Each patient will be impressed with alginate in order to obtain models of the dental arches and elaborate a guide plate made of acetate. This plate will present grooves that will be used as references to standardize the insertion and tilt of the automated periodontal probe (Florida Probe System, Florida Probe Corporation, Gainesville, FL, USA). The visible plaque index for each patient, rated dichotomously (O'Leary et al. 1972), will be determined by the percentage of tooth surfaces with deposits of plaque stained with disclosing solution.