Evaluating mandibular cortical index quantitatively binarized images, so images must be thresholded prior to analysis.23 Weighted Kappa index, which was calculated with a program named ComKappa,25 was used as a measure of intra-observer agreement for cortical index evaluation. Kolmogorov-Smirnov and Levene’s tests were used to check for the normality and homogeneity of the data. ANOVA was used to evaluate whether Fractal Dimension differs significantly between the patients having Class 1, Class 2 and Class 3 MCI morphology using P value as 0.05 with 95% confidence interval. As multiple comparisons were made, Bonferroni was used as post-hoc test. The data of Lacunarity (P:0.012) did not have normal distribution in mandibular cortices which were classified as Cl 2, so Kruskal Wallis test was used to evaluate whether Lacunarity differs significantly between the patients having Class 1, Class 2 and Class 3 and Mann Whitney U test with Bonferroni correction was used for paired comparisons. SPSS 10.0 for Windows (SPSS, Inc., Chicago, IL) was used for the statistical analysis. ResuLts The agreements between the observations Table 1. Weighted Kappa statistic results. Observations First Observation - Second Observation Second Observation - Third Observation First Observation - Third Observation Table 2. Characteristics of the studied parameters. Fractal Dimension Lacunarity Analysis 286 European Journal of Dentistry MCI Cl 1 Cl 2 Cl 3 Total Cl 1 Cl 2 Cl 3 Total N 22 20 10 52 22 20 10 52 are given in Table 1. Interpretation of the Kappa statistics was quoted from the guidelines of Landis and Koch: Less than 0.00 poor agreement, 0.00-0.20 slight agreement, 0.21-0.40 fair agreement, 0.41-0.60 moderate agreement, 0.61-0.80 substantial agreement, 0.81-1 almost perfect agreement.26 There was substantial agreement among the observations in this study. Table 2 shows the descriptive statistics of the variables. The data of Fractal Dimension was showing normal distribution (P:0.200 for Cl 1, P:0.112 for Cl 2, and P:0.200 for Cl 3); and it was homogeneous (FD P:0.744). However, the data of Lacunarity did not show normal distribution in radiographs which were classified as having CL 2 mandibular cortical shape (P:0.200 for Cl 1; P:0.012 for Cl 2; and P:0.200 for Cl 3). ANOVA test results showed that there were statistically significant difference between Fractal Dimension (P=0.000) values in patients having different MCI morphology (Table 3). As multiple comparisons were made, Bonferroni was used as post-hoc test (Table 4). It was found that there were statistically significant difference between the Fractal Dimension of radiographs which were classified as having Cl 1 and Cl 2 (P=0.000); and Measure of Agreement (Kappa) SE 0.010 0.010 0.014 0.008 0.036 0.035 0.034 0.024 SE 0.103 0.101 0.100 1.639 1.704 1.684 1.680 0.640 0.485 0.439 0.568 Interval for Mean Lower Bound Upper Bound 1.682 1.744 1.746 1.710 0.790 0.633 0.592 0.665 Approx. Sig. 0.000 0.000 0.000 Min. Max. 1.576 1.611 1.650 1.576 0.426 0.379 0.360 0.360 1.755 1.781 1.783 1.783 1.025 1.028 0.642 1.028 Value 0.718 0.780 0.805 0.049 0.042 0.043 0.054 0.169 0.158 0.106 0.175 Mean SD 1.660 1.724 1.715 1.695 0.715 0.559 0.516 0.617