Effectiveness of different obturation techniques in the filling of simulated lateral canals.

The purpose of this in vitro study was to evaluate the ability of lateral compaction of gutta-percha and of five thermoplasticized gutta-percha filling techniques to obturate simulated lateral canals. Sixty extracted single-rooted human teeth were instrumented at the working length to a #35 file before creating three simulated lateral canals on the mesial and distal surfaces of the root, one in each third, using a #15 engine reamer. After enlarging root canals to a #45 file, the teeth were randomly divided into six equal groups of 10 and obturated according to the following techniques: lateral compaction of gutta-percha (group A), hybrid technique (group B), Ultrafil (group C), Obtura II (group D), System B + Obtura II (group E), and Thermafil (group F). AH26 was used as the sealer. A greater number of simulated lateral canals were obturated when Ultrafil, Thermafil, and System B + Obtura II were used, in comparison with canals obturated with the hybrid technique, Obtura II, or lateral compaction of gutta-percha. This difference was statistically significant (p < 0.05). No statistically significant differences were found between results obtained in the obturation of simulated lateral canals in the different thirds of the root (p > 0.05).

Dissection of the NF-Y transcriptional activation potential.

NF-Y is a trimeric CCAAT-binding factor with histone fold subunits (NF-YB/NF-YC) and bipartite activation domains located on NF-YA and NF-YC. We reconstituted the NF-Y activation potential in vivo with GAL4 DBD fusions. In the GAL4-YA configuration, activation requires co-expression of the three subunits; with GAL4-YB and GAL4-YC, transfections of the histone fold partners are sufficient, provided that the Q-rich domain of NF-YC is present. Combinations of mutants indicate that the Q-rich domains of NF-YA and NF-YC are redundant in the trimeric complex. Glutamines 101 and 102 of NF-YA are required for activity. We assayed NF-Y on different promoter targets, containing single or multiple GAL4 sites: whereas on a single site NF-Y is nearly as powerful as VP16, on multiple sites neither synergistic nor additive effects are observed. NF-Y activates TATA and Inr core elements and the overall potency is in the same range as other Q-rich and Pro-rich activation domains. These results represent the first in vivo evidence of subunit interactions studies and further support the hypothesis that NF-Y is a general promoter organizer rather than a brute activator.

Radiographic assessment of simulated external root resorption cavities in maxillary incisors.

Upper central and lateral incisors of three human skulls were used to assess radiographically the possibility of detecting cavities of different sizes and locations, drilled to simulate external root resorptions. The sequence of radiographs was evaluated by three endodontists, who were unaware of the experiment being done, using a 2 x magnifier. The first observation was done without comparing the radiographic images of the different cavities with the preoperative radiograph. For the second round of observation, each sequence was compared with the preoperative X-ray. The results showed that small cavities were more difficult to detect than the medium and large ones. Moreover, cavities located on the proximal surfaces were more easily detected than those located on the buccal surfaces. Finally, when the observers could compare with the preoperative radiographs (second round of observation), the rate of detection was considerably higher.

Disintegration of endodontic cements in water.

The disintegration of three endodontic cements in water was determined quantitatively and qualitatively. The materials studied were Ketac-Endo (KE), Tubli Seal (TS), and AH26 (AH). Specimens were immersed in water for 48 h (GI), 7 (GII) and 45 days (GIII). The solid residue was then determined. For the qualitative analysis three groups of tubes were filled with the materials and stored in water for the same periods. The exposed surface was photographed. Results expressed as percentage of original mass in the quantitative analysis for loss of mass due to dissolution were: GI = KE 2.39 (0.70); TS 3.56 (0.37); AH 4.94 (2.83); GII = KE 2.84 (0.30); TS 2.50 (0.50); AH 0.66 (0.26); GIII = KE 1.60 (0.84); TS 1.03 (0.42); AH 1.22 (0.54). Tukey's least significant difference (0.05) was 2.94. In the qualitative experiment KE disintegration was far more evident than that suffered by other materials. The quantitative results had no correlation with the qualitative observations probably due to the difference in the moment when the materials were immersed.

Apical sealing ability of a new glass ionomer root canal sealer.

This study compared the sealing ability of Ketac Endo with and without smear layer and Tubli Seal. Thirty upper central incisors and canines with straight canals were instrumented and randomly divided into three equal groups of 10. All teeth were obturated with laterally condensed gutta-percha. An additional group of five teeth with unobturated++ root canals served as positive controls. The sealers were Tubli Seal (group A), Ketac Endo (group B), and Ketac Endo preceded by the removal of the smear layer (group C). The teeth were immersed in India ink for 7 days, centrifuged for 5 min at 3000 rpm, cleared, and then examined under a light microscope at X 50 magnification. The mean value of ink penetration for group A was 0.14 mm, for group B 0.24 mm, and for group C 0.48 mm. No statistically significant differences were observed among groups (p > 0.05).