Intracanal nickel element distribution after root canal preparation using five nickel-titanium instruments and its cytotoxicity on dental pulp cells.

OBJECTIVES

This study investigated the distribution of nickel elements in root canals after root canal preparation using five different nickel-titanium instruments, as well as its cytotoxicity on dental pulp cells.

MATERIALS AND METHODS

Root canal preparations were performed on extracted dental slices using five nickel-titanium instruments. The distribution of nickel within the root canal was analyzed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Field Emission Electron Probe Micro-Analyzer (EPMA). Surface changes of new and reused instruments were examined by Scanning Electron Microscopy (SEM). Conditioned medium from prepared tooth slices was used to culture dental pulp cells, with cell proliferation assessed via the CCK-8 assay and morphology observed under a light microscope.

RESULTS

No significant increase in nickel residue was observed after seven consecutive preparations with the same instrument. However, elemental nickel residue was significantly higher in the apical parts compared to the middle and coronal parts intra-canal. The Reciproc Blue (RB) system showed notably higher nickel residues in the apical area. Surface wear was observed on the instruments after use. The conditioned medium did not significantly affect the morphology or proliferation of cultured pulp cells.

CONCLUSIONS

Nickel residues did not increase significantly with repeated use of the same instruments. All instruments showed higher residue in the apical parts, with the RB system exhibiting the highest levels. There were no significant changes in the instrument morphology after preparation. The use of five nickel-titanium instruments did not negatively affect the proliferation of dental pulp cells. However, the cumulative impact of nickel on cytotoxic effects requires further investigation.

CLINICAL RELEVANCE

This study revealed the distribution of nickel residues in the root canals after root canal instrumentation, in addition to providing an informative reference about the potential effects of nickel-titanium instruments on the results of regenerative endodontic therapy.