Lithium Disilicate Veneering Ceramic for Zirconia Restorations
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Solution Overview
Problem
Current veneering ceramics for dental restorations face challenges in achieving high mechanical, chemical, and aesthetic requirements while minimizing manufacturing effort, with issues such as insufficient edge strength and high tool wear during post-processing.
Innovation Solution
A translucent veneering ceramic based on lithium disilicate and yttrium-stabilized zirconium dioxide is developed, composed of specific components (SiO2, Nb2O5, B2O3, Al2O3, Li2O, Na2O, ZrO2) with a thin glass layer formed during crystallization, providing excellent adhesion and surface quality without the need for separate glaze firing, and allowing for laser-induced crystallization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If leucite-containing dental ceramics are used, then the veneering ceramic can be manufactured with conventional processes, but the flexural strength is insufficient (approx. 80 MPa) and does not meet high mechanical requirements
Solution Approach 1:
The patent changes the chemical composition parameters by replacing leucite with lithium disilicate as the main crystal phase, and adjusts the glass phase composition to include specific oxides (B2O3, Al2O3, SiO2) in defined ratios. This parameter change achieves flexural strength >120 MPa while maintaining manufacturability through controlled crystallization processes
Solution Approach 2:
The patent creates a composite material system combining lithium disilicate crystals with a specific glass phase containing multiple oxides. This composite structure provides both high strength from the crystal phase and good processing characteristics from the glass phase, resolving the contradiction between strength and ease of manufacture
2Ease of operation
If lithium disilicate glass ceramic is used, then the glass ceramic can be shaped into dental products when hot with good mechanical processing, but the edge strength of the restored tooth is insufficient and high tool wear occurs during post-processing
Solution Approach 1:
The patent modifies the glass composition by adding specific oxides (B2O3: 1.0-9.0 wt%, Al2O3: 1.2-6.0 wt%, SiO2: 55.0-72.5 wt%) to change the melting and crystallization characteristics. This enables the material to achieve optimal balance between hot pressability and post-processing strength, eliminating tool wear while maintaining ease of shaping
Solution Approach 2:
The patent utilizes controlled phase transitions during heating - first forming a glassy starting material that can be shaped, then inducing crystallization to lithium disilicate phase that provides strength. This two-stage phase transition resolves the contradiction between ease of shaping and final strength
3Manufacturing precision
If separate glaze firing is performed to improve surface quality, then the surface quality improves, but the manufacturing effort and process complexity increase
Solution Approach 1:
The patent merges the glaze formation step with the crystallization step into a single heating process. The glass phase in the starting material forms a glassy surface layer during crystallization, eliminating the need for separate glaze firing while achieving high surface quality. This consolidation reduces manufacturing complexity
Solution Approach 2:
The glass phase in the starting material automatically forms a protective glassy surface layer during the crystallization process without requiring external glaze application. This self-service mechanism provides surface quality improvement as an inherent part of the crystallization process, reducing additional manufacturing steps
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 achieves high surface quality, excellent adhesion to zirconium dioxide, and reduced manufacturing complexity, enabling efficient production and application in dental restorations with improved mechanical and chemical resistance.
Implementation Method 1
The starting material is sintered into blanks. These blanks are pressed into dental products at 700°C to 1200°C. During plastic deformation, the lithium disilicate glass ceramic described has only a slight reaction with the neighboring investment material.
Implementation Method 2
The veneering ceramic has very good adhesion to the zirconium dioxide. Therefore, the use of an opaque or liner is not absolutely necessary.
Data Source
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AI summary
The invention relates to veneering ceramics for dental restorations, wherein the framework ceramic is made of yttrium-stabilized zirconium dioxide. The aim of the invention is to develop a translucent veneering ceramic based on lithium disilicate and a method for applying the veneering ceramic for dental restorations made of yttrium-stabilized zirconium dioxide. Said veneering ceramic should not contain any leucite, lithium metasilicate, or ß-spodumene and should have very good chemical resistance, high adhesive strength with respect to zirconium dioxide, and good surface quality. According to the invention, said aim is achieved for a veneering ceramic on yttrium-stabilized zirconium dioxide in that the veneering ceramic is produced from the following components: a) SiO2 55.0 - 72.5 mass percent; b) Nb2O5 6.0 - 19.8 mass percent; c) B2O3 1.0 - 9.0 mass percent; d) Al2O3 1.2 - 6.0 mass percent; e) Li2O 5.0 - 16.5 mass percent; f) Na2O 1.4 - 11.0 mass percent; and g) ZrO2 0.5 - 4.0 mass percent, and is provided with a thin glass layer formed during the crystallization on the surface of the veneering ceramic.