Ceramic Orthodontic Bracket with Alumina Coating for Torque Strength
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Solution Overview
Problem
Conventional ceramic orthodontic brackets are aesthetically pleasing but lack the strength to withstand the tensile and flexural stresses applied during orthodontic treatment, often fracturing under the torque forces required to correct tooth alignment.
Innovation Solution
A ceramic injection molded (CIM) orthodontic bracket with a polycrystalline ceramic body and a coating of alumina or silicon dioxide is developed, which improves torque strength and counteracts defects associated with the ceramic injection molding process, such as blisters and cracks, by distributing tensile stresses and preventing microcrack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If ceramic brackets are used to improve cosmetic appearance, then aesthetic appeal is improved, but strength and resistance to fracture deteriorate
Solution Approach 1:
The patent applies composite materials by combining polycrystalline ceramic with a glass matrix to form a composite bracket body. The ceramic particles (5-50 μm) dispersed in the glass matrix create a material that maintains the aesthetic translucency of ceramic while the glass matrix provides enhanced toughness and fracture resistance, resolving the contradiction between cosmetic appeal and strength.
Solution Approach 2:
The patent changes the microstructural parameters of the ceramic by controlling grain size (5-50 μm) and incorporating a glass matrix phase. This parameter change transforms the material from pure ceramic (brittle) to a ceramic-glass composite with optimized mechanical properties, achieving both aesthetic appearance and sufficient torque strength to withstand orthodontic forces.
2Ease of manufacture
If ceramic injection molding is used to manufacture brackets, then ease of manufacture is improved, but manufacturing precision deteriorates due to blisters and cracks
Solution Approach 1:
The patent addresses the porosity and defect issues inherent in ceramic injection molding by incorporating a glass matrix that fills voids and binds ceramic particles. The glass phase accommodates shrinkage and prevents blister formation during sintering, while the controlled porosity (0.1-5% volume fraction) actually enhances toughness without compromising surface quality or requiring complex manufacturing processes.
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 coated CIM bracket exhibits significantly higher torque strength, reducing the likelihood of fracture during handling, installation, and clinical use, thus enhancing the durability and cosmetic appeal of the orthodontic treatment.
Implementation Method 1
a first coating of alumina or silicon dioxide in continuous and direct contact with at least a portion of the CIM bracket body, including the surfaces of the archwire slot
Implementation Method 2
counteracts defects associated with the ceramic injection molding process, such as blisters and cracks, by distributing tensile stresses and preventing microcrack formation
Data Source
AI summary
An orthodontic bracket for coupling an archwire with a tooth. The orthodontic bracket including a ceramic injection molded (CIM) bracket body including an archwire slot that is configured to receive the archwire therein. The CIM bracket body including a polycrystalline ceramic. A coating of alumina or silicon dioxide is in continuous and direct contact with at least the surfaces of the archwire slot. The orthodontic bracket is characterized by unexpectedly high torque strength. The ceramic injection molded (CIM) bracket body may include a polycrystalline ceramic having a grain size distribution characterized by an average grain size in the range of larger than 3.4 μm to about 6 μm such that the orthodontic bracket is also characterized by unexpectedly high fracture toughness. A method of making the orthodontic bracket includes injection molding a bracket using a ceramic powder, sintering the molded bracket, and coating the ceramic injection molded bracket.