Dental plaque

Dental plaque is a sticky, soft and colorless film of bacteria that constantly builds up on the surfaces of teeth and gums. Not removing tooth plaque bacteria from the mouth regularly, can lead to tooth decay and dental cavities (caries) or periodontal problems (such as gingivitis and periodontitis).

What causes dental plaque on your teeth

Dental plaque is comprised of colonies of bacteria and other microorganisms mixed with bacteria by-products, dead cells and food residuals. Tooth plaque formation starts immediately after a tooth is cleaned. The micro organisms of dental plaque are all naturally present in the oral cavity, and are normally harmless. Failure to remove dental plaque by regular toothbrushing allows its build up in a thick layer. As it matures, different types of micro organisms appear. At the lower layers of plaque, nearest the tooth surface, the composition of dental plaque changes in favour of anaerobic bacteria.

Their anaerobic respiration is producing acids which consequently lead to :

• demineralization of the adjacent tooth surface, and dental caries.
• irritation of the gums around the teeth (gum inflammation), leading to gingivitis (red, swollen, bleeding gums), periodontal disease and tooth loss.
• tooth plaque build up can also become mineralized and form calculus.

The main health problems of the oral cavity can be related to the accumulation of dental plaque on teeth.

The process of dental plaque formation

Dental plaque formation starts almost immediately after toothbrushing. Some minutes after brushing your teeth, saliva derived glycoprotein deposits start to cover the tooth surface with what is referred to as "pellicle". The formation of pellicle is the first step in dental plaque formation.

The pellicle is then colonized by Gram-positive bacteria such as Streptococcus sanguis, Streptococcus mutans, and Actinomyces viscosus becoming what is known as dental plaque. Bacteria cells interact with pellicle components enabling plaque to firmly adhere to the tooth surface.

After 1 to 3 days following the initiation of plaque formation:

• the first bacteria colonies start to multiply and expand
• new bacteria species start to colonize the tooth plaque. These new species include also Gram-negative bacteria such as Fusobacterium nucleatum, Prevotella intermedia, and Capnocytophaga.

Substances produced by the already accumulated bacteria enrich the plaque environment making it favourable for the growth of other species of bacteria. One week after the first plaque accumulation, new Gram-negative species may be found, such as Porphyromonas gingivalis, Campylobacter rectus, Eikenella corrodens, Actinobacillus actinomycetemcomitans, and oral spirochetes (Treponema species).

While the dental plaque formation continues Gram-negative species become dominant over the Gram-positive species. The overgrowth of Gram-negative anaerobic bacteria is considered as one of the main causative factors of gingivitis and periodontitis. This fact increases the importance of regular dental plaque removal with tooth-brushing before the Gram-negative anaerobic bacteria have the time to grow and put your oral health at risk.


- Cloverdale Dentist