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My own revision cards > Soft Linings, Relines, Rebases and Copies > Flashcards

Soft Linings, Relines, Rebases and Copies Flashcards

1
Q

What is a soft resilient lining?

A

Soft cushioned lining inside the denture to stop pressure points and make eating more comfortable.

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2
Q

What are the indications for a soft lining?

A
  • Persistent pain under denture
  • Reduction of pain during function:
    • Sharp bony ridges (after xla)
    • Superficial mental nerve (the nerve may come to the surface after xla
      bone resorption).
    • Thin atrophic mucosa
    • Parafunctional habits (bruxism, attrition)
  • Previous positive experience of resilient linings – pts tend to get used to comfort of lined denture.
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3
Q

What are the two main families of lining materials?

A

Silicone - preferred if lining made in lab. Soft and effective but will need replacing within 1-2 years.

Acrylic-

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4
Q

What is a silicone lining material made of?

A

Poly-dimethyl silicone
Silica fillers
Plasticisers

*heat cured. Chemistry similar to light bodied silicone used for impressions

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5
Q

What are the adv of silicone lining materials?

A

Feel softer to the patient when 2mm thick

Material is ‘Elastic’ – instantly deforms under load- Spreads load from one area to all surrounding area.

Remain soft forever

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6
Q

What are the downsides of silicone lining materials?

A

Need special burs when adjusting

Silicone is inert – Can’t chemically bond to rest of denture and requires an adhesive to glue it to the denture. Adhesive can fail and peel off. Can be sharp and uncomfortable to pt.

Porous - prone to colonization with Candida

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7
Q

What is an acrylic lining material made of?

A

Powder: Acrylic polymers e.g. butyl methacrylate, Benzoyl peroxide.
Liquid: methacrylate monomers, plasticisers

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8
Q

What are the adv / disadv of acrylic lining materials?

A

Similar chemistry to PMMA – good because they bond to PMMA denture base chemically. Don’t need an adhesive.

Softness gained from plasticiser. [otherwise rigid].

Plasticisers leach out as they aren’t chemically bound to anything. Can leave behind hard material.

Visco-elastic: takes time to deform so doesn’t feel as soft to pt as silicone.

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9
Q

List the properties of acrylic materials: minimum thickness, compliance, glass transition temp, bond to denture base, surface finish, durability.

A

2-3mm minimum thickness
Compliance (softness) decreases with time (due to plasticiser)
20-30 degrees glass transition phase
good bond to denture base
Good surface finish
? durability- not reliable. Pts warned – needs to be replaced every year.

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10
Q

What is glass transition temp?

A

Temp at which a rubbery material becomes rigid and hard.
Acrylic – mouth around 37 degrees so should be rubbery, but if pt has cold drink it can harden the material.

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11
Q

List the properties of silicone materials: minimum thickness, compliance, glass transition temp, bond to denture base, surface finish, durability.

A

2mm minimum thickness
Compliance (softness): remains soft permanently
-130 degrees glass transition phase
Bond to denture base: requires a bonding agent. Prone to debond.
Poor surface finish
? durability - not reliable. Pts warned – needs to be replaced every year.

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12
Q

Permanent soft liners may ___ the denture

A

weaken

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13
Q

Why are permanent soft liners used?

A

Semi-permanent option for patients:
Chairside soft reline - lasts 3-6 months
Lab based materials - 1-3 years
*Last resort’ option

Can be used around undercuts in tuberosity region. Used as an obturator e.g. part of palate removed for pt so soft lining used to gain retention from walls of maxillary sinus.

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14
Q

What should we consider prior to a permanent soft liner?

A

Pts with problems with painful areas / sensitivity – consider if occlusion balanced. Relieve parts of a denture where there’s an anatomical feature that is becoming tender to bite down on.

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15
Q

If a denture becomes ill fitting due to the change in shape of the tissues beneath them over time e.g. after xla, how are they treated to make them fit again?

A

Relined

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16
Q

What problems can occur when an upper denture is relined?

A
  • Can increase OVD - esp in patients where there is limited room
  • Increases thickness of palate - pt might feel it more with tongue
  • Exothermic polymerisation - methacrylate used but still warm to pt so might be uncomfortable for some.
  • Monomers can be irritant / allergen
  • Destroys post dam. - may reduce retention
  • Reline materials not as fully cured as lab materials.
17
Q

What is a lab reline - closed mouth technique?

A

Pt biting together in occlusion whilst light bodied silicone imp material is setting. Need to border mould while it is setting.
Sent to lab where model is cast and heat cured acrylic reline carried out.

18
Q

What is the rebase technique?

A

Alternative on upper denture to avoid excessive thickening of palate.
Same procedure as reline:
Lab procedure only – need a light bodied silicone wash of denture and lab pours model. Lab then removes whole of fitting surface and replaced with new material e.g. PMMA – strong, well cured, new post dam included.

19
Q

Describe the process of lab rebase.

A

The whole fitting surface of denture is removed and replaced in lab.
No increase in OVD or thickening of palate.
Can include new post dam.

20
Q

What are the adv / disadv of chairside relining / rebasing?

A

Adv: immediate result. Fewer stages for errors to creep in.

Disadv:
*Inferior physical & mechanical properties.
*Materials not as strong as PMMA so may have free-flowing monomer. *Partial dentures: reline material may lock into undercuts or in between standing teeth making denture difficult to remove.

21
Q

What are the adv / disadv of lab relining / rebasing?

A
  • Good physical & mechanical properties
  • Rebasing possible

*Pt without denture for some time
*Errors may creep in due to impression taking, model pouring, flasking etc.
*If heat used to polymerise lining - the existing base material may warp

22
Q

Why would we need to rebase a denture?

A

Short term improvement- May be in process of making a new denture for pt.

23
Q

What are the indications for a chair-side hard reline?

A
  • Mainly used for lower dentures
  • Prev dentures very satisfactory - but now ill fitting due to bone resorption
  • New dentures satisfactory (occlusion and neutral zone fine) but unstable or unretentive.
24
Q

How do we reline a denture chairside?

A
  1. Apply rebase aid
  2. Mix material. When at stringy stage place on denture fitting surface.
  3. Insert into mouth and ask pt to bite together. Carry out muscle trimming.
25
Q

What is a tissue conditioner?

A

*Soft material. Can offer instant improvement in fit and relief of pain.
Lasts a week e.g. pt has ulcers or stitches removed.
Quick procedure

26
Q

What are the components of tissue conditioner materials? e.g. Viscogel
& what is the setting reaction?

A

Powder: acrylic beads - usually higher methacrylates such as poly (eythlmethacrylate)

Liquid: ethyl alcohol to dissolve polymer beads to form a gel and Plasticiser.

Setting mechanism - gelation. No chemical reaction occurs.

27
Q

What are the properties of temporary resilient lining materials? (tissue conditioners)

A
  • Initial plastic flow
  • Very soft - but degrades rapidly
  • Only useful for 1-2 weeks.
  • Easily dislodged during cleaning
28
Q

List the uses for tissue conditioners

A
  • Temporary pain relief
  • Helps diagnose the cause of pain
  • Tx planning - to see if permanent soft lining would be of benefit to pt
  • Temporary improvement in fit of denture while new ones being made
29
Q

What is a copy denture?

A
  • Duplicate or replica of denture that attempts to reproduce the aspects of pts denture that was satisfactory to pt
    -Selective improvement of aspects that pt / dentist was dissatisfied with.
30
Q

How is a copy denture made?

A
  1. Take a mould of existing denture using silicone putty
  2. A wax / acrylic replica of old denture constructed. Same shape / fit of original denture
  3. Record occlusion whilst replica wax in mouth. Similar to record rims. Add wax to get planes and OVD right.
  4. Lab: articulate and set up teeth for wax try in.
  5. After successful try in, take a wash impression and process to fit.
31
Q

What are the indications for a copy denture?

A

> for pts who have worn the same denture for many years
Older pts
Pts with problems adapting to new dentures (when older set previously been satisfactory).

32
Q

What are the adv of a copy denture?

A
  • Shape of denture very similar to previous denture. Pts adapt to new denture more easily.
  • time saving. Less clinical stages
  • Fewer imps required - more tolerable than primary / secondary imps.
  • Appearance of denture can be maintained.
33
Q

What are the contraindications for a copy denture?

A

Prev dentures unsatisfactory - > teeth not in neutral zone, multiple defects. Wouldn’t want to copy the same defects.

34
Q

What tx options are there if prev dentures were never satisfactory?

A
  1. Conventional remake
  2. Copy technique if older successful set can be found
35
Q

If a denture has been successful and comfortable for pt for many years, but is now loose / showing wear, what tx options are there?

A
  1. Copy dentures
  2. Conventional dentures
36
Q

What are the tx options if dentures have become recently loose, but otherwise pt is happy?

A
  1. Rebase upper, Reline lower
  2. Copy dentures
  3. Conventional dentures

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