Oral Flora and Dysbiosis Overview

Study Notes

Oral Flora

Normal oral flora comprises bacteria, fungi (e.g. Candida albicans), protozoa (e.g. Entamoeba gingivalis, Trichomonas tenax) and occasionally viruses (e.g. herpes simplex virus) that reside in the oral cavity.

Functions of Oral Flora

They defend against colonization by harmful microorganisms, contributing to host nutrition by synthesizing vitamins.
They induce an immunological response by acting as antigens.
Certain bacteria regulate pH, preventing an acidic environment, which promotes tooth decay.

Dysbiosis

An imbalance in the normal oral flora can occur due to poor oral hygiene, immunosuppression, or antibiotic use.
This imbalance can lead to an overgrowth of harmful bacteria, leading to tooth decay, periodontal disease, and systemic infections.

Types of Oral Flora

Bacteria:
- Streptococci
- Lactobacilli
- Actinomyces
- Veillonella
- Porphyromonas, Prevotella, and Fusobacterium
Fungi:
- Candida species
Viruses:
- Latent viruses like Herpes Simplex Virus (HSV) may be present in the oral mucosa, without causing disease unless triggered by stress.
Protozoa:
- Entamoeba gingivalis and Trichomonas tenax are found in the mouth but their role in oral health is unclear.

Factors Affecting Oral Flora Growth

Anatomical Factors:
- Tooth Surfaces: Ideal for biofilm formation (dental plaque)
- Tongue: Rough surface provides niches for both aerobic and anaerobic bacteria.
- Gingival crevice: Area between tooth and gum, low oxygen, rich in nutrients, favoring anaerobic bacteria.
- Mucosal Surfaces: Constantly shedding, making it difficult for bacteria to adhere long-term. However, some species like Streptococcus can colonize these areas.
Saliva:
- Washes away food particles and unattached microorganisms.
- Contains antimicrobial components (lysozyme, immunoglobulins) that control microbial growth.
- Provides nutrients for oral microorganisms.
Gingival Crevicular Fluid (GCF):
- Inflammatory exudate released into the gingival sulcus.
- Contains immune cells (neutrophils) and antibodies (IgG) that help control bacterial growth, particularly in the subgingival area.
- Provides proteins and peptides as nutrients for bacteria, especially anaerobes that thrive in inflamed tissues.
Nutrition:
- A balanced diet with adequate carbohydrates, proteins, vitamins, and minerals is crucial for the growth and metabolism of oral bacteria.
- Diets rich in fiber promote a healthier oral microbiome.
- Excessive sugar consumption promotes the growth of harmful bacteria, particularly Streptococcus Mutans.
- Streptococcus Mutans utilizes sugars to produce acids that contribute to tooth decay and dental caries.
- Acidic foods and beverages temporarily lower oral pH creating an environment conducive to harmful bacteria.