Smooth flexible versus active tapered shaft design using NiTi rotary instruments

Area of Science:

• Endodontics
• Dental Materials Science
• Biomaterials

Background:

• Nickel-titanium (NiTi) rotary instruments are widely used for root canal preparation.
• Shaft design variations, such as smooth flexible versus active tapered, may influence preparation outcomes.
• Understanding these differences is crucial for optimizing endodontic procedures.

Purpose of the Study:

• To compare the effects of smooth flexible and active tapered NiTi rotary instrument designs on root canal preparation.
• To evaluate dentine removal, transportation, and centering ability.
• To assess canal aberrations after preparation.

Main Methods:

• Micro-computed tomography (micro-CT) was used to analyze 3D canal morphology before and after preparation.
• Ten extracted mandibular molars per group were prepared using Lightspeed (smooth flexible) or GT-rotary (active tapered) NiTi files.
• Quantitative analysis of dentine removal, transportation, and centering ratio was performed.

Main Results:

• The active tapered design removed significantly more dentine in the middle and apical root thirds compared to the smooth flexible design.
• Both instrument types showed some degree of canal straightening, with no significant difference between them.
• No significant canal transportation or aberrations were observed, with small absolute values for net transportation and centering ratio.

Conclusions:

• The smooth flexible shaft design does not offer morphological advantages over the active tapered design in NiTi rotary canal preparation.
• Instrument selection should consider factors beyond shaft design, as it did not significantly impact canal straightening or aberrations.
• Further research may explore other design elements influencing NiTi rotary instrument performance.