Progressive versus constant tapered shaft design using NiTi rotary instruments

Area of Science:

• Endodontics
• Dental Materials Science

Background:

• Nickel-titanium (NiTi) rotary instruments are widely used in endodontic therapy.
• Instrument design, particularly the taper of the shaft, may influence canal preparation outcomes.
• Understanding how different taper designs affect dentine removal and canal centering is crucial for optimizing root canal treatment.

Purpose of the Study:

• To compare the effects of a progressive tapered shaft design (ProTaper) versus a constant tapered shaft design (K3) on root canal preparation using NiTi rotary techniques.
• To evaluate dentine removal, canal transportation, and centering ability of these two file systems in mesial canals of mandibular molars.

Main Methods:

• Extracted mandibular molars (n=10 per group) were scanned using micro-computed tomography (micro-CT) before and after preparation with ProTaper or K3 files.
• Three-dimensional analysis quantified changes in canal volume, curvature, dentine removal, and centring ratio.
• Visual inspection assessed canal aberrations.

Main Results:

• Both ProTaper and K3 instruments demonstrated comparable total dentine removal and similar amounts of dentine removal in specific horizontal regions (P > 0.05).
• ProTaper instruments showed a tendency for coronal "transportation" (center displacement) towards the furcation, while K3 instruments exhibited apical displacement towards the outer side of the curvature.
• No severe canal aberrations were observed with either instrument system.

Conclusions:

• The progressive taper of ProTaper files resulted in less influence from mid-root curvature, leading to better apical centering.
• However, ProTaper instruments demonstrated a greater tendency for coronal transportation towards the furcation compared to K3 files.
• Both NiTi file systems achieved comparable dentine removal, but exhibited different transportation patterns in curved canals.