PI I: Plaque index of Silness and Loe.
Can be done for individual teeth, teeth grouped together, individual full mouth or totaling a group of people.
This index could be indicated to assess oral hygiene areas of need.
The purpose of this index, according to Wilkins (2005), is to "assess the thickness of biofilm at the gingival area"
(pp. 328-329).
This is an example of an OHI index that deals with plaque.(Nathe, 2005).
It is a reversible index.
Systematically the gingival areas of distal, facial mesial and buccal are observed, 4 surfaces.
A probe or explorer is needed to perform this index.

To do this index begin by drying the teeth and visually inspect them.
Observe the cervical third determine where the plaque has extended to.
Next, take a probe and pass it just under the free gingival margin, about 1mm, with a sweeping motion on an area that appears to have no plaque. If no plaque is on probe after this then the score for that area is '0'. If biofilm does adhere to the probe the value assigned would then be '1'.

The Criteria for grading is as follows for each area:
0= No biofilm
1= Biofilm adheres to free gingival margin and adjacent area of tooth. This can be recognized by exploring or using a disclosing agent if desired.
2= Moderate build up of soft material on tooth. This can usually be seen with the naked eye.
3= Larger amount of soft matter witihin gingival pocket, on tooth and gingival margin.

To assess 1 tooth take all scores and divide by 4.
Example: 0+0+0+2=2
2/4=0.5
To assess a whole mouth take each individual tooth score then divide it by the teeth in the mouth.
Example: For 20 teeth in the mouth each with a score of 0.5x20=10
10/20=0.5 is considered a good plaque score.

Scores are determined for the following readings:
Excellent: 0
Good: 0.1-0.9
Fair: 1.0-1.9
Poor: 2.0-3.0

Wilkins, E. M. (2005). Clinical Practice of the Dental Hygienist (9th ed.). Philadelphia, Pennsylvania: Lippincott Williams & Wilkins.

Nathe, C. N. (2005). Dental Public Health (2nd ed.). Upper Saddle River, New Jersey: Pearson Prentice Hall.

Kristina - nice review. Ms. Lesser