Question

Explain how the bacteria are able to attach firmly to teeth such that the bacteria can only be removed with scraping.

Answer 1

Answer

           "Biofilm is an association of microorganism in the the form of community in which microbial cells are adhere to each other on a living or non living surface with in a self produced matrix of extracellular polymeric substance". Plaque formed on teeth is a type of biofilm.

Explanation

               Plaque dental may cause tooth decay as well gum disease.

Visibility

           Dental plaque is visible by using red disclosing tablets or cotton swab smearing green food coloring on teeth. So red or green colour left on teth represent dental plaque.

Discovery

              In a letter to Royal society in 1683, Antonie Van Leeuwenhoek described his observation of "white little matter between his teeth".

Development of dental plaque

               It occurs in five steps:

1. Adhesion of microorganism to a surface.

2. Individual colonization and organization of cells.

3. Secretion of exopolymeric substances and development into three dimensional structure.

4. Dissemination of progeny biofilm cells.

Why Plaque is so hard to be removed

                       

as we know that teeth surface is negatively charged with hydroxyapatite. when white surface of teeth come in conatact with bacterial and host product in saliva nad gingival cruvicular fluid, a thin layer of conditioning film is formed called "acquired pellicle". This layer is covered in positively charged molecules, such as salivary glycoproteins, statherin, histamine, proline-rich protein and alpha amylase, and byproduct from gingival crevicular fluid.

Some bacterial compounds such as glucsyltransferase and glucan are also found in acquired pellicle. Due to the presence of these compounds it is difficult to scrap bacterial plaque from teeth.

Answer 2

The first step in the formation of the plaque is the adsorption of the bacterial molecules to the cell surface. The pellicle, which is a protein film, acts like an adhesive to the tooth surface, the pellicle attracts the bacterial molecule to get attached, hence, the colonization of the microbes.  

Due to the presence of the pellicle, the bacteria are stick to the tooth enamel at the surface. That is why; it becomes difficult to get rid of bacteria without scrapping them off.