Denture Lining Materials Overview

Denture Lining Materials

• Denture lining materials are soft materials used to create a cushion on the fitting surface of dentures.
• Two main types exist: tissue conditioners and soft liners (acrylic or rubber).

Tissue Conditioners

• Definition/Use: Temporary cushion to prevent masticatory loads from transferring to underlying tissue. Used post-surgery, for functional impressions, and to treat irritated denture-bearing mucosa.
• Composition: Powder (ethyl methacrylate polymer), liquid (aromatic ester, ethyl alcohol, butyl phthalate).
• Reaction: Solvent liquid (not monomer), gelation reaction (physical), volatile evaporation as solvent.
• Properties: Very low hardness, flowable, no reaction with tissue (good biological effect), weight loss (solvent evaporation), small dimensional change.
• Replacement: Needs replacing every 5 days due to plasticizer loss; kit includes lubricants for easy excess material removal.

Soft Liners

• Use: For knife-edge ridges, thin mucosa, patients with bruxism or clenching, and patients having psychological issues with hard dentures.
• Requirements: Resilient, dimensionally stable, adheres to the denture base, good rupture properties, and compatibility with tissue (easy processing and low water absorption).
• Classification: Temporary and permanent based on acrylic/rubber type (cold-cure, plasticized, heat-cure). Temporary liners are replaced due to plasticizer loss and water absorption; permanent ones due to fungal growth.
• Classification details: options for how they are made (chair-side or laboratory). Permanent options can last several months.

Recent Advances

• Light-activated type: Single paste in opaque plastic cartridges.
• Addition of nanoparticles: To improve anti-microbial and antifungal properties.
• Acting as mechanical barrier: To decrease water absorption and solubility of chemical components.
• Creating a roughness of the fitting surface: To improve tensile bond between the denture and soft liner.
• New materials: heat cured polyphosphazine, fluorinated nitrogen, and phosphorous elastomers are examples of recent advances and newer materials.

Temporary Soft Liners

• Composition: PMMA, MMA, initiator, tertiary amine, plasticizer and aromatic ester, ethanol.
• Reaction: Chemical polymerization reaction.
• Properties: Loose resiliency (after 1 month), poor adhesion, cracking on the surface, not easy to clean, and poor biological effects.

Permanent Soft Liners

• Types/Preparation: Heat or cold cured acrylic or rubber (silicone), room temperature vulcanization (RTV), and heat temperature vulcanization (HTV).
• Properties: Fungal and bacterial growth can cause rapid degradation, leading to bad odor.
• Manipulation: Laboratory-processed/fabricated