Abstract
In root canal therapy, irrigating solutions are employed to eliminate the bacterial load and also prepare dentin for sealer interaction. The aim of this research was to assess how irrigating solutions employed on their own or in sequence affected the tooth structure. The best way to prepare the tooth for obturation using hydraulic calcium silicate cement (HCSC) sealers and gutta-percha, thus guiding clinicians on a matched irrigation-obturation strategy for optimized root canal treatment was investigated. The effect of irrigating solutions on dentine was investigated by assessing changes in dentin microhardness, ultrastructure and mineral content, organic/inorganic matter, surface roughness and Young’s modulus. The interaction of four root canal sealers with the dentin was analysed by assessing the changes in microhardness of the dentin after sealer placement and also the sealer to dentin interface by scanning electron and confocal laser microscopy. The irrigating solutions damaged the dentin irreversibly both when used on their own and in combination. The best sequence involved sodium hypochlorite followed by chelator and a final rinse with sodium hypochlorite and obturation using HCSC sealers that enabled the restoration of dentin properties. The HCSC sealers did not rely on chelator irrigating solutions for a good material adaptation to dentin.
Highlights
In root canal therapy, irrigating solutions are employed to eliminate the bacterial load and prepare dentin for sealer interaction
There was a significant reduction in dentin microhardness in protocols B and D when 5% NaOCl (G4; NaOCl-5; Cerkamed, Stalowa Wola, Poland) was used (p = 0.02; p = 0.002). 17% EDTA (G9; EDTA; Sigma, Stoinheim, Germany; Protocol E), 17% EDTA/1% benzalkonium chloride (EDTA-BC; Sigma, Stoinheim, Germany; Protocol F-G10) and saline (Protocol G-G11) used without the NaOCl did not affect the microhardness of dentin (p = 0.70; p = 0.10; p = 0.86 respectively)
The inclusion of the 1% BC in EDTA counteracted the effects of the 5% NaOCl on Group 8 and no reduction in the dentin microhardness occurred in Protocol D (p > 0.05)
Summary
In root canal therapy, irrigating solutions are employed to eliminate the bacterial load and prepare dentin for sealer interaction. Mechanical instrumentation creates a smear layer which forms over the dentin surface blocking dentinal tubules This smear layer can be removed by calcium chelating agents such as 17% EDTA which dissolve inorganic debris, this subsequently reduces the mineral content of dentin causing peritubular and intertubular dentinal erosion[4]. As none of these irrigants can be regarded as optimal, they are used together to reduce the microbial load and prepare the root canal dentin for the root canal obturation.
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