Lithium Disilicate Glass-Ceramic Composition for Direct Milling

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Solution Overview

Problem

Lithium disilicate glass-ceramics used in dental restorations require a separate heat treatment step to convert from the softer lithium metasilicate phase to the stronger Li2Si2O5 phase, which adds processing time and causes material deformation.

Innovation Solution

A lithium disilicate glass-ceramic composition comprising SiO2, Li2O, Al2O3, K2O, P2O5, Na2O, ZrO2, and TiO2, with specific ratios of Na2O, ZrO2, and TiO2, and TiO2, ZrO2, SiO2, and Li2O, that allows milling in the fully crystallized state without additional heat treatment, producing a glass-ceramic with 70-85% Li2Si2O5, 5-20% Li2SiO3, and 2-18% Li3PO4 phases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If lithium disilicate glass-ceramics are milled in the Li2Si2O5 phase, then the material strength is high, but the machinability is poor

Engineering Contradiction:

Improvematerial strengthVSAvoidmachinability

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The patent changes the chemical composition parameters of the glass-ceramic material by introducing specific ratios of Na2O, ZrO2, and TiO2. This compositional modification enables the material to maintain high strength while achieving improved machinability through controlled crystallization during milling, resolving the contradiction between strength and ease of manufacture

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent applies preliminary crystallization treatment to the glass-ceramic material before milling operations. By pre-forming the Li2Si2O5 crystalline phase structure, the material achieves both high strength and improved machinability during subsequent milling, as the crystalline structure provides strength while the controlled composition enables clean cutting

Inventive Principle:

Principle #10Preliminary action

2Strength

If a heat treatment step is added to convert Li2SiO3 to Li2Si2O5 phase, then the material strength is improved, but the processing time increases

Engineering Contradiction:

Improvematerial strengthVSAvoidprocessing time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The patent merges the crystallization process with the milling operation by designing a composition that undergoes controlled in-situ crystallization during milling. This eliminates the separate heat treatment step while still achieving the desired Li2Si2O5 phase transformation, thereby reducing processing time while maintaining strength improvement

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

By modifying the chemical composition parameters (Na2O, ZrO2, TiO2 ratios), the patent enables the material to crystallize at lower temperatures and faster rates during milling, eliminating the need for prolonged separate heat treatment while still achieving complete phase transformation to Li2Si2O5

Inventive Principle:

Principle #35Parameter changes

3Strength

If a heat treatment step is added to convert Li2SiO3 to Li2Si2O5 phase, then the material strength is improved, but material deformation occurs

Engineering Contradiction:

Improvematerial strengthVSAvoidmaterial deformation

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent applies preliminary compositional design with specific Na2O, ZrO2, and TiO2 ratios that enable controlled crystallization during milling. This preliminary preparation allows the material to transform to the strong Li2Si2O5 phase while maintaining dimensional stability, avoiding the deformation that occurs with conventional post-milling heat treatment

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the chemical composition parameters to enable lower-temperature, faster crystallization during milling. This parameter modification allows the phase transformation to occur without significant thermal gradients or prolonged heating, thereby achieving strength improvement while minimizing thermal deformation and maintaining manufacturing precision

Inventive Principle:

Principle #35Parameter changes

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 enables high-strength dental milling blanks that can be directly milled into dental prostheses without deformation, achieving mechanical and optical properties without additional heat treatment, with flexural strength over 300 MPa and translucency from gingival to incisal.

Implementation Method 1

crystallizing the quenched intermediate

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Implementation Method 2

heating the calcined intermediate

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

quenching the heated calcined intermediate thereby producing a quenched intermediate

Methodology Applied

Scientific EffectQuenching: Cooling

Data Source

PatentUS20250326683A1Lithium disilicate glass-ceramics

Publication Date: 2025.10.23 JAMES R GLIDEWELL DENTAL CERAMICS

AI summary

In one example, a lithium disilicate glass-ceramic produced from a composition comprising SiO2, Li2O, Al2O3, K2O, P2O5, Na2O, ZrO2, and TiO2, wherein Na2O, ZrO2, and TiO2 are present in the composition in an amount such that Na2O/(TiO2+ZrO2) (wt. %/wt. %) is between 0.5 and 1.25. In another example, a lithium disilicate glass-ceramic produced from a composition comprising SiO2, Li2O, Al2O3, K2O, P2O5, Na2O, ZrO2, and TiO2, wherein TiO2, ZrO2, SiO2 and Li2O are present in the composition in an amount such that ((TiO2+ZrO2)/(TiO2+ZrO2+SiO2+Li2O))×100 (wt. %/wt. %) is between 3.5 and 4.