Tooth surface is never dry (in physiologic conditions) and gets covered by a thin proteinaceous layer called the acquired enamel pellicle (AEP).
24 This 100 to 1000 nm thick film is attached to the enamel surface due to selective physical forces and plays an important role in determining the fate of an oral microbiome.
25 Selective oral streptococci have the ability to attach to this pellicle as initial colonizers and occupy sites at the tooth surface and selective oral sites such as the tongue and buccal epithelium.
26 Once established, these colonizers provide attachment sites for secondary and tertiary colonizers leading to a complex ecosystem of symbiotic microbial communities—the dental biofilm known as “plaque.” The communities stabilize and live with a simple cross-feeding model in harmony with the host until the balance is tipped offleading to dysbiosis. The modifiable factor of dysbiosis can range from being a change in the salivary flow, lifestyle changes (like inclusion of more sugar in the diet), poor oral hygiene, or an underlying disease. Dysbiosis leads to a shift in the microflora, such as from aerobic to anaerobic and aciduric bacteria. The predominance of aciduric bacteria around the tooth surface causes the dissolution of mineral salts from enamel leading to one of the most common dental diseases of the world—dental caries. Based on the location and depth of lesion, the dental caries can be on the enamel, root, or reach deep into the pulp. Enamel and dentin caries is caused by
S mutans and
Lactobacillus species. Initial enamel caries is referred to as “white spot lesions” and can be reversed if the bacterial growth is arrested and symbiosis of oral microorganisms is achieved. But if the carious lesion reaches deeper tissues, it can even lead to irreversible pulpitis rendering the tooth nonvital. Because bacteria are site specific, certain bacteria like
Aggregatibacter actinomycetemcomitans,
Porphyromonas gingivalis, and
Prevotella intermedia, etc, can target the supporting structures of the tooth leading to periodontitis and gingivitis.
27 Periodontal disease is a chronic bacterial infection characterized by persistent inflammation, connective tissue breakdown, and alveolar bone destruction. With advancing gingivitis and periodontitis,
Actinomyces and other anaerobic species can
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.
In cases of gingivitis and periodontitis, excessive microbial load and the oral epithelium’s innate immune responses can lead to inflammation and tissue breakdown. Hence, supragingival and subgingival debridement of the tissue (such as scaling and root planing) targeted toward the reduction of plaque and microflora can help revert disease states to health. Untreated pulpal or periodontal pathology may progress to the neighboring soft tissues, causing cellulitis and osteomyelitis if bone is infected. The host’s local defense factors, regional anatomy, microbial load, and bacterial virulence will determine the extent of the damage. Because dental diseases are multifactorial, the presence of bacteria and the host tissue response along with predisposing factors like immunocompromised state, malnutrition, smoking, and poor oral hygiene can lead to severe destructive orofacial lesions like cancrum oris.
Figure 45.2 shows the progression of bacterial infections in the mouth.
For dental-related infections, the advantage of reducing microbial load by caries excavation and scaling and root planing should be utilized before resorting to antibiotics. In today’s era of increased antibiotic resistance and improved culture sensitivity testing, the identification of the associated bacteria is of utmost importance. Dentist should be encouraged to prescribe antibiotics only if necessary. Patient compliance, nutrition support, and medical care including analgesics, antipyretics, and anti-inflammatory drugs constitute the proper management of every infection.