Polymer Burn-Out Material for Dental Investment Casting

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Solution Overview

Problem

Conventional materials used in investment casting processes for dental restorations often result in cracks and defects due to thermal expansion, as they do not exhibit the melting behavior of waxes, leading to increased pressure on the investment material and subsequent cracking.

Innovation Solution

Radically polymerizable compositions containing a radically polymerizable monomer, an initiator, and an inert component that is soluble in the polymer matrix but undergoes phase separation at a critical temperature, allowing for thermal expansion reduction through bleeding out of the inert component, thereby minimizing crack formation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If alternative materials (curable resins, plastic-wax hybrids) are used instead of conventional waxes for model production, then productivity and manufacturing capability are improved, but thermal expansion behavior worsens causing cracks in investment material

Engineering Contradiction:

Improvemodel production efficiencyVSAvoidcrack-free casting

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The invention uses a composite material system consisting of a curable resin matrix combined with encapsulated wax particles. This composite structure allows the material to exhibit both the ease of modern additive manufacturing and the beneficial thermal behavior of traditional waxes, resolving the contradiction between productivity and reliability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the thermal parameters of the model material by incorporating wax particles that melt at specific temperatures. This transforms the material's thermal expansion behavior from continuous (resin-only) to staged (resin then wax melting), reducing pressure on investment material and preventing cracks while maintaining modern manufacturing capabilities

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If curable resins with non-meltable duromers are used for manual modelling, then ease of operation is improved, but melting behavior worsens leading to pressure on investment material

Engineering Contradiction:

Improvemanual modelling capabilityVSAvoidmelting behavior

Core Design Contradiction:

Ease of operationVSTemperature

Solution Approach 1:

The invention segments the model material into two functional components: a curable resin matrix providing ease of operation and structural integrity, and dispersed wax particles providing controlled melting behavior. This segmentation allows each component to fulfill its specific function without compromising the other

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The wax particles act as an intermediary mechanism between the curable resin and the investment material. During heating, the wax particles melt and provide a cushioning effect, mediating the thermal stress that would otherwise be transmitted directly to the investment material and causing cracks

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If additive processes are used for model production, then productivity is improved, but material behavior worsens due to lack of melting capability

Engineering Contradiction:

Improverapid prototyping capabilityVSAvoidthermal expansion pressure

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The invention converts the potentially harmful thermal expansion of additive-manufactured models into a beneficial process. By incorporating melting wax particles, the controlled volume reduction during wax melting compensates for thermal expansion, transforming what would be harmful pressure into a pressure-relief mechanism that protects the investment material

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 materials achieve significant reduction in thermal expansion, preventing cracks and defects in investment casting, ensuring fault-free moulds and restorations, even for large-volume models, by allowing the inert component to bleed out and reduce pressure on the investment material.

Implementation Method 1

an inert component (c) which is soluble in the polymer formed by polymerisation of the monomer (a), wherein the solubility of component (c) decreases with increasing temperature, with the result that a phase separation takes place above a particular temperature

Methodology Applied

Scientific EffectPhase separation: Phase Change

Implementation Method 2

radically polymerizable compositions which contain (a) at least one radically polymerizable monomer, (b) at least one initiator for the radical polymerisation

Methodology Applied

Scientific EffectRadical polymerization: Photopolymerisation

Data Source

PatentUS11472905B2Polymer-based burn-out material for the lost-wax technique

Publication Date: 2022.10.18 IVOCLAR VIVADENT AG

AI summary

Modelling material which includes (a) at least one radically polymerizable monomer, (b) at least one initiator for the radical polymerization and (c) at least one inert component. The inert component (c) is soluble in the polymer formed by polymerization of the monomer (a), wherein the solubility of component (c) decreases as the temperature increases, with the result that a phase separation takes place above a particular temperature. The material is suitable in particular for the production of models of dental restorations for investment casting processes.