Dental Composites With Segmented Polymerization For Low Shrinkage
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Solution Overview
Problem
Dental composites face challenges with high polymerization shrinkage force (PSF) leading to material stress and cracks during curing, which existing strategies attempt to mitigate but often result in slow curing times.
Innovation Solution
Radically polymerizable dental materials containing specific transfer reagents, multifunctional (meth)acrylates, monomolecular and bimolecular photoinitiators, and fillers, optimized to reduce PSF while allowing for rapid curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multifunctional methacrylates are used for crosslinking polymerization, then mechanical strength is improved, but polymerization shrinkage force increases
Solution Approach 1:
The patent segments the polymerization process into two distinct stages: a first polymerization step using monofunctional methacrylates that allows volume compensation through viscous flow, and a second polymerization step using multifunctional methacrylates that provides crosslinking and mechanical strength. This temporal segmentation resolves the contradiction by separating the volume contraction phase from the crosslinking phase, allowing each to occur under optimal conditions without generating excessive shrinkage force.
Solution Approach 2:
The patent applies preliminary action by first establishing a polymer network through monofunctional methacrylate polymerization before introducing multifunctional methacrylates. This preliminary polymerization creates a framework that can accommodate subsequent crosslinking while minimizing overall shrinkage force buildup, as the initial polymerization occurs when the material still has sufficient viscosity to flow and compensate for volume changes.
2Force
If polymerization shrinkage is compensated by viscous flow, then shrinkage force is reduced, but curing time increases
Solution Approach 1:
The patent employs periodic action by dividing the curing process into two distinct time periods: a first polymerization period where monofunctional methacrylates polymerize and provide volume compensation through viscous flow, and a second polymerization period where multifunctional methacrylates polymerize to provide crosslinking. This periodic approach allows shrinkage compensation to occur during the first period when viscous flow is effective, while crosslinking occurs during the second period, thereby reducing overall shrinkage force without requiring excessively long curing times.
3Productivity
If rapid curing is achieved, then productivity is improved, but polymerization shrinkage force increases
Solution Approach 1:
The patent segments the curing process into two rapid sequential steps that can both be completed within a clinically acceptable time frame. The first step uses monofunctional methacrylates for rapid polymerization with volume compensation, and the second step uses multifunctional methacrylates for rapid crosslinking. This segmentation allows each step to proceed quickly without generating excessive shrinkage force, as the volume compensation mechanism is active during the first rapid polymerization before crosslinking begins in the second rapid step.
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 low PSF and rapid curing, suitable for dental applications with improved mechanical properties and reduced marginal gaps in fillings.
Implementation Method 1
radically polymerizable dental materials which contain (a) 0.01 to 5 wt.-% of at least one transfer reagent, (b) 5 to 60 wt.-% of at least one multifunctional (meth)acrylate or of a mixture of mono- and multifunctional (meth)acrylates, (c) 0.01 to 3.0 wt.-% of a combination of at least one monomolecular and at least one bimolecular photoinitiator
Data Source
AI summary
Radically polymerizable material, which contains (a) 0.01 to 5 wt.-% of at least one transfer reagent, (b) 5 to 60 wt.-% of at least one multifunctional (meth)acrylate or a mixture of mono-and multifunctional (meth)acrylates, (c) 0.01 to 3.0 wt.-% of a mixture of at least one monomolecular and at least one bimolecular photoinitiator, (d) 30 to 90 wt.-% of at least one filler, and (e) optionally additive(s), wherein the material contains as transfer reagent (a) at least one allyl sulfone of Formula I and/or a vinyl sulfone ester of Formula II.