[The effect of smear layer on apical microleakage]

Area of Science:

• Endodontics
• Dental Materials Science
• Microbiology

Background:

• The smear layer, a hybrid layer of debris and dentinal fluid, can impede the sealing of root canal fillings.
• Effective management of the smear layer is critical for preventing apical and coronal leakage in endodontic treatments.

Purpose of the Study:

• To investigate the impact of different irrigating solutions on smear layer removal.
• To evaluate the subsequent effect of smear layer presence or absence on apical microleakage in root-filled teeth.

Main Methods:

• 51 human teeth underwent root canal instrumentation and were irrigated with various solutions (EDTA, tetracycline hydrochloride, citric acid, NaClO, NaCl).
• Smear layer presence was assessed using scanning electron microscopy (SEM).
• Apical microleakage was quantified using a glucose penetration model over 30 days.

Main Results:

• Groups treated with EDTA, tetracycline hydrochloride, or citric acid showed no smear layer and significantly reduced apical microleakage compared to control groups (P<0.05).
• Teeth with smear layer present (1% NaClO only or 0.9% NaCl) exhibited increased leakage.
• Microleakage was highest in the group irrigated with 0.9% NaCl.

Conclusions:

• Complete removal of the smear layer from the root canal walls is essential for minimizing apical microleakage.
• Specific irrigating solutions effectively remove the smear layer, thereby enhancing the seal of root canal fillings.