Root canal obturation leakage evidenced by micro-CT and dye penetration

Objective: Root canal obturation was evaluated three-dimensionally using micro-CT and dye penetration test.

Method: 30 single-canal extracted teeth were obturated with cold lateral condensation of gutta-percha plus root canal sealer. Obturation was evaluated first with the radiographic image and then with the micro-CT image, with the use of a scoring system (1-4), in which the lower the score, the better the obturation. Dye (food red in macrogol and propylene glycol) was also applied to see whether the defects were connected to each other to make pathways to the apex. The eluting time until exit of the dye through the apex was recorded.

Results: Micro-CT images often demonstrated air spaces that were not shown in the radiographs. Air spaces were observed within obturation materials and root canal dentinal walls, suggesting that some defects of root canal fillings were not detected on two-dimensional radiographs. 26 out of the 30 samples had significantly higher (P<0.0001, Student`s t-Test ) micro-CT scores (mean= 3.1; SD= ±0.8) than radiographic scores (mean= 1.8; SD= ±0.8), indicating that the obturation images on radiographs were camouflaged to be better. In addition, the dye solution was able to penetrate the filled canal until the apex in almost all samples, even in those which appeared to be well obturated. This means that sometimes, these hidden defects form continuous channels where contaminating agents like bacteria and oral fluids may pass through. On the other hand, such channels may also allow the passage of medicaments for certain re-treatment procedures.

Conclusion: Defects in root canal obturations, such as air spaces, that may serve as pathways are sometimes not shown by radiographs.