Rotary Endodontic Instrument with Irregular Cutting Edges
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Solution Overview
Problem
Existing rotary endodontic instruments face issues such as screwing phenomena, jamming, breakage, and surface scratches in dental canals, leading to inefficient machining and potential infection sources due to microcavities.
Innovation Solution
A rotary endodontic instrument with a blade featuring alternating regular and irregular working edges, where the irregular edges have a succession of hollows and bumps, allowing for efficient cutting while the regular edges smooth out irregularities, reducing the risk of screwing and breakage, and facilitating easy chip evacuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rotary instruments have a helical cutting edge, then cutting efficiency is improved, but screwing phenomena occur causing the instrument to sink into the canal
Solution Approach 1:
The cutting edge is designed with asymmetric geometry featuring alternating convex and concave portions along its length. This asymmetric configuration prevents the continuous helical engagement that causes screwing while maintaining effective cutting through the convex portions, resolving the contradiction between cutting efficiency and screwing risk.
Solution Approach 2:
The cutting edge is segmented into multiple discrete convex portions separated by concave portions. This segmentation interrupts the continuous cutting action, preventing the instrument from sinking into the canal like a screw while still providing effective material removal through each convex segment, thus eliminating screwing phenomena while maintaining productivity.
2Productivity
If irregular edges are used to improve cutting efficiency, then machining speed increases, but scratches and microcavities are created on the canal wall
Solution Approach 1:
The cutting edge is divided into convex cutting portions and concave spacing portions. The convex portions provide aggressive cutting for high machining speed, while the concave portions create spacing that prevents continuous contact and reduces the formation of deep scratches and microcavities, thus resolving the contradiction between productivity and surface quality.
Solution Approach 2:
Different portions of the cutting edge have different geometries: convex portions are designed for aggressive cutting with sharper angles to maximize material removal, while concave portions provide spacing and reduce contact pressure. This local differentiation allows the instrument to achieve high machining speeds without creating excessive surface damage, resolving the contradiction between cutting efficiency and surface quality.
3Object-affected harmful factors
If only slight cuts are made to avoid scratches, then surface quality is maintained, but shaping becomes very time-consuming
Solution Approach 1:
The cutting edge alternates between convex portions that perform aggressive cutting for rapid material removal and concave portions that provide spacing and reduce surface damage. This segmentation allows the instrument to achieve both high shaping speed and acceptable surface quality, resolving the contradiction between productivity and surface smoothness.
4Force
If mechanical stresses are concentrated in the same area, then cutting force is increased, but the risk of instrument breakage increases
Solution Approach 1:
The cutting edge is segmented into multiple convex portions separated by concave portions. This segmentation distributes the mechanical stresses across multiple discrete locations along the cutting edge rather than concentrating them in one area, reducing the risk of instrument breakage while maintaining effective cutting force through each convex segment.
Solution Approach 2:
The cutting edge features localized convex portions with high cutting capability and concave portions with reduced material. This local differentiation allows concentrated cutting force to be applied at specific convex points while the concave portions provide stress relief and prevent overall instrument failure, resolving the contradiction between cutting force and breakage risk.
Data Source
Figure 1
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AI summary
The invention relates to an endodontic instrument having a blade (2), the active portion (202) of which has at least two working edges, wherein, according to the invention, in at least one segment of the active portion (202), at least one of the working edges is regular and at least one other of the working edges is irregular, having a succession of recesses where the edge is closer to the longitudinal axis (10) and protrusions where the edge is further away from the longitudinal axis (10), the irregular working edge(s) being situated, in each cross section of this segment, at a distance from the longitudinal axis (10) which is less than or equal to the distance between the longitudinal axis (10) and the regular working edge or one of the regular working edges.