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Effect of Rotational Modes on Torque/Force Generation and Canal Centering Ability during Rotary Root Canal
Satoshi Omori1, Arata Ebihara1, Keiko Hirano1
1Department of Pulp Biology and Endodontics, Division of Oral Health Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University (TMDU), 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8549, Japan.
Materials (Basel, Switzerland)
|October 14, 2022
Summary
Different rotational modes affect nickel-titanium endodontic instruments. ProTaper Gold instruments with R240/120 and Optimum Torque Reverse motion showed reduced force, while ProTaper Universal instruments demonstrated improved canal centering with these modes.
Area of Science:
- Endodontics
- Dental Materials Science
- Biomaterials Engineering
Background:
- Nickel-titanium (NiTi) rotary instruments are crucial in endodontic therapy.
- Heat treatment significantly alters NiTi alloy properties, influencing instrument performance.
- Understanding rotational modes' impact is vital for optimizing root canal preparation.
Purpose of the Study:
- To compare the torque/force production and canal shaping ability of heat-treated ProTaper Gold (PTG) and non-heat-treated ProTaper Universal (PTU) NiTi instruments.
- To evaluate the influence of different rotational modes (reciprocating R150/30, R240/120; Optimum Torque Reverse motion (OTR); continuous rotation (CR)) on instrument performance.
Main Methods:
- J-shaped resin canals were instrumented using PTU and PTG with an automated device under four rotational modes (R150/30, R240/120, OTR, CR).
- Maximum force, torque, and canal centering ratios were measured (n=10 per group).
- Statistical analysis involved two-way ANOVA and Bonferroni tests (α = 0.05).
Main Results:
- ProTaper Gold instruments exhibited lower upward force with R240/120 and OTR compared to R150/30 and CR.
- OTR produced lower clockwise torque in PTU than R150/30, and in PTG compared to R240/120 and CR.
- R240/120 and OTR modes resulted in less canal deviation for PTU compared to CR, particularly near the apex.
Conclusions:
- The R240/120 and OTR rotational modes reduced screw-in force in ProTaper Gold instruments.
- These modes enhanced canal centering ability in ProTaper Universal instruments.
- Observed differences are likely attributable to the microstructural variations induced by heat treatment in the NiTi alloys.
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