Complete dentures - security and liners Flashcards
Denture security
Patient’s main concern A function of Retention & Stability Need to consider three surfaces: Occlusal Polished Fitting
Denture retention
Ability to resist those forces attempting to displace the denture at right angles to the supporting tissues
Effectiveness of fitting surface and peripheral seal
Denture stability
Ability to resist those forces attempting to displace it in directions, other than at right angles to the
supporting tissues
Size and shape of the residual alveolar ridge
Types of liners (linings)
Permanent
Semi-permanent
Temporary
Permanent liners
*adding more plastic to denture* Heat cured PMMA -under pressure, in laboratory -greater strength, less porosity, greater durability -more expensive, takes longer -hard material Autopolymerising PMMA -chairside -quicker, but not very good -element of porosity, less polymerised (exothermic reaction) -compromised strength and durability -hard material Soft liners
Hard permanent liners - indications
Relining dentures
Additions to dentures
Placement of post dams
Soft permanent liners - indications
Relining dentures
Tender mandibular ridge
Over mental foramen
Needs to be at least 4mm thick
Permanent liners - composition
Heat cured silicone – cured in the laboratory
Autopolymerising silicone – cured at chairside
Permanent liners - indications
Friable but well-lubricated mucosa
Habituated patient
Obturators
Temporary liners - classification
Soft liners
Functional impression materials
Tissue conditioners
Temporary liners - composition
Usually PEMA, dibutyl phthalate, ethyl alcohol, benzyl salicylate
(types vary in proportions)
Temporary liners - indications
Immediate dentures
Relief of pain
Conditioning of tissues
Functional impression material
Retention may be broken by
Remaining tooth or particular muscle attachment
- overextended into buccal sulcus
- ** (first few mins of encore)
PMMA
Polymethylmethacrylate
Dentures are made of PMMA
Heat cured zinc oxide impression
Trim 3mm round periphery and trim any undercuts
Closed mouth technique with opposing denture in (dictates height of denture)
Make sure patient is biting at right height - check freeway space is the same
Problem with silicone impression material
Hydrophobic
Heat cured silicone impression
Used heavy bodied -more accuracy but less resolution Processed onto denture in laboratory Bonding critical Bonds best to fresh acrylic Lasts 6/12-3 years
Which impressions are more difficult - upper or lower
Uppers
Perforations needed to minimise thickness of material and any resulting increase in face height
Autopolymerising (laboratory cure)
After a while, autopolymerising liners distinguishable from rest of denture because with time they stain due to slight porosity
Some contain a plasticiser and remain relatively soft for a period of months (Coe ‘super soft)
Autopolymerising (chairside cure)
Plasticised, autopolymerising, PMMA and PEMA)
Dispensed as powder/ liquid, good handling properties, quick set
Linings, additions, post-dams
Automix, autopolymerising
Softer than laboratory cured
More compatible with mucosa
Used for cleft lip and palate patients and oncology patient
-usually cleft lip and palate are surgically closed at birth
