Chapter 11 Lab Exercises
Section 16 Dental Biofilms: Detection and Quantification of Plaque
Page 2 Instructor

Dental Biofilms: Detection and Quantification of Plaque

Instructor Version (go to Student Version)

Subject Area(s) microbiology
Intended Audience
K-6, high school biology, independent study/science fair, introductory undergraduate microbiology
Type laboratory exercise
Revision Date March 18, 2004


This is an exercise which can be carried out to illustrate the presence of biofilms on the teeth of students. It requires no special equipment and very little time. It could be included in a class on oral microbiology or as an object lesson for introductory microbiology students. The minimal requirement in time and equipment makes this an excellent choice for a lesson in a health-related class at the elementary or middle school level.


Students should be able to define a biofilm, describe the differences between biofilm (surface-attached) and planktonic (suspended bacterial cells) bacteria, and be able to describe why bacteria usually grow on surfaces.


Given a dental plaque disclosing agent, students should be able to evaluate the amount of plaque on their teeth.


  1. Students will be provided with a dental plaque disclosing agent and an index to evaluate the amount of plaque found on their teeth.


1 dental plaque disclosing agent such as Trace Disclosing Tablets which can be obtained from a local dentist. These tablets are chewed by the student and plaque is revealed as a red stain on the teeth. This stain is subsequently removed by brushing. The active ingredients in the Trace product are D and C Red #28.
Safety Note: Please do not use iodine on students. Due to its toxicity, Iodine/Potassium iodide solutions used to reveal plaque should be left in the hands of dental professionals. Obtain nontoxic dental plaque disclosing agents such as "Trace Disclosing Agents" to reveal plaque in students.


Assessment will be made by the instructor through visual evaluation of each student's stain results. This exercise may be assessed using the Quigley Hein plaque index1,2


This exercise results in the ability to evaluate the amount of plaque by an index. There are no subsequent activities to this exercise.


1Quigley, GA and Hein, JW. Comparative cleaning efficacy of manual and power brushing. J Am Dent Assoc 1962; 65:26-29.

2Addy, M., M.A. Slayne and W.G. Wade, 1993. Methods for the Study of Dental Plaque Formation and Control, IN Denyer, S.P., S.P. Gorman and M. Sussman, Microbial Biofilms: Formation and Control, Blackwell Scientific Publications, Oxford.

Educational Program Curricula and Teaching Resources

Supported in part by the Waksman Foundation for Microbiology
Developed in collaboration with Dr. John Lennox, Education Editor, Penn State Altoona
© 1999-2008 Center for Biofilm Engineering,