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Questions and Answers
What does PMMA stand for?
What is another name for PMMA?
In what year was PMMA introduced to the market?
What is a dental application of PMMA?
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Why is it important for the dental profession to be aware of PMMA allergies?
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What is a non-dental application of PMMA?
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What is the classification of PMMAs based on their setting reaction?
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How do Light-cured PMMAs polymerize?
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What is an advantage of Heat-cured PMMAs?
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What is a characteristic of Chemically cured PMMAs?
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What is a benefit of Light-cured PMMAs?
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What is an advantage of Chemically cured PMMAs in chairside procedures?
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What happened to the cytotoxicity of all products after several extractions using aqueous cell culture medium?
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Which of the following products were found to be significantly more toxic than heat-polymerizing products?
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What was the effect of formaldehyde at a concentration of 50 nmol/ ml on cell numbers?
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What was the effect of MMA on DNA and protein metabolism at a concentration of 2 mm?
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What is the recommended storage method for dentures to reduce the number of residual monomers?
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What was the effect of MMA at a concentration of 5 μM on permanent L-929 cells?
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What type of products should be preferred over auto polymerizing materials if possible?
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Which of the following substances elicited severe cytotoxic effects?
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What is the role of Candida albicans in the etiology of a certain disease?
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What is the effect of EGDMA on the two caries pathogens?
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What is the difference between the denture pellicle of stomatitis patients and sound subjects?
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What is the effect of a rough surface structure of PMMA-based dentures on Candida albicans?
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What is the role of salivary compounds in the adhesion of Candida albicans?
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What is the risk of dentures transferring microbes from the oral cavity to the gastrointestinal tract or respiratory system?
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What is the relevance of regular careful denture hygiene?
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What is the consequence of Staphylococcus aureus transferred to the gastrointestinal tract or respiratory system?
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What is the primary factor influencing local reactions to implantation?
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What can be done to reduce the risk of pulp irritation when using auto-polymerizing PMMA resins?
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What is the critical temperature regarding irreversible pulpitis?
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What is the recommended practice for polymerization of PMMA temporaries?
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What is the effect of heat-polymerized products on local reactions compared to auto-polymerizing materials?
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What is the result of rapid release of MMA from bone cements?
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What is the significance of the 1st and 16th days of the implantation period in the study on rats and rabbits?
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What is the recommendation for patients at risk regarding their dentures?
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Study Notes
Introduction to PMMA
- PMMA stands for Poly(methyl methacrylate), a synthetic polymer derived from methyl methacrylate.
- It is also known as Acrylic, Acrylic glass, Plexiglas, and Acrylite.
- German company Röhm & Haas AG introduced PMMA to the market under the trademark Plexiglas in 1933.
- British chemists Rowland Hill and John Crawford discovered PMMA and registered it under the trademark Perspex.
Dental Applications
- Dental polymethyl-methacrylates (PMMAs) are used primarily for:
- Dentures
- Orthodontic devices
- Individual impression trays
- Temporary crowns
- The application of PMMA as a veneering material no longer plays a major role.
Non-dental Applications
- PMMAs are used in daily life for non-dental purposes as:
- Bone cements
- Acrylic glass
- A base for various stains
- Artificial fingernails
- Nail varnish
Classification
- PMMAs are classified into three categories based on the setting reaction:
- Light-cured
- Heat-cured
- Chemically (auto) cured
- Characteristics of each classification:
- Light-cured: polymerizes through exposure to visible light, lower residual monomers, and reduced shrinkage.
- Heat-cured: polymerizes when exposed to elevated temperatures, established technique, good mechanical properties, and suitable for chairside procedures.
- Chemically (auto) cured: polymerizes through a chemical reaction between the powder and liquid components, simplicity, and no need for external heat or light sources.
Cytotoxicity
- Cytotoxicity of all products decreased after several extractions using aqueous cell culture medium.
- Auto polymerizing acrylics are significantly more toxic than heat-polymerizing products.
- Formaldehyde caused pronounced toxic effects, but MMA generated no noticeable toxic alterations at equivalent concentrations.
- The TC50 (median toxic concentration) of MMA in permanent L-929 cells was 5 μM after an incubation period of 2 days.
Microbial Effects
- The cross-linking agent EGDMA may increase the proliferation of Streptococcus sobrinus and Lactobacillus acidophilus.
- Candida albicans plays an important role in the etiology of “denture stomatitis”.
- Adherence or accumulation of Candida albicans was promoted by a rough surface structure of PMMA-based dentures.
- Permanent soft, porous relining materials promoted adhesion in some patients, but not in all.
Clinical Practice Advice
- Regular careful denture hygiene is important to prevent the transfer of pathogenic microbes from the oral cavity to the distal gastrointestinal tract or respiratory system.
- Patients at risk should disinfect their dentures regularly with, for instance, chlorhexidine.
- Temporary restorations should be removed before polymerization reaches the maximum setting temperature.
- Polymerization of PMMA temporaries should be completed outside the oral cavity.
Implantation Studies
- Local reactions are primarily dependent on the amount of substances leached and their toxicity.
- Heat-polymerized products should cause fewer effects than auto-polymerizing materials.
- Tissue irritation decreased between the 1st and 16th days of the implantation period.
- Rapid release of MMA from bone cements was verified under simulated in vivo conditions.
Pulp Reactions
- Auto-polymerizing PMMA resins caused pulp irritations when used for temporary restorations.
- This might be due to the release of residual monomers, particularly during the first days after polymerization.
- The setting of the material may cause high temperatures (80–120°C) that could be responsible for irritation of the dental pulp.
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Description
This quiz covers the properties and reactions of Poly Methyl Methacrylate (PMMA), including its composition, setting reaction, and toxicity. It also explores the material's effects on the body, including systemic toxicity, local toxicity, and tissue compatibility.
