Dental plaque does not literally “eat” teeth, but the bacteria within this sticky film initiate a potent chemical attack that dissolves the tooth structure. Plaque is a colorless to pale yellow microbial biofilm that constantly forms on the surfaces of teeth and along the gumline. It is a complex community of living microorganisms encased in a gluey matrix, allowing them to adhere strongly to the enamel. This biofilm becomes destructive when its internal environment is altered by consuming certain foods, beginning a cycle of acid production that leads to decay.
The Chemical Process of Damage
The true damage to the tooth is caused by the metabolic byproduct of specific bacteria residing within the plaque biofilm. When a person consumes fermentable carbohydrates, such as sugars and starches, the bacteria rapidly metabolize these compounds for energy. A particular group of microorganisms, including Streptococcus mutans, are highly efficient at this process and are considered cariogenic because of their ability to thrive in and create an acidic environment.
The main byproduct of this bacterial sugar consumption is organic acid, primarily lactic acid. This acid is produced within minutes of eating or drinking and accumulates within the sheltered environment of the plaque biofilm. The concentration of acid causes a sharp drop in the pH level on the tooth surface, which ultimately begins the process of chemically dissolving the tooth’s protective layer.
Understanding Demineralization
The acidic attack from the plaque causes demineralization, which is the removal of mineral content from the tooth structure. Tooth enamel is the hardest substance in the human body, composed primarily of crystalline calcium and phosphate ions in a structure known as hydroxyapatite. When the pH drops below approximately 5.5—the critical pH—the acid begins to pull these ions out of the enamel lattice.
This mineral loss weakens the enamel, making the tooth surface softer and more porous. Demineralization is a continuous process that occurs every time the mouth becomes acidic after a meal or snack. Fortunately, the body has a natural defense mechanism called remineralization, where ions present in saliva are reincorporated into the damaged enamel once the pH returns to normal. Dental decay results when the periods of acid attack and demineralization consistently outweigh the repair provided by remineralization.
Progression to Dental Decay
If demineralization continues unchecked, the localized mineral loss eventually causes a structural failure in the enamel, leading to the formation of a cavity, or dental caries. Initially, this damage may appear as a white, chalky spot on the tooth surface, indicating subsurface mineral loss. As the process advances, the decay breaks through the enamel and reaches the underlying layer known as dentin.
Dentin is softer than enamel and contains microscopic tubules that lead directly to the tooth’s inner pulp, where the nerves and blood vessels reside. Once the decay reaches this second layer, the process of destruction accelerates, often causing sensitivity or pain. If the infection progresses further into the pulp, it can cause severe pain, inflammation, and infection, requiring extensive treatment like a root canal or extraction. Unremoved plaque can also harden into tartar, which irritates the gums and contributes to gingivitis and periodontitis.
Preventing Plaque Buildup
Controlling plaque requires consistent daily habits focused on mechanical removal and chemical support for the enamel. Effective plaque removal involves several key practices:
- Brushing the teeth for a minimum of two minutes twice daily, ensuring all surfaces are cleaned.
- Using fluoride toothpaste, which strengthens the enamel and supports remineralization, making the tooth structure more resistant to acid attacks.
- Flossing once a day to remove plaque that accumulates between teeth and below the gumline.
- Limiting the intake of sugary and starchy foods to reduce the fuel source plaque bacteria need to produce acids.
- Scheduling regular professional cleanings to remove hardened plaque, called tartar, that cannot be removed by home care alone.