A micro-computed tomographic evaluation of apical root canal preparation using three instrumentation techniques

Area of Science:

• Endodontics
• Dental Materials Science
• Biomaterials Engineering

Background:

• Root canal preparation aims to clean and shape the canal space.
• Traditional stainless steel hand files can lead to procedural errors like dentine removal and transportation.
• Advancements in instrumentation, such as rotary nickel-titanium systems, offer potential improvements.

Purpose of the Study:

• To compare the morphological changes in the apical third of root canals prepared using three different techniques.
• To evaluate dentine removal, canal roundness, and transportation.
• To assess the correlation between prepared canal dimensions and final instrument size.

Main Methods:

• Micro-computed tomography (micro-CT) was used to scan 40 molar teeth before and after preparation.
• Three instrumentation groups were compared: stainless steel K-files, K-files with FlexMaster refinement, and a hybrid ProTaper/FlexMaster sequence.
• Apical preparation was analyzed for volumetric change, roundness, transportation, and dimensional accuracy.

Main Results:

• Rotary nickel-titanium instrumentation resulted in smaller volumetric changes (less dentine removed) compared to stainless steel.
• The hybrid rotary technique produced more rounded preparations (P < 0.001) that closely matched final instrument dimensions (P < 0.001).
• A trend towards less canal transportation was observed with rotary nickel-titanium instruments.

Conclusions:

• Stainless steel hand preparation is less conservative of apical dentine.
• Rotary nickel-titanium instruments, even with less experienced operators, precisely shape canals with minimal risk of iatrogenic damage.
• These instruments enable larger apical preparations while maintaining canal morphology.