The aim is to acquaint students with some of the infections associated with plaque, specifically dental caries (tooth decay) and periodontal (gum) diseases, and to enable them to carry out some simple diagnostic tests which are potentially available to the dentist. An indication of plaque quantity is obtained using disclosing tablets; calculation of decayed, missing and filled teeth (DMFT) could provide information on past dental procedures and caries experience. The exercise is designed to be completed within one laboratory session, so that incubation and culture of microorganisms is not required. Students carry out Gram staining and darkground microscopy of plaque; darkground microscopy enables the visualization of motile, anaerobic spirochetes which, if present in sufficient numbers, may be associated with gingivitis and gum disease. Incubation of saliva with sucrose and monitoring of the pH enables comparison of acidogenicity, which may be an indicator of plaque cariogenicity (caries-inducing ability). The lab report enables more in-depth exploration of additional chairside procedures available to dentists, including visual inspection of teeth and gums, X-rays, and some of the more recently developed diagnostic methods. The policy of "minimum intervention" in dentistry continues the preventative rather than curative strategy which is the normal procedure in today's profession. A more sophisticated exercise is described elsewhere within ASM curriculum resources: "A laboratory class exploring oral biofilms and the contamination of toothbrushes." Information therein may be useful for supplementation.