11. Reline and rebase Flashcards
What is a rebase?
A rebase is the laboratory replacement of the majority of the denture base following clinical impressions of the fit surface
EXAM Q
Explain the difference between a reline and a rebase.
A rebase is the laboratory replacement of the majority of the denture base following clinical impressions of the fit surface whereas a reline is the addition of material (either temporary, semi-permenant or permenant) to the fit surface of the denture, usually at the chair side but maybe in the laboratory
Reline
The addition of material (either temporary, semi-permenant or permenant) to the fit surface of the denture, usually at the chair side but maybe in the laboratory
What’s important to consider with reline and rebase?
Both techniques will only improve the ‘fit’ of the dentures (and a moderate amount of extension if done skilfully)
They cannot correct gross under extension, occlusal faults or tooth position faults.
EXAM Q
What are the indications for a rebase?
Residual ridges have resorbed and adaptation of the bases poor
Immediate denture 3-6 months after insertion
Construction of new dentures may cause physical or mental stress
What are the general considerations with a rebase?
. Patient wishes / informed consent
* Oral tissues healthy
* Denture base extension adequate
* Aesthetics satisfactory
* Occlusion correct : a-p relation
* OVD satisfactory
* Speech satisfactory
EXAM Q
Clinical process for rebasing?
- Check extension and correct with border moulding or
reduce - Adjust to even occlusal contact if necessary
- Remove undercut areas from dentures
- Make relief holes in anterior palate of upper
- Load with suitable impression material – zinc-oxide
eugenol or polyvinylsiloxane ( use of adhesive for
PVS) - Closed mouth impression technique to maintain
occlusal relations (an open-mouth technique may lead
to a substantial denture shift and occlusal discrepancies)
. Models are poured in stone
. Upper plaster occlusal
index provides key to
maintain correct tooth
position and height
EXAM Q
Indications for reline?
- Usually a temporary solution – hard / soft
- Improves fit only
- Treat pathology (denture-induced trauma, denture-
induced stomatitis / denture-induced hyperplasia) - Aid to diagnosis – i.e. a soft lining may relieve
persistent pain under a lower denture (parafunction, low
pain threshold) and suggest use of a permanent resilient
lining material. A hard reline may improve looseness and suggest a rebase is performed.
EXAM Q
Describe the materials for relining complete dentures
Hard or soft reline materials. And explain a bit about them… see coming slides.
(This is just for understanding not a Q on the exam.)
What might happen with the initial hard chairside reline application to a lower denture
Deterioration of material and colour change, perhaps the adherence of the liner to the denture is failing. So a soft reline material can be applied to the upper and lower dentures to reduce trauma to damaged tissues while they recover prior to taking impressions in the construction of new dentures.
For hard reline materials what should we not use?
Methylmethacrylate- it is not useful as MMA monomer is too irritant and exothermic reaction (damage to tissues).
What should we use for hard reline materials?
‘Total Hard’, ‘Colacryl’
What about these materials?
They are a mix of Polyethylmethacrylate powder, butylmethacrylate monomer,
Dibutylphthalate plasticiser, tertiary amine activator (as it is a chemically activated not heat activated reaction).
Sets by chemical polymerisation rxn.
PBMA monomer when polymerised is tolerable by tissues (and does not irritate).
What is important to remember when relining dentures?
Makes the upper palate thick (because you’re simply adding material to it, px often complains about this which is why relining is often seen as a temporary procedure not a long term solution.)
Maybe best on the lower denture (bearing in mind it will increase the OVD of the dentures)
What are the soft reline materials?
Resilient liner and tissue conditioner
What about resilient liner?
A soft material which absorbs
occlusal load and reduces pressure on the
tissues (is elastic)
What about tissue conditioners?
A soft material applied
temporarily to a denture to allow a more even
distribution of forces and improved fit
i.e. as
unhealthy tissue recovers this material adapts
to maintain fit (is pseudo-elastic and will flow under pressure)
What’s the classification of resilient liners?
Permanent: (Molloplast-B : heat-cured silicone –
produced in laboratory on model from clinical
impression)
- Temporary: Total Soft (acrylic), Mollosil (silicone)
Tissue conditioners and examples?
There are various makes (Acrylic based).
. Coe Comfort
* Visco-gel
* F.I.T.T.
Mouth life - days rather
than months!
What’s the tissue conditioners made out of?
Powder – polyethylmethacrylate
* Liquid - dibutylphthalate plasticiser and ethanol
Tissue conditioners set by
gelation process not chemical rxn.
(PEMA granules swell in alcohol and stick
together, plasticiser maintains softness). As alcohol and plasticiser leach away as it hardens
Tissue conditioners are
Temporary reline for denture-induced
stomatitis, tramatised / abused tissues
Tissue conditioners- must
must change weekly as harden quickly, clean
gently, avoid alkaline peroxidase cleaners
(Steradent), hypochlorite (Milton’s soln.) may
increase length of use and reduce candidal colonisation.
What is a rebase?
the laboratory replacement of the majority of the denture base following clinical impressions of the fit surface
