Evaluation of the effect of the inversion filter on enhancing the visibility of the mandibular incisive canal in comparison with the original images.

BACKGROUND: The mandibular incisive canal (MIC) is a neural canal containing one of the lower branches of the inferior alveolar nerve, called the mandibular incisive nerve, which can get damaged and cause complications during the removal of bone from the interforaminal region. OBJECTIVES: The aim of this study was to determine the effect of the inversion filter (IF) on improving the visibility of MIC as compared to the original images. MATERIAL AND METHODS: In this retrospective, descriptive, analytical study, 343 samples of digital panoramic radiography were examined. The images were analyzed with and without IF. The frequency and confidence intervals (CIs) of identifying MIC were used to determine its visibility, both with IF and in the original images. Besides, the difference between the maximum and minimum diameters of the canal as well as the distance from MIC to the alveolar crest and to the mental foramen were examined. For statistical analysis, McNemar's test and the paired t-test were used, and the concordance was calculated using the kappa coefficient. RESULTS: No significant differences were found in the prevalence of the incisive canal, or in its unilateral or bilateral visibility between the original and filtered radiography in this study (p = 0.42 and p = 0.67, respectively). The absolute values of the interval difference between MIC and the mental foramen, the maximum and minimum diameters of MIC, and the distance from MIC to the alveolar crest were statistically significant between the filtered and original radiography, although the difference was clinically unimportant. CONCLUSIONS: The use of IF produced results similar to the original radiography; its application neither increased the clarity nor improved the visibility of the incisive canal.