Endodontic Instrument Rough Surface Reduces Cutting Forces
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Solution Overview
Problem
Existing endodontic instruments face challenges with high cutting forces, risk of breakage, and difficulty in evacuating large shavings, while manufacturing methods are complex and costly, and abrasive coatings are fragile.
Innovation Solution
An endodontic instrument with a nickel-titanium active part featuring a rough surface with craters providing irregular edges, reducing cutting forces and facilitating easy evacuation of small shavings, manufactured using wire spark erosion and chemical cleaning processes, and heat treatment for enhanced durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If grinding is used to produce smooth surfaces on endodontic instruments, then manufacturing precision is improved, but cutting efficiency deteriorates and instrument reliability worsens due to rounded edges
Solution Approach 1:
The patent changes the surface parameter from smooth to rough by controlling the grinding process to leave micro-asperities on the surface. This roughness (Ra 0.2-2.0 μm) maintains cutting efficiency while the overall geometric precision is preserved, resolving the contradiction between surface smoothness and cutting effectiveness
Solution Approach 2:
The patent applies different surface qualities to different regions: the cutting edges maintain sharpness and precision for effective cutting, while the body surfaces have controlled roughness for debris removal. This local differentiation resolves the contradiction by optimizing each region for its specific function
2Strength
If abrasive coatings are applied to enhance abrasive properties, then cutting efficiency is improved, but instrument reliability deteriorates due to coating detachment and fragmentation
Solution Approach 1:
The patent extracts the abrasive function from separate coatings and integrates it directly into the instrument material through controlled surface roughness. The micro-asperities on the surface provide inherent abrasiveness without requiring fragile external coatings, eliminating the reliability issue while maintaining cutting efficiency
Solution Approach 2:
The patent creates a composite surface structure where the base material and surface layer work together - the bulk material provides structural integrity while the roughened surface layer provides abrasive properties. This integrated composite approach eliminates coating detachment problems while maintaining enhanced abrasive capabilities
3Productivity
If cutting edges are made sharp to improve cutting efficiency, then productivity is improved, but instrument reliability worsens due to increased risk of breakage
Solution Approach 1:
The patent applies this principle by creating a flexible, elastic instrument body that can deflect under load. The superelastic nickel-titanium alloy allows the instrument to bend without permanent deformation or breakage, maintaining sharp cutting edges while preventing catastrophic failure through controlled flexibility
Solution Approach 2:
The patent incorporates superelastic material properties that provide inherent cushioning against excessive forces. The material's ability to undergo large elastic deformations before permanent damage acts as a built-in safety mechanism, protecting sharp edges from breakage during operation
4Reliability
If mechanical smoothing treatments are applied to eliminate burrs, then instrument reliability is improved, but cutting efficiency deteriorates due to rounded edges
Solution Approach 1:
The patent changes the approach from eliminating all surface irregularities to controlling and optimizing them. By maintaining controlled micro-asperities (Ra 0.2-2.0 μm) rather than achieving perfect smoothness, the instrument retains edge sharpness for cutting while eliminating harmful large burrs, resolving the contradiction between burr elimination and edge sharpness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The instrument achieves reduced cutting forces, improved abrasive properties, and easier shaving evacuation, with a robust and cost-effective manufacturing process that minimizes the risk of breakage and obstruction.
Implementation Method 1
a step of cutting out a bar of nickel-titanium alloy by a wire spark erosion method
Implementation Method 2
a step of cleaning the instrument formed by a chemical process, so as to preserve the roughness of said faces
Implementation Method 3
heat treatment for enhanced durability
Data Source
AI summary
The invention relates to an endodontic instrument comprising a shaft to be secured in an instrument-carrier and an active part to be introduced into a root canal, the active part comprising a plurality of faces (21, 22, 23) and at least one edge (25, 26, 27) formed by the intersection of two faces; at least two of said adjacent faces having a surface with a roughness presenting an arithmetic mean deviation from the mean line Ra, selected such that 0.5μm<Ra<4.5pm, in such a way that the edge formed by the intersection of said two faces has the profile of an irregular jagged line in the space presenting at least one deviation from the mean line, higher than 0.5pm.