Detection of Vascular Pathways of Oral Mucosa Influencing Soft- and Hard Tissue Surgeries by Latex Milk Injection

The method of latex milk injection was used bilaterally on human cadavers, which were donated to the Department of Macroscopic and Clinical Anatomy of the Medical University of Graz, Austria, complying with the Department’s Donation Program and according to Styrian burial law. 10 fresh cadavers (5 male-5 female, age 43–90) were selected. The path of the blood vessels in oral mucosa, utilized in combination with a layer-by-layer dissection protocol and CT, were analyzed. Latex milk injection together with the examination of the blood vessels in the oral mucosa (Figure 1 and Figure 2) Penetrate the center of the sagittal suture between the parietal bones with a drill (see Table of Materials) to reach into the superior sagittal sinus. Design an incision in the carotid triangles parallel to the sternocleidomastoid muscle by Nr. 20 or Nr. 15 surgical blades. Then, separate the edges of the skin, adipose tissue, and the muscles with a Weitlaner retractor (140 mm, 3/4 teeth) to expose the surgical site. Gently reveal the CCAs using Nr. 15 surgical blades and block the end using serrated dressing forceps. After that, cannulate the CCAs and superior sagittal sinus carefully with a metal catheter. Isolate the catheter using a ligature with alternating knots on each side of the CCA. Fix the catheter very securely to prevent any leakage of Thiel's intravascular solution or latex milk when injected under pressure. Subsequently, perfuse the corpse tissues via the CCAs and superior sagittal sinus simultaneously with an intravascular solution (e.g., Thiel's or phosphate buffer solution) using an air pressure pump system (0.25–0.5 bar) for ~10–15 min. NOTE: The main components of the intravascular and embalming Thiel's solution are composed of ammonium nitrate (fixative), potassium nitrate (fixative), 4-chloro-3-methylphenol (fixative), sodium sulfite (fixative), boric acid (disinfection), ethylene glycol (preservation of tissue plasticity), hot water (softening of the tissues), as well as formalin (disinfection, tissue fixative, and embalming)16,17,18,19,20. (Optional) Before injection of the latex milk, inject 20–30 mL of diluted ammonia to clear the vessels. Carefully mix a red color agent with 150 mL of latex milk (see Table of Materials). Inject the mixture using an air pressure pump system for about 10–15 min into the CCAs. NOTE: Take care during the mixing and injection of the latex milk to keep it as bubble-free as possible. If a bubble is present, a gap develops inside the vessel, which might result in rupture of the artery during surgical intervention performed on the cadaver. During the injection, use the same pressure or slightly higher to completely distribute the latex milk into the finer vessels in the orofacial region. After complete filling and staining of the CCAs and the subbranches, obstruct them with surgical vessel clamps to prevent the exiting of the injected latex milk. Embalm the specimens for approximately 6–8 months in Thiel's solution inside chrome vanadium corrosion resistant steel tanks. Keep the corpses in zipper polyethylene plastic bags for another 6 months with antifungal and preservative agents such as chlorocresol. During this period, the excess amount of extracellular liquid is pushed out of the body, and the specimens become ready for dissection. NOTE: Following the completion of the fixation period, the tissues and the blood vessels of the maxillofacial region are ready and capable of withstanding the rigidity of dissection. The stained arteries can be analyzed by CT scans. Some of the subbranches in the palate, vestibule, tongue, and maxillofacial region are observable without removal of the mucosa. Finally, specimens are dissected by using 2.5x magnification loupes and Nr. 15C surgical blades. Mucosal elevation can be performed by dissecting the stained arteries layer by layer, and the course of the vessels and their variations can be macroscopically assessed.