Prosthodontics (including DM) Flashcards
Major connector
Definition: connects parts of the prosthesis located on one side of the arch with those on the opposite side
Example lingual bar
Minor connector
Minor connectors are those components that serve as the connecting link between the major connector or the base of a removable partial denture and the other components of the prosthesis, such as the clasp etc.
K class?
Class I Bilateral edentulous areas located posterior to the natural teeth. Front
K class?
Class II A unilateral edentulous area located posterior to the remaining natural teeth. Side
K class?
Class III A unilateral edentulous area with natural teeth remaining both anterior and posterior to it. Kinda side
K class?
Class IV A single, but bilateral (crossing the midline), edentulous area located anterior to the remaining natural teeth. Back
Clasps must be
o Passive when seated (no orthodontic appliance type movements)
o Be able to flex (so the denture can be removed)
o Terminal 1/3 must be below the survey line
o Needs a opposing reciprocal component
Undercut engage: CoCr clasps
0.25mm
Undercut engage: SS clasps
0.5mm
Undercut engage: gold clasps
0.75mm
RPI system
To reduce the strength of the abutment tooth when the denture is loaded
o R – mesial Rest (changes fulcrum location)
o P – distal guiding Plate
o I – I shaped retentitve clasp (occlusal forces allow disengagement of clasp terminus)
Clasp assembly
o Retentative arm – below survey line so to engage the abutment
o Reciprocal arm – above or on the survey line
o Rest
o Minor connector
Disinfection of dentures
o 2 minutes in 10,000ppm (1%) sodium hypochlorite or sodium dichloroisocyanurate (Actichlor)
Support definition
Resistance to vertical load (occlusal forces during function) directed through denture to underlying mucosa.
Function of rests
Aim to apply forces vertically to the tooth (Rest seat - this needs prep (keeping to the enamel)
Tissue conditioners
Allows more equal distribution of load and assumption of more normal mucosal position (this is a temporarily placed material).
o They are commonly used in the situation that the tissues have trauma (maybe from an ill fitting denture), the dentist wishes for the tissues to recover during this time (ideally for the patient to not wear their denture – not popular) and so a compromise is to place this soft tissue conditioner to allow the soft tissues to recover.
Permanent resilient lining (soft lining)
o Ideally 2-3mm thick.
o Like tissue conditioners but these are permanent and are for patients who cannot tolerate a hard base, helpful to avoid pain from nerves.
o Elastic: cushioning effect
o Permanently soft: durable property overtime.
Permanent resilient lining (soft lining) - acrylic cold
temporary soft liner, done at chairside (softest of all four) – harden quickly due to leaching of alcohol and plasticiser to the saliva.
Permanent resilient lining (soft lining) - acrylic hot
lab processed, softness due to higher methacrylate and plasticizer (alcohol and plasticizer also leach into the saliva).
Permanent resilient lining (soft lining) - silicone
Water absorption of these materials puts them at risk of bacterial/fungal growth (candida albicans).
Heat cure
Cold cure: solidify at room temp, still are lab processed. Bond of this material to the PMMA plate is weak (often peels away).
Acrylic teeth
Attachment
* Chemical bonding of plate with the teeth.
Physical properties
* Suffer from abrasion
* Occlusal adjustment in the lab/chairside is much easier compared with porcelain.
* High cross-linking of the resins makes them resistant to crazing.
Porcelain teeth
Attachment
* mechanically to the denture base.
Aesthetics
* Slightly more translucent
* Depth of colour achievement
Sound
* Make a “clicking” when contacting
Physical properties
* Brittle – can fracture and chip.
Clinical application
* Not for patients with atrophic ridges as they transmit greater force through these soft tissues.
Paraffin wax properties
o Paraffin wax (mineral)
From petroleum residues following distillation.
Brittle at room temp.
Softens: 37-55 degrees
Melts: 48-70 degrees
Addition of microcrystalline to paraffin wax?
Addition of beeswax to paraffin wax?
Clasps and survey lines: diagonal survey line
Occlusally approaching clasp
Clasps and survey lines: High survey line
Gingivally approaching T-roach clasp
Clasps and survey lines: low survey line
I bar clasp
The lingual bar
A minimum of 7mm space from the sulcus depth to the gingival margin is required to prescribe a lingual bar.
This allows 3 ½ mm bar width and 3 ½ mm clearance from the gingival margin for patient comfort and hygiene.
Covers less gingival margins than the cobalt chrome plate and
may also be used when there is spacing between anterior teeth so the connector is not visible through the tooth spaces.
The dental bar
The dental bar requires a minimum total crown height of 9mm for this connector to be used.
Bar width of 5mm and 2mm clearance from gingival margin and 2 mm clearance from the incisal tip of the tooth as shown.
PROVIDES BRACING.
Why are CoCr dentures favourable?
The cobalt chrome designs are thinner in section than the PMMA and can free up the gingival margins so are more hygenic and comfortable for the patient
Mid palatal bar requirements
Tooth-borne support gained through use of…
Occlusal rests
onlays
connectors
overdenture abutments
Mucosa-borne support is achieved through…
Saddles/connectors
Support type: bounded saddles
tooth support possible
Support type: free-end saddles
tooth/mucosa borne at best
Support type: large saddles
mucosa borne
Possible functions: saddles
retention
support
bracing
Possible functions: connector
support
indirect retention
bracing
Possible functions: clasp
retention
support
bracing
Possible functions: rests
support
indirect retention
Hook type
Embrasure hooks
Indirect retention: definition
Prevention of displacement of saddle away from the ridge by extension of the denture. Provides “remote” retention.
What is this?
Swing lock denture for a kennedy class I
Definition: bracing
Providing resistance to lateral/horizontal forces on the denture
Why is the RPI system advantageous?
- Undue stress is not placed on the abutment tooth.
- The load is spread to the tissues more evenly.
Definition: direct retention
Resistance of a denture to vertical movement away from the tissues (an undercut) when a displacing force is applied.
Primary stress bearer for the maxillary arch
crest of alveolar ridge and the horizontal plate of palatine bone
Primary stress bearing area for the mandibular arch
the buccal shelf area.
Definition: stability
The resistance of a denture to displacement by functional forces
ICP or RCP: occlusion is stable with sufficient index teeth
ICP - avoid changing the occlusion with the prosthesis
ICP or RCP: occlusion is unstable with insufficient index teeth.
Occlusion measured using FWS
RCP if ICP is not reproducible
Denture hygiene: mechanical
Soap and soft brush
Microwave
Ultrasonic
Denture hygiene chemicals: Alkaline peroxides
“light-duty” cleaner
Active ingredient: sodium perborate
NOT for soft linings
Denture hygiene chemicals: alkaline hypochlorites
Anti-microbial
Possibly corrosive for metals
Short soak (10mins) - if metal
Denture hygiene chemicals: acids
NO LONGER USED!
Denture hygiene chemicals: enzymes
expensive choice
When should you be rinsing the denture?
After every meal
Can you sleep with the denture in?
Remove denture at night!
First stage of cleaning for denture
SOFT brush with soap and water
NOT TOOTH PASTE
Denture hygiene: Chemical cleaners should be used with ____ water.
COLD
Overnight, what should I do with my denture?
Leave it in COLD water.
