Multi-layered dental appliance
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Solution Overview
Problem
Orthodontic appliances made from a relatively stiff polymeric material cause discomfort and can cause the polymeric materials to absorb moisture and swell, compromising mechanical tooth-repositioning properties, leading to reduced efficiency and extended treatment time, and repeated contact can abrade and crack the appliance.
Innovation Solution
A multi-layered dental appliance with alternating thermoplastic polymers maintaining a constant stress profile, providing consistent repositioning force and resistance to moisture, staining, and cracking, formed from layers such as PETg and PCTg or PC, optionally with additional layers for enhanced properties like moisture barrier and mold release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a relatively stiff polymeric material is used to effectively exert stable repositioning force, then tooth repositioning efficiency is improved, but discomfort is caused to the patient and the polymeric material absorbs moisture and swells
Solution Approach 1:
The appliance is divided into multiple layers with different polymer materials, each layer serving specific functions: the inner layer uses a softer polymer to reduce discomfort and moisture absorption, while the outer layer uses a stiffer polymer to maintain repositioning efficiency. This segmentation allows each layer to optimize its properties independently.
Solution Approach 2:
The patent employs composite material construction by combining different polymeric materials in a multi-layered structure. The composite structure integrates the advantages of both softer polymers (comfort, moisture resistance) and stiffer polymers (repositioning force) to resolve the contradiction between efficiency and comfort.
2Ease of operation
If the polymeric material is made thinner to improve flexibility and comfort, then ease of operation is improved, but the appliance prematurely cracks from repeated placement
Solution Approach 1:
The appliance structure is segmented into multiple layers, allowing the inner layer to be thinner and more flexible for comfort, while the outer layer provides additional structural thickness and strength to prevent cracking. This segmentation enables independent optimization of each layer's thickness.
Solution Approach 2:
Different regions of the appliance have different material properties and thicknesses. The inner layer contacting oral tissues is made with softer, thinner material for comfort, while the outer layer has greater thickness and stiffness for durability, creating local quality variations that satisfy different functional requirements.
3Device complexity
If a single-layer polymeric structure is used to simplify manufacturing, then device complexity is reduced, but the appliance cannot maintain constant stress profile over extended treatment period
Solution Approach 1:
The appliance is segmented into multiple layers, each with different material properties that contribute to maintaining a constant stress profile over time. The layered structure allows differential deformation and stress distribution, preventing stress relaxation that occurs in single-layer structures.
Solution Approach 2:
The composite material structure combines polymers with different mechanical properties to create a multi-layered system that maintains stable stress characteristics. The composite construction provides complementary properties that compensate for stress relaxation, ensuring consistent treatment force over extended periods.
4Strength
If the polymeric material is made stiffer to maintain structural integrity, then strength is improved, but the material abrades prematurely from repeated contact with teeth
Solution Approach 1:
The appliance is segmented into an inner layer and outer layer, where the inner layer uses a softer polymer that is more resistant to abrasion from repeated contact with teeth, while the outer layer uses a stiffer polymer to maintain structural integrity and provide the necessary repositioning force.
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 multi-layered dental appliance maintains efficient tooth repositioning without cracking or discomfort, ensuring consistent force over extended use, and improves durability and cosmetic appearance.
Implementation Method 1
The orthodontic dental appliance is made from a relatively stiff polymeric material selected to effectively exert a stable and consistent repositioning force against the teeth of a patient
Implementation Method 2
the warm and moist environment in the mouth can cause the polymeric materials in the dental appliance to absorb moisture and swell
Data Source
AI summary
A dental appliance for positioning or retaining the alignment of a patient's teeth includes a polymeric shell having a plurality of cavities configured to receive one or more teeth. The shell comprises at least three alternating polymeric layers, including a first layer of a thermoplastic polymer A and a second layer of a thermoplastic polymer B, where polymer B is chemically distinct from polymer A. Each of the thermoplastic polymers A and B has a flexural modulus of about 1.0 GPa to about 4.0 GPa and a glass transition temperature (Tg) greater than about 40° C. The multilayered structure increases mechanical durability, crack resistance, and dimensional stability over extended wear periods, and may optionally provide performance-enhancing properties such as moisture resistance, stain resistance, and improved comfort. The appliance may be manufactured by thermoforming a multilayered polymeric film and is suitable for use as an orthodontic aligner or retainer tray.