J Korean Acad Conserv Dent.  2002 Nov;27(6):577-586. 10.5395/JKACD.2002.27.6.577.

Scanning electron microscopic study on the efficacy of root canal wall debridement of rotary Ni-Ti instruments with different cutting angle

• Jeon IS
• Kum KY
• Park SH
• Yoon TC

• KMID: 1987316
• DOI: http://doi.org/10.5395/JKACD.2002.27.6.577

Abstract

The purpose of this in vitro study was to compare the effects of root canal debridement following rotary Ni-Ti instruments with positive versus negative rake angle. Seventy sound, extracted human anterior teeth & premolars were randomly divided into four groups. The used rotary instruments were Ni-Ti HERO 642(Micro-Mega in France, 20 specimen), Ni-Ti ProFile(Maillefer, Ballaigues, Switzerland, 20 specimen), stainless steel engine reamer(Mani, Matsutani Seisakusho Co.,Japan, 20 specimen) and negative control group(10 specimen) was only extirpated with barbed broach(Mani, Matsutani Seisakusho Co.,Japan) Group 1 & 2 teeth were prepared to a #40 at the apex followed by 1 mm using crown-down technique. Group 3 teeth were instrumented from a #15 to a #40 in sequential order. After preparation and final irrigation, the roots split longitudinally into a bucco-lingual direction. Root halves were cross-sectioned in apical third portion again. all root specimens were prepared for SEM investigation & photographed. Separate evaluations were undertaken for smear layer on prepared walls with a five score-index for each using reference photograph in root halves. the penetration depth of smear layer into dentinal tubules was also estimated in the other halves. the following results were obtained : 1. Smear layer was observed on all the prepared walls with three experimental groups except negative control group 2. Smear layer characteristics 1) HERO 642 groups showed snowy & dusty appearance & were observed only few some dentinal tubuli open on the prepared walls, and the penetration depth of it into dentinal tubules may be 1-2 microm thick. 2) ProFile groups showed shiny & burnished appearance & complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli and penetration depth of it into dentinal tubules may be 1-2 microm thick. 3) Engine reamer groups showed obviously file's passed tracks on the prepared walls & were observed complete root canal wall covered by a homogenous smear layer with no open dentinal tubuli. The results revealed that a completely clean root canal could not be achieved regardless of positive & negative rake angle, which is in accordance with the majority of studies on root canal cleanliness. In conclusion, throughout irrigation with antibacterial solutions or chelating agents is recommended to remove the smear layer on prepared canal walls.

Keyword

smear layer; positive & negative rake angle; debridement; HERO 642; ProFile

MeSH Terms

Bicuspid
Chelating Agents
Debridement
Dental Pulp Cavity
Dentin
Electrons
France
Humans
Nickel
Smear Layer
Stainless Steel
Switzerland
Titanium
Tooth
Track and Field
Chelating Agents
Nickel
Stainless Steel
Titanium

Figure

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  Fig. 1 Scanning electron micrograph of canal wall prepared with Ni-Ti HERO 642(×1,500).

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  Fig. 2 Scanning electron micrograph of canal wall prepared with Ni-Ti ProFile(×1,500).

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  Fig. 3 Scanning electron micrograph of canal wall prepared with stainless-steel engine reamer(×1,500).

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  Fig. 4 Scanning electron micrograph of canal wall extirpated with barbed broach but not instrumented(×1,500).

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  Fig. 5 the penetration depth of smear layer into dentinal tubules was observed on canal wall prepared with Ni-Ti HERO 642(×3,000, ×5,000).

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  Fig. 6 the penetration depth of smear layer into dentinal tubules was observed on canal wall prepared with Ni-Ti ProFile(×3,000, ×5,000).

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  Fig. 7 the penetration depth of smear layer into dentinal tubules was observed on canal wall prepared with stainless-steel engine reamer(×3,000, ×5,000).

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  Fig. 8 the penetration depth of smear layer into dentinal tubules was observed on canal wall extirpated with barbed broach but not instrumented (×3,000, ×5,000).

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  Fig. 9 Total scores of smear layer at apical third in each groups

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