Low-Viscosity Photo-Curable Resin for Tough Orthodontic Aligners
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Solution Overview
Problem
Low viscosity resins traditionally used in 3D printing do not produce polymers that are hard, tough, and resistant to stress relaxation, making them incompatible with the production of orthodontic appliances like aligners.
Innovation Solution
Development of photo-curable resins with low viscosity and reduced hydrogen bonding units, featuring oligomers with a number-average molecular weight greater than 3,000 Da and initiators, which can be 3D printed and cured to form polymeric materials with high toughness and resistance to stress relaxation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If low viscosity resins are used for 3D printing, then ease of printing is improved, but mechanical strength and toughness deteriorate
Solution Approach 1:
The patent changes the molecular weight parameter of the oligomer from conventional low values to greater than 3,000 Da, which fundamentally alters the resin's properties. This parameter change enables the resin to maintain low viscosity for easy printing while producing a cured polymer with high mechanical strength and toughness, resolving the contradiction between ease of printing and mechanical strength
Solution Approach 2:
The patent creates a composite resin system combining specific oligomers (with molecular weight > 3,000 Da) and initiators in controlled ratios. This composite formulation produces a cured polymer that integrates the benefits of low viscosity for printing with enhanced mechanical properties, including hardness, toughness, and stress relaxation resistance
2Duration of action of moving object
If traditional low viscosity resins are used, then viscosity is reduced for better printing, but resistance to stress relaxation deteriorates
Solution Approach 1:
By changing the oligomer molecular weight parameter to greater than 3,000 Da, the patent achieves a dual benefit: the resin maintains low viscosity for successful 3D printing while the cured polymer exhibits superior resistance to stress relaxation, thereby resolving the contradiction between duration of action and reliability
3Strength
If hydrogen bonding units are increased to improve toughness, then mechanical toughness is improved, but water uptake increases
Solution Approach 1:
The patent changes the chemical composition parameter by limiting hydrogen bonding units to less than 20 wt %, which prevents excessive water uptake while still achieving the desired toughness through alternative mechanisms, including the specific molecular weight selection and crosslinking chemistry
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 resulting polymeric materials exhibit mechanical properties suitable for orthodontic appliances, including high tensile modulus, flexural stress, and elongation at break, while maintaining low water uptake and hydrogen bonding, enabling effective production of aligners and other orthodontic devices.
Implementation Method 1
the photo-curable resin comprises an oligomer 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.