additions and repairs Flashcards
common types of denture fractures
5
- Midline complete common
- Tooth detaches from denture base - bond between has broken
- Loss of flange
- Acrylic saddle detaches from Co/Cr baseplate - bond between 2 diff materials
- Clasp fracture/bent
why do dentures fracture
8
Impact
Drop in sink/floor
Acrylic in thin section e.g. palate
Work hardening of metal – overtime, eventually fails
Parafunctional habits – bruxist will wear and break dentures compared to non
Occlusion – deep overbite
Soft linings – not as strong so denture consequently weaker, so more likely to fracture
Denture processing problem- porosity
Bonding between tooth & base acrylic or acrylic & Co/Cr
how to repair loss part of denture
e.g. part of acrylic flange lost
impression taken with fracured denture in mouth
disinfected
cast poured adn new acrylic processed into defect
denture and impression go to lab
how to simple repair of denture
e.g. midline fracture for complete denture
if fractured pieces can be located together - disinfect and send to lab (no impression neede)
cast poured, fractured area removed and new acrylic processed
how to repair loss of acrylic tooth
Easy if tooth debonded and patient has the tooth
* Self cure acrylic
Tricky if patient lost the tooth
* Try and match the shade and mould of the rest of denture teeth, cut denture tooth down to fit pink acrylic (may need to modify acrylic)
* Most practices will have a stock so maybe able to do chairside
repeat failures…..
ask why?
occlusion; failure in tooth to acrylic bond
may need to redesign prosthesis - consider this for all types of repairs
acyrlic to CoCr denture consider
Bond not great between acrylic-CoCr
* Usually break in weaker areas - join
May need to add retentive tags, solder on tags and/or use 4-META or silicoat Co/Cr to retain acrylic on Co/Cr
Consider prognosis of remaining teeth - should design have features for their loss?
temporary repairs
e.g. Friday afternoon, get pt to comeback to do permanent repair
- Self-cure acrylic
- Cyanoacrylate glue (superglue)
- Usually chairside
strengtheners that can be added into denture
3
wire mesh (maxilla)
glass fibre mesh (maxilla)
stainless steel wire (mandible)
usually for pts with parafunctional habits or pt with repeat breaks
harder to repair afterwards if breaks again
self denture repair
Many repair kits available online to buy
Some ingenious repairs
Easy to get it wrong rendering denture useless
Mislocated pieces, meaning denture no longer fits
Discourage their use – advise seek help from a dental professional
types of additions
3
immediate
post-immediate
retention
Additions are for partial dentures & not complete dentures
immediate addition
When a tooth is lost after denture construction & tooth added on the day of tooth extraction
Adjacent to denture
Take impression with denture in place, send to lab they will attach the new tooth, you extract the tooth and fit the new denture
Save the pt social embarrassment
post immediate addition
When a tooth is lost after denture construction & at a later date a tooth added
Immediate addition isn’t possible or desirable
Tooth extracted, let socket heal for 2-3 weeks, then impression with denture in place and tooth added on at this later date
retention addition
When denture retention is inadequate a clasp is added to try to improve retention
* Usually a wrought stainless steel clasp
Take impression with denture in place, sent to lab and cast made and technician make clasps to add onto denture to improve retention
clincal issues for additions
**Additions usually require an impression of the arch with the denture in the mouth **during the impression
Sometimes can-do chairside addition in self-cure acrylic
* often temporary
Adding to acrylic dentures easier than Co/Cr
* Sometimes cannot add to a Co/Cr eg: lower incisor when lingual bar connector
* Would be better to make quick temporary immediate denture for pt to avoid social embarrassment
* May need to add retentive tags, solder on tags and/or use 4-META or silicoat Co/Cr to retain acrylic on Co/Cr
flexible dentures
clincal issues
nylon based, get in and around undercuts
Adding to or repairing flexible dentures is virtually impossible due to weak bonding between tooth and nylon and generally longevity is short-term
* Difference in hardness between teeth and nylon – have weak bond between them
* Build into consent process
* Pt needs to understand that any other teeth that they lose in lifespan of denture will require a new denture
acyrlic forms
heat cure
self cure
heat cure properties generally better
powder components in acrylic
3
Polymer – PMMA beads
Initiator – Benzoyl Peroxide (0.5 %)
Pigments – salts of Cd/Fe or organic dyes
liquid components in acrylic
4
Monomer – MMA (methymethacrylate)
Cross linking agent – Ethyleneglycoldimethacrylate (10%)
Inhibitor – Hydroquinone
Activator – ONLY Self cure – N,N’-dimethyl-p-toluidine (1%)
mixing and processing of acrylic
Use correct P:L
* Monomer shrinks by 21%
* P:L by weight = 2.5:1 reduces shrinkage to 5-6 %
Stages
Sandy-stringy-dough-rubbery-hard
Caution in additions/repair: If don’t get denture out whilst rubbery, denture will be stuck wedged in undercuts as progress to hard stage
Free radical addition polymerisation
Exothermic
* Pt may get uncomfortable – spray 3:1 cold water
Water bath/electrical oven
* Cycle 65°C to decompose benzoyl peroxide
* Do not exceed 100.3 °C (BP of monomer)
* E.g.7 hrs at 70 °C and then 100 °C for 3 hrs
advantages of acrylic
4
cheap
easy to add or reline or repair
technically easier to make
aethetic
disadv of acrylic
7
Low impact resistance
* E.g. drop on bathroom floor or sink
Poor resistance to fracture fatigue
* needs to be thick esp in bruxists - BULKY
Poor impact strength
* needs to be thick - BULKY
Water absorption and so prone Candida growth
Allergy to residual monomer
Denture whitening (alterations in microstructure)
Risks to technician’s