Multilayer Oxide Ceramic Dental Restorations with Aligned Sintering

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Solution Overview

Problem

Existing methods for producing multilayer oxide ceramic bodies for dental applications face challenges in achieving distortion-free thermal densification and homogeneous color distribution, leading to unsuitable sintering kinetics and aesthetic issues in mimicking natural teeth' optical properties.

Innovation Solution

The use of presintered multilayer oxide ceramic blanks with varying layers containing La2O3, Al2O3, and MgO, which aligns sintering behavior and ensures no distortion during thermal densification, allowing for precise control of color and translucence properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional sintering processes are used for multilayer oxide ceramic bodies with different compositions, then coloration and shaping can be achieved, but distortion occurs during thermal densification due to incompatible sintering kinetics

Engineering Contradiction:

Improvedistortion-free sinteringVSAvoidsintering process complexity

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The invention modifies the sintering behavior of different ceramic layers by adjusting compositional parameters (additives like SiO2, Al2O3, TiO2 in varying amounts) and processing parameters (presintering temperature, holding time, and heating rates) to achieve compatible sintering kinetics across layers with different colorations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

A presintering step is introduced before final sintering to pre-densify the ceramic body and reduce porosity to below 10%, which aligns the sintering behavior of different layers and prevents distortion during subsequent thermal densification

Inventive Principle:

Principle #10Preliminary action

2Illumination intensity

If oxide ceramics are colorated to imitate natural teeth, then aesthetic appearance is improved, but homogeneous color distribution and translucence control become difficult

Engineering Contradiction:

Improveoptical propertiesVSAvoidcolor distribution homogeneity

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

Different layers of the ceramic body are assigned different colorations and translucence properties to mimic the natural stratification of teeth, with each layer containing specific colorants (metal oxides like Fe2O3, Cr2O3, NiO) in controlled amounts to achieve desired optical effects

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention controls color distribution by adjusting the concentration of colorant additives and sintering parameters (temperature, time, atmosphere) to achieve homogeneous coloration within each layer while maintaining different optical properties between layers

Inventive Principle:

Principle #35Parameter changes

3Strength

If multilayer ceramic bodies are densified thermally, then mechanical properties are improved, but distortion occurs due to different sintering kinetics of layers with varying compositions

Engineering Contradiction:

Improvemechanical propertiesVSAvoiddimensional stability

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The invention achieves compatible sintering kinetics by modifying compositional parameters (adding specific oxides in controlled amounts) and processing parameters (presintering temperature and holding time) so that all layers densify at similar rates during thermal treatment, maintaining dimensional stability while achieving high mechanical strength

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Presintering is performed as a preliminary densification step to reduce porosity and pre-align the microstructure of different layers before final sintering, which prevents distortion during subsequent thermal densification while still achieving the required mechanical properties

Inventive Principle:

Principle #10Preliminary action

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

This approach results in distortion-free, accurately fitting dental products with excellent aesthetic appearance and improved sintering kinetics, effectively mimicking natural teeth' optical properties.

Implementation Method 1

thermal densification by further sintering without distortion

Methodology Applied

Scientific EffectSintering: Sintering

Implementation Method 2

Pure ZrO2 undergoes a tetragonal-to-monoclinic phase transformation at temperatures below 950° C. which is accompanied by a considerable increase in volume

Methodology Applied

Scientific EffectPhase transformation: Phase Change

Data Source

PatentUS20240009973A1Multilayer oxide ceramic body with aligned sintering behaviour

Publication Date: 2024.01.11 IVOCLAR VIVADENT AG

AI summary

Multilayer oxide ceramic bodies and in particular presintered multilayer oxide ceramic blanks and oxide ceramic green bodies, which comprise at least two different layers and are suitable for dental applications, wherein at least one layer contains La2O3 and the at least two different layers differ in their content of La2O3. These bodies can be thermally densified by further sintering without distortion and are therefore particularly suitable for the production of dental restorations. The invention also relates to a process for the production of such multilayer oxide ceramic bodies as well as a process for the production of dental restorations using the multilayer oxide ceramic bodies.