Pellicle The surface of enamel and dentin attracts salivary glycoproteins and bacterial products creating the pellicle layer. This thin layer forms on the surface of the enamel within minutes of its exposure. These glycoproteins include
proline-rich proteins that allow bacterial adhesion. Pellicle somewhat protects enamel, but not dentin, from acid and abrasion.
Plaque formation Plaque is a
biofilm composed of several different kinds of
bacteria and their products that develop over the enamel on the pellicle. Plaque formation takes several days to weeks and will cause the surrounding environment to become acidic, if not removed.
First bacteria The first bacteria to attach to these pellicle glycoproteins are
gram-positive, aerobic
cocci such as
Streptococcus sanguinis. These bacteria produce the
enzyme glucosyltransferase. Glucosyl transferase converts
sucrose into
exopolysaccharides. These exopolysaccharides create a sticky environment that allows other bacteria to attach to the initial colonies and protect them from acids. As the plaque develops and expands,
oxygen can no longer diffuse into the colonies. After a few days,
anaerobic, gram-negative cocci, rods, and filaments begin to colonize the plaque. After several weeks, the cocci, rods, and filaments grow together forming colonies known as corncobs. This anaerobic environment causes
facultative anaerobes such as
S. mutans and
Lactobacilli to break down sucrose through
fermentation pathways. These bacteria produce
lactic acid as a metabolic byproduct. If the concentration of lactic acid becomes high enough, the pH around the plaque will drop below 5.5, and
demineralization will occur. ==References==