Thermoplastic Resin Block Void Suppression via Compression
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Solution Overview
Problem
Conventional dental prosthetic materials, such as metal alloys and thermosetting acrylic resins, face challenges like complex preparation processes, metal allergies, resource depletion, and poor mechanical strength, particularly in thick products where voids occur due to thermal contraction, affecting appearance, mechanical strength, and workability during milling.
Innovation Solution
A process for producing a resin block using a thermoplastic resin composition with inorganic particles, where the resin has a fluidizing temperature between 310 to 500°C and is subjected to a compressive operation before solidification to minimize voids, using an injection-molding machine with a projection mechanism, ensuring the resin block has no voids greater than 1.0 mm and is suitable for milling via CAD/CAM systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If thermosetting acrylic resins are used as base materials for blocks, then the blocks can be formed, but the mechanical strength is poor and not strong enough for use as prosthetics for true molar teeth or bridges on where high pressures of occlusion are subject to be applied
Solution Approach 1:
The patent changes the fundamental parameter of the resin material from thermosetting acrylic resin to thermoplastic resin, which has superior mechanical strength properties. This parameter change enables the material to withstand high occlusion pressures required for molar teeth and bridges while maintaining manufacturability through melting and molding processes.
Solution Approach 2:
The patent creates a composite material system by combining thermoplastic resin with inorganic fillers and pigments. This composite approach enhances the mechanical strength of the base resin while adding functional properties such as wear resistance, aesthetic appearance, and controlled processing characteristics through the selected filler and pigment components.
2Volume of stationary object
If a thermoplastic resin composition is used to form thick products, then the material can be processed, but voids occur due to thermal contraction during cooling, affecting appearance, mechanical strength, and workability
Solution Approach 1:
The patent applies preliminary compression to the thermoplastic resin composition before solidification. By exerting compressive force during the critical cooling phase when thermal contraction occurs, the resin is prevented from forming voids, ensuring dense, void-free thick products with excellent appearance and mechanical strength.
Solution Approach 2:
The patent utilizes the phase transition of thermoplastic resin from molten state to solid state as the basis for the compression process. By applying compression during the phase transition period when the material is still pliable but beginning to solidify, the resin density is maximized and void formation is prevented while the material maintains sufficient flowability to fill the mold completely.
3Ease of manufacture
If conventional melt-forming methods are used for thick products, then the products can be formed, but voids occur inside the formed body due to thermal contraction, resulting in defective products
Solution Approach 1:
The patent introduces a preliminary compression step that is applied to the resin composition before complete solidification. This preliminary action of compression counteracts the thermal contraction that occurs during cooling, preventing void formation and ensuring high product reliability without compromising the ease of manufacture through established injection molding or compression molding processes.
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 resulting resin block exhibits excellent mechanical strength, appearance, and workability, preventing defects and breakage, allowing for precise dental prosthetics with improved productivity and cost-effectiveness, suitable for high-pressure applications like molar teeth and bridges.
Implementation Method 1
a thermoplastic resin composition containing a thermoplastic resin having a fluidizing temperature in a range of 310 to 500°C
Implementation Method 2
when a thermoplastic resin or a composition that contains it is cooled from a molten state down to a solid state, the portions of the thermally inflated resin are, first, cooled and solidified as they come in contact with the open air or the mold. That is, a contraction of the volume of the whole formed body appears as vacuum gaps inside the formed body.
Implementation Method 3
pushing a projecting member into one side surface of the cavity filled with the thermoplastic resin composition over a contact area of not more than 50% on the basis of the area of the whole one side surface before the thermoplastic resin composition is completely solidified
Data Source
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AI summary
A resin block that can be favorably used for obtaining dental prosthetics through the milling work, containing very little voids, having excellent property for being cut, exhibiting excellent appearance and mechanical strength, and without permitting the formation of defective products. The resin block contains a thermoplastic resin having a fluidizing temperature in a range of 310 to 500°C and inorganic particles in an amount of 30 to 150 parts by mass per 100 parts by mass of said thermoplastic resin. The inorganic particles are at least one kind of inorganic oxide particles selected from the group consisting of silica particles, silica composite particles of silica and other metal oxides, titania particles, and titania composite particles of titania and other metal oxides. The resin block has a thick portion of a thickness of at least not less than 5 mm, and does not contain any void whose length is not less than 1.0 mm.