Temporary Soft Lining Materials Flashcards
What is the function of Cold cure (RT) soft acrylics
- Used to treat irritated mucosa that support a denture allowing it to heal
- Absorbs some masticatory impact and distributes it evenly
- Shock absorber and dat
Do Cold cure (RT) soft acrylics generally have better or worse properties
CCSAs are usually worse
In what ways are CCSAs generally worse than heat cured acrylics
- Contains 3-5% free (residual) monomer that can leach out
- Higher water uptake
- Poorer mechanical properties
These are therefore temporary SLMs
Describe the composition of the powder phase of CCSAs (RT)
- Poly ethyl methacrylate (PEMA)
- OR a copolymer of butyl methacrylate and ethyl methacrylate
- PMMA
- Benzoyl peroxide initiator
Describe the composition of the liquid phase of CCSAs (RT)
- Ethyl Methacrylate AND/OR
- Butyl Methacrylate AND/OR
- Methyl methacrylate
All liquids contain - Cross linking agent e.g. ethylene glycol dimethacrylate
- Plasticiser e.g. citrate plasticiser/di-butyl phthalates
- Tertiary amine e.g. N,N dimethyl-p-toluidine (DMPT)
What is a potential drawback of MMA monomer
Can cause mucosal irritation
How do CCSAs compare to Tissue conditioners (similarities and differences)
Their function is similar but they differ like this:
- CCSAs contain a polymerisable monomer in the liquid phase
- CCSAs therefore set via a free radical addition polymerisation reaction
- CCSAs last longer than TCs
What are some advantages of using CCSAs (RT)
- They’re viscoelastic materials
- Compliant (soft)
- Bonds to PMMA (denture base material)
- Simple to use
- Can be used chair-side
What are some disadvantages of using CCSAs (RT)
- Lasts for 2-3 weeks
- Releases residual monomer that can cause mucosal irritation
- Porous, can allow ingress of microorganisms
- Difficult to remove from the denture (due to bonds that may form with the PMMA on the denture base)
Describe the function of Tissue Conditioners
- Treats irritated mucosa supporting the dentures by absorbing and distributing masticatory forces
- Shock absorber
How are Tissue Conditioners actually used in practice
- In the treatment of denture related stomatitis
- Denture liners - initially to treat traumatised tissue but remain on the denture as a liner
- Functional impression material - created as the patient wears a provisional denture over 24 hours ish
- Piezographs - impression moulded by tongue, lips and cheeks over 5-10 mins, recording of the denture space by means of pressure
- Maxillofacial prostheses
How are Tissue Conditioners dispensed
Powder and Liquid
Describe the composition of the powder phase of Tissue Conditioners
- PEMA
- OR a copolymer of butyl methacrylate and ethyl methacrylate
Describe the composition of the liquid phase of Tissue Conditioners
- Plasticiser e.g. dibutyl phthalate, benzyl salicylate OR acetyl tribute citrate
- Ethanol (6-15%)
NOTE: no monomer in liquid phase so no polymerisation reaction on setting
Describe the setting reaction of tissue conditioners
Via Gelation:
- Alcohol swells the polymer beads (chains)
- This allows penetration by the plasticiser between the swollen polymer beads, allowing the polymer chains to move more easily
- Gel is formed by polymer chain entanglement (physical process, not chemical)
What effects on handling and gelation will increasing the powder/liquid ratio with tissue conditioners have
- Increase the viscosity of the gel
- Affect its final compliance (softness)
- Increase rate of gelation
What does increasing temperature do to the setting process of tissue conditioners
increases the rate of gelation
What effect does decreasing the molecular weight and particle size of the polymer powder have on the setting reaction of tissue conditioners
Both of these increase the rate of gelation
What effect does increasing the amount of ethanol have on the setting reaction of tissue conditioners
Increased rate of gelation
What is the benefit of CCSAs and TCs being viscoelastic
these materials can conform to the anatomy of an edentulous ridge with an applied force, spreading it out
What are the advantages of Tissue Conditioners
- Compliant (soft)
- Bonds to PMMA (denture base material)
- Simple to use
- Can be used chair side
What are the disadvantages of Tissue Conditioners
- Hardens in the mouth - loss of ethanol and plasticiser into the oral environment
- All ethanol lost within 24 hours
- Possible toxicity of the plasticiser
- Porous, can allow ingress of micro-organisms
- Difficult to remove from the denture
Do SLMs and TCs have high or low water uptake
High
What can the high water uptake of SLMs and TCs lead to
Staining and microbial colonisation
