Thiourea Redox Initiator for Wet Dental Polymerization

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Solution Overview

Problem

Current polymerizable compositions for dental treatments face challenges in curing under wet conditions and maintaining long-term storage stability without discoloration or toxicity, particularly due to issues with existing initiator systems that are either inhibited by water or contain toxic components.

Innovation Solution

A polymerization initiator system comprising an organic peroxide as an oxidizing agent, cysteine as a reducing agent, and a polymerization promoter, where both components contain (meth)acrylates, ensuring effective curing and stability while avoiding toxicity and discoloration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a redox-radical polymerization initiator system consisting of an organic peroxide and an aromatic tertiary amine is used under water-free conditions, then polymerizability of monomers is maintained, but under wet conditions as in the oral cavity, polymerization of monomers is inhibited

Engineering Contradiction:

ImprovepolymerizabilityVSAvoidcurability under wet conditions

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent changes the chemical parameters of the initiator system by replacing the aromatic tertiary amine with a thiourea derivative. This parameter change allows the system to maintain polymerization activity under wet conditions while preserving storage stability, thus resolving the contradiction between polymerizability and curability under wet conditions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The thiourea derivative acts as an intermediary substance that facilitates polymerization under wet conditions. It mediates between the organic peroxide oxidizing agent and the monomers, enabling effective polymerization in the presence of water without compromising the stability of the composition during storage.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If a water-soluble reducing agent such as ascorbic acid and a water-soluble oxidizing agent such as persulfate are used, then satisfactory curing property is achieved even in the presence of water, but storage stability is so low that microencapsulation is necessary

Engineering Contradiction:

Improvecurability under wet conditionsVSAvoidstorage stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent changes the solubility parameter of the reducing agent by using a thiourea derivative with limited water solubility instead of highly water-soluble ascorbic acid. This parameter change enables the composition to maintain satisfactory curability under wet conditions while achieving adequate storage stability without requiring microencapsulation.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If ascorbic acid is used as a reducing agent, then curability under wet conditions is achieved, but the polymer containing ascorbic acid undergoes discoloration

Engineering Contradiction:

Improvecurability under wet conditionsVSAvoiddiscoloration

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent employs a thiourea derivative that serves as a short-living reducing agent effective for initiating polymerization but does not cause long-term discoloration. Unlike ascorbic acid which continues to undergo oxidation and cause discoloration, the thiourea derivative completes its function without generating harmful discoloration effects in the final polymer product.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Productivity

If acetylthiourea and N-benzoylthiourea are used as polymerization initiators, then outstanding curing property is achieved, but they are highly toxic to humans and have been unsuitable for use in the oral cavity

Engineering Contradiction:

Improvecuring propertyVSAvoidtoxicity

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by selecting a specific thiourea derivative structure that provides the necessary polymerization initiation capability while having reduced toxicity compared to acetylthiourea and N-benzoylthiourea. The molecular structure is optimized to maintain effectiveness in the oral cavity environment while minimizing harmful effects on human tissues.

Inventive Principle:

Principle #3Local quality

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 proposed system achieves satisfactory curability under wet conditions and long-term storage stability, ensuring the polymerizable composition is free from discoloration and toxicity, with enhanced handling properties and adhesion to dental materials.

Implementation Method 1

a polymerization initiator system consisting of an organic peroxide, a cysteine, and a polymerization promoter, wherein the organic peroxide is incorporated as an oxidizing agent and the cysteine as a reducing agent

Methodology Applied

Scientific EffectRedox reactions: Redox Reactions

Implementation Method 2

these compositions cure through such mechanisms as cold (chemical) polymerization and photopolymerization

Methodology Applied

Scientific EffectCold polymerization:

Implementation Method 3

a polymerization initiator system consisting of an organic peroxide, a cysteine, and a polymerization promoter

Methodology Applied

Scientific EffectChemical polymerization:

Data Source

PatentEP2712888B1Polymerizable compositions

Publication Date: 2016.03.09 GC CORP

AI summary

A polymerizable composition that comprises a first component comprising a (meth)acrylate and an organic peroxide as an oxidizing agent and a second component comprising a (meth)acrylate and a cysteine as a reducing agent which has a partial structure represented by the following structural formula, the first component and/or the second component further comprising a polymerization promoter: