues) were more conspicuous around CDL-incisions than around CMES- and HFMES- incisions. Light microscopy examination of the 60 H-E stained sections harvested on day 1 demonstrated alike that the extent of LTD was greater around CDL-incisions than around CMES- and HFMES- incisions. Moreover, evaluation of the 40 immunohistochemically stained sections harvested on day 3 ascertained a statistically significant difference in the epithelial proliferation rate between CDL- and MES- (either CMES or HFMES) incisions. The detection of microabscesses and bacterial contamination in sections derived from specimens harvested from the oral mucosa on day 3 made impossible the evaluation of the post-traumatic inflammation. Nevertheless, upon evaluation of the 20 H-E stained sections derived from specimens harvested from the abdominal skin a significantly greater extent of inflammatory infilitration was recorded around CDL-incisions in comparison with scalpelincisions. The extent of inflammatory infiltration did not differ significantly between MES- (either CMES or HFMES) and scalpel- incisions. Finally, the results regarding all investigated outcomes did not differ significantly between CMES- and HFMES- incisions. Conclusions: Based on the above results, the following conclusions may be deduced: 1. The CDL-related LTD, demonstrated by both macroscopic and light microscopy findings in the present study, is significantly greater than the MES-related LTD. 2. The progress of reepithelization is different, depending on the applied tissue-ablative instrument: the epithelial proliferation rate around CDL-incisions was significantly greater than the one around scalpel-incisions. 3. The extent and intensity of inflammatory infiltration in sections derived from skin specimens are significantly greater around CDL-incisions and comparable around scalpel- and MES incisions. 4. The extent of LTD related to CDL and MES and the progress of reepithelization do not differ significantly between skin and oral mucosa despite the different conditions prevailing in these anatomical sites. Nonetheless, the extent and intensity of the inflammatory infiltration are significantly different due to the presence of a large bacterial population in the oral cavity. 5. MES is equally and similarly effective as far as the LTD and the wound healing processes are concerned (progress of reepithelization, extent and intensity of inflammatory infiltration), regardless of the current frequency produced by the respective electrosurgical unit.
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