Thermal reactions of brushite cements.

Area of Science:

• Biomaterials Science
• Calcium Phosphate Cements
• Chemical Kinetics

Background:

• Brushite cement, a calcium phosphate-based material, is crucial for bone regeneration.
• Understanding its thermal reaction kinetics is vital for optimizing its properties.
• Beta-tricalcium phosphate (beta-TCP) and monocalcium phosphate monohydrate (MCPM) are key components.

Purpose of the Study:

• To investigate the in situ thermal reactions of brushite cement at 37°C.
• To determine the influence of various parameters on the cement's reaction kinetics and phase formation.
• To correlate thermal behavior with thermodynamic and solubility data.

Main Methods:

• In situ isothermal calorimetry at 37°C.
• Systematic variation of beta-TCP/MCPM weight ratio and liquid-to-powder ratio.
• Analysis of beta-TCP synthesis route and milling duration.
• Assessment of sulfate, citrate, and pyrophosphate ion effects.

Main Results:

• Complex thermograms observed, especially with excess MCPM or additives.
• Simultaneous endothermic MCPM dissolution and exothermic beta-TCP dissolution initiate the reaction.
• Exothermic brushite crystallization follows, with endothermic monetite crystallization in excess MCPM.
• Additives broadened or delayed the main exothermic peak, particularly pyrophosphate ions.

Conclusions:

• The thermal reaction pathway of brushite cement is complex and influenced by reactant ratios and additives.
• Reaction kinetics are governed by simultaneous dissolution and subsequent crystallization processes.
• Thermodynamic and solubility data provide a robust framework for understanding brushite cement behavior.