However, failure to remove plaque by regular tooth-brushing allows them to proliferate unchecked and thereby build up in a thick layer, which can by virtue of their ordinary metabolism cause any of various dental diseases for the host. Those microorganisms nearest the tooth surface typically obtain energy by fermenting dietary sucrose; during fermentation they begin to produce acids. The bacterial equilibrium position varies at different stages of formation. Below is a summary of the bacteria that may be present during the phases of plaque maturation:

Early biofilm: primarily Gram-positive cocci
Older biofilm (3–4 days): increased numbers of filaments and fusiforms
4–9 days undisturbed: more complex flora with rods, filamentous forms
7–14 days: Vibrio species, spirochetes, more Gram-negative organisms

Dental plaque as a biofilm
Dental plaque is considered a biofilm adhered to the tooth surface. It is a meticulously formed microbial community, that is organised to a particular structure and function. Plaque is rich in species, given the fact that about 1000 different bacterial species have been recognised using modern techniques.A clean tooth surface would immediately be colonised by salivary pellicles, which acts as an adhesive. This allows the first bacteria (early colonisers) to attach to the tooth, then colonise and grow. After some growth of early colonisers, the biofilm becomes more compliant to other species of bacteria, known as late colonisers. Early colonisers
mainly Streptococcus species (60–90%)
Eikenella spp. Haemophilus spp. Prevotella spp. Propionibacterium spp. Capnocytophaga spp. Veillonella spp. Late colonisers
Aggregatibacter actinomycetemcomitans
Prevotella intermedia
Eubacterium spp. Treponema spp. Porphyromonas gingivalisFusobacterium nucleatum is found between the early and late colonisers, linking them together.
This keeps the oxygen levels in the mouth at a semi-stable homeostatic condition, which allows the bacteria to survive. Consequences of plaque build-up
Gingivitis
Gingivitis is an inflammatory lesion, mediated by host-parasite interactions that remains localised to the gingival tissue, it is a common result of plaque build-up around the gingival tissues. The bacteria found in the biofilm elicit a host response resulting in localized inflammation of the tissue. This is characterized by the cardinal signs of inflammation including a red, puffy appearance of the gums and bleeding due to brushing or flossing. Gingivitis due to plaque can be reversible by removal of the plaque. However, if left for an extended period of time, the inflammation may begin to affect the supporting tissues, in a progression referred to as periodontitis. : 96–97  The gingivitis response is a protective mechanism, averting periodontitis in many cases. Periodontitis
Periodontitis is an infection of the gums which leads to bone destruction around the teeth in the jaw. Periodontitis occurs after gingivitis has been established, but not all individuals who have gingivitis will get periodontitis. : 111  Plaque accumulation is vital in the progression of periodontitis as the bacteria in plaque release enzymes which attack the bone and cause it to break down, and at the same time osteoclasts in the bone break down the bone as a way to prevent further infection. This can be treated with strict oral hygiene such as tooth brushing and cleaning in between the teeth as well as surgical debridement completed by a dental professional.