A method for retrieving endodontic or atypical nonendodontic separated instruments from the root canal: a report of two cases

Removing Fractured Endodontic Files with a Tube Technique-The Strength of the Glued Joint: Tube-Endodontic File Setup

One recommended technique for removing broken root canal instruments is to glue the fragment into a cannula adapted to it (i.e., the tube technique). The aim of the study was to determine the influence of the adhesive kind and length of the joint on the breaking force. During the investigation, 120 files (60 H-files and 60 K-files) and 120 injection needles were used. Fragments of broken files were glued into the cannula using one of three materials: cyanoacrylate adhesive, composite prosthetic cement, or glass ionomer cement. The lengths of the glued joints were 2 and 4 mm. After the polymerization of adhesives, a tensile test was carried out to find a breaking force. The results were statistically analyzed (p < 0.05). For 4 mm lengths of glued joints, the breaking force was higher than for 2 mm for both file types (K and H). In the case of K-type files, the breaking force was higher for cyanoacrylate and composite adhesives than glass ionomer cement. For H-type files, no significant difference in joint strength was found between binders at 4 mm, while at 2 mm, a much better connection was obtained for cyanoacrylate glue than prosthetic cements.

Evaluation of the effects of the solution used for electrochemical dissolution of nickel-titanium endodontic files on dentine structure, microhardness and cell viability

AIM

To evaluate the effects of the [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution used in the electrochemical dissolution process of fractured endodontic files, as well as its NiTi-containing product, on dentine hardness, topography and human fibroblast viability.

METHODOLOGY

Sixty single-rooted human teeth were evaluated for dentine microhardness using the Vickers hardness test and the area and number of dentinal tubules by scanning electron microscopy. The samples were divided according to the dentine surface treatment: distilled water; 17% EDTA; [NaF 12 g L^-1  + NaCl 1 g L^-1 ]; and 17% EDTA + [NaF 12 g L^-1  + NaCl 1 g L^-1 ]. Thirty-six single-rooted human teeth were divided according to the irrigation protocol: Dulbecco's Modified Eagle's Medium + 10% foetal bovine serum; 5.25% NaOCl; [NaF 12 g L^-1  + NaCl 1 g L^-1 ]; and [NaF 12 g L^-1  + NaCl 1 g L^-1  + NiTi]. The extracts in contact with the apical foramen were used in the MTT assay to evaluate human fibroblast viability, with dilutions of 100%, 50%, 25% and 12.5%. Statistical tests used were paired t-tests, one-way anova, Tukey's test, Kruskal-Wallis test and Dunn's post-test.

RESULTS

The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution did not modify dentine microhardness or the average dentinal tubule area. However, EDTA induced changes in dentine structure and microhardness (P < 0.05). The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution, and its NiTi-containing product had lower cytotoxicity than NaOCl at dilutions of 25% and 50% (P < 0.01).

CONCLUSIONS

The [NaF 12 g L^-1  + NaCl 1 g L^-1 ] solution did not alter dentine microhardness or damage the dentine structure. It also demonstrated lower cytotoxicity than NaOCl.