Kim Loos Dr. Kimberly A. Loos practices general dentistry in San Jose, California. She is also a clinical instructor at University of Pacific School of Dentistry and an editor for Dentistry On-Line. There are other modifying factors which affect the location of cavities and their progression, but the factor you are most interested in is plaque. Plaque is composed of bacteria and their by-products.
Dental plaque is actually quite complex.
The accumulation of plaque on teeth is quite organized and takes place in a certain sequence. First, the bacteria must adhere to tooth structure. Primarily, certain species of Streptococci are able to create a sticky matrix which allows them to adhere to clean tooth structure. Once they adhere, they multiply to form a matlike covering so other organisms can come along and adhere to the mat. The formation of plaque undergoes many changes and each change is dependent upon the previous step.