A periapical lesion occurs as periapical tissue reacts to a dental pulp anaerobic infection. This phenomenon may result from carious lesions, tooth fractures, or iatrogenic and other circumstances that allow for bacteria to penetrate into the pulpal tissues. Objectives: This study histologically evaluated experimentally induced periapical lesions using the Autodesk AutoCAD 2010 software. Additionally, based on the amounts of alveolar bone destruction sizes in the mouse model regions, a proposed experimental periapical lesion gradation criterion was created. Methods: Twelve BALB/c mice were utilizised in a periapical model, whereby their mandibular right first molars were coronally opened, allowing for pulp exposure to host oral bacterial flora. Th ese mice were sacrificed two and four weeks following pulp exposure. Following each sacrifice, hemimandibles were fixed in 4% paraformaldehyde, decalcified in 3% formic acid, embedded in paraffin and cut into 4-μm-thick sections. The sections were stained with haematoxylin- eosin and examined with light microscopy (40x). Section images that included the mandibular first molar distal roots and passed through the apical foramens were selected for analysis. The periodontal ligament sizes were measured using the Autodesk AutoCAD 2010 software. Results: There was a highly significant lesgion size difference at the two different time points following the lesion induction (p=0.002). The periapical lesions were classified according to periapical bone resorption sizes. We determined the values of quartiles (25% and 75%) and median areas (50%) of the mean lesion values at both experimental periods. These data enabled for scoring of the lesions with grades from 1 to 4. The area of the normal periodontal ligament space was assigned with a grade of 0. Conclusion: This newly designed gradation criteria represent a significant advantage compared with the previous descriptive methods used for determining periapical tissue bone destruction levels. It The criteria achieves this advantage by excluding subjectivity, facilitating a numerical presentation of the data and reducing the possibility of making errors by using the highly availably Autodesk AutoCAD 2010 software.
