J Korean Acad Conserv Dent.  2004 Sep;29(5):446-453. 10.5395/JKACD.2004.29.5.446.

Shaping ability of four rotary nickel-titanium instruments to prepare root canal at danger zone

• Choi SD
• Jin MU
• Kim KO
• Kim SK

• KMID: 1987124
• DOI: http://doi.org/10.5395/JKACD.2004.29.5.446

Abstract

The aim of this study was to evaluate the shaping abilities of four different rotary nickel-titanium instruments with anticurvature motion to prepare root canal at danger zone by measuring the change of dentin thickness in order to have techniques of safe preparation of canals with nickel-titanium files. Mesiobuccal and mesiolingual canals of forty mesial roots of extracted human lower molars were instrumented using the crown-down technique with ProFile, GT(TM) Rotary file, Quantec file and ProTaper(TM). In each root, one canal was prepared with a straight up-and-down motion and the other canal was with an anticurvature motion. Canals were instrumented until apical foramens were up to size of 30 by one operator. The muffle system was used to evaluate the root canal preparation. After superimposing the pre- and post-instrumentation canal, change in root dentin thickness was measured at the inner and outer sides of the canal at 1, 3, and 5 mm levels from the furcation. Data were analyzed using two-way ANOVA. Root dentin thickness at danger zone was significantly thinner than that at safe zone at all levels (p < 0.05). There was no significant difference in the change of root dentin thickness between the straight up-and-down and the anticurvature motions at both danger and safe zones in all groups (p > 0.05). ProTaper removed significantly more dentin than other files especially at furcal 3 mm level of danger and safe zones (p < 0.05) Therefore, it was concluded that anticurvature motion with nickel-titanium rotary instruments does not seem to be effective in danger zone of lower molars.

Keyword

Shaping ability; Ni-Ti rotary instrument; Root canal preparation; Danger zone; Anticurvature filing; ProTaper

MeSH Terms

Dental Pulp Cavity*
Dentin
Humans
Molar
Root Canal Preparation
Tooth Apex

Figure

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  Figure 1 Both halves of the muffle with C clamp to maintain muffle-to-muffle and muffle-to-resin relationships. A tooth is embedded in acrylic resin in the muffle. C clamp also serves as a convenient handle during experimental procedure.

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  Figure 2 Levels of cross-section. Roots were sectioned horizontally 1, 3, and 5 mm levels from the furcation.

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  Figure 3 Computer captured images. A, before root canal instrumentation; B, after canal instrumentation.

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  Figure 4 Thickness of root dentin (mm) at danger and safe zones before and after root canal instrumentation (mean ± S.D., n = 80 each). *Root dentin thickness at danger zone was significantly thinner than that at safe zone (p < 0.05).

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