Visible Plaque Score

Measurement of plaque

Amount of accumulation

Several indices for recording supragingival plaque have been developed. The two most frequently used are the Plaque Index (PI), developed by Silness and Loe (1964), and O'Leary's Plaque Index (O'Leary et al, 1972).

The Silness and Loe Plaque Index has a four-point scale:
- Score 0 = The tooth surface is clean.
- Score 1 = The tooth surface appears clean, but dental plaque can be removed from the gingival third with a sharp explorer.
- Score 2 = Plaque is visible along the gingival margin.
- Score 3 = The tooth surface is covered with abundant plaque.

O'Leary's Plaque Index is based on the visible continuous plaque along the gingival margin after staining. Four or six sites per tooth are examined, and the percentage of tooth surfaces exhibiting stained plaque is calculated. Unlike Silness and Loe's PI, no attempts are made to evaluate the area of tooth surface covered by plaque. O'Leary's Plaque Index is most commonly used for evaluation of the oral hygiene standard of the individual patient and for patient motivation, based on self-diagnosis.

Used in dental practice, the Plaque Index is capable only of revealing areas that the patient has failed to clean effectively, even though he or she may have made a special effort on the day of the dental appointment; it does not indicate the rate at which plaque forms in the individual or the oral hygiene status 1 week before or after the dental appointment. This accounts for the failure by clinicians as well as examiners in clinical studies to observe the correlation between on one hand, the amount and location of plaque and, on the other, the sites of carious lesions.

Despite these limitations, disclosure of plaque by staining is the fastest and most efficient method for self-diagnosis by the patient. The technique also allows the clinician to locate remaining plaque and to demonstrate the close relationship between the localization of plaque and the presence of gingivitis and dental caries . Prevention of dental caries and gingivitis must, therefore, be based on plaque control.

The telemetric method, developed by Graf and Muhlemann (1966), allows in vivo measurement of the "true" pH on the tooth surface beneath the undisturbed plaque.

The importance of the age, amount, and composition of plaque, as well as different concentrations of sugar, can thereby be evaluated. Using the telemetric method, Imfeld (1978a) showed that rinsing with a 10% sucrose solution causes a dramatic drop in pH to below 4 in 3-day-old interdental plaque. Such plaque is typical for the approximal surfaces of the molars and premolars in a toothbrushing population. In contrast, the fall in pH in immature lingual plaque (12 hours old) is very limited.

Firestone et al (1987) used the same telemetric test in vivo, measuring the pH drop after subjects rinsed with a 10% sucrose solution. Four different sites on molars with approximal plaque were compared to plaque-free approximal surfaces. The authors concluded: "removing plaque from interdental surfaces significantly reduced the exposure of the surfaces to plaque acids following sucrose rinse. This further supports mechanical removal of plaque from interdental surfaces as a means of reducing dental caries."

In toothbrushing populations, that is, those who have an established habit of using a toothbrush and fluoride toothpaste daily, dental plaque more than 2 days old is located mainly on the approximal surfaces of the molars and premolars, partly subgingivally.

Access with a toothbrush to the wide approximal surfaces is limited by the buccal and lingual papillae. At least in European countries, although daily toothbrushing with a fluoride dentifrice is an established oral hygiene habit, special aids to approximal oral hygiene 3/4 such as dental floss, dental tape, toothpicks, and interdental brushes 3/4 are used daily by fewer than 10% of the population. These conditions explain why caries, gingivitis, and marginal periodontitis are much more prevalent on the approximal surfaces of the molars and premolars than on the buccal and lingual surfaces of the dentition.

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