1. SOFT LINERS AND DENTURE ADHESIVES

2. SOFT LINERS INTRODUCTION
A soft lining material may be defined as a soft, elastic and resilient material forming all or part of the fit (impression) surface of a denture.
Acts as a cushion between the hard denture base and tissues
Elastic and resilient

3. CLASSIFICATION
International Organization for Standardization (ISO) has issued two international standards related to soft liner materials:
Resilient lining materials for removable dentures–Part 1: short-term materials and soft lining materials and
Resilient lining materials for removable dentures–Part 2: materials for long-term use.

4. Based on duration of use
Short term liners : Upto 1 month
Intermediate liners : 1-6 months
Long term liners : 1 year or longer

5. Based on composition:
(1) Heat-polymerised acrylic resin
(2) auto polymerized acrylic resin
(3) heat polymerised silicone,
(4) auto polymerized silicone
(5) treatment liners (tissue conditioners).

6. Available Materials
The commercially available soft lining materials generally fall into two basic groups:
Silicone type and
Acrylic type materials

7. Acrylic resin soft liners
Both heat processed and auto-polymerizing types have powder and liquid components
Powder : acrylic polymers and copolymers; benzoyl peroxide- initiator
Liquid : methyl methacrylate monomer and a plasticizer.
Purpose of the plasticizer : usually di-n-butyl phthalate, is to reduce the transition of the polymer from liquid to solid below mouth temperature.
No adhesive is required

9. Silicone rubber materials
Composed of polymers of dimethyl siloxane—a viscous liquid that can be crosslinked to give good elastic properties.
The crosslinking agent: alkyl-silane
Catalyst: an organometal salt or benzoyl peroxide
E.g.: molloplast b, flexibase.

10. IDEAL PROPERTIES Ease of processing
Minimal dimensional change during processing
Water absorption should be minimal
Minimal solubility in saliva
Resilience
Bonding to poly(methyl methacrylate)
Adequate tear resistance
Easily cleansability and maintenance
Nontoxic, odourless, and tasteless
Aesthetically acceptable

11. TREATMENT LINERS / TEMPORARY SOFT LINERS/ TISSUE CONDITIONERS

12. COMPOSITION Consist of a two-component powder and liquid system
Powder : higher methacrylate, e.g. poly(ethyl methacrylate) and copolymers
Liquid : mixture of ethyl alcohol as solvent and dibutyl phthalate as plasticizer
Leaching and evaporation of these components leads to rapid hardening of the material in the mouth.
Tissue conditioners need to be replaced every 2-3 days in the mouth

14. INDICATIONS FOR SHORT TERM SOFT LINERS/ TISSUE CONDITIONERS
Treatment and conditioning of abused/ irritated denture supporting tissues prior to impression making for new dentures
2. For provisional adjunctive/ diagnostic purposes such as recovery of vertical dimension of occlusion and correcting occlusion of old prosthesis
3. Temporary relining of immediate dentures/ immediate surgical splints

15. 5. Tissue- conditioning during implant healing
4. Relining cleft palate speech aids
5. Tissue- conditioning during implant healing
6. Functional impression materials

16. MECHANISM OF GELATION
Gelation of tissue conditioners is a physical process ( devoid of any chemical reaction or any monomeric substances that could cause tissue irritation).
Upon mixing the powder and liquid, the alcohol and plasticizer mix diffuses into the swellable acrylic beads.
Gelation involves the entanglement of outer polymer chains of swollen beads, resulting in a tacky set gel with high cohesive properties.

17. MECHANISM OF ACTION
Tissue conditioners show combination of both viscous fluid and elastic solid behaviour
Viscous behaviour allows adaptation gel to inflamed/ irritated mucosa, improving the fit of denture
During chewing, the material demonstrates a time dependent elastic behaviour that allows it to recover initial deformation, absorbing impact forces and cushioning the underlying tissues.
Short-term soft liners used for functional impressions differ from those used for tissue conditioning
Functional impression material should display good flow but with minimal elastic recovery, and exhibit adequate dimensional stability in terms of weight change , water sorption and solubility

18. INDICATIONS FOR LONG TERM SOFT LINERS
1. Thin, non-resilient mucosal coverage
The provision of a resilient liner beneath a rigid denture base can improve both masticatory efficiency and oral comfort for patients presenting with a reduced thickness or lessened resilience of the oral mucoperiosteum.

19. 2. Poor ridge morphology where the mental nerve is at the crest of the ridge
In some individuals, the gradual resorption of bone can lead to the mental nerve lying on the surface of the alveolar ridge.
The nerve can be trapped between the denture and the tissue causing pain.
Inclusion of appropriate relief on the master cast together with a soft lining may help to reduce the pressure on the nerve.

20. 3. Persistent denture sore mouth
It may be due to occlusal problems, underlying bony irregularities, reduced keratinization of the epithelium with increasing age, and atrophic changes in postmenopausal women.
If these have been eliminated but discomfort persists, soft lining materials may be used to line the fit (impression) surface of the denture.
To be effective, a permanent soft lining should be about 2 to 3mm thick.
The lining acts to absorb part of the force of occlusion, releasing the stored energy as elastic recoil.
It therefore increases a patients ability to use a denture comfortably and may lead to relief of the symptoms of chronic soreness.

21. 4. Acquired or congenital oral defects
Soft lining material could be used for the cleft palate patient, or an acquired oral defect related to trauma, to improve retention of the denture by engaging undercuts.
Soft lining materials are also used for obturators after maxillofacial surgery.

22. 5. Xerostomia
A soft lining may be indicated in those with a reduced saliva flow, possibly as a result of degenerative changes in the salivary glands, radiotherapy or drug therapy.
However, the use of silicone resilient liners which lack wettability may result in trauma to the mucosa due to friction if the denture is loose and is dragged across the tissues.
Candidal colonization of permanent resilient linings is a common feature in the edentulous patient with a dry mouth.

23. 6. The need to promote mucosal healing
After implant surgery or with immediate dentures the dentures can be lined with resilient liners.
The soft lining material assists in producing an even distribution of functional load over the entire denture bearing area, avoiding local concentration of stress and to a limited degree reducing the overall load falling onto the denture bearing area.

24. 7. In cases of bilateral undercuts
Placing a rigid acrylic resin denture is difficult and there is a problem of retention.
Its use in this situation allows the denture to be placed over the prominence and since the soft material is elastic, it will spring back into close contact with the undercut area.

25. 8. Irregular foundation
In the presence of a maxillary torus, mandibular tori, prominent mylohyoid ridges or in irregular bony foundations, soft lining may be indicated because there is usually an associated very thin mucosa covering these bony projections.

26. 9. Single denture opposing natural teeth
In patients who have single denture either maxillary or mandibular opposing natural teeth or patients who are bruxers, the soft lining material acts to absorb part of the force of occlusion, releasing the stored energy as elastic recoil

27. 10.Mandibular distal extension base partial dentures
For improving retention in mandibular distal extension base partial dentures where there is retromylohyoid undercut and the presence of teeth limits the available paths of placement, resulting in an absence of valuable retentive and stabilizing areas of the denture extensions.
To overcome this problem, acrylic resin material in undercut region of the retromylohyoid fossa is replaced with soft lining material.

28. CONTRAINDICATIONS Contraindications for use of soft liners are:
drastic loss of vertical dimension,
altered plane of occlusion,
short denture borders,
dramatically changed tissues,
dissatisfying original esthetics.
“ Liners are not a panacea for the correction of all denture base problems and the patient should understand that eventually a reline, rebase, or remake of the prosthesis will be necessary.”

29. TECHNIQUES FOR USING SOFT LINERS

30. As a tissue conditioner
Pre-requisites:
Dentures should have adequate coverage of the bearing areas
Adequate OVD
No occlusal interferences

31. 2. Preparation of the denture.
From the denture base all undercuts and some area immediately on the ridge to a depth of 1mm or more is removed.
Borders and flanges maintained as vertical stops
If the denture base is short, it should be extended using self cure acrylic resin to provide support for the soft material
Dentures should be provided with room for the conditioning material that is sufficient to allow the displaced and traumatized tissue over to a normal state.

32. PREPARATION AND PLACEMENT OF THE TISSUE CONDITIONER IN THE MOUTH
Material used is a three component system; the polymer (powder), the monomer (liquid) and a liquid plasticizer (“Flow Control”).
For conditioning tissues, a ratio of 1 ¼ parts of polymer to 1 part of monomer is recommended with the addition of approximately ½ cc of the plasticizer (flow control).

37. INDIRECT METHOD OF PROCESSING SOFT LINERS

44. FOR FUNCTIONAL IMPRESSIONS
Maxillary trial base with occlusion and mandibular impression tray in centric relation at acceptable vertical dimension of occlusion. Flat rims in maximum contact are
without inclines.

45. Initial application of thicker tissue-conditioning material.

46. Final conditioner impression after two applications of thinner conditioning material.
Detailed areas are shown in mylohyoid and retromylohyoid areas.

47. Polysulfide rubber impression with mouth open
Polysulfide rubber impression with mouth open. Excellent tissue detail is produced

48. OTHER TYPES OF SOFT LINERS
Fluorinated soft lining material
Excellent viscoelastic properties
Adheres well to denture base as the
fluorinated copolymer adheres
physically to the acrylic resin
Composition: Fluorinated copolymer –
50% vinylidene fluoride, 30% chlorotrifluoroethylene and 20% tetrafluoroethylene by weight

49. Kregard
Ethyl acetate solution containing a fluorinated soft resin.
Applied to the surface of the tissue conditioner leaving the surface coated by a thin film of the resin after the solvent evaporates.
Hence, components of tissue conditioner will not leach out leading to:
Increased duration of viscoelasticity of the conditioner
More smoother and abrasion resistant
Decreased contamination

51. MAINTENANCE
Should not be cleaned by scrubbing with a hard brush in order to prevent tearing of the material.
The use of soft brush under running water is recommended.
Soaking denture in cleanser is not recommended.
Most of denture cleansers are acidic and are absorbed by tissue conditioners and retained even after rinsing with water
Mild acid can later be released when denture is placed in the mouth and can cause irritation.
Longevity in wear is limited. Hardening takes place in 4-8 weeks. Close observation and re-application required

52. LIMITATIONS
Reduction of the denture base strength.

53. Loss of softness and resilience.

54. 3. Colonisation by Candida albicans.
Intaglio surface of mandibular complete denture shows presence of Candida albicans on the soft liner material.

55. 4. Difficulty in keeping soft linings clean using normal denture cleaning methods.
5. Dimensional instability.
Some soft linings lose their plasticizer with time, and most of them absorb water.
These factors may cause dimensional changes.

56. 6. Failure of adhesion.
A common problem of soft- lined dentures is the failure of adhesion between the soft lining and the denture base.

57. Methods used to increase bonding between liner and denture base resin:
Surface roughening using lasers and alumina abrasion
Chemical etching with acetone, methylene chloride
Oxygen plasma treatment

58. DENTURE ADHESIVES

59. INTRODUCTION DEFINITION
“As a material used to adhere a denture to oral mucosa” (GPT 8)

60. Soluble Insoluble classification Creams Pastes Powder Pads
Synthetic wafers
Insoluble

61. 1. Based on components:
Natural gum - Karaya gum.
Synthetic gum - Grantez polymer.
2. Based on duration of action:
Long acting - Poly vinyl methyl ether maleate
Short acting – carboxy methyl cellulose
3. Based on forms:
Powder.
Cream
Paste

62. Soluble group Blend of polymer salts-
short acting- carboxy methyl cellulose (CMC)
long acting – polymethylvinyl-ether maleic anhydride (PVM-MA).
CREAM POWDER
Petrolatum Calcium acetate
Mineral oil Silicon dioxide
Polyethylene oxide
ANTI CLUMPING AGENT
BINDING AGENT

63. FLAVORING -Menthol and peppermint oil
COLOR - dye
PRESERVATIVES-Sodium borate and methylparaben or polyparaben

64. Powder formulation
Cream formulation
Degree of hold is less.
Duration of action is short.
Can be used in smaller quantities.
Easy to clean of denture and tissue.
Initial hold is achieved soon.
Degree of hold is high
Duration of action is long.
Requires more material.
Difficult to clean of denture and tissue.
Initial hold is achieved comparatively late.

65. Insoluble group Pads Synthetic wafers
laminated fabric with a water-activated
component impregnated within the fabric’s mesh
Adhesive ingredients may be sodium alginate or ethylene oxide polymer.

66. Composition: Components Action Poly vinyl methyl ether maleate,
Karaya gum,
Methyl cellulose,
Hydroxy methyl cellulose,
Carboxy methyl cellulose sodium.
Adhesive properties.
Sodium borate,
Sodium tetra borate,
Hexa chlorophene.
Antimicrobial agent

67. Propythy-hydroxy benzoate
Preservative and anti fungal
Sodium lauryl sulfate
Wetting agent
Magnesium oxide
Filler
Silicon-di-oxide, calcium stearate
To minimize clumping
Petrolatum, mineral oil, poly ethylene oxide
Binder
Menthol, Pepper mint oil & oil of winter green
Flavoring agent

68. Mechanism of action
Swell to obliterate the space between the base of denture and the oral mucosa.
1.WATER ABSORPTION
-50 to 150 percent
2.BIOADHESION BY CARBONYL GROUPS
Bioadhesive And Bio Cohesive Forces
Polymethyl vinyl ether-maleaic anyhride
Sodium carboxymethyl cellulose
Grasso ,Denture adhesives changing attitudes,JADA1996, 177,1,90-96

69. Viscous gel
Before applying adhesive
After applying adhesive

70. INTERFACIAL FORCE Influence:
Increase the coefficient of surface tension of the fluid
Forms a viscous gel on contact with water
Increases cohesiveness of the film of saliva by increasing viscosity of the film.
Grasso ,Denture adhesives changing attitudes,JADA1996, 177,1,90-96

71. Ideal requirements
Physically it should be in a powder, cream, or a gel form.
nontoxic, non-irritant, and biocompatible with the oral mucosa.
odorless and tasteless.
easy to apply and to remove from the tissue surface of the denture.
Should not promote microbial growth.
Should retain its adhesive properties for 12–16 h.
Provide comfort, retention and stability to the denture,

72. INDICATIONS Jaw relation records Try in Insertion of denture
Immediate dentures
Reduction of tissue irritation
Systematic diseases
Maxillofacial surgery patients
Administration of drug therapy
For extra severity of stable denture
Osseointegrated implants
Removable partial dentures

73. Contraindications Allergy Inadequate ill fitting and function dentures
Excessive loss of vertical dimension
Broken dentures
Improperly using denture adhesive

74. ADVANTAGES
Reduces irritation
Increases masticatory efficacy
Psycological benefit
Retention
Stability
DISADVANTAGES
Poor oral hygiene
Tissue destruction-insoluble adhesives

75. Can Denture Adhesives Contribute To Oral Pathoses?
Growth of microorganisms in denture adhesives
Denture adhesives often include antimicrobial agents such as hexachlorophene, sodium tetra borate, methyl salicylate, sodium borate and amphotericin (Kim 2003, Okzan 2012).
Adhesives do not have an inhibitory effect upon the oral flora, whereas others were claimed to promote Streptococcus mitis and C. albicans growth (Stafford, 1971).
Adisman (1989) denture adhesives have a cushion effect and thereby prevent the food bolus going underneath the denture and eventually inhibit C. albicans growth.

76. APPLICATION
CREAMS
Two approaches
Thin beads
Small spots

77. Thin bead technique:

78. Spot technique:

79. advantages A more controlled application
Less likelihood of applying an excessive amount
Elimination of ooze
Easier to achieve a more even distribution
Helps impress upon the patient that he/she has control of the amount used

80. Powder form:

81. Pads and synthetic wafers
fabric carrier impregnated with an adhesive.

82. Denture maintenance
Daily removal of adhesive product from tissue surface
Prosthesis soaked in water over night, so readily rinsed off.
Running hot water over tissue surface of denture while scrubbing with a hard toothbrush.
Adhesive on ridge is removed by rinsing with warm or hot water and then firmly wiping the area with gauze or a washcloth saturated with hot water .

83. Ada REQUIREMENTS Product composition should be supplied
Should not affect the integrity of denture
Biologically acceptable
Effective function as adherant

84. Polygrip
Fixodent
Fitty dent
Fixon

85. Cushion grip
Sea bond
End slip