Multi-Layer Oxide Ceramic Sintering Distortion Control

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Solution Overview

Problem

Existing methods for manufacturing multi-layer oxide ceramic bodies for dental applications suffer from distortion during thermal densification due to differing sintering kinetics of combined ceramic powders, leading to unsuitable results for dental restorations.

Innovation Solution

A presintered multi-layer oxide ceramic blank with a coefficient of distortion less than 0.4, calculated based on Vickers hardness measurements, is developed, ensuring no significant distortion during final sintering by aligning the sintering behavior of different layers through the use of dopants, varying particle sizes, and degrees of partial densification.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If multi-layer oxide ceramic bodies are manufactured by combining different ceramic powders, then aesthetic appearance and coloration are improved, but distortion occurs during thermal densification due to differing sintering kinetics

Engineering Contradiction:

Improveaesthetic appearanceVSAvoiddistortion during sintering

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by adding specific dopants (such as Al2O3, SiO2, or TiO2) to individual ceramic layers with different coloration requirements. Each layer is locally modified with dopants that adjust its sintering kinetics to match the reference layer, allowing multi-colored aesthetic appearance while preventing distortion during thermal densification.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the chemical composition parameters of different ceramic layers by introducing dopants in varying concentrations. This modifies the sintering behavior of each layer to align with the reference layer's sintering kinetics, enabling distortion-free manufacturing of multi-layer ceramic bodies with enhanced aesthetic properties.

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If dopants are added to align sintering behavior of different layers, then distortion is reduced, but manufacturing complexity increases

Engineering Contradiction:

Improvedistortion controlVSAvoidmanufacturing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by pre-calculating and pre-determining the optimal dopant types and concentrations for each ceramic layer before manufacturing. The reference layer's sintering kinetics are established first, and dopant compositions for other layers are predetermined to match this reference, simplifying the overall manufacturing process while ensuring distortion control.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If different particle sizes and degrees of partial densification are used to align sintering kinetics, then sintering behavior is unified, but processing difficulty increases

Engineering Contradiction:

Improvesintering behavior alignmentVSAvoidprocessing difficulty

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The patent changes physical parameters such as particle size distribution and degree of partial densification in addition to chemical composition. By adjusting these parameters in combination with dopant addition, the sintering kinetics of different layers are aligned with the reference layer, achieving unified sintering behavior while managing processing complexity through systematic parameter optimization.

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 allows for the production of dental restorations with high accuracy and aesthetic appeal, as the ceramic bodies are sintered without distortion, maintaining their shape and optical properties, thus addressing the limitations of prior art.

Implementation Method 1

aligning the sintering behavior of different layers through the use of dopants

Methodology Applied

Scientific EffectSintering: Sintering

Implementation Method 2

coefficient of distortion less than 0.4, calculated based on Vickers hardness measurements

Methodology Applied

Scientific EffectVickers hardness test: Vickers Hardness Test

Data Source

PatentUS11413122B2Controlling of sintering kinetics of oxide ceramics

Publication Date: 2022.08.16 IVOCLAR VIVADENT AG

AI summary

The invention relates to multi-layer oxide ceramic bodies and in particular to presintered multi-layer oxide ceramic blanks and oxide ceramic green bodies suitable for dental applications. These bodies can be thermally densified by further sintering without distortion and are thus particularly suitable for the manufacture of dental restorations. The invention also relates to a process for the manufacture of such multi-layer oxide ceramic bodies as well as to a process for the manufacture of dental restorations using the multi-layer oxide ceramic bodies.