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Table 2 Overview of special-shape methods of root canal files

From: The state of the art and future trends of root canal files from the perspective of patent analysis: a study design

Code

Special-shape

Performance

Advantage

Limitation

CN209595930 [56]

3D

SS

GCR

Insufficient strength

CN207400812 [57]

S-shape

SS

GCR

Weak chip removal function

US10136962 [58]

More curvature

SS

LR

No easy access to the inside of the root canal

CN209032679 [59]

Helical shape

SS

GC

Out of alignment with the root canal axis

CN201676027 [60]

Normal

Without two edges

LR

A single type of preparation

EP2140 828 [61]

Small tip

Three spiral grooves

LR

Small contact area affects cutting performance

CN211460595 [62]

Optimized tip

Two special surfaces

GCR

Non-streamline design tends to cause steps

CN203724240 [63]

Vertical cutting pattern

Vertical

NCE

Vertical grain affects chip removal efficiency

CN209933021 [64]

Multiple spiral grooves

Many

GCR

Too many spiral grooves affect the strength of the files

CN203943750 [65]

N/A

Left-hand blade

NCE

Left-handed blades are not versatile for users

US11083539 [66]

Tubular

Zigzag structure

NCE

Large size and inconvenient operation

CN109498186 [67]

Composite cutting edges

Discontinuous

NCE

The spiral groove is in the opposite direction of the cutting edge

CN213552491 [68]

Multi-pronged cone

Spiral

GCR

Not easy to control when rotating at a high speed

CN211884087 [69]

Smooth

None

IS

No cutting edge leads to poor cleaning ability

US20100119990 [70]

Interrupted shapes

Discontinuous

NCE

Continuously interrupting spiral grooves affect chip removal

EP3170471 [71]

Spiral wound wire sets

Discontinuous

NCE

Spiral wound wire sets may not be strong enough to bond with the substrate

CN206518609 [72]

Improved handle

Change to the universal handle

GV

Difficult to expand the scope of use

CN211049650 [73]

Improved handle

Extended handle

GV, GVI

The handle is too long to affect the operation

CN206910406 [74]

Improved handle and blade

Change of angle

GV

Unstable bending part

CN205339178 [75]

Improved handle

The changed direction of the handle

GV, GVI

Difficult to disassemble

CN108542513 [76]

Improved handle

Change to floating seat

GC, GV

Unstable force transmission during use

  1. GCR Good chip removal, SS Space spiral, LR Low resistance, GC Good convenience, NCE No continuous embedding, IS Improve safety, GV Good versatility, GVI Good visibility