Extrusion of root-filling material.
Overfilling with both gutta-percha and sealer was detected in all 20 canals in the TF group (Tables 1 and 2; Fig. 2). Overfilling with gutta-percha was not found in any of the specimens in the LC and BF groups; however, extrusion of sealer was detected in five canals in the BF group and three in the LC group (Table 1; Figs 3-5). The risk for overfilling with either gutta-percha or sealer was statistically significantly (P = 0.000) higher in the Thermafil group than in the two other groups (Table 2). No differences could be detected between the LC and BF groups (Table 2). Voids.
Radiographic evaluation by digital radiography of the fillings revealed no voids in the TF group, whereas small voids were present in 18 and 19 of the 20 fillings in the LC and BF groups, respectively (Tables 1 and 2; Figs 4 and 5). The average total length of the voids (_SD) per canal was 0.9 _ 0.6 mm for the LC group and 0.6 _ 0.3 mm for the BF group. The majority of the voids (71%) were in the middle part of the root filling, whilst 12% were in the apical filling and 17% in the coronal filling. The risk of voids was statistically significantly lower (P = 0.000) in the TF group than in the LC and BF groups. No differences could be detected between the LC and BF groups (Table 2).
In the BF technique, sections studied with the microscope revealed no gaps between the master cone and the Thermafil plastic core or the Thermafil gutta-percha (Fig. 6). Sealer.
Sections studied under the microscope showed no gaps between the root fillings/sealer and the canal wall in any of the three groups. In TF fillings, no sealer could be seen under the microscope. In the LC and BF groups, the sealer layer was thickest in the lower middle third of the canal, usually between 10 and 100 mm. Voids demonstrated in the radiographs were also verified in the sections studied with the microscope when the sectioning had occurred through such an area. The voids were typically located between the canal wall and the gutta-percha; however, a thin but continuous layer of sealer was seen covering the canal wall (Figs 7 and 8).
Figure 2.(A, B) A radiograph showing two plastic canals filled with the TF technique. Projections A and B are taken at 08 and 908. Note the high quality of the filling in the canal where no voids can be detected. Apical extrusion of the root filling is evident.
Table 1. The occurrence of overfilling and voids with the three techniques.
Table 2. Statistical evaluation of the hypothesis of no difference between the filling techniques (Fisher's exact tests, two-sided).
Figure 3. Minor apical extrusion of sealer was detected in some canals filled with the BF and LC techniques.
Figure 4. (A, B) A radiograph showing two plastic canals filled with the BF technique. Despite apical patency, no extrusion of the root-filling material can be seen. Small voids can be seen in the root filling (arrows).
Figure 5. (A, B) A radiograph showing plastic canals filled with the LC technique. Small voids can be seen in the root filling (arrows).
Figure 6. A cross-section of a BF filling. Master point (MP), Thermafil plastic core (TF-core), gutta-percha from the Thermafil point (TF-GP) and sealer are seen in the section, level 2a (see Fig.1).
Figure 7. Avoid (shown in Fig. 5A, right arrow) between the sealer and the gutta-percha in a LC filling (section level 3b, see Fig.1).
Figure 8. Avoid (shown in Fig. 4A, arrow) between the sealer and the gutta-percha in a BF filling (section level 3a, see Fig.1).