The effects of sequential and continuous chelation on dentin.

Area of Science:

• Dental biomaterials science
• Tooth ultrastructure analysis
• Root canal irrigation efficacy

Background:

• Dentin ultrastructure is crucial for tooth mechanical integrity and dentin-biomaterial interfaces.
• The effects of novel root canal irrigation protocols on dentin require thorough investigation.
• Sodium hypochlorite (NaOCl) and etidronate (HEDP) represent a new continuous chelation irrigation approach.

Purpose of the Study:

• To comprehensively characterize and compare the effects of continuous (NaOCl/HEDP) and sequential (NaOCl/EDTA) chelation irrigation protocols on dentin ultrastructure.
• To evaluate the impact of these protocols on dentin's surface roughness, chemical composition, and collagen integrity.
• To provide insights into the potential clinical implications for dentin and biomaterial interface stability.

Main Methods:

• Dentin samples (blocks, powder, root canals) were treated with saline (control), NaOCl/EDTA, or NaOCl/HEDP.
• Ultrastructural analysis was performed using light and electron microscopy.
• Surface roughness, chemical composition (FTIR, EDS), and collagen degradation (ninhydrin assay) were quantified.

Main Results:

• NaOCl/HEDP treatment resulted in partially degraded, mineralized collagen fibers with minimal subsurface alteration.
• NaOCl/EDTA dissolved hydroxyapatite, exposing collagen fiber bundles.
• No significant difference in surface roughness was observed between the NaOCl/HEDP and NaOCl/EDTA protocols.

Conclusions:

• Continuous chelation (NaOCl/HEDP) yields a frail surface collagen layer, while sequential chelation (NaOCl/EDTA) exposes bare collagen fibers.
• These distinct ultrastructural modifications may predispose dentin and its interfaces to structural failures.
• Understanding these effects is critical for optimizing root canal irrigation strategies and ensuring long-term dental restoration success.