Two-Component Polymethacrylate Bone Cement Paste Stability
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Solution Overview
Problem
Current two-component polymethacrylate bone cements with dibenzoyl peroxide as an initiator face storage stability issues due to spontaneous decay when dissolved in the liquid monomer, leading to limited storage life and low mechanical strength of the hardened cement, making them unsuitable for load-bearing applications like joint endoprostheses.
Innovation Solution
A pasty two-component polymethacrylate bone cement is developed, where one component contains a distillable methacrylate monomer, a soluble polymer, insoluble particulate polymer, and an aromatic amine accelerator, while the other component consists only of dibenzoyl peroxide and a non-radically polymerizable liquid, ensuring storage stability and high mechanical strength upon mixing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If dibenzoyl peroxide is dissolved in the liquid monomer to form a two-component bone cement paste, then the cement can be processed in paste form, but the initiator shows spontaneous decay which limits storage life
Solution Approach 1:
The system is divided into two separate paste components: Component A contains the monomer, polymer, and accelerator, while Component B contains the dibenzoyl peroxide initiator suspended in a carrier liquid. This segmentation prevents the initiator from being dissolved in the monomer, eliminating spontaneous decay while maintaining paste form processability when components are mixed.
Solution Approach 2:
A carrier liquid is introduced as an intermediary substance to suspend the dibenzoyl peroxide in Component B. This carrier liquid allows the initiator to be in a paste form without being dissolved in the monomer, thus preventing spontaneous decay while enabling paste processing. The carrier liquid mediates between the need for paste form and storage stability.
2Strength
If dibenzoyl peroxide is used as the initiator in two-component bone cement, then high mechanical strength can be achieved, but storage life is limited due to spontaneous decay
Solution Approach 1:
The system separates the initiator (dibenzoyl peroxide) into a distinct Component B, preventing its dissolution in the monomer and eliminating spontaneous decay. This maintains the high mechanical strength properties of dibenzoyl peroxide while extending storage life by preventing premature initiator activity.
Solution Approach 2:
The carrier liquid in Component B preliminarily stabilizes the dibenzoyl peroxide by suspending it without dissolution, preventing spontaneous decay before mixing. This preliminary stabilization action allows the cement to be stored for extended periods while maintaining the capability to achieve high mechanical strength upon mixing.
3Reliability
If a carrier liquid is used to suspend the initiator, then storage stability is improved, but the compressive strength falls below ISO5833 specifications
Solution Approach 1:
The amount of carrier liquid is precisely controlled to be less than 5% by weight of the total cement composition. This parameter change ensures that the carrier liquid provides sufficient suspension stability for storage while minimizing its negative impact on the mechanical strength of the hardened cement, allowing compressive strength to meet ISO5833 specifications.
Solution Approach 2:
The carrier liquid is localized to Component B and does not mix with the monomer in Component A until the moment of use. This local quality approach ensures that the carrier liquid provides storage stability where needed while not interfering with the polymerization process and mechanical strength development in the final cement product.
4Reliability
If the initiator is kept in solid undissolved state, then storage stability is significantly improved, but the cement cannot be formulated as a two-component paste system
Solution Approach 1:
The carrier liquid acts as an intermediary that allows the solid dibenzoyl peroxide to be formulated into a paste form in Component B without dissolving. This intermediary enables the cement to be handled and applied as a two-component paste system while maintaining the storage stability benefits of the undissolved initiator state.
Solution Approach 2:
The physical state of Component B is changed from solid to paste by adding a small amount of carrier liquid. This parameter change allows the cement to be formulated and applied as a two-component paste system while the carrier liquid amount is controlled to be less than 5% to maintain storage stability of the suspended initiator.
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 cement achieves compressive strength of ≥70 MPa, flexural strength of ≥50 MPa, and flexural modulus of ≥1800 MPa, meeting ISO5833 standards, and can be easily processed and stored in cartridges for use in load-bearing applications.
Implementation Method 1
The two paste-like components contain separate components of redox initiator systems, which only react after the two paste-like components have been mixed to form free radicals, which trigger the free-radical polymerization of the methacrylate monomer, which leads to the hardening of the mixed cement paste.
Implementation Method 2
The two paste-like components contain separate components of redox initiator systems, which only react after the two paste-like components have been mixed to form free radicals
Data Source
AI summary
A paste-like, two-component polymethacrylate bone cement is proposed.This bone cement comprises a paste-like component A, containing AI at least one distillable, radically polymerizable methacrylate monomer, AII at least one polymer soluble in AI, AIII at least one particulate polymer insoluble in AI with a particle size of not more than 500 µm, AIV at least one radical stabilizer, and AV at least one accelerator from the group of aromatic amines, and a paste-like component B, containing BI dibenzoyl peroxide, BII at least one non-radically polymerizable, liquid substance at room temperature in which dibenzoyl peroxide has a solubility of less than 5.0 wt% at room temperature, and wherein, after mixing the paste-like component A with the paste-like component B in the resulting self-hardening cement paste, the weight fraction of the liquid substance BII is less than 2.0 wt%.Furthermore, a method for producing a self-hardening bone cement paste using the paste-like two-component polymethacrylate bone cement is described.