RP 4 - Relines, repairs and additions Flashcards
What is a reline?
adding new base material to the fitting surface of an existing denture in a quantity sufficient to fill the space which exists between the original denture contour and the altered tissue contour
(providing a new fitting surface for a denture or part of a denture)
What is a rebase?
replacing the entire denture base material of an existing denture
Are relines and rebases done chairside or in the lab?
reline - usually chairside
rebase - lab
What are the 3 categories of relines?
- temporary
- soft
- permanent
What are the features of a temporary reline?
no particularly resilient and will only last for a shortish period of time
What are the features of a soft reline?
provides some cushioning inside the denture
Where are the more resilient types of relines usually done?
in the lab rather than chairside
When may temporary relines be provided?
- tissue conditioning - when grossly ill fitting dentures or tissues very inflamed etc
- post immediate dentures
- after implant surgery
When may soft relines be provided?
- parafunctional habits e.g. bruxism
- very atrophic ridges
- cancer/cleft patients (obturator)
What are the downsides of soft relines?
plasticiser leaches, deteriorate/harden with time, harbours microorganisms
What 4 types of soft lining materials are available?
- heat cured acrylics
- self cured acrylics
- heat cured silicones
- self cured silicones
some can be used chairside and some need technical processing
Describe heat cured acrylics (as a soft lining material)
powder is methacrylate based (such as polyethyl methacrylate) activated by benzoyl peroxide in liquid containing monomer and plasticiser
Describe self cured acrylics (as a soft lining material)
like heat cured acrylics but rather than heat is is a tertiary amine that acts upon the benzoyl peroxide
Describe heat cured silicones (as a soft lining material)
processed against acrylic. contain a siloxane material and a filler of silica
Describe self cured silicones (as a soft lining material)
similar to impression materials for composition and setting
What type of soft lining material is coe-soft?
self cured acrylics (can be done chairside)
What type of soft lining is Molloplast B?
heat cured silicone (placed and processed in the lab)
What type of material are permanent relines typically made of?
usually hard acrylic (heat cured, usually placed in the lab)
What situations might permanent relines be used in?
- useful in peripheral seal problems
- correction of errors following inadequate master impression
- immediate/post-immediate dentures
- prolongs lifespan of some older dentures
What kind of denture would you consider for a rebase?
the denture is loose fitting, the teeth are not worn and are in good condition
What is done before recording an impression in the denture?
undercuts removed from the denture
What will happen is undercuts are left on the denture when taking an impression?
when trying to remove the denture from the cast in the lab the model will break
What impression technique is used when providing a rebase?
a wash impression is taken in the denture, and a closed mouth technique is used so that the occlusion remains unchanged
After recording an acceptable impression, what is the next step when providing a rebase?
(disinfected)
the impression is poured in stone
Once the stone model of the impression is set, what is the next step when providing a rebase?
a plaster overcast is made
What is a plaster overcast and what does it do?
goes over the occlusal surface of the teeth, ensures that the denture is in the same location with the occlusal surface to the stone model when the lining is going to be placed
Once the denture has been removed from the model, what s the next step when providing a rebase?
carve the post-dam at the junction of the hard and soft palate on the model
occasional you may cut a second post-dam further forward if you believe the patient may struggle with the posterior extension
In the lab, what is done to the original denture once it has been removed from the cast when providing a rebase?
cut out the palate of the denture (the denture will then look like a horseshoe) then resite it onto the overcast
What do you use to hold the denture in place when you are putting the cast, overcast, and cut-back denture back together?
sticky wax
After cutting back the denture palate, why is there now a gap between the denture and model? What is done about this?
the gap was previously filled by the impression material, the gap is then filled with wax
After adding wax to the peripheries of the cut-back denture, why can the overcast then be removed when providing a rebase?
the overcast can be removed as it has served its purpose to maintain the position of the denture in relation to the model and also maintained the vertical dimension
When rebasing a denture, as well as placing wax to the peripheries, where else is wax added?
the palate - this will become the rebased palate of the denture
What technique is used to rebase a denture with acrylic?
the dundee injection technique
- the denture is flasked, the wax is boiled out and removed, separator is applied and the acrylic injected into the mould
How is acrylic injected into a a denture mould?
the flask and injector in place, turn the clamp handle slowly until acrylic flows out of the flask as shown by the arrows
After the acrylic is injected into the flask, what is the next step during the rebase of a denture?
flask is placed into a clamp and processed, once processed the denture is ground to shape and polished
What are the common types of denture fractures?
- midline
- tooth detaches from denture base
- loss of flange
- acrylic saddle detaches from Co/Cr baseplate
- clasp fracture/bent
Why may a denture fracture?
- impact
- acrylic in thin section
- work hardening of metal
- parafunctional habits
- occlusion - deep overbite
- soft linings
- denture processing problem - porosity
- bonding between tooth and base acrylic or acrylic and Co/Cr
What do you do if a patient presents with a denture for repair and there doesn’t seem to be any missing parts. (simple repair)?
if fractured pieces can be located together, disinfect and send to lab (no impression needed), cast poured, fractured area removed, new acrylic processed
If a patient presents with a denture for repair and part of the denture is missing, what do you do?
impression taken with fractured denture in mouth, disinfected, sent to lab, cast poured and new acrylic processed into defect
What repairs may be more challenging?
repairs between acrylic and cobalt chrome because the bond between the two materials is not ideal
What may you have to do when repairing a fracture between acrylic and cobalt chrome?
may need to add retentive tags, solder on tags and/or use 4-META or silicoat Co/Cr to retain acrylic on Co/Cr
What materials may be used for temporary repairs?
- self-cure acrylic
- cyanoacrylate glue
(usually chairside)
When may a denture be unrepairable?
e.g. when its smashed into multiple pieces or lots of missing
What are the different types of additions to a denture?
- immediate addition
- post-immediate addition
- retention
What kind of dentures can additions be done to?
partial not complete
What is an immediate addition?
when a tooth is extracted after denture construction and a tooth is added on the day of tooth extraction
How do you complete an immediate addition?
before the tooth is extracted record an impression with the denture in place, send the impression and denture to the lab, who would then remove the tooth on the cast that was to be extracted and add it on to the denture
denture can then be fit for the patient at the same visit as the extraction
What is a post-immediate addition?
when a tooth is lost after denture construction and at a later date a tooth is added
How long after an extraction would the patient usually return for an impression for a post-immediate addition?
2-3 weeks after extraction
What is a retention addition?
when denture retention is inadequate a clasp is added to try to improve retention (usually a wrought stainless steel clasp)
When providing additions what are some of the clinical issues to consider?
- additions usually require an impression of the arch with the denture to be added to in the mouth during the impression
- sometimes can do chairside addition in self-cure acrylic - often temporary
How do additions differ between acrylic and cobalt chrome dentures?
adding to acrylic dentures is easier than Co/Cr
- sometimes can’t add to a Co/Cr e.g. lower incisor when there’s a lingual bar connector
- may need to add retention tags, solder on tags and/or yse 4-META or silicoat to retain acrylic on Co/Cr
