Chapter 2. Features of Operative Interventions in Oral Surgery

Surgical interventions in the maxillofacial region (MFR) differ from surgical interventions performed in other areas of the human body by a number of features. These features are caused by the complexity of the anatomical structure of this region, the variety of physiological functions performed by various organs and tissues of the face (i.e. vision, hearing, smell, breathing, etc.). However, the most important thing - the face - reflects the individuality of a human, his/her personality and is of great importance for personal and public life. In this regard, the technique of performing surgical procedures in the oral and maxillofacial region has high aesthetic requirements.

The face and the oral cavity consist of organs and tissues, the anatomical, topographical and functional features of which are characterized by close interconnection and even interdependence.

In terms of length and volume, a large proportion of the anatomical region falls on the masticatory apparatus, which represents the initial part of the digestive system. The rest of the MFR is represented by the sense, speech organs and the upper respiratory tract. An essential feature of the MFR is that within a relatively small anatomical zone, there are organs, that are very important and at the same time very diverse in the functions they perform. The structure of the facial skeleton and the ligamentous apparatus is also characterized by a complex interconnection. Anatomical, topographical and functional diversity of muscles, integumentary tissues, abundant innervation and blood supply, the pathways of lymph outflow of organs and tissues ― all of this allows us to distinguish the MFR as one of the most complex regions requiring a deep study from a doctor of clinical specialty.

The bony skeleton of the face consists of six paired and three unpaired bones, which are motionlessly connected to each other and to the base of the skull by bone sutures.

The lower jaw (mandible) is the only movable bone of the facial skeleton. It is connected to the base of the skull by a complex temporomandibular joint (TMJ), the uniqueness of which is that it is paired. The lower jaw, due to the peculiarities of the TMJ, moves in three planes, consists of a body with the alveolar process and two branches extending from the body at different angles and ending in condylar and coronal processes. The body of the jaw is formed by two (outer and inner) plates of compact bone substance, the space between which is filled with cancellous bone. The mandibular canal passes through the entire body of the jaw, which has a different position in relation to the lower edge of the jaw and the roots of the teeth.

The muscles of the MFR are divided into facial and masticatory muscles.

• The facial muscles are located relatively superficially under the skin. Their function is related to the physical and mental health of a person. Some of them are involved in the expansion or narrowing of the natural (oral, nasal, and optical) slits of the face.
• The group of masticatory muscles includes the muscles that lift the lower jaw up, push it forward and to the side, and those, that carry out the movement of the lower jaw down. The group of muscles that lift the lower jaw is conditionally referred to the posterior group, and the lowering ones belong to the anterior group of the masticatory muscles.

The MFR integuments, both the skin and the mucous membranes, are distinguished by great mobility. This is due to their elasticity, as well as the presence of a well-defined layer of loose subcutaneous and submucosal fatty tissue. The mucous membrane is not equally mobile everywhere. In the region of the alveolar processes and the hard palate, it is devoid of submucous fatty tissue, and, therefore, there is no mobility of the mucous membranes in these anatomical regions. The mucous membrane of the oral cavity and oropharynx is covered with a stratified squamous epithelium, in which (unlike the epithelium of the skin) there are no hair follicles, perspiratory glands or a stratum lucidum. The thickness of this epithelium is usually larger than that of the skin. Only the epithelium located in the regions that are actively involved in the act of chewing is subject to keratinization. The mucous and serous glands are located mainly under the non-keratinized epithelium. The second layer of the mucous membrane (lamina propria) consists of loose connective tissue located superficially between the epithelial outgrowths and in the deeper parts of the submucosa passing into the fibrous-adipose tissue.

The red border of the lips is richly vascularized, which gives it its color. This is due to the presence of long epithelial outgrowths, between which there are high connective tissue papillae of the layer of lamina. The buccal submucosa contains a significant amount of adipose tissue; the actual mucous layer of the membrane has a loose consistency, and is covered with non-keratinized epithelium. The epithelium of the gingiva on the vestibular side is distinguished by more apparent signs of keratinization than on the lingual side. In the presence of teeth, the stratified squamous epithelium becomes a rudimentary odontogenic epithelium, which attaches to the circular ligament; after the loss of teeth, this feature disappears.