صناعة

SOFT DENTURE LINING MATERIALS

ثاني اسنان موصل
23 / 11 / 2015
(250)

SOFT LINING MATERIAL (SLM); is a soft, elastic, and resilient material forming all or part of the fit (tissue) surface of the denture. It usually acts as a cushion between the hard denture base and the tissue, reducing the masticatory forces that are transmitted by the prosthesis to the underlining tissues.

• IDEAL PROPERTIES OF SLM

• 1. ease of manipulation and processing.
• 2. good dimensional stability.
• 3. low water absorption and
• 4. low solubility.
• 5. permanent resiliency.
• 6. sufficient adhesion to denture base to avoid separation during use.
• 7. tear resistant.
• 8. easy and unaffected cleaning.
• 9. biocompatibility.
• 10. oderlessness and tastelessness.
• 11. good esthetic and color stability.
• 12. easy to repair and adequate shelf life.


• CLASSIFICATION

• .SLM can be classified according to their chemical composition:

• 1. acrylic-based lining material
• 2. silicone-based lining material
• 3. polyphosphazine fluoroelastomers

• SLM can be classified according to their use:

• 1. tissue conditioning materials.
• 2. functional impression materials.
• 3. interim denture reline materials.
• . SLM can be classified according to their
• period of use:
• 1. temporary
• 2. intermediate
• 3. permanent

• INDICATIONS

• 1. Senile and pre-senile atrophy like compromised mastication and desquamation and thinning of the surface epithelium. Thus SLM will replace the missing natural resiliency of the aged tissues to avoid the compression of the sensory nerve endings between the hard denture base and the bone and to provide a more even distribution of the functional load.



2. chronic residual ridge soreness.
3. deficiency of oral mucosa.
4. sharp and knife edge residual ridge.
5. extensive bony prominence or projections (when surgery is contraindicated).
6. maxillofacial prosthesis;
a. SLM may be indicated for the fitting surface of the obturator when it is likely to rest on a delicate tissue.
b. SLM may be used to fabricate or reline mouth guards.

7. nerve soreness like superficial mental nerve soreness.

8. reduced tolerance to denture like in patients with nutritional deficiencies, psychological disturbance and bruxing tendencies with a flat or delicate tissues. These patients complain from
generalized low pain threshold or generalized discomfort.
9. reduced salivary flow will reduce the lubrication of the tissues and increases the friction between the denture and the mucosa. SLM reduces the effect of poor lubrication.
10. retention problems, SLM can improve the retention either by engaging the undercuts on the crowns of the overlaid teeth ( over denture) or implants, or by engaging alveolar ridge undercuts.
11. medical appliances, e.g. Molloplast-B is used to fabricate tracheal stoma prosth

LIMITATION

1. loss of softness in acrylic –based SLM.
2. difficulty in cleaning due to low abrasion resistance.
3. growth of microbes.
4. discoloration especially in acrylic –based SLM due to absorption in water or solubility in water.
5. dimensional instability.
6. low tear resistance.
7. SLM reduce the strength of heat cured acrylic denture base due to reduction in thickness of the denture base and to the solvent action of silicone adhesive and soft acrylic monomer.
8. difficulty in finishing and polishing.
9. hypersensitivity.
10. failure in adhesion between SLM and denture base


• CHEMICAL COMPOSITION
• 1. ACRYLIC-BASED SLM: they consist of powder (polymer), and liquid (a mixture of a polymerizable acrylic monomer and a plasticizer). Two types of acrylic-based SLM are available; cold cured and heat cured liners.
• 2. SILICONE-BASED SLM: they are similar in composition to the silicone impression material. They are basically polydimethylsiloxane which is a viscous liquid that is cross-linked to give a rubber with good elastic properties. Two types of silicone-based SLM are available; cold-cured liners (e.g. GC reline which is supplied as two pastes), and heat cured liners (e.g. Molloplast-B liner which is supplied as a one paste system).
• 3. POLYPHOSPHAZINE FLUOROELASTOMER: have recently become available for use as denture SLM. They are supplied in sheet form and are manipulated in a similar manner to the heat cured products.

• MANIPULATION OF SLM

• 1. A thickness of 2-3 mm of SLM is required for adequate cushioning.
• 2.The cold cured products are temporary SLM (less than 1 month or intermediate liner (1-6 months). They are used in place of tissue conditioner in cases where it is not practical to replace tissue conditioner every 2-3 days. These materials harden within a period of a few weeks or a few months. Therefore, they require a regular replacement. These materials can be readily applied to an existing
• denture by the dentist, in a chairside technique.
• 3.The heat cured products are permanent SLM (1 year or longer). They remain soft for longer time than intermediate SLM. These materials are processed simultaneously with the hard acrylic denture base.

• TISSUE CONDITIONERS

• Tissue conditioners (TC) are soft denture liners which may be applied to the fitting surface of a denture. They are used to provide a temporary cushion which prevents masticatory loads from being transferring to the underlying hard and soft tissues. These materials should flow for 24-36 hours after mixing in order to;
1.to allow for soft tissues changes once "trauma" has been removed.
• 2. to capture the shape of the supporting tissues in function.

• INDICATIONS

• 1. traumatized soft tissues as a result of wearing an ill-fitting denture to allow tissue recover before recording impressions for new dentures.
• 2. they applied to the denture of patients who have undergone surgery to reduce pain and to help prevent traumatization of the wound.
• 3. they are used when teeth are being added to a denture as an immediate denture (very shortly after the extraction).
• 4. they are used as functional impression material to be obtained over a period of a few days.


• CHEMICAL COMPOSITION
• TC are supplied as powder and liquid:
• - powder:polymer beads of polyethylmethacrylate.
• - liquid: solvent (ethyl alcohol) and plasticizer (butylphthalyl butylglycolate).

• MANIPULATION

• TC are used in chairside technique according to following steps;
• 1. The freshly material is applied to the fitting surface of the denture.
• 2. the denture is then seated in the patient's mouth whilst the TC is still in a fluid state.
• 3. the denture and the patient's soft tissues should be inspected after 2-3 days to ascertain the successfulness of the procedure.
• 4. at the end of the 2-3 days, the material is either replaced or an adequate functional impression has been obtained to make a new denture.
• Note: the TC should be replaced every 2-3 days.