Evaluating mandibular cortical index quantitatively Visual perception of human eye and brain has an one observation and Cl 3 in the other observation. inevitable role in all kinds of evaluations performed However, there were some cases which were on radiographs.32 This limits the repeatability and classified as Cl 1 in one of the observations and as a consequence of this, clinical application of Cl 2 in the other or Cl 2 in one of the observations these measurements or evaluations. and Cl 3 in the other. This means that, probably As in other fields of medicine,33 Fractal some early cases of Cl 2 may be classified as Cl Dimension has also found applications in 1 and similarly, some late cases of Cl 2 may be dental studies.34,35 It is found to be efficacious in classified as Cl 3 in some observations. Fractal discriminating osteoporotic patients from non- Dimension and Lacunarity can differentiate osteoporotic ones36 and both Fractal Dimension Cl 1 from both Cl 2 and Cl 3 but they cannot and Lacunarity could discriminate dentate from differentiate Cl 2 from Cl 3. The appearance of edentulous regions in mandibular posterior Cl 1 and Cl 3 are widely different from each other region.37 In MCI evaluations, the porosity of but the appearance of Cl 3 and late Cl 2 cases mandibular cortical bone is evaluated visually may resemble each other so Fractal Dimension and a limitation in its repeatability, especially and Lacunarity cannot discriminate them. In between different observers, is reported to be this study, the number of radiographs which a serious problem for the method to be used were classified as Cl 3 was relatively less than clinically.18 Contrary to the subjective nature of MCI the radiographs which were classified as Cl 1 evaluations, Fractal Dimension and Lacunarity and Cl 2 and this might also have a role on not are quantitative measurement methods and discriminating Cl 2 from Cl 3. have no dependency on observers. According Halling et al compared mean bone mineral to the results of this study, it can be concluded density measurement by heel DEXA in the that both Fractal Dimension and Lacunarity can osteopenic (MCI 3 group) and normal groups (MCI discriminate patients having Cl 1 from Cl 2 and 1 and MCI 2 groups were combined) and they Cl 1 from Cl 3 mandibular cortical morphology reported that a negative finding is highly predictive but they cannot differentiate Cl 2 from Cl 3. The of the absence of osteopenia/osteoporosis as mandibular cortex has more complex structure defined by the DEXA measurements.39 Combining in patients having Cl 2 MCI classification than this finding with the results of this study, a Cl 1. So the finding of this study is concordant threshold value for Fractal Dimension and with the description of Fractal Dimension Lacunarity can be generated by studying with because more complex objects have a higher large sample sizes and patients having higher Fractal Dimension. Lacunarity is related to the Fractal Dimension and lower Lacunarity values distribution of gap sizes: the objects having low from these thresholds can be conveyed to bone lacunarity are homogeneous because all gap sizes densitometry clinics for further evaluation to are the same, whereas high lacunarity objects rule out the possibility of osteoporosis especially are heterogeneous.22 Lacunarity is low in objects when the patient has other risk factors in addition. having higher Fractal Dimension.22 According Calculating Fractal Dimension and Lacunarity to the results of this study, the structure of the may somewhat be time consuming and prevent cortical bone which is classified as Cl 1 has less the method to be a real time method because the porous structure than Cl 2 and Cl 3 cortices, and radiographs should be scanned first. However, the sizes of the gaps are less similar to each other digital panoramic machines are replacing the in Cl 1 than Cl 2 and Cl 3 radiographically. conventional machines in many of the countries As reported in a study performed by Taguchi and this would increase the applicability of the et al, mandibular cortical shape which is defined procedure. Fractal Dimension and Lacunarity are as Cl 2 has a greater range of appearances quantitative measurements and they don’t have radiographically than Cl 1 and Cl 3 because early observer dependency as radiomorphometric cases can sometimes be defined as Cl 1 by some indices based on panoramic radiographs. The observers and also some late cases of Cl 2 can be only part that depends on the observer is to defined as Cl 3 by other observers.38 In this study choose the place of the ROI. there was no case which was classified as Cl 1 in 288 European Journal of Dentistry