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VOLUME 7 , ISSUE 5 ( November, 2006 ) > List of Articles


Correlations Between Two Plaque Indices in Assessment of Toothbrush Effectiveness

MaryAnn Cugini, Maureen Thompson, Paul R. Warren

Citation Information : Cugini M, Thompson M, Warren PR. Correlations Between Two Plaque Indices in Assessment of Toothbrush Effectiveness. J Contemp Dent Pract 2006; 7 (5):1-9.

DOI: 10.5005/jcdp-7-5-1

License: CC BY-NC 3.0

Published Online: 01-02-2008

Copyright Statement:  Copyright © 2006; The Author(s).



The Rustogi et al. Modified Navy (RMNPI) and Turesky et al Modification of the Quigley Hein (TQHPI) plaque indices are commonly used to measure plaque removal. This study evaluated the possible correlations of both indices using data relative to a single use assessment of plaque removal using commercially available toothbrushes.


Single use crossover study designs have been previously reported. Disclosed plaque was scored pre- and post-brushing using both the RMNPI and the TQHPI. Sixty subjects, with an initial mean RMNPI score of 0.6 or greater, were enrolled and completed the study. No minimum score was required for TQHPI. After the initial scoring, the order for each index was randomized so that each subject was scored with either RMNPI followed by TQHPI or vice versa. Two manual toothbrushes [Oral-B® CrossAction® (CA) and Colgate® Navigator. (NA)] and one battery-powered brush (Crest® SpinBrush. Pro) (SBP) were evaluated in the trial. One examiner performed all clinical measurements. Pearson correlations were performed on whole mouth, buccal, and lingual plaque scores for the CA toothbrush.


Strong positive correlations were found between the two plaque indices for pre- and post-brushing scores for the whole mouth and on lingual and buccal surfaces, where Pearson correlation coefficients ranged between 0.963 and 0.995. There was no correlation between the pre-brushing plaque score and the amount of plaque removed by brushing indicating that higher plaque levels before brushing do not necessarily predict that greater amounts of plaque will be removed during toothbrushing. Each toothbrush was found to be safe and significantly reduced plaque levels after a single brushing (t-test, p=0.0001). Significantly greater plaque reductions were found with the CA than the NA and SBP toothbrushes at whole mouth, lingual, and approximal surfaces for both indices (analysis of variance (ANOVA), p . 0.0002 for all comparisons).


Strong positive correlations were found between two plaque indices (the RMNPI and TQHPI) for pre- and post-brushing scores at whole mouth, lingual, and buccal surfaces as assessed using data from a single use assessment of plaque removal.

Efficacy data from this study demonstrated the CA toothbrush provided superior cleaning when compared to the NA manual toothbrush and SBP battery toothbrush.

Clinical Implications

Two commonly used indices for assessing plaque removal in clinical studies are RMNPI and TQHPI. However, each index differs in the way plaque is scored. This study used both indices to assess comparative toothbrush efficacy and showed a strong correlation between indices for both pre- and postbrushing plaque scores. The result suggests that both indices demonstrate sufficient sensitivity to differentiate toothbrush efficacy.


Cugini M, Thompson M, Warren PR. Correlations Between Two Plaque Indices in Assessment of Toothbrush Effectiveness. J Contemp Dent Pract 2006 November;(7)5:001-009.

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