Superelastic Dental Instrument Machining via Phase Control
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Solution Overview
Problem
Conventional methods for manufacturing superelastic endodontic instruments, such as grinding and twisting, introduce machining stresses and require high-temperature tooling, which can lead to material failure and are not suitable for precise dental instruments.
Innovation Solution
A method involving annealing a superelastic material blank to a specific phase structure, followed by machining at ambient temperature to form desired configurations like helical or non-helical flutes without twisting, and subsequent heat treatment with rapid quenching to achieve superelastic properties, reducing stress and eliminating the need for high-temperature tooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional twisting or grinding methods are used to manufacture superelastic endodontic instruments, then helical flutes can be formed, but machining stresses are introduced into the material which can propagate early material failure
Solution Approach 1:
The patent applies parameter changes by controlling the phase structure of the superelastic material through heat treatment parameters (temperature, time, atmosphere) before machining. The material is maintained in an austenite phase or austenite-martensite mixture phase during machining, which fundamentally changes the material's mechanical properties and stress response, allowing flute formation without introducing harmful machining stresses
Solution Approach 2:
The patent utilizes phase transitions by heating the superelastic material to transform it from martensite phase to austenite phase or an austenite-martensite mixture phase before machining operations. This phase transition enables the material to undergo deformation during flute formation without permanent stress accumulation, as the material can reversibly transform during the machining process
2Ease of manufacture
If high-temperature tooling is used for twisting superelastic materials, then the material can be formed, but the tooling becomes corrosive and requires special handling
Solution Approach 1:
The patent applies parameter changes by optimizing the heating temperature range (500-700°C) and heat treatment time to achieve the desired austenite phase transformation without requiring excessive temperatures. This controlled parameter approach enables material formation while minimizing thermal exposure that would cause tooling corrosion
Solution Approach 2:
The patent applies preliminary action by performing the phase transformation heat treatment on the material before the actual machining or forming operations. The material is pre-heated and held in the austenite phase, making it ready for stress-free flute formation at lower temperatures, thereby eliminating the need for high-temperature tooling during the forming process
3Shape
If superelastic blanks are twisted during fluting, then helical configuration is achieved, but the material is over-stressed and subject to failure
Solution Approach 1:
The patent utilizes phase transitions by maintaining the superelastic material in austenite phase or austenite-martensite mixture phase during the flute formation process. The material's ability to undergo reversible martensitic transformation during deformation allows helical configuration to be achieved without permanent stress accumulation that would lead to failure
Solution Approach 2:
The patent applies beforehand cushioning by pre-heating the material to transform it into the austenite phase before machining. This phase transformation acts as a cushioning mechanism that absorbs the stresses of deformation, allowing the material to undergo significant shape change during flute formation without risking failure
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
This method produces superelastic dental instruments with higher flexibility and resistance to torsional breakage, reducing machining-induced stresses and enabling the production of a variety of dental instruments with precise configurations without the need for high-temperature tooling.
Implementation Method 1
the material is converted from the austenite phase to the martensite phase by the stress applied during the twisting operation. Thus, the superelastic material undergoes stress-induced martensite transformation from a 100% austenite phase
Implementation Method 2
a blank of superelastic material is provided in or brought to an annealed state comprising a phase structure that is a rhombohedral phase, a combination of an austenite phase and a martensite phase
Implementation Method 3
the dental instrument is then heat treated, for example at a temperature of at least about 300°C, followed immediately by rapid quenching to a superelastic condition
Data Source
Figure 1~2A
Figure 2B
Figure 3
AI summary
Method for manufacturing a dental instrument having a desired machined configuration, without twisting the instrument. A blank of superelastic material is brought to an annealed state comprising a phase structure including a rhombohedral phase alone or in combination with austenite and/or martensite, or a combination of martensite and austenite. In this annealed state, a portion of the annealed material is removed at low temperature, for example less than about 100EC, and advantageously at ambient temperature, to form a final machined configuration for the instrument. The instrument is then heat treated and rapidly quenched to a superelastic condition.