topic 4 Denture Lining Materiioals.pptx

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1. Denture Lining Materials 1 Dr. Sadaf Humayoun Associate Professor & HOD Dental Materials Rawal Institute of Health Sciences

2. Denture lining materials “ Denture Relining is a procedure used to resurface the tissue side of a denture with new base material, producing an accurate adaptation to the denture foundation area” ( GPT 2005)  Classified into 3 main groups Hard reline materials. Tissue conditioners. Soft lining materials. 2

3. Denture lining materials Indications Contraindications In cases where fitting surfaces of acrylic dentures needs replacement, due to bone resorption, to improve the fit of the denture. Poor quality denture base In immediate dentures, after 3-6 months of their construction. Exaggerated bone resorption Loose denture at the time of delivery Abused or traumatic oral tissues Geriatric or chronically ill patient, unable to tolerate a hard denture base. Poor teeth arrangement To heal traumatized soft tissues before recording an impression Unsatisfactory jaw relationship Speech problems Undercuts TMJ problems

4. Denture lining materials Classified into 3 main groups 1. Hard reline materials. 2. Tissue conditioners. 3. Soft lining materials. a) Temporary soft liners b) Permanent soft liners

5. 1. Hard reline materials Chair side relining technique is used. Divided into 2 types. Both types are categorized as auto polymerizable resins. Both types polymerize easily at mouth or room temperature. 5

6. 1. Hard Reline Materials Type 1 Powder Polymer beads Polymethylmethacrylate Initiator Benzoyl peroxide Pigments Inorganic salts Liquid Monomer Methylmethacrylate Plasticizer Di-n- butylphthalate Tg Chemical activator Tertiary amine 6 Composition : Autopolymerizing resins ( readily polymerize at room temperature or mouth temperature). Type 2 Powder Polymer beads Polyethylmethacrylate Initiator Benzoyl peroxide Liquid Monomer Butylmethacrylate Tg Chemical activator Tertiaty amine Pigments Inorganic salts

7. 1. Hard Reline Materials Manipulation: Relieve the fitting surface i.e. grinding away some of the hard surface of acrylic base. Powder and liquid are mixed and applied over the fitting surface of the acrylic base. Seated into the patient’s mouth whilst still fluid. Closed mouth technique (mouth closed into gentle contact) is used. The reline soon becomes rubbery having the recorded patients soft tissue impression. The denture is removed from the patients mouth and is allowed to bench cure because of exothermic heat. The relined denture is normally ready for trimming n polishing within 30 minutes. 7

8. 1. Hard Reline Materials 8 Advantages Disadvantages It provides a chairside reline to the denture. Direct contact with the oral tissues is a disadvantage. In cases where fitting surfaces of acrylic dentures needs replacement, due to bone resorption, to improve the fit of the denture. Methyl methacrylate in the monomer may cause allergic reaction. In immediate dentures, after 3-6 months of their construction. Low values of glass transition temperature ( Tg ) in both type 1 and type 2 materials may lead to increased dimensional instability. Loose denture at the time of delivery May become porous due to air entrapment during mixing which decreases patient acceptance and increases debris contamination and colonization by microorganisms. Geriatric or chronically ill patient Operator has little control over the thickness of the material which may modify the vertical relationship and may cause anteroposterior positional error or lateral cant. Increase in thickness of the “palate” of an upper denture , which patients often find unacceptable Properties:

9. Denture lining materials Classified into 3 main groups 1. Hard reline materials. 2. Tissue conditioners. 3. Soft lining materials. a) Temporary soft liners b) Permanent soft liners

10. 2. Tissue Conditioners Soft denture liners . Applied to the fitting surface of the denture. Provides temporary cushion to the fitting surface. Plastic flow continues for 24-36 hours after mixing and therefore capture a functional shape of supporting tissues. Several applications in denture works. 10

11. Applications: Help in recovery of traumatized soft tissues , due to ill-fitting dentures. Reduce pain and help prevent traumatization of the wound of patients who have undergone surgery. It can help in stabilization of an immediate denture at the time of insertion ( Addition of the tooth into the denture base that needs to be extracted). It can help in recording a functional impression of soft tissues over a period of a few days. 2. Tissue Conditioners

12. 2. Tissue Conditioners Composition: Amount of solvent and plasticizer is very crucial. 7.5% - 40% of liquid contains alcohol. Powder may be pigmented or unpigmented. 12 Powder Polymer beads Polyethymethacrylate Liquid No monomer------ not irritant Solvent Ethyl alcohol Tg Plasticizer Butylphthalyl butylglycolate Tg Physical process

13. 2. Tissue Conditioners Manipulation: (chairside technique) On mixing powder and liquid, physical process occurs. Smaller polymeric beads get dissolved and larger beads swell up on absorbing solvent. Freshly mixed material is applied to the fitting surface of the denture and is seated in the patients mouth while still in fluid state. Fluid state of the material ensures a cushion of reasonable thickness without undue increase in height of the denture. Final set material is gel-like and ideally should form a regular layer over the whole of the fitting surface of the denture. High methacrylate, ethyl methacrylate, plasticizer and solvent gives softness. Normally denture and patient’s soft tissues are inspected after 2-3 days. 13

14. 2. Tissue Conditioners Properties: Non-irritant due to the absence of acrylic monomers from the liquid component. Initially very soft and Viscoelastic ( perform both as a tissue conditioner and functional impression material). Undergo permanent deformation under even small load. Material do not remain permanently soft. Time taken for the material to become hard and loose the cushioning effect varies from days to a couple of weeks. Conditioner should be replaced after 2- 3 days till the tissue has healed properly. 14

15. Denture lining materials Classified into 3 main groups 1. Hard reline materials. 2. Tissue conditioners. 3. Soft lining materials. a) Temporary soft liners b) Permanent soft liners

16. 3. Soft Lining Materials Can be sub divided into Temporary soft lining materials. Permanent soft lining materials. 16

17. Denture lining materials Classified into 3 main groups 1. Hard reline materials. 2. Tissue conditioners. 3. Soft lining materials. a) Temporary soft liners b) Permanent soft liners

18. 3. Soft Lining Materials Temporary soft lining materials: Almost similar to tissue conditioners. Supplied as powder liquid formulation. Composition and manipulation same as tissue conditioners. Viscoelastic in nature. Retain their softness for longer duration than tissue conditioners i.e. up to a month or two. Selection of denture cleanser is very crucial for temporary soft liners as oxygenating type cleanser, cause surface degradation and pitting of the material. 18

19. 3. Soft Lining Materials Temporary soft lining materials ; Applications: In cases where it is not practicable to replace the conditioner every 2 – 3 days as they take longer to harden and do not require frequent replacement. They may be used as a means of temporarily improving the fit of an ill fitting denture until such a time as a new denture can be constructed. As a diagnostic aid to ascertain whether the patient would benefit from a permanent soft lining. Both tissue conditioners and temporary soft liners will go hard with surface becoming rough and irregular, increasing the risk of trauma and colonization by Candida in this hardened state, increasing the risk of a denture-induced stomatitis.

20. Denture lining materials Classified into 3 main groups 1. Hard reline materials. 2. Tissue conditioners. 3. Soft lining materials. a) Temporary soft liners b) Permanent soft liners

21. 3. Soft Lining Materials Permanent soft lining materials: Commonly used in patients that cannot tolerate a hard base. In patients with thin mandibular mucosa . These materials should remain permanently soft for the life time of the denture. Elasticity of these materials is very important. Requirements of Permanent/ long term Soft Liners: Permanently soft, ideally for the life time of the denture. Should be elastic in order to give a cushioning effect and prevent unacceptable distortions during service. The lining should adhere to the denture base. The material should be non-toxic, non-irritant and incapable of sustaining the growth of harmful bacteria or fungi. 21

22. Available Permanent soft lining materials 22 Acrylic Addition Two paste and similar to addition cured silicone elastomeric impression materials Condensation Paste: Hydroxyl terminated polydimethylsiloxane polymer with filler & Liquid: Crosslinking agent ( Tetraethylsilicate ) and a catalyst ( organo -tin compound). P:L—condensation crosslinking reaction with Alcohol byproduct. Cold cure Chairside technique. Can be readily applied to an existing denture. Harden with in a period of a few weeks or at best a few months, therefore require regular replacements. Polyphosphazine Sheet form Silicone Cold cure Heat cure Processed in the lab at the same time with the acrylic base. Powder : polyethyl or butyl methacrylate beads with initiator and pigment. Liquid: butylmethacrylate & Plasticizer Heat cure (Processed in lab) Single paste of vinyl terminated polydimethylsiloxane polymer with filler and an initiator. Vinyl gp . undergo chain extension, increases viscosity & Crosslinking, develop elasticity. Tendency to peel away (Processed in lab)

23. 3. Soft Lining Materials Heat cure acrylic (Permanent soft liner) : It is in powder liquid formulation. Powder consist of poly ethyl or poly butyl methacrylate (rely for softness on higher methacrylate and a plasticizer) along with some peroxide initiator and pigment. Liquid consists of butyl methacrylate and plasticizer. Dough is formed which is then heat treated simultaneously with the hard acrylic base in the laboratory and are normally applied to a new denture. 23

24. 3. Soft Lining Materials Heat cure silicone (Permanent soft liner) : It is used in the same way as heat cure acrylic. Presented in a single paste formulation. Paste consist of polydimethylsiloxane polymer with pendant or terminal vinyl groups (chain linking and crosslinking). The paste also contains inert fillers and initiators which breakdown on heating to initiate the crosslinking reaction. 24

25. 3. Soft Lining Materials Cold cure silicone elastomers (Permanent soft liner) : Both addition and condensation types are similar to the silicone elastomers used as impression materials. Cold curing silicones are cured at room temperature but are generally processed in the laboratory. Alternative method is to use an overcast instead of an articulator. Normally a cast is poured into the dentures Casts with dentures are mounted on an articulator The fitting surface of the denture is relieved to make space for the lining The fluid mix is applied to the fitting surface of the denture The dentures repositioned in the casts The articulators closed into occlusion The material allowed to set.

26. 3. Soft Lining Materials Polyphosphazine : Supplied in sheet form. Manipulated similar to the heat cure silicone products. Polymerize by heat cure. Curing cycle can be, 74°C for 8 hours. OR 74 °C for 2½ hours followed by 100 °C for 30 minutes. 26

27. 3. Soft Lining Materials Properties: All types are soft and give an adequate cushioning effect . Cushioning effect depends upon the thickness of material. 2-3 mm is sufficient for adequate cushioning effect. Harden through loss of alcohol and leaching of plasticizer. The silicones have good elastic properties and retain their shape after setting despite being subjected to masticatory loading. Acrylic materials are viscoelastic and gradually become distorted. Adequate bond with the denture base for acrylic and heat cured silicone products. Cold cure silicone has tendency to peel away. Some permanent soft liners are adversely affected by denture cleansers . Oxygenating cleansers may cause surface pitting in acrylic linings whilst brushing accelerates the rate of silicone soft liners detachment. 27

28. Soft Lining Materials Comparison of Acrylic & Silicone Soft Lining Materials Acrylic Soft Liner Silicone Soft Liner Less resilient High resilient Hardens by time More water sorption Good bonding with base material Poor bonding to acrylic denture base material Acceptable tear resistance Low tear resistance Better abrasion resistance Low abrasion resistance Resistant to damage by denture cleansers Lower r esistance to damage by denture cleansers More susceptibility to microorganism growth

29. 3. Soft Lining Materials None of the soft lining materials can be considered truly permanent in nature since none could be expected to last the full lifetime of a denture, requiring regular review of patients.

30. Self-administered Relining Materials Such products contain methacrylate or vinyl polymers along with a plasticizer and a solvent. They enable patient to improve the fit of a denture and provide a soft cushioning effect without having to visit the dentist. They should be limited for short term emergency use as long term use of such products can lead to harmful effects on the hard and soft oral tissues such as irritation, severe bone loss and tumors related to their use.

31. Rebasing “It is the laboratory procedure of replacing the entire denture base material on an existing prosthesis.” Indications: Where the observed clinical changes are moderate to severe. Some processing fault in the denture base for e.g. porosity. Discoloration of base material. Where porcelain teeth have been used.