Masticatory: stratified squamous keratinized epithelium covering the gingiva and the hard palate. The lamina propria is tightly bound to the underlying bone, is immovable, and helps withstand the masticatory pressure.
Lining: stratified squamous nonkeratinized epithelium lining the lips, cheeks, in the vestibules, floor of the mouth, alveolar processes, ventral surface of tongue and soft palate. The lamina propria is not tightly bound to bone and is designed for protection and mobility.
Specialized: This specialized masticatory mucosa containing papillae and taste buds lines the dorsal surface of tongue.
Oral mucosa: The stratified squamous epithelium acts as a mechanical barrier to oral microorganisms.6 A rapid oral epithelial turnover rate helps limit the attachment of bacteria to the mucosa.7 Moreover, several studies have shown the ability of oral keratinocytes to distinguish between commensal and pathogenic microorganisms by mediating the production of immunoinflammatory responses by their dendritic cells5,8,9 as well as a wide range of cytokines like interleukin IL-1β, tumor necrosis factor-alpha, granulocyte-macrophage colony stimulating factor, etc.10
Odontoblasts: They represent the first line of defense on the tooth surface. Studies have shown that grampositive and gram-negative bacteria can activate the toll-like receptors TLR2 and TLR4.11,12 The upregulation of these factors can lead to the secretion of several antimicrobial agents, proinflammatory cytokines, and chemokines.13 Odontoblasts also secrete broad-spectrum antimicrobial agents like β-defensins that are effective against oral bacteria.14
Gingival crevicular fluid (GCF): GCF is composed mainly of serum components and organic molecules, such as albumins, globulins, lipoproteins, and cellular components. The concentration of immune cells present in GCF is higher than the peripheral blood with polymorphonuclear neutrophils being the most predominant.15
Saliva: A versatile clear fluid consisting of organic and inorganic components that continuously bathes the oral cavity. An adult secretes an average ∼1 to 1.5 L of saliva per day, 90% of which is secreted by the major salivary glands (parotid, submandibular, and sublingual glands).16,17 The remaining 10% is contributed by the minor salivary glands. Saliva plays an important
role in both innate and acquired immunity. Proteins like lactoferrin (that binds iron), lysozyme (that can break down bacterial cell wall structures), histatins (inhibiting the growth of Candida albicans), and lactoperoxidase act as general antimicrobial enzymes. Other proteins like salivary amylase, cystatins, proline-rich proteins, mucins, peroxidases, and statherin are also primarily involved in innate immunity.18
gain entry to the exposed root surfaces causing root caries. As long as bacteria are present on the hard tissue and do not enter the systemic circulation, the best mode of treatment is to excavate the carious lesion with a suitable dental bur and restore the structure and function of the tooth by restorations like the use of an amalgam or composite. In cases of extensive decay extending to the pulp, root canal treatment or extraction is required.
FIGURE 45.2 Progression of bacterial infection in the oral cavity: from tooth to bone, on the periodontium, and other tissues of the mouth such as the tongue.
Depending on the severity of infection and presence of local factors, the treatment will range from a minor change in brushing habits or type of brush/toothpaste to mechanical debridement of factors by a dental professional. Figure 45.3 shows an example of pre- and postscaling leading to reduction in the local factors and inflammation. Table 45.1 summarizes the various treatment options for common bacterial infections of the oral cavity.
FIGURE 45.3 Pre- (left) and postscaling (right) and root planing. Removal of plaque depicts the underlying inflammation and bleeding of gingiva that heals in 2 weeks with proper oral hygiene maintenance.
TABLE 45.1 Summary of treatment options for most common bacterial infections of the oral cavity