Low-Viscosity Photo-Curable Resins for Tough Orthodontic Aligners
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Solution Overview
Problem
Traditional low viscosity resins used in 3D printing do not produce polymers that are hard, tough, and resistant to stress relaxation, making them unsuitable for producing orthodontic appliances like aligners.
Innovation Solution
The development of low-viscosity, photo-curable resins with specific oligomers and initiators, which have a number-average molecular weight greater than 3,000 Da and contain less than 20 wt% hydrogen bonding units, enabling the production of polymers with enhanced mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low viscosity resins are used for 3D printing, then the resin flows easily and can be printed with conventional printers, but the produced polymer lacks hardness, toughness, and resistance to stress relaxation
Solution Approach 1:
The patent changes the molecular weight parameter of the oligomer to greater than 3,000 Da and reduces hydrogen bonding units to less than 20 wt%, which fundamentally alters the polymerization behavior and final material properties while maintaining low viscosity during printing
Solution Approach 2:
The resin composition combines specific oligomers with initiators and optional additives to create a composite system that achieves both low viscosity for printing and high mechanical properties in the cured polymer
2Productivity
If traditional low viscosity resins are used, then the printing process is simple and fast, but the resulting polymer exhibits poor stress relaxation resistance
Solution Approach 1:
By changing the molecular weight parameter to greater than 3,000 Da and controlling hydrogen bonding units below 20 wt%, the patent achieves a resin that maintains low viscosity for fast printing while producing polymers with superior stress relaxation resistance
3Strength
If high molecular weight oligomers are used to improve polymer strength, then the polymer becomes harder and tougher, but the resin viscosity increases and becomes unsuitable for conventional 3D printing
Solution Approach 1:
The patent optimizes the molecular weight parameter to greater than 3,000 Da (but not excessively high) and controls hydrogen bonding units to less than 20 wt%, achieving a balance where the polymer gains sufficient hardness while the resin maintains printability
Solution Approach 2:
The patent creates local quality differences by having the resin itself have low viscosity for printing while the cured polymer structure provides high mechanical properties, achieving different properties in different states (uncured vs. cured)
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
These resins allow for the direct fabrication of orthodontic appliances that exhibit high toughness and resistance to stress relaxation, while maintaining a low viscosity suitable for 3D printing processes.
Implementation Method 1
photo-curable resin comprising an oligomer having a number-average molecular weight of greater than 3,000 Da; and a photoinitiator
Data Source
AI summary
This disclosure provides low-viscosity resins for producing polymers with properties suitable for use in various mechanical appliances, such as orthodontic appliances (e.g., aligners). The low-viscosity resins may be photo-curable and can be used with direct fabrication methods and equipment. In various embodiments, the polymeric materials produced from the low-viscosity resins described herein have high toughness while remaining resistant to stress relaxation. Low-viscosity, photo-curable resins described herein have reduced hydrogen bonding in comparison to traditional materials (e.g., materials having high urethane content) used in orthodontic appliances.