Hydroxyapatite–Calcium Carbonate Composites for Controlled Bone Remodeling
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Solution Overview
Problem
Existing bone graft materials like hydroxyapatite (HA) are slow to resorb and have low water solubility, while alternatives such as calcium sulfate and calcium carbonate either resorb too quickly or lack osteoconductivity, and methods to incorporate calcium carbonate into HA result in powders that cannot be sintered to high density.
Innovation Solution
A two-phase composite is created by sintering hydroxyapatite with a carbonatable calcium component at 800-1200°C and treating it with a carbon dioxide source to convert excess calcium into calcium carbonate inclusions, maintaining a Ca/P ratio greater than 1.67, resulting in a dense, granular material with controlled remodeling rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If calcium carbonate is incorporated into hydroxyapatite to accelerate resorption, then remodeling rate is improved, but the material cannot be sintered to high density and transforms to oxide groups above 825°C
Solution Approach 1:
The patent applies preliminary action by adding the carbonatable calcium component to the hydroxyapatite before sintering, so that the carbonate phase forms in advance during the sintering process rather than attempting to maintain carbonate after high-temperature sintering. This allows the material to be sintered to high density first, then the carbonate phase develops subsequently to provide accelerated remodeling.
Solution Approach 2:
The patent changes the chemical composition parameter by incorporating a carbonatable calcium component (such as calcium hydroxide or calcium oxide) into the hydroxyapatite structure, creating a Ca/P ratio greater than 1.67. This compositional modification enables the material to achieve both high density through sintering and subsequent carbonate phase formation for accelerated remodeling.
2Reliability
If hydroxyapatite is used as a bone graft material, then osteoconductivity is improved, but resorption rate is slow and water solubility is low
Solution Approach 1:
The patent creates a composite material system combining hydroxyapatite with a carbonatable calcium component, forming a two-phase composite after sintering and carbonation. The hydroxyapatite phase provides osteoconductivity while the calcium carbonate phase formed from the carbonatable component provides accelerated resorption, thus combining the benefits of both materials.
Solution Approach 2:
The patent applies local quality by creating distinct phases within the material: the hydroxyapatite phase maintains osteoconductivity while the calcium carbonate inclusions provide rapid resorption. This spatial differentiation of functions within the composite material allows simultaneous achievement of both osteoconductivity and accelerated remodeling.
3Strength
If sintering temperature is increased to improve density, then strength is improved, but carbonate groups transform to oxide groups above 825°C
Solution Approach 1:
The patent uses preliminary action by incorporating the carbonatable calcium component before sintering, allowing the carbonate phase to form after the sintering process is complete. This sequence enables high-temperature sintering to achieve density and strength without carbonate loss, followed by carbonate phase development at lower temperatures to maintain composition stability.
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 composite provides enhanced biocompatibility and predictable remodeling rates, with improved strength and density compared to previous methods, suitable for bone grafting applications.
Implementation Method 1
sintering said composition at temperatures between 800 °C and 1200 °C
Implementation Method 2
treating said sintered hydroxyapatite material with a carbon dioxide source to convert at least a portion of said carbonatable calcium component to a discontinuous calcium carbonate phase
Data Source
Figure 1A~1B
Figure 1C~2A
Figure 2B~2C
AI summary
Carbonated calcium phosphate compositions and methods of preparation, affording enhanced biophysical properties.