Setting Teeth for RPD Flashcards
what is the aim when setting artificial teeth for partial dentures
to have the teeth set in a position that will complement the existing teeth
restore the arch, aesthetics and function
what is the benefit of achieving the aims of setting artificial teeth for partial dentures
- improve patient self confidence
- protect denture privacy
is there a difference when setting teeth for a CoCr base or a PMMA base?
no difference
although or CoCr bases the scheme for mechanical retention for the PMMA to metal base must be considered
(post or mesh depending on available space)
what is involved in setting teeth for RPD
- choosing artificial teeth
- matching these to the natural teeth
- customising artificial teeth
- setting teeth to the exisiting dentition
- trial dentures
what material are artificial teeth made out of
- acrylic (most popular)
- porcelain
what are the properties of plastic / acrylic teeth
- chemical bond with the denture base
- natural appearance and silent in function
- tough
- soft (low abrasion resistance)
- easily trimmed and polished / customised
- cold flow under pressure
- insoluble in mouth fluids, some dimensional change
what are the properties of porcelain
- mechanical attachment with the denture base (silance coupling agent, no chemical bond, anterior teeth have a metal pin for mechanical retention)
- natural appearance
- noise in function
- brittle
- friable (grinding removes surface glaze)
- hard (high resistance to abrasion but will wear down opposing dentition)
- inert in mouth fluids (no dimensional changes)
- high heat distortion (no permanent deformation under forces of mastication)
- nightmare to trim down
what are the properties of modified acrylic / composite / polymers
- chemical bond with denture bond
- partial bonding - recommended mechanical and / or bonding agent (4-meta)
- higher abrasion resistance
what is something that you must do in clinic that cannot be achieved in the lab
matching shade of the artificial teeth to the natural teeth
use natural light
difficult to match using a photograph
what information should be taken from a tooth / mould chart
- shape of tooth > square > ovoid > tapered - length of anterior teeth - height of central incisor - width of central incisor
how do acrylic teeth bond to the denture base
chemical bond
how do porcelain teeth bond to the denture base
mechanical bond provided by a metal retention pin incorporated within the tooth on anterior teeth
posterior teeth have a hallowed area that will fill with the denture base
what happens when the space available on the edentulous saddle is smaller than the width of the remaining teeth
this will necessitate a compromise for setting teeth
how should the tooth mould be adjusted
remove from the ridge lap
> removal from the length of the root ie the cervical margin or the incisal top can affect the shape
> trimming incisal edge can make it look square and unnnatural
> important to trim from the back
the more the ridge lap is reduced, what happens
the less bonding area is available
the softer bonding area if reduced can affect the bond with the enamel layer having a harder surface
can be more easily broken off
what can be done to prevent tooth de-bonding
- trim teeth with diamond cutters
- use a post for retention when space is limited for PMMA
- ensure no wax or grease on teeth surface
- no mould seal present when processing
- try to avoid heavy contact on the denture teeth (cuspal interference)
- no wax or grease
- no mould seal
- add a drop of monomer onto before acrylic
why can holes be found in a denture base
to assist with retention
is overlapping teeth in a denture always a bad thing
no
sometimes it isn’t when completing irregular work
overlapping can create a more natural looking denture when creating the dental arch
what is correct with regards to setting a lateral
the lateral should be within the arch
the lateral should not overlap the central outside the arch
what is correct in the emergence profile: sagittal view
the central is in line with the natural tooth
the central should not protrude beyond the natural tooth
what is the occlusion: natural tooth guidance
- the wear facets on the natural teeth should be checked
- the artificial teeth must conform to the existing tooth surface wear
- the natural tooth guidance is followed by the artificial teeth
- check the tooth guidance using the canine teeth or groups of teeth such as premolars
what is the denture base like at the trial denture stage
a temporary base that will be discarded at the processing stage of denture production
- a rigid base with wax saddle
- light cured acrylic or shellac
- a trial to establish tooth positioning / finishing lines may be used for cobalt chromium then teeth are positioned onto the CoCr base once constructed for trial
- duplicate cast or master cast blocked out with plaster
- positive fit on cast
- clasps may be incorporated if required
how can you provide symmetry to the appearance
- set teeth to the long axis of the corresponding tooth
- contact points should also correspond to the natural dentition
what should be adjusted chairside
final adjustment of tooth length
if the denture is not tooth supported some movement is to be expected
can be an advantage to set teeth chairside
