Two-Component Dental Composite Viscosity Increase via Thiol-Ene Reaction
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Solution Overview
Problem
Current dental flowable composites face challenges in achieving a balance between adaptation and manipulation due to their viscosity characteristics, with existing technologies struggling to provide adequate initial adaptation and subsequent manipulation while maintaining mechanical strength and minimizing water absorption.
Innovation Solution
A two-component flowable dental composition comprising a base paste with polythiol and methacrylate, and a catalyst paste with polyene, methacrylate resin, photoinitiator, and base catalyst, utilizing nucleophile-initiated thiol/ene Michael addition and light-initiated radical polymerization to achieve a viscosity-increasing mechanism that allows for sequential curing and improved mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a flowable composite is formulated to have low viscosity for good adaptation, then adaptation to tooth substrate is improved, but manipulation and mechanical strength deteriorate
Solution Approach 1:
The composite is divided into two separate pastes (base paste containing polythiol and catalyst paste containing polyene and photoinitiator) that are mixed immediately before use. This segmentation allows each paste to be stored separately in stable states, and only upon mixing do they undergo rapid polymerization to achieve high mechanical strength, thus resolving the contradiction between low viscosity for adaptation and high strength for durability
Solution Approach 2:
The base paste and catalyst paste are prepared in advance with all necessary components pre-formulated and stabilized. The polythiol and polyene are pre-synthesized and stored separately without premature reaction. This preliminary preparation ensures that when mixed, the polymerization reaction proceeds rapidly and completely, achieving both good adaptation (from controlled mixing) and high mechanical strength (from complete curing)
2Ease of operation
If a flowable composite is formulated to have low viscosity for good adaptation, then adaptation to tooth substrate is improved, but manipulation time and workability deteriorate
Solution Approach 1:
The composite exhibits dynamic rheological properties where viscosity changes over time after mixing. Initially, the mixed paste maintains lower viscosity for a brief period allowing manipulation and adaptation, then undergoes rapid viscosity increase as polymerization progresses. This dynamic behavior provides an optimal working window for clinical manipulation while ensuring complete curing for mechanical strength
Solution Approach 2:
The polymerization reaction is controlled to proceed through distinct stages with changing parameters: initial rapid polymerization provides quick viscosity build-up for manipulation, followed by slower curing to achieve final mechanical properties. The base catalyst enables nucleophile-initiated polymerization at room temperature, while photoinitiator provides light-curable acceleration, creating a multi-stage curing profile that optimizes both manipulation time and final strength
3Device complexity
If conventional single-component flowable composites are used, then formulation simplicity is maintained, but water absorption and polymerization stress increase
Solution Approach 1:
The composite utilizes a dual-polymer system combining polythiol and polyene polymers with complementary properties. This composite material approach creates a cross-linked network structure that reduces polymerization shrinkage stress and improves dimensional stability, thereby reducing water absorption and eliminating the harmful effects associated with conventional single-component composites while maintaining formulation clarity through defined component ratios
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 solution enables a rapid viscosity increase upon mixing, maintaining workability and achieving superior mechanical strength with reduced polymerization stress and improved stability, addressing the limitations of existing technologies in terms of adaptation, manipulation, and mechanical properties.
Implementation Method 1
the base catalyst is capable of promoting nucleophile-initiated thiol-ene Michael addition reaction at room temperature upon a paste/paste mixing
Implementation Method 2
a paste/paste mixing followed by light irradiation to initiate a light-induced polymerization to achieve a final curing
Data Source
Figure 1(a)~1(c)
Figure 2
Figure 3
AI summary
Described is a stable, two-component low viscosity composite that is capable to achieve excellent adaptation to walls/substrates due to its intrinsic flow ability and is also capable of rapid viscosity increasing and being manipulated prior to cure by light upon mixing of such a two-paste composite due to one distinguished reaction promoting partial network formation thus to allow a practitioner further manipulate a firm composite. Upon a completed manipulation by the practitioner, such a mixed material should be readily cured into final solid form by using conventional curing light.