## 4 Discussion  
Interest in knowing whether the eruption of the third molar occurs over time or not, or if we can predict its evolution, has been ongoing, as reflected in the dental literature. Several methods to predict third molar eruption have been presented using lateral radiographs, bite-wings, anterior-posterior radiographs, periapical radiographs or panoramic radiographs [6]. Of the radiographic techniques used to assess mandibular third molar space and mandibular linear dimensions and angles, panoramic radiography yielded one of the most accurate estimates [29; 30; 31]. Besides panoramic radiography, it is the most popular radiological record for the dental clinician and a common research image for assessing mandibular third molars for extraction [32]. [PERSON] et al. described a transparent  
Figure 5: Visual example of correct prediction The pink line represents third molar diameter, the yellow line represents retromolar space, and blue lines represent the angle of eruption: image (**a**) shows partial retained third molar is classified as erupted tooth by the software; image (**b**) confirms the eruption of third molar (panoramic one year later). The screenshots have been taken using the windows version of PDApp. device to overlay panoramic images that assesses the probability of third molar eruption or impaction [33]. Later, [PERSON] et al. developed a method for predicting eruption based on cephalometric and panoramic radiographic measurements [34]. It has been demonstrated that the greater the angulation, the greater the probability of tooth impaction. [PERSON] et al. identified that a critical third molar angle of 27.0\({}^{\circ}\) is unfavorable for functional eruption; the authors established this threshold because this angulation tends to enlarge over time [35]. Basically, if the third molar has low initial angulation and an adequate retromolar space for eruption, then eruption without pathology is possible. The exact prediction of third molar eruption is still a challenge in clinical dental practice. Prediction during growth of the patient could be of great interest and help in planning future dental treatments (surgical exodentia but not dental extraction, orthodontics, or prosthesis). Clinical assessment through the use of reliable and simple predictive tools is essential for evaluating the status of eruption of mandibular third molars. The relevant literature describes several approaches for predicting the probability of impaction on orthopantomogram (OPG) images, including methods by [PERSON], [PERSON], and [PERSON], although they were not found to be reliable or accurate [36; 37]. Previously, [PERSON] et al. (1998) concluded that third molar impaction is a predictable event that involves eight variables (long axes of second and third molars, functional occlusal plane, mandibular plane, gonal angle, mandibular canal reference, mandibular midline, orbital reference), but it is difficult to apply in clinical practice [22]. In a previous study, we compared two predictive methods based on analyzing the retromolar space, space available for eruption ([PERSON] and [PERSON]'s method), and the direction of tooth eruption ([PERSON]'s method), factors that were considered the most important in third molar eruption. [PERSON]'s method demonstrated more utility in assessing eruption prediction in clinical practice [21]. Although these methods are widely used in clinical practice and scientific investigations/studies, they all rely on manual measurements which require much time and effort. There is also a high degree of subjectivity (both intra- and inter-observer) in the data analysis obtained from manual methods, and the inconvenience of applying them in routine clinical practice is also a major factor that hinders use. Recently, [PERSON] et al. [38] presented a tool to automatically measure the molar angulations on panoramic radiographs and predict whether or not a molar will erupt.