Root Microcracks Formation during Root Canal Instrumentation Using Reciprocating and Rotary Files.

Area of Science:

• Endodontics
• Dental Materials Science

Background:

• Root canal preparation is crucial for endodontic success.
• Nickel-titanium (NiTi) instruments are widely used for root canal shaping.
• Different motion kinematics (continuous rotation vs. reciprocating) may influence dentinal integrity.

Purpose of the Study:

• To compare dentinal crack formation using NiTi instruments with continuous rotation versus reciprocating motion.
• To evaluate the influence of different NiTi systems on dentinal microcrack generation.

Main Methods:

• Extracted human mandibular first molars were used.
• Root canals were prepared using K-files (control), ProTaper Universal (manual and rotary), One Shape, and WaveOne systems.
• Prepared roots were sectioned and examined under a stereomicroscope for dentinal microcracks.

Main Results:

• No cracks were observed with K-files.
• Cracks occurred in 15.6% (manual PTU), 12.4% (rotary PTU), 21.9% (OS), and 6.2% (WO) of samples.
• The One Shape system showed the highest incidence of cracks, though not statistically significant.

Conclusions:

• Dentinal crack formation is independent of motion kinematics.
• Reciprocating motion instruments may lead to fewer dentinal cracks compared to continuous rotation.
• Manual and rotary NiTi sequential systems demonstrated fewer microcracks than single-file systems in continuous rotation.