Relines and copy dentures Flashcards
soft linings ?
Soft cushioned lining inside the denture to stop pressure points and make eating more
comfortable
what are some indications of soft linings ?
- Persistent pain under denture
- Reduction of pain during function
- Sharp bony ridges
- Superficial mental nerve
- Thin atrophic mucosa
- Parafunctional habits
- Previous positive experience of resilient linings
what are the 2 different families of materials we use for soft linings?
- silicone
- acrylic
what is the chemistry of silicone materials ?
pros and cons of silicone
- Feel softer to the patient when 2mm thick
- Material is ‘Elastic’ – instantly deforms
under load - Remain soft forever
- Need special burs when adjusting
cons
* Silicone is inert and requires an adhesive
to glue it to the denture
* Prone to colonization with Candida due to porous property
- last yr or 2
describe acrylic ?
feeling
pros and cons of acrylic ?
- Being acrylic they bond well to the denture base
- They get their softness due to the inclusion of plasticisers
- Plasticisers ‘Leach out’ in time leaving the
material hard - Don’t feel as soft to the patient as silicone due to being visco-elastic (takes time to deform)
properties of acrylic and silicone
what are some further uses of soft linings ?
copy denture?
“A copy denture is a duplicate or
replica of a denture that attempts to
reproduce those aspects of a patient’s
denture that the patient is satisfied
with, while selectively improving those
aspects with which the patient and
clinician have been dissatisfied.’’
how do we make a copy centre ?
- make mould of existing denture
- lab turn it into wax/ acrylic replica of pts original denture
- us them in pts mouth and record occlusion
- then send to lab and they will replace wax teeth with actual teeth
- we try it in and then take a wash impression
pros and cons of copy dentures ?
- Shape of denture very similar to previous denture
- Patient’s adapt to new dentures more easily
- Time saving
- Fewer clinical stages
- Fewer impressions required only wash
- Impression more tolerable than 1° / 2°
- Appearance can be maintained
indications for copy dentures ?
- Patients who have worn the same set for many years
- Older patients
- Patients with problems adapting to new dentures – when an older set
has previously been satisfactory
contraindications for copy dentures ?
Previous dentures unsatisfactory:
* Teeth not in the neutral zone
* Multiple defects
when do we use a reline ?
when denture no longer fits in mouth this can be due to bone shrinking away
what is a reline ?
If a denture becomes ill fitting due to the change in the shape of the tissues beneath over time, they can be relined to make them fit again
what materials do we use for relines
Materials we use can be hard setting or soft
Usually Acrylics
Can be done at chairside or in the lab ( pt without denture for some time ) can be hard or soft
what is a reline?
- chair side
- hard or soft
- permanent addition to their denture
- we use acrylic material (hard0 or soft material (soft)
what are some problem associated with chair side hard reline ?
Problems – largely with upper dentures
* Can increase OVD – especially when relining upper denture
* Increases thickness of palate= tongue may stick out more
* Exothermic polymerisation
* Monomers can be irritant / allergenic
* Destroys post-dam – retention may not be ideal
* Reline materials not as fully cured as lab materials
how do we do a lab reline ?
- Impression taken with denture in situ (closed mouth technique)
- Light bodied silicone used
- Sent to lab where model is cast and heat cured acrylic reline carried out
what else can we do instead of lab reline ?
lab rebase
* Whole of fitting surface is removed and replaced – can only be done in
the lab
* No increase in OVD
* No thickening of palate
* Can include a new post dam
relining/ rebasing chairside pros and cons?
Advantages
* Immediate result
* Fewer stages for errors to creep in
Disadvantages
* Inferior physical & mechanical properties
* Monomer
* For partial dentures, reline material may lock into undercuts or in between standing
teeth
relining rebasing lab pros and cons
Advantages
* Good physical & mechanical properties
* Rebasing possible = can get post dam, and thin palate
Disadvantages
* Patient without denture for some time
* Errors may creep in due to impression taking, model pouring, flasking etc
* If heat is used to polymerise the lining, the existing base material may warp
indications for chair side hard reline
- for lower dentures :
- Previous dentures very satisfactory, but now ill fitting due to bone
resorption - New dentures satisfactory occlusion and neutral zone but unstable or
unretentive
summary
what are tissue conditioners ?
Quick procedure, can offer
instant improvement in fit and relief of pain
lasts for a week
acts as a soft liner
describe the tissue conditioner reaction
Composition
* Powder
* Acrylic beads
* usually higher methacrylates
e.g. poly (ethyl methacrylate)
* Liquid
* Ethyl alcohol
* Plasticizer
Setting mechanism
* Gelation – no chemical reaction
occurs
uses of tissue conditioner
- To offer temporary relief from pain
- To help diagnose cause of pain
- To see if permanent soft lining would be of benefit
- Temporary improvement in fit of denture while new ones are being
made
properties of tissue conditioners
- Initial plastic flow
- Very soft – but
degrades rapidly - Only useful for 1 to 2
weeks - Easily dislodged during
cleaning
