Correlation between Volpe-Manhold calculus index scores and actual calculus area

Although the Volpe-Manhold Calculus Index (VMI) is used frequently in clinical trials, it is not clear how representative this index is of the actual tooth surface area covered with calculus. This study correlated the mean VMI and mean calculus area, as measured objectively by using computer-assisted planimetry, in 40 subjects with a wide range of calculus deposition. The resulting statistically significant (p less than 0.05) correlation coefficient of .93 indicates a strong correlation between the VMI and mm2 calculus area, confirming the suitability of this index for use in calculus clinical trials.