The Plaque Formation Rate Index (PFRI) of Axelsson describes the accumulation of dental plaque at 24 hours after a professional dental clearing. This index can help identify patients at increased risk for caries, as described below.
NOTE: This is similar to the Calculus Surface Index, described earlier in this section.
Procedure:
(1) The teeth are cleaned by a professional dental hygienist.
(2) The patient does not brush or clean the teeth for the next 24 hours.
(3) 24 hours after the cleaning the teeth are examined for adherent plaque.
Surfaces examined on each tooth (6):
(1) mesiobuccally
(2) bucally
(3) distobuccally
(4) mesiolingually
(5) lingually
(6) distolingually
PFRI =
= (total number of surfaces showing plaque) / ((number of teeth examined) * (6 surfaces examined)) * 100%
Interpretation:
• minimum PFRI: 0%
• maximum PFRI: 100%
Percentage of Surfaces Affected
Level
Score
0%
none
0
1 - 10%
very low
1
11 - 20%
low
2
21 - 30%
moderate
3
31 - 40%
high
4
> 40%
very high
5
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