Objective To compare the mandibular indices differences between periodontitis and non- periodontitis subjects by digital panoramic tomograms in order to find a simple and effective method to evaluate the density of alveolar bone and study the relativity between local bone loss and systemic bone loss. Methods Standard digital panoramic tomograms of sixty periodontitis subjects and sixty non- periodontitis subjects were taken. Density and height cortical width（CW） and panoramic mandibular index（PMI） of alveolar bone were measured on the digital panoramic tomograms. SPSS 12.0 was used for statistics analyses. Results The periodontitis subjects had lower height of alveolar bone（8.76 mm vs. 11.85 mm, P=0.000）, lower density of alveolar bone（106.08 vs. 113.33, P=0.034）, thinner cortical width（3.80 mm vs. 4.27 mm, P=0.008）, while the difference of PMI between the two groups was not significant （P>0.05）. The relativity between both density and height of alveolar bone with CW was significant（P0.05）. Conclusion The optical method is a simple and effective method to measure the density of the alveolar bone. Compared with the non- periodontitis subjects, the periodontitis subjects not only have alveolar bone changed significantly but also have thinner cortical width.
