Calcium Phosphate Bone Material Silicate Substitution
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Solution Overview
Problem
The substitution of silicate into hydroxyapatite for bone replacement materials leads to thermal instability and the formation of undesirable secondary phases when the silicate content exceeds a certain limit, limiting its application in synthetic bone grafts.
Innovation Solution
Co-substituting a trivalent cation, such as yttrium, with silicate ions into the hydroxyapatite lattice to balance charge and increase the silicate substitution limit without phase decomposition, allowing for higher silicate content and the production of biphasic or multiphase materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If silicate substitution level is increased to enhance bone healing rate and quality, then bone bonding speed is improved, but thermal stability deteriorates and secondary phases form
Solution Approach 1:
The patent changes the chemical composition parameters by introducing a trivalent cation (such as yttrium, aluminium, or lanthanide elements) to substitute for calcium in the hydroxyapatite lattice. This compositional modification allows higher silicate substitution levels (up to approximately 12 wt% silicate or 3.66 wt% silicon) while maintaining thermal stability during sintering at typical temperatures (approximately 1200°C or above), preventing the formation of unwanted secondary phases like tricalcium phosphate.
Solution Approach 2:
The patent creates a composite substitution structure where two different ions (silicate and trivalent cation) simultaneously substitute into the hydroxyapatite lattice at specific ratios. The general formula Ca10-yMx(PO4)6-x(SiO4)x(OH)2-x+y represents this composite substitution approach, where the trivalent cation M balances the charge introduced by silicate substitution, enabling higher silicate content while maintaining phase purity and thermal stability.
2Quantity of substance
If silicate substitution exceeds the compositional limit, then higher silicon content is achieved, but phase purity deteriorates due to formation of secondary phases
Solution Approach 1:
The patent modifies the compositional parameters by establishing specific ranges for silicate (x up to approximately 12 wt%) and trivalent cation (y) content in the hydroxyapatite lattice. By controlling these parameters within defined ranges and maintaining appropriate ratios between them, the patent achieves high silicon content while preserving phase purity and preventing the formation of secondary phases during sintering.
Solution Approach 2:
The patent applies local quality by introducing a specific trivalent cation substitution at the calcium lattice sites to locally balance the charge imbalance caused by silicate substitution at phosphate sites. This localized compositional adjustment ensures that even at high overall silicate levels, the local charge balance is maintained, preventing phase decomposition and preserving material purity.
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 stabilizes the material at typical sintering temperatures, enabling higher silicate substitution levels and the creation of synthetic bone materials with enhanced properties, closer to natural bone mineral composition, and allowing for the production of biphasic and multiphase compositions with increased silicon content.
Implementation Method 1
The trivalent cation is believed to substitute for the calcium ion in the hydroxyapatite lattice
Implementation Method 2
The silicate ion is believed to substitute for the phosphate ion in the hydroxyapatite lattice
Implementation Method 3
When the level of silicate substitution passes this limit, the hydroxyapatite may become thermally unstable at typical sintering temperatures (for example approximately 1200°C or above)
Data Source
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AI summary
A synthetic calcium phosphate-based biomedical material comprising silicon and a trivalent cation.