Method: Data for this project were obtained from a series of five plaque studies involving healthy adult volunteers. All studies were reviewed by an ethics committee and participants gave fully informed consent.
In study 1 (n=14) and study 2 (n=18), two examiners independently assessed the levels of erythrosine-disclosed plaque (12 hours after last brushing) on all scorable teeth using either MQHI or GMPI.
In study 3 (n=83) and study 4 (n=94) Plaque was assessed (MQHI) after brushing; all visible plaque was then collected from buccal and lingual surfaces and wet weight determined (PW).
In study 5 (n=15), plaque was assessed (MQHI) and collected from one side of the mandible and the contra-lateral side of the maxilla 24 hours after last brushing, and wet weight (PW) detremined.
The correlation between MQHI and MPGI (study 1 and 2) was based on buccal scores only. Standard regression analysis was used to calculate the correlation between the plaque indices. To assess the correlation between MQHI and wet plaque weight was transformed (square root; 4th root).
Results: The correlation coefficients between MQHI and GMPI were 0.93 and 0.82 for Study 1 and 2 respectively. The correlation coefficients between MQHI and PW (4th root) were 0.56, 0.47 and 0.78 for Studies 3, 4 and 5 respectively.
Conclusion: A significant correlation was found between MQHI and GMPI and between the MQHI and PW; taking the 4th root of PW improved the correlation.