It has been used for years to reconstruct oral mucosa, mouth, jaw and facial defects. It is also used in the repair of the conjunctival mucosa of the eye, oral pharyngeal reconstructive surgery, and reconstruction of vaginal defects. Oral mucosal grafting was reintroduced in 1941 by Humby from the first introduction and then by Burger. Since then, the long segment has gained widespread use in urethral reconstruction of anterior urethral strictures, hypospadias, epispadias, and bladder extrophy.
As a free graft for urological reconstruction, the oral mucosal graft has many advantages such as continuous availability, suitable immunological properties, easy harvest, excellent tissue properties. In addition, it provides easy-to-use properties, minimal contracture formation and adaptation to a humid environment.
Biology of the Oral Mucosa
The entire oral cavity is lined with a protective epithelial membrane, which is the oral mucosa. Anatomically, the oral mucosa is located between the outer skin and the mucosal lining of the gastrointestinal tract and shows the characteristics of both tissues. According to standard and accepted dental terminology, buccal mucosa refers to the oral mucosa covering the inner cheek of the oral cavity. The labial mucosa refers to the alveolar mucosa of the inner lower lip, and the lingual mucosa refers to the mucosa covering the tongue. These are collectively referred to as oral mucosal grafts.
The epithelium of the oral mucosa is stratified and flat and keratinized in areas subject to significant friction, such as the palate. Oral epithelium is supported by lamina propria, a dense collagen tissue. In highly mobile areas such as the soft palate and the floor of the mouth, the lamina propria is connected to the underlying muscle with loose submucosal support tissue. In contrast, it spreads over the surface bone of the oral mucosa, such as the hard palate and tooth bearing protrusions. In these areas, the lamina propria is tightly connected to the periosteum by a relatively thick fibrous submucosa. Along the oral mucosa, abundantly small salivary glands of both mucous and serous varieties are distributed in the submucosa. The oral mucosa makes it architecturally comparable with the stratified squamous epithelium of the penile and glanular urethra and remarkably adaptable for urethral replacement.
The oral mucosa consists of a thick, non-keratinized stratified squamous avascular epithelium with mild vascular lamina propia underneath. These features contrast with the bladder mucosa and penile skin, both of which have a thin epithelium and a thick lamina propria. The oral mucosa is about 5.0 mm deep, and its thickness is directly related to the male sex and indirectly varies with age. Oral epithelial cells are inoculated with polymicrobial intra and extracellular plant, mainly streptococcus. However, this species includes Actinobacillus, Tannerella orsythensis, Fusobacterium nucleatum, Prevotella intermedia, Porphyromonas gingivalis, oral Campylobacter Eikenella corrodens, and Treponema denticola actinomycetemcomitans.
Despite these severe microbial exposures, inflammatory infiltration is rarely witnessed under histological examination of the oral mucosa in healthy individuals. The reasons for this are the suppressive activity mediated between the polymicrobial flora, the production of antimicrobial peptides by the epithelium. Mucosal epithelial cells of the oral cavity inhibit microflora colonization with persistent exfoliation and mucous-associated lymphoid tissue (MALT), a specialized immune system. The lamina propria of a well-lubricated oral mucosa graft can be considered as a secondary barrier that prevents microorganisms from entering adjacent tissue layers.
And it exhibits remarkable antimicrobial properties including lymphocytes, immunoglobulin-synthesizing plasma cells, monocytes, macrophages, polymorphonuclear neutrophils, mast cells. Existing sebaceous glands are located in the lamina propria and are more common in the lip mucosa than in the buccal mucosa. It can be demonstrated by immunohistochemical staining that nerve fibers and blood vessels from the submucosa infiltrate into the lamina propria, thereby providing a mechanism for angiogenesis and revascularization of tissue during grafting. The oral mucosa is highly flexible, resistant to repeated exposure to compression, tension and shear forces. This flexible and resistant increases the surface area of the epithelial-lamina propria interface, partially consisting of diffuse projections of connective tissue to the epithelial layer. And it can be partially credited to the lamina propria-oral epithelial interface, which provides the resisting capacity of the oral mucosa. Unlike the gastrointestinal tract mucosa, there is no muscularis mucosa layer between the epithelial and lamina propria layers of the oral mucosa.
Surgical anatomy of the oral mucosa
The morphology of the oral mucosa varies from region to region and is related to functional demands. These regional differences are present in the nature of the submucosa, the morphology of the epithelial-connective tissue, the composition of the lamina propria, the thickness of the epithelium, and the type of keratinization.
Anatomy of the labial mucosa
The upper and lower boundaries of the mandibular labial mucosal are indicated by the vermilion border of the lower lip and the vestibular fold between the lower lip and the anterior border of the mandible, respectively. The lateral borders are formed by the outer commissures of the lower lip. The mental nerve, which is the terminal branch of the lower alveolar nerve of the mandibular part of the trigeminal nerve, innervates the mandibular labial alveolar mucosa. The mental nerve exits the mandible between the first and second premolars via the mental foreman. The surgeon should plan the incision for harvesting the medial labial mucosa to the middle of the dog to avoid damaging the mental nerve and compromising sensations in the lower lip.
The mandibular labial alveolar mucosa receives its blood supply from the inferior labial artery (a branch of the facial artery), the mental artery (continuation of the inferior alveolar artery), as well as the anastomoses from the buccal artery. Mental and buccal arteries are both branches of the maxillary artery, both the facial artery and the maxillary artery are divisions of the external carotid artery. The lip mucosa is elastic, thin, resistant and technically easy to collect and does not require stitching at the harvest site. However, the buccal mucosa provides a larger graft and has a more robust quality oral mucosa.
Anatomy of the buccal mucosa
The vertical border of the buccal mucosa is the maxillary and mandibular vestibular folds, while the anterior and posterior borders are formed by the outer commissure of the lips and the anterior tonsillar column, respectively. The buccal mucosa is innervated primarily by the long buccal nerve and by the anterior, middle and posterior upper alveolar nerves of the second part of the trigeminal nerve. In addition, there is limited sensory innervation from the facial nerve. Blood supply of the buccal mucosa occurs through the buccal artery, the anterior superior alveolar artery of the infraorbital artery, the middle and posterior upper alveolar arteries, and the accessory vessels from the transverse facial artery. The buccal mucosa is tough, flexible, easy to collect, easy to use and leaves no visible scar on the donor area.
The mucous membrane covering the lower lateral surface of the tongue is indistinguishable from the lining of the rest of the oral cavity. The mucosal structure that covers the lateral and lower surface of the tongue is the same as that covering the rest of the oral cavity. The mucosa covering the tongue does not have a specific functional property and, like the buccal mucosa, the tongue mucosa is constantly present.
It is easy to collect and has suitable immunological and tissue properties. Because the lining of the oral cavity is limited, the buccal mucosal graft (BMG) may not be sufficient for the treatment of complex long urethral strictures that require a larger supply of graft tissue. An ideal donor site for replacement urethroplasty would have properties comparable to the buccal mucosa, but it is easier to harvest and provide adequate sized grafts. Although there is little or no use of buccal mucosal grafts, possible complications include numbness, difficulty in opening the mouth, deviation or retraction.
The lateral side of the tongue has mucosal pathways up to 7 to 8 cm long, and all patients may have two grafts. The collection technique is simple, quick and does not require nasal intubation or special retraction and also leaves a hidden scar in the donor area. Lingual mucous grafts are similar to labial grafts. In patients with a small mouth or difficult mouth opening, the tongue is a good alternative to the oral mucosa graft collection site. The patients reported only a mild mouth discomfort at the donor site. For all these reasons, the tongue appears to be a good alternative donor site for graft harvesting. However, lingual mucosal grafts are thin and not used as widely as buccal mucosal grafts.
Author: Ozlem Guvenc Agaoglu