This work aimed to produce didactic material so that the student of the Dentistry Course can understand the topographic relationship of the mandible canal with the alveolar process and the roots of permanent teeth in a diaphanized model, right at the beginning of the course.
Regarding the technical sequence of diaphanization, when working with teeth, there are divergences in the literature regarding the moment for the injection of the dye in the root canals. There are authors that inject before descaling and other, after [13, 14]. When carrying out a pilot study in the mandible, the India ink injected into the canal after clarification was not contained in the mandible canal. It is believed that the fluidity of the ink, as well as the decalcification of the bone by hydrochloric acid, allowed the ink to overflow around the canal, not allowing visualization of the contour of the mandible canal. Thus, the technique was adapted, with changes in steps: injecting material into the MC before starting bone decalcification. For this, we chose material that could be injected in liquid form and that, over time, would set, occupying the entire canal. The material chosen probably suffered chemical action during the diaphanization process and also did not remain in the canal. It is necessary to find another material that can be injected into the canal without suffering the action of chemical agents or that can be injected into the canal after the entire diaphanization process without interfering with the final result of the clarification.
By introducing the metallic ligature inside the channel, it was possible to observe that the MC has a descending trajectory from the mandibular foramen reaching a region very close to the apex of the third and second lower molars, passing midway between the alveolar ridge and the margin of the mandible reaching the region of the lower premolars, as described by [10]. According to Berberi et al. [15] which describe the canal as a path that starts at the mandible foramen, exteriorizing itself in the mental foramen.
The mandibular canal assumes a downward trajectory from the second molar towards the first, with the distal root of the second molar being closest to the mandibular canal [16]. After that, it assumes an ascending trajectory towards the second premolar in 82.75% of the cases. This upward trajectory was not so evident in the diaphanized jaw in this study. The distance of the MC in relation to the RA of the teeth depends on the tooth considered [10]. The distal root of the mandibular second molars is usually closer to the upper limit of the canal in relation to most of the analyzed teeth. However, when third molars are considered, they are even closer together. This was especially evident on the left side, where the root apex of the third molar is much closer to the CM than the root apex of the second. The absence of the first molar on both sides did not allow observation in this region. However, it was certainly possible to observe a much greater distance from the root apex of the lower premolars.
Regarding the differences in the clarification result between the body and ramus of the mandible, it can be suggested that the quality of the bone differs in the two portions that make up the mandible. The thickness of the body of the mandible, as well as the thickness of the cortical bone itself, seem to influence the time required for bone decalcification. Even leaving the bone for 9 consecutive days submerged in acid, the result of the process was insufficient. In the ramus, where there is less bone thickness, the clarification allowed us to recognize the contour formed predominantly by compact bone, especially in the region of the coronoid process and the mandibular notch. Internally, cancellous bone was identified, extending even through the condylar process.
As an example of what is done in studies of teeth [17], it could be suggested to define the end point of decalcification by means of radiographic taking of the anatomical piece. This strategy would certainly guarantee the identification of total bone decalcification, leading to greater transparency of the bone as a whole, at the end of the diaphanization process.
It must be considered that the bone used for this work has been in the anatomy laboratory for a long time, having thus undergone several processes with different substances that today have fallen into disuse, how to boil the piece, macerate with paraffin, leave 200 volumes in peroxide, finally in formaldehyde and glycerin. Perhaps this type of processing has influenced the diaphanization process.
Another suggestion would be to perform a CT scan prior to diaphanization. In this way, tomographic images could help in the interpretation of the mandibular canal arrangement, even though direct vision along the entire canal is not possible in the diaphanized mandible.