Lithium Silicate Glass Ceramic Dental Crowns
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Porcelain-fused-to-metal crowns face issues due to differences in thermal expansion coefficients, leading to cracking and reduced durability, and the multi-visit process for fitting is cumbersome for patients.
Innovation Solution
A lithium silicate glass ceramic is used with a palladium-tin alloy substrate, where the alloy has a slightly higher thermal expansion coefficient than the lithium silicate, providing enhanced strength and stability, and simplifying the fabrication process by reducing the risk of separation during temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If porcelain is used as the restorative material, then aesthetics are improved, but the material cracks due to differences in thermal expansion coefficient with the metal substrate
Solution Approach 1:
The patent changes the material parameter by replacing traditional porcelain with lithium disilicate glass ceramic, which has a thermal expansion coefficient (9-11 x 10^-6 /°C) that closely matches the metal substrate (7-13 x 10^-6 /°C). This parameter matching prevents thermal stress-induced cracking while maintaining the aesthetic properties of the restorative material.
Solution Approach 2:
The invention uses a composite material system consisting of lithium disilicate glass ceramic combined with a metal substrate. This composite approach leverages the aesthetic properties of glass ceramic while ensuring mechanical compatibility through carefully selected material properties, particularly the thermal expansion coefficient match between the two materials.
2Reliability
If a porcelain-fused-to-metal crown is fabricated, then the tooth is protected and restored, but the fabrication process requires multiple visits and laboratory assistance
Solution Approach 1:
The patent enables preliminary action by allowing the dentist to complete all preparatory steps including taking impressions and selecting the restoration in a single visit. The pre-fabricated lithium disilicate glass ceramic crowns are designed to fit precisely without requiring complex laboratory adjustments, enabling same-day delivery and eliminating the need for temporary crowns and multiple follow-up visits.
3Ease of manufacture
If traditional porcelain is used, then the restoration can be fabricated, but the strength is insufficient compared to lithium silicate glass ceramic
Solution Approach 1:
The patent dramatically improves strength by changing the material composition from traditional porcelain to lithium disilicate glass ceramic. This material transformation increases the flexural strength from approximately 70-125 MPa for conventional porcelain to over 300 MPa for lithium disilicate, while maintaining workability and aesthetic properties.
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 lithium silicate glass ceramic offers three times the strength of porcelain, improved aesthetics, and stability at elevated temperatures, resulting in a longer-lasting and more efficient dental restoration with accurate tooth color and reduced complexity in fabrication.
Implementation Method 1
the alloy has a slightly higher coefficient of thermal expansion than the lithium silicate, providing enhanced strength and stability, and simplifying the fabrication process by reducing the risk of separation during temperature changes
Data Source
Figure 1A~2
Figure 3
AI summary
Dental restorations such as crowns, are made from lithium silicate glass ceramic that is heated and pressed onto a metal substrate, the latter being shaped to an impression or scan of the area of the mouth to receive the restoration. The metal substrate is made from an alloy selected to exhibit a coefficient of thermal expansion which is slightly greater than the CTE of the lithium silicate. In a preferred embodiment, the CTE of the lithium silicate glass ceramic is in the range of 11.5 to 12.5 and the alloy is selected to have a CTE of 12 to 13.5. A palladium tin alloy provides that CTE in the preferred embodiment.